Elementary School Science Quiz: Why Some Mixtures Make Substances
20 questions · exam conditions
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Why Some Mixtures Make SubstancesQuestion 1 of 20

Comparing these mixtures, which one is most likely a physical change (no new substance formed)?

Mixture A: A metal paper clip left in wet air for several days turns orange-brown and flaky.
Mixture B: Sugar stirred into warm water disappears, and the water tastes sweet.

Which choice best explains why one is physical and the other is chemical?

Mixture B is physical because the sugar is still sugar in tiny pieces and can be gotten back by evaporating the water. Mixture A is chemical because the metal reacted with air and water and became a new substance with new properties.
Mixture B is chemical because warm water always causes reactions. Mixture A is physical because it happened slowly over days.
Both are physical because they can both be reversed by stirring. If you stir long enough, the orange-brown color will go away.
Both are chemical because both look different after time. Any change that you can see means a new substance formed.
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Elementary School Science Quiz

Elementary School Science Quiz: Why Some Mixtures Make Substances

Practice Why Some Mixtures Make Substances in Elementary School Science with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Why Some Mixtures Make Substances, giving you a quick way to practice the rules, question types, and explanations that matter most for Elementary School Science.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Comparing these mixtures, which one is most likely a physical change (no new substance formed)?

Mixture A: A metal paper clip left in wet air for several days turns orange-brown and flaky.
Mixture B: Sugar stirred into warm water disappears, and the water tastes sweet.

Which choice best explains why one is physical and the other is chemical?

  1. Mixture B is physical because the sugar is still sugar in tiny pieces and can be gotten back by evaporating the water. Mixture A is chemical because the metal reacted with air and water and became a new substance with new properties. (correct answer)
  2. Mixture B is chemical because warm water always causes reactions. Mixture A is physical because it happened slowly over days.
  3. Both are physical because they can both be reversed by stirring. If you stir long enough, the orange-brown color will go away.
  4. Both are chemical because both look different after time. Any change that you can see means a new substance formed.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically applying principles to predict outcomes and recognizing patterns in chemical vs. physical changes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, comparing metal rusting (chemical - reacts with air/water to form new substance) with sugar dissolving (physical - sugar still sugar in tiny pieces). Choice A is correct because it correctly identifies that one mixture is chemical (substances reacted - evidence is new properties like orange-brown color and flaky texture) while other is physical (substances just dissolved/mixed - evidence is no reaction indicators, reversible), and correctly recognizes dissolving is physical (substance still there in tiny pieces) while reacting is chemical (new substance formed). This shows the student understands difference between reacting (chemical - substances transform) and mixing/dissolving (physical - substances stay themselves) and can apply understanding to new situations, not just memorize examples. Choice D represents a common error where students focus on whether change is visible rather than whether new substance formed. This typically happens because students may focus on whether they can see a change rather than on type of change, and students may not yet grasp that dissolving = breaking into tiny pieces (physical) vs. reacting = transforming into new substance (chemical). To help students: Practice applying principles to new situations: given new mixture, predict if chemical or physical by checking for indicators. Emphasize that observable evidence (temperature change from reaction, gas, irreversibility) reveals underlying process (reacting vs. mixing/dissolving). Watch for: Students who think chemical change must be obvious/dramatic, missing gradual reactions like rust and students who can categorize memorized examples but don't understand underlying principles of reactivity, energy, reversibility, and property changes.

Question 2

Based on the examples, a student tested yeast in two cups.

Cup 1: Yeast + sugar + warm water. After 10 minutes, bubbles formed and a new smell appeared.
Cup 2: Yeast + sugar + cold water. After 10 minutes, there were very few bubbles.

What does this suggest about how temperature can affect whether new substances form?

  1. Temperature does not matter because mixing the same ingredients always makes the same amount of new substance at the same speed.
  2. Warm water can help a reaction happen faster, so new substances may form more quickly. Cold water can slow the reaction, so fewer bubbles may appear at first. (correct answer)
  3. Cold water always creates more new substances because it keeps the yeast from dissolving. Dissolving stops chemical changes from happening.
  4. Warm water makes bubbles because it has more air in it, not because anything reacts. Bubbles never show a chemical change.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically understanding reactivity differences and connecting observable evidence to underlying processes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, yeast + sugar + water at different temperatures shows how temperature affects reaction rate - warm water speeds up the chemical reaction (more bubbles), cold water slows it down (fewer bubbles). Choice B is correct because it correctly explains that reactivity determines outcome - some substances react (yeast + sugar produce gas) while temperature affects how fast, and correctly applies principle that chemical changes show energy changes (gas production) that vary with conditions. This shows the student understands principles that determine outcome (reactivity, energy changes) and how conditions affect chemical reactions without changing whether they occur. Choice D represents a common error where students think bubbles are just trapped air from stirring and don't recognize gas production as key evidence of chemical change. This typically happens because students may not understand that gas bubbles from reaction itself (not trapped air) indicate chemical change, and students may think physical mixing and chemical reacting are the same thing. To help students: Teach principles, not just examples: chemical changes show energy change (temperature without external heat, gas), and conditions like temperature affect reaction rate. Compare side-by-side examples at different temperatures to show same reaction happening at different speeds. Watch for: Students who don't check for energy changes (temperature from reaction, gas) as key evidence and students who think bubbles never indicate chemical change (confusing trapped air with produced gas).

Question 3

Looking at what happened when different substances were mixed, which pair shows a physical change in both cases (no new substance formed)?

Pair 1: Baking soda + vinegar (fizzing, bubbles).
Pair 2: Salt + water (clear salty liquid; can evaporate to get salt back).
Pair 3: Sand + water (sand settles; can filter).
Pair 4: Yeast + sugar + warm water (bubbles over time; new smell).

  1. Pair 1 and Pair 4, because bubbles always mean the substances are just mixing with air.
  2. Pair 2 and Pair 3, because dissolving and filtering are ways to mix and then separate without making new substances. (correct answer)
  3. Pair 1 and Pair 2, because both make the solid disappear, so both must be chemical changes.
  4. Pair 3 and Pair 4, because changes that take longer are always physical changes.
Explanation: This question tests 5th graders' ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically distinguishing physical from chemical changes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, Pair 1 (baking soda + vinegar) and Pair 4 (yeast + sugar + water) are chemical changes with gas production, while Pair 2 (salt + water) and Pair 3 (sand + water) are physical changes that can be reversed. Choice B is correct because it correctly identifies that Pair 2 and Pair 3 show physical changes - dissolving and filtering are ways to mix and then separate without making new substances. This shows the student understands that physical changes are reversible and don't create new substances. Choice C represents a common error where students think both dissolving and reacting are chemical changes because solids disappear. This typically happens because students focus on whether the solid is visible rather than whether new substances form. To help students: Practice categorizing changes: make two columns (physical/chemical) and sort examples based on evidence like reversibility, gas production, temperature change from reaction. Watch for: Students who group dissolving with chemical changes because the solid 'disappears'.

Question 4

Based on the examples, apply what you know to a new situation.

Example: Vinegar + baking soda makes bubbles and the cup feels cooler (a chemical change).
Example: Oil + water forms two layers and can be separated (a physical change).

Comparing these mixtures, what would you most likely observe if you mixed sand + water, and why?

  1. You would see fizzing bubbles because any solid mixed with water reacts and makes gas.
  2. You would see the sand settle or stay visible, with no bubbles, and you could separate it by filtering. This suggests a physical change because the sand and water stay the same substances. (correct answer)
  3. You would see the water change temperature by itself because all mixtures release energy when stirred.
  4. You would see the sand disappear and become a new liquid, because disappearing always means a new substance formed.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically applying principles to predict outcomes in new situations and recognizing patterns in chemical vs. physical changes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, predicting sand + water based on examples of vinegar + baking soda (chemical) and oil + water (physical). Choice B is correct because it correctly applies principle that chemical changes show energy changes and irreversibility while physical don't / correctly recognizes observable pattern that chemical changes show temperature change without external heat, gas production, and new properties. This shows the student understands can apply understanding to new situations, not just memorize examples / observable evidence reveals underlying process (reacting vs. mixing/dissolving). Choice D represents a common error where students think all dissolving is chemical change because substance 'disappears' (it's physical - substance still there, can recover it). This typically happens because dissolving looks so dramatic (substance disappears) that 5th graders think it must be chemical, but substance is still present in tiny pieces and can be recovered / students may memorize examples without understanding principles, so can't apply to new situations. To help students: Practice applying principles to new situations: given new mixture, predict if chemical or physical by checking for indicators. Watch for: Students who can list examples but can't explain why or apply to new situations.

Question 5

Comparing these mixtures, which one most likely formed a new substance?

Mixture A: Oil + water. Two layers formed after sitting.
Mixture B: Sugar + water. The sugar dissolved and the water tasted sweet.
Mixture C: Baking soda + vinegar. Fizzing and bubbles appeared.
Mixture D: Sand + water. The sand settled and could be filtered out.

  1. Mixture A, because layers show the liquids changed into a brand-new substance that cannot be separated.
  2. Mixture B, because dissolving means the sugar disappeared and turned into a different substance.
  3. Mixture C, because bubbles and fizzing are evidence that a gas formed and the substances reacted. That is a chemical change that makes new substances. (correct answer)
  4. Mixture D, because settling proves the sand changed into a new substance that is heavier than water.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically recognizing patterns in chemical vs. physical changes and connecting observable evidence to underlying processes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, comparing multiple mixtures: oil + water (physical - layers form), sugar + water (physical - dissolves), baking soda + vinegar (chemical - reacts with bubbles), sand + water (physical - settles). Choice C is correct because it correctly identifies that chemical changes show energy changes and irreversibility while physical don't, and correctly recognizes observable pattern that chemical changes show temperature change without external heat, gas production, and new properties. This shows the student understands observable evidence reveals underlying process and can distinguish reactivity (substances transform) from mixing (substances stay themselves). Choice B represents a common error where students think all dissolving is chemical change because substance 'disappears' (it's physical - substance still there, can recover it). This typically happens because dissolving looks so dramatic (substance disappears) that 5th graders think it must be chemical, but substance is still present in tiny pieces and can be recovered. To help students: Demonstrate reversibility: evaporate salt water to show salt still there (physical), show can't un-mix baking soda and vinegar (chemical). Emphasize that observable evidence (temperature change from reaction, gas, irreversibility) reveals underlying process (reacting vs. mixing/dissolving). Watch for: Students who think dissolving is chemical because substance 'disappears' and students who can categorize memorized examples but don't understand underlying principles of reactivity, energy, reversibility, and property changes.

Question 6

Looking at what happened when different substances were mixed, a student observed these results.

Test 1: Food coloring + water. The color spread through the water, but there were no bubbles and no temperature change.
Test 2: Baking soda + vinegar. Lots of bubbles formed, and the cup felt colder.

Which statement best explains the difference between Test 1 and Test 2?

  1. Both tests formed new substances because the mixtures looked different after mixing. Any visible change means a chemical change happened.
  2. Test 1 is chemical because color spreads, and Test 2 is physical because bubbles are just trapped air from stirring.
  3. Test 1 is physical because the coloring just mixed into the water and can be diluted. Test 2 is chemical because the substances reacted, making gas bubbles and a temperature change. (correct answer)
  4. Test 1 is chemical because it happens quickly, and Test 2 is physical because it happens in a cup.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically distinguishing dissolving from reacting and recognizing patterns in chemical vs. physical changes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, comparing food coloring + water (physical - just mixing, no reaction indicators) with baking soda + vinegar (chemical - react with bubbles and temperature change). Choice C is correct because it correctly identifies that one mixture is chemical (substances reacted - evidence is temperature change from reaction, gas produced, irreversible) while other is physical (substances just dissolved/mixed - evidence is no reaction indicators, reversible), and correctly explains that reactivity determines outcome - some substances react (acids + bases) while others just mix (food coloring + water). This shows the student understands difference between reacting (chemical - substances transform) and mixing/dissolving (physical - substances stay themselves) and observable evidence reveals underlying process. Choice B represents a common error where students don't recognize temperature change from reaction itself as key evidence and think bubbles are just trapped air from stirring. This typically happens because students may not understand that temperature change must come from reaction itself (not external heat) to indicate chemical change, and students may think physical mixing and chemical reacting are the same thing. To help students: Compare side-by-side examples: salt + water (dissolves - physical) vs. baking soda + vinegar (reacts - chemical), identify evidence for each. Teach principles, not just examples: chemical changes show energy change (temperature without external heat, gas), irreversibility, new properties; physical changes show mixing, dissolving, reversibility. Watch for: Students who confuse temperature change from adding hot water (physical) with temperature change from reaction (chemical) and students who think chemical changes must be obvious/dramatic, missing gradual ones like rust.

Question 7

Based on these examples, apply the pattern to a new situation:

Example A: Baking soda + vinegar made bubbles and the cup felt cooler (new substance formed).
Example B: Food coloring + water only changed color and could still be poured and mixed (no new substance).

New situation: A student mixes two clear liquids and sees a solid form and sink to the bottom, even though neither liquid was a solid before. What is the best conclusion?

  1. It is probably a physical change because solids always sink in liquids. The solid is just one liquid that got heavier.
  2. It is probably a chemical change because a new solid forming is evidence of a new substance. This change is not just dissolving or simple mixing. (correct answer)
  3. It is probably a physical change because both starting liquids were clear. Clear liquids cannot react to make new substances.
  4. It must be a chemical change only if the mixture also turns hot. If there is no heat, new substances cannot form.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically applying principles to predict outcomes in new situations and recognizing patterns like precipitate formation as evidence of chemical change. Some mixtures form new substances through chemical reactions, shown by evidence like a new solid (precipitate) forming unexpectedly, which isn't just dissolving or mixing, while physical changes lack such transformation and are reversible without new properties. For this question, the new situation of two liquids forming a solid indicates chemical (precipitate as evidence of new substance), unlike examples of physical color change or chemical bubbling. Choice B is correct because it correctly applies the principle that forming a new solid (precipitate) is evidence of chemical change and new substance, not physical mixing, showing the student can apply understanding to new situations by connecting observable evidence to underlying processes. Choice A represents a common error where students think sinking means physical (confusing settling with reaction), which typically happens because 5th graders may not distinguish between physical separation and chemical formation of new solids, focusing on movement rather than transformation. To help students: Practice applying principles to new mixtures, like predicting if precipitate indicates chemical by comparing to examples of dissolving (physical) vs. reacting (chemical), and emphasize evidence like unexpected new solids reveals reaction; watch for students who confuse physical sinking with chemical precipitate or think clear liquids can't react.

Question 8

Looking at what happened when different substances were mixed, a student tried two mixtures.

Mixture 1: Baking soda + vinegar. It fizzed right away, made lots of bubbles, and the cup felt colder.
Mixture 2: Salt + water. The salt seemed to "disappear," there were no bubbles, and the water tasted salty.

Why did Mixture 1 create a new substance, but Mixture 2 did not?

  1. Mixture 1 made a new substance because bubbles and a temperature change show the substances reacted. Mixture 2 is a physical change because salt dissolved into tiny pieces and can be gotten back by evaporating the water. (correct answer)
  2. Mixture 1 made a new substance because vinegar is a liquid and baking soda is a powder. Mixture 2 did not because both salt and water are used in cooking.
  3. Both mixtures made new substances because the solids seemed to disappear in the liquids. If you cannot see the solid anymore, it must have changed into something new.
  4. Neither mixture made a new substance because mixing always keeps substances the same. Bubbles only mean air got trapped, not that anything new formed.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically distinguishing dissolving from reacting and connecting observable evidence to underlying processes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, comparing baking soda + vinegar (react to make new substances - evidence is bubbles, temperature drop, irreversible) with salt + water (dissolve but stay same substances - evidence is no temperature change, no gas, reversible by evaporating). Choice A is correct because it correctly identifies that one mixture is chemical (substances reacted - evidence is temperature change from reaction, gas produced, irreversible) while other is physical (substances just dissolved/mixed - evidence is no reaction indicators, reversible), and correctly recognizes dissolving is physical (substance still there in tiny pieces) while reacting is chemical (new substance formed). This shows the student understands the difference between reacting (chemical - substances transform) and mixing/dissolving (physical - substances stay themselves) and can apply understanding to new situations, not just memorize examples. Choice C represents a common error where students think all dissolving is chemical change because substance 'disappears' (it's physical - substance still there, can recover it). This typically happens because dissolving looks so dramatic (substance disappears) that 5th graders think it must be chemical, but substance is still present in tiny pieces and can be recovered. To help students: Explicitly teach difference between dissolving (physical - substance breaks into tiny pieces but still itself, can recover) and reacting (chemical - substances transform into new substance, can't easily recover). Compare side-by-side examples: salt + water (dissolves - physical) vs. baking soda + vinegar (reacts - chemical), identify evidence for each. Watch for: Students who think any dramatic change is chemical (including dissolving) and students who think dissolving is chemical because substance 'disappears'.

Question 9

Comparing these mixtures, which statement best explains the pattern you notice about mixtures that create new substances?

Mixture A: Oil + water formed two layers and could be separated by letting it sit.
Mixture B: Iron left outside in wet air slowly turned orange-brown and flaky over days.
Mixture C: Sugar + water made a sweet liquid and could be separated by evaporating the water.

  1. Mixtures make new substances when they look different right away, because slow changes are never chemical.
  2. Mixtures make new substances when the original materials react and change into something with new properties, often hard to reverse. (correct answer)
  3. Mixtures make new substances when they can be separated, because separating proves something new formed.
  4. Mixtures make new substances when they form layers, because layers show the substances combined into something new.
Explanation: This question tests 5th graders' ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically recognizing patterns in chemical vs. physical changes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, oil + water (physical - separates), iron rusting (chemical - new substance forms), sugar + water (physical - dissolves, recoverable). Choice B is correct because it correctly explains that mixtures make new substances when the original materials react and change into something with new properties, often hard to reverse - this captures the essence of chemical change. This shows the student understands the fundamental principle distinguishing chemical (substances transform) from physical (substances stay themselves) changes. Choice A represents a common error where students think chemical changes must be immediate, missing gradual reactions like rust. This typically happens because students may think chemical change must be obvious/dramatic, missing gradual reactions. To help students: Include examples of both fast (baking soda + vinegar) and slow (rusting) chemical changes to show timing doesn't determine type of change. Watch for: Students who think chemical changes must happen quickly or dramatically.

Question 10

Based on the examples below, how can you predict whether mixing will make a new substance?

Example A: Food coloring + water turned the water blue, with no bubbles and no temperature change.
Example B: Baking soda + vinegar made bubbles and the cup felt cooler.

What is the best rule to use?

  1. If the mixture changes color in any way, it always formed a new substance. Color is the only thing that matters in science.
  2. If the mixture makes bubbles or changes temperature on its own and cannot be easily reversed, it likely formed a new substance. If it just mixes or dissolves and can be reversed, it likely did not. (correct answer)
  3. If you stir long enough, any mixture will form a new substance. The main factor is how long you mix it.
  4. If one of the starting materials is a liquid, a new substance always forms. Liquids are more reactive than solids.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically applying principles to predict outcomes and recognizing patterns in chemical vs. physical changes from observable evidence. Some mixtures create new substances (chemical changes) because the substances react, breaking apart and recombining, shown by bubbles, temperature change from the reaction, or irreversibility, while physical changes like dissolving show no such evidence and are reversible, like food coloring mixing with water (still the same substances, can be separated). For this question, the principle is that chemical changes show energy changes and irreversibility while physical don't; comparing food coloring + water (physical - color change but reversible, no energy shift) with baking soda + vinegar (chemical - bubbles, cooling, irreversible). Choice B is correct because it correctly applies the principle that chemical changes show bubbles or temperature change on their own and are hard to reverse, while physical changes just mix and are reversible, showing the student can apply understanding to new situations, not just memorize examples, and recognizes observable evidence reveals underlying processes. Choice A represents a common error where students think color change always means chemical (missing that it's often physical, like mixing dyes), which typically happens because 5th graders focus on visible changes without considering if new substances form or if it's reversible. To help students: Explicitly teach difference between physical (mixing/dissolving - reversible, no energy change) and chemical (reacting - irreversible, energy indicators), using side-by-side examples and having students predict outcomes by checking for bubbles, temperature, and reversibility; watch for students who over-rely on color or appearance without checking for reaction evidence like gas or inherent temperature shifts.

Question 11

Looking at what happened when different substances were mixed, a student did two dissolving tests:

  • Salt + water: No bubbles formed. The water tasted salty. The salt could be recovered by evaporating the water.
  • Sand + water: Sand stayed visible and could be filtered out.

Which statement best explains why neither test formed a new substance?

  1. Neither test formed a new substance because the materials did not react. They either dissolved into tiny pieces or stayed separate, and both mixtures can be separated back to the originals. (correct answer)
  2. Both tests formed new substances because the water looked different after mixing. Any change in look means a chemical change.
  3. Salt + water formed a new substance because the salt disappeared. Sand + water did not because sand is heavier than water.
  4. Neither test formed a new substance because chemical changes only happen with powders. Salt and sand are not powders.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically understanding that dissolving and simple mixing are physical changes, and connecting lack of reaction evidence to no new substances forming. Some mixtures don't create new substances because they are physical changes - substances dissolve into tiny pieces or stay separate but remain themselves, with no gas, temperature change, or irreversibility, and can be recovered by evaporating or filtering. For this question, both salt + water (dissolving - reversible by evaporating) and sand + water (mixing - reversible by filtering) are physical, with no reaction indicators. Choice A is correct because it correctly recognizes both as physical (no reaction, recoverable originals), showing the student understands dissolving is physical (substance still there in tiny pieces) and can distinguish it from reacting based on lack of evidence like bubbles or energy changes. Choice C represents a common error where students think dissolving is chemical because the substance 'disappears' (it's physical - can recover it), which typically happens because 5th graders focus on visibility and think vanishing means transformation, not realizing it's still the same substance. To help students: Explicitly teach dissolving as physical by demonstrating recovery - evaporate salt water, filter sand water - and contrast with chemical examples showing irreversibility; watch for students who think disappearing means chemical or can list examples but don't understand principles of no energy change and reversibility indicating physical.

Question 12

Looking at what happened when different substances were mixed, a student did two tests:

Test 1: She mixed baking soda and vinegar in a cup. It fizzed, made lots of bubbles, and the cup felt cooler.
Test 2: She mixed salt and water in a cup. The salt "disappeared," there were no bubbles, and it still tasted salty.

Why did Test 1 create a new substance, but Test 2 did not?

  1. Test 1 is a chemical change because the substances reacted and made gas and a temperature change. Test 2 is a physical change because the salt dissolved into tiny pieces but stayed salt, and it could be gotten back by evaporating the water. (correct answer)
  2. Both tests are chemical changes because in both cups the solid seemed to disappear. If you cannot see the solid anymore, that means a new substance formed.
  3. Test 2 is a chemical change because salt water tastes different than plain water. Test 1 is a physical change because bubbles are just air getting trapped.
  4. The difference is the size of the cup and how fast the student stirred. Faster stirring always creates new substances, but slower stirring does not.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically distinguishing dissolving from reacting and connecting observable evidence like gas production and temperature changes to underlying processes. Some mixtures create new substances through chemical changes because the substances react, breaking apart and recombining into something new, shown by evidence like gas bubbles, temperature change from the reaction itself, or irreversibility, while other mixtures involve physical changes where substances just mix or dissolve into tiny pieces but remain the same, like salt in water where the salt is still salt and can be recovered. For this question, it compares baking soda + vinegar (react to make new substances - evidence is bubbles, temperature drop, irreversible) with salt + water (dissolve but stay same substances - evidence is no temperature change, no gas, reversible by evaporating). Choice A is correct because it accurately identifies that one mixture is chemical (substances reacted - evidence is temperature change from reaction, gas produced, irreversible) while the other is physical (substances just dissolved - evidence is no reaction indicators, reversible), showing the student understands the difference between reacting (chemical - substances transform) and dissolving (physical - substances stay themselves). Choice B represents a common error where students think all dissolving is a chemical change because the substance 'disappears' (it's physical - substance still there, can recover it), which typically happens because dissolving looks dramatic to 5th graders, who may not yet grasp that the substance is still present in tiny pieces and can be recovered. To help students: Compare side-by-side examples like salt + water (dissolves - physical) vs. baking soda + vinegar (reacts - chemical), identify evidence for each, and demonstrate reversibility by evaporating salt water to show salt still there (physical) while showing you can't un-mix baking soda and vinegar (chemical); watch for students who think any dramatic change like disappearing is chemical, or who confuse dissolving with reacting because they focus on visibility rather than underlying processes like energy changes and reversibility.

Question 13

Based on the examples below, what determines whether mixing will make a new substance?

Example 1: Sugar + water made a clear sweet liquid. No bubbles formed, and you could get sugar back by evaporating the water.
Example 2: Yeast + sugar + warm water slowly made bubbles and a new smell over time. You could not easily get the original sugar back.

  1. A new substance forms whenever the mixture becomes clear, because clear liquids are always new substances.
  2. A new substance forms when the substances react, shown by evidence like gas bubbles, a new smell, or being hard to reverse. (correct answer)
  3. A new substance forms only when the mixture is heated, because heat is the only way to cause change.
  4. A new substance forms whenever one substance seems to disappear, because disappearing means it is gone forever.
Explanation: This question tests 5th graders' ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically applying principles to predict outcomes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, comparing sugar + water (dissolves - physical, reversible) with yeast + sugar + warm water (reacts - chemical, bubbles and new smell, irreversible). Choice B is correct because it correctly explains that a new substance forms when the substances react, shown by evidence like gas bubbles, a new smell, or being hard to reverse. This shows the student understands principles that determine outcome (reactivity, energy changes, reversibility, property changes). Choice D represents a common error where students think all dissolving is chemical change because substance 'disappears' (it's physical - substance still there, can recover it). This typically happens because dissolving looks so dramatic (substance disappears) that 5th graders think it must be chemical, but substance is still present in tiny pieces and can be recovered. To help students: Teach principles, not just examples: chemical changes show energy change (temperature without external heat, gas), irreversibility, new properties; physical changes show mixing, dissolving, reversibility. Watch for: Students who think dissolving is chemical because substance 'disappears'.

Question 14

Based on the examples, answer the question.

Example 1: Salt + water. Observations: no bubbles, no temperature change, tastes salty, and you can get salt back by evaporating the water.
Example 2: Iron nail left in a wet place for many days. Observations: orange-brown coating forms, the surface becomes flaky, and it does not easily change back to shiny iron.

Comparing these examples, which choice best explains why Example 2 formed a new substance but Example 1 did not?

  1. Example 2 is a physical change because it happens slowly, while Example 1 is chemical because it happens quickly.
  2. Example 1 is a chemical change because the salt disappears, while Example 2 is physical because the nail stays solid.
  3. Example 2 is a chemical change because the iron reacts with air and water to make a new substance with new properties. Example 1 is a physical change because salt only dissolves and can be reversed by evaporation. (correct answer)
  4. Example 2 formed a new substance because the nail was bigger than the salt grains, and bigger objects react more.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically distinguishing dissolving from reacting and recognizing patterns in chemical vs. physical changes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, comparing salt + water (dissolve but stay same - no bubbles, reversible) with iron nail rusting (react to make new substance - color change, flaky, irreversible). Choice C is correct because it correctly identifies dissolving is physical (substance still there in tiny pieces) while reacting is chemical (new substance formed) / correctly recognizes observable pattern that chemical changes show temperature change without external heat, gas production, and new properties. This shows the student understands difference between reacting (chemical - substances transform) and mixing/dissolving (physical - substances stay themselves) / can apply understanding to new situations, not just memorize examples. Choice A represents a common error where students think if change isn't dramatic (explosion, color), it's not chemical (missing gradual reactions like rust) / can't distinguish reactivity (substances transform) from mixing (substances stay themselves). This typically happens because students may think chemical change must be obvious/dramatic, missing gradual reactions / students may memorize examples without understanding principles, so can't apply to new situations. To help students: Demonstrate reversibility: evaporate salt water to show salt still there (physical), show can't un-mix baking soda and vinegar (chemical). Watch for: Students who think chemical changes must be obvious/dramatic, missing gradual ones like rust.

Question 15

Comparing these mixtures, which evidence best supports the idea that a new substance formed?

Mixture A: Salt + water. The salt is not visible, but the water tastes salty.
Mixture B: Vinegar + baking soda. Bubbles form and the cup feels colder.

Which choice correctly uses evidence to decide which mixture formed a new substance?

  1. Mixture A formed a new substance because the salt disappeared, so it must be gone forever. Mixture B did not because both materials were still in the cup.
  2. Mixture B formed a new substance because gas bubbles and a temperature change are signs of a reaction. Mixture A is a physical change because dissolving keeps the salt the same in tiny pieces. (correct answer)
  3. Both mixtures formed new substances because both were mixed in a cup. Mixing in a container always causes a chemical change.
  4. Neither mixture formed a new substance because you can still see liquid in both cups. If a liquid remains, no chemical change can happen.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically connecting observable evidence to underlying processes and distinguishing dissolving from reacting. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). Reactions show evidence like energy changes (temperature, gas) that mixing doesn't. For this question, comparing salt + water (physical - dissolves, no reaction evidence) with vinegar + baking soda (chemical - bubbles and temperature change show reaction). Choice B is correct because it correctly identifies that chemical changes show energy changes and irreversibility while physical don't, and correctly recognizes dissolving is physical (substance still there in tiny pieces) while reacting is chemical (new substance formed). This shows the student understands observable evidence reveals underlying process and can distinguish reactivity (substances transform) from mixing (substances stay themselves). Choice A represents a common error where students think all dissolving is chemical change because substance 'disappears' (it's physical - substance still there, can recover it). This typically happens because dissolving looks so dramatic (substance disappears) that 5th graders think it must be chemical, but substance is still present in tiny pieces and can be recovered. To help students: Compare side-by-side examples: salt + water (dissolves - physical) vs. baking soda + vinegar (reacts - chemical), identify evidence for each. Demonstrate reversibility: evaporate salt water to show salt still there (physical), show can't un-mix baking soda and vinegar (chemical). Watch for: Students who think dissolving is chemical because substance 'disappears' and students who don't check for energy changes (temperature from reaction, gas) as key evidence.

Question 16

Comparing these mixtures, why did mixing baking soda and vinegar create a new substance, but mixing sand and water did not?

Mixture 1: Baking soda + vinegar fizzed and made bubbles right away.
Mixture 2: Sand + water looked cloudy, then the sand settled to the bottom. The sand could be filtered out.

  1. Baking soda and vinegar reacted and made gas, but sand and water only mixed and could be separated again. (correct answer)
  2. Baking soda and vinegar made bubbles because they were stirred, but sand and water were not stirred enough.
  3. Sand and water did not react because sand is heavier, but baking soda and vinegar reacted because they are lighter.
  4. Sand and water made no new substance because it stayed the same color, but baking soda and vinegar made a new substance because it changed sound.
Explanation: This question tests 5th graders' ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically understanding reactivity differences. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). For this question, baking soda + vinegar react to make new substances (evidence is immediate bubbles from gas production) while sand + water just mix physically (evidence is sand settles, can be filtered out). Choice A is correct because it correctly identifies that baking soda and vinegar reacted and made gas (chemical change - new substance formed), but sand and water only mixed and could be separated again (physical change - no new substance). This shows the student understands that reactivity determines outcome - some substances react (acids + bases) while others just mix (sand + water). Choice B represents a common error where students think bubbles come from stirring rather than from a chemical reaction producing gas. This typically happens because students may not understand that gas production must come from the reaction itself, not from physical agitation. To help students: Compare side-by-side examples: salt + water (dissolves - physical) vs. baking soda + vinegar (reacts - chemical), identify evidence for each. Watch for: Students who think bubbles can only come from stirring or who don't recognize gas production as evidence of chemical change.

Question 17

Looking at what happened when different substances were mixed, a student made this claim:

Student: "If you can get the original materials back, then no new substance formed."

Example 1: Salt + water (you can evaporate the water to get salt back).
Example 2: Baking soda + vinegar (after fizzing, you cannot easily get the original substances back).

Based on these examples, is the student's claim correct?

  1. No, the claim is incorrect because dissolving always makes a new substance even if it can be reversed.
  2. Yes, the claim is correct because being reversible is a good clue of a physical change. If it is hard to reverse, it is more likely a chemical change that formed new substances. (correct answer)
  3. No, the claim is incorrect because bubbles are the only clue that matters, not whether you can reverse it.
  4. Yes, the claim is correct because any mixture that looks different must be reversible if you wait long enough.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically understanding reactivity differences and distinguishing dissolving from reacting. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). Reversibility is key - physical changes are easily reversible, chemical are not. For this question, specific context: salt + water (physical, reversible) vs baking soda + vinegar (chemical, hard to reverse). Choice B is correct because it correctly applies principle that chemical changes show energy changes and irreversibility while physical don't / correctly explains that reactivity determines outcome - some substances react (acids + bases) while others just mix (salt + water). This shows the student understands principles that determine outcome (reactivity, energy changes, reversibility, property changes) / dissolving is physical change (common misconception). Choice A represents a common error where students think all dissolving is chemical change because substance 'disappears' (it's physical - substance still there, can recover it) / think reversibility doesn't matter (it's a key indicator). This typically happens because dissolving looks so dramatic (substance disappears) that 5th graders think it must be chemical, but substance is still present in tiny pieces and can be recovered / students may think reversibility doesn't matter (it's a key indicator). To help students: Demonstrate reversibility: evaporate salt water to show salt still there (physical), show can't un-mix baking soda and vinegar (chemical). Watch for: Students who think reversibility doesn't matter (it's a key indicator).

Question 18

Looking at what happened when different substances were mixed, a student recorded these results:

  • Sand + water: sand stays visible, settles to the bottom, no bubbles, easy to filter.
  • Oil + water: two layers form, no bubbles, easy to separate by letting it sit.
  • Vinegar + baking soda: fizzing bubbles form quickly and the cup feels cooler.

Based on these examples, what is the best way to predict whether mixing will make a new substance?

  1. A new substance forms whenever two substances are both liquids, because liquids mix more completely than solids.
  2. A new substance forms when the substances react, shown by clues like gas bubbles, a temperature change, or a change that is hard to reverse. If they just mix or can be separated easily, no new substance formed. (correct answer)
  3. A new substance forms whenever a substance disappears from sight, because that means it turned into something new.
  4. A new substance forms based on the size of the container, because larger containers allow more space for reactions.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically applying principles to predict outcomes and recognizing patterns in chemical vs. physical changes. Some mixtures create new substances (chemical changes) because the substances actually react together - their tiny parts break apart and recombine into something new, which shows evidence like temperature change (from reaction itself), gas production, unexpected color change, precipitate, or irreversibility. Other mixtures don't create new substances (physical changes) because substances just mix together or one breaks into tiny pieces, but each substance stays itself - like salt dissolving in water (salt still salt, just in tiny pieces) or sand mixing with water (both still separate). Dissolving is physical change because substance breaks apart but is still itself and can be recovered / Reactions show evidence like energy changes (temperature, gas) that mixing doesn't / Reversibility is key - physical changes are easily reversible, chemical are not. For this question, specific context: comparing baking soda + vinegar (react to make new substances - evidence is bubbles, temperature drop, irreversible) with sand + water or oil + water (mix but stay same - no bubbles, reversible). Choice B is correct because it correctly explains that reactivity determines outcome - some substances react (acids + bases) while others just mix (salt + water) / correctly applies principle that chemical changes show energy changes and irreversibility while physical don't. This shows the student understands principles that determine outcome (reactivity, energy changes, reversibility, property changes) / can apply understanding to new situations, not just memorize examples. Choice C represents a common error where students think all dissolving is chemical change because substance 'disappears' (it's physical - substance still there, can recover it). This typically happens because dissolving looks so dramatic (substance disappears) that 5th graders think it must be chemical, but substance is still present in tiny pieces and can be recovered. To help students: Teach principles, not just examples: chemical changes show energy change (temperature without external heat, gas), irreversibility, new properties; physical changes show mixing, dissolving, reversibility. Watch for: Students who think dissolving is chemical because substance 'disappears'.

Question 19

Based on the examples, a teacher says: "Not all changes are chemical changes. Some are just physical mixing."

Example 1: Ice melting into liquid water.
Example 2: Iron left outside for weeks turns orange-brown and flaky (rust).

Comparing these changes, which statement is most accurate?

  1. Both are physical changes because both take time and happen without stirring. Time is the main reason new substances form.
  2. Ice melting is a physical change because it is still water and can be frozen again. Rusting is a chemical change because a new substance forms with new properties that are hard to reverse. (correct answer)
  3. Ice melting is a chemical change because the water looks different after it melts. Rusting is physical because it happens slowly and is not dramatic.
  4. Both are chemical changes because both involve water. If water is present, a new substance always forms.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically distinguishing physical changes like phase changes from chemical changes like rusting, and applying principles of reversibility and property changes. Some changes are chemical because substances transform into new ones with different properties, like rust being flaky and irreversible, while physical changes like melting keep the substance the same and are easily reversible, like refreezing water. For this question, comparing ice melting (physical - still water, reversible) with iron rusting (chemical - new substance with new properties, hard to reverse). Choice B is correct because it correctly explains ice melting as physical (reversible, same substance) and rusting as chemical (new properties, irreversible), showing the student understands underlying principles of reactivity, reversibility, and property changes, and can apply them beyond mixing to other changes. Choice C represents a common error where students think visible changes like melting are chemical (focusing on appearance rather than if new substance forms), which typically happens because 5th graders may confuse dramatic but reversible changes with irreversible transformations, or think slow changes like rust are physical since not dramatic. To help students: Use examples to teach principles - melt and refreeze ice (physical) vs. show rusted iron can't be easily undone (chemical), emphasizing new properties and irreversibility indicate chemical; watch for students who think any visible change is chemical or believe slow changes aren't chemical, missing gradual reactions like rust.

Question 20

Comparing these mixtures, one student says: "If you can get the original materials back, it was not a chemical change."

Mixture 1: Salt + water (you can evaporate the water and get salt back).
Mixture 2: Baking soda + vinegar (it fizzed and you cannot get the original substances back).

Is the student's idea correct, and why?

  1. Yes, it is mostly correct because being able to reverse the change is a clue for a physical change. Salt water can be reversed, but the fizzing mixture cannot be easily reversed after it reacts. (correct answer)
  2. No, it is not correct because reversibility does not matter in science. Only the color of the mixture tells you whether a new substance formed.
  3. No, it is not correct because dissolving is always a chemical change. Salt water must have formed a new substance since the salt disappeared.
  4. Yes, it is correct because every mixture can be reversed if you wait long enough. Baking soda and vinegar will turn back into the originals overnight.
Explanation: This question tests a 5th grader's ability to explain why some mixtures result in new substances while others do not (NGSS 5-PS1-4), specifically understanding reactivity differences and applying the principle of reversibility to distinguish chemical from physical changes. Some mixtures are chemical changes because substances react and transform into new ones, making them hard to reverse, while physical changes like dissolving allow easy recovery of originals, with no transformation. For this question, reversibility is key - salt + water is physical (evaporate to recover salt) while baking soda + vinegar is chemical (fizzing reaction, can't easily reverse). Choice A is correct because it correctly explains that reversibility indicates physical change (salt water recoverable) vs. chemical (fizzing mixture irreversible, new substances formed), showing the student understands principles like irreversibility as evidence of chemical processes and can apply them. Choice C represents a common error where students think dissolving is always chemical because the substance 'disappears' (it's physical - still there, recoverable), which typically happens because 5th graders focus on visibility rather than reversibility or underlying lack of transformation. To help students: Practice demonstrating reversibility with examples - evaporate salt water (physical) vs. attempt to reverse reacted mixtures (chemical), teaching that if you can get originals back easily, no new substance formed; watch for students who think disappearing means chemical or ignore reversibility, confusing physical dissolving with reaction.