Why Some Mixtures Make Substances
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5th Grade Science › Why Some Mixtures Make Substances
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?
It is probably a physical change because both starting liquids were clear. Clear liquids cannot react to make new substances.
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.
It is probably a physical change because solids always sink in liquids. The solid is just one liquid that got heavier.
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.
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?
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.
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.
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.
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'.
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.
Mixtures make new substances when they look different right away, because slow changes are never chemical.
Mixtures make new substances when they can be separated, because separating proves something new formed.
Mixtures make new substances when the original materials react and change into something with new properties, often hard to reverse.
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.
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?
If one of the starting materials is a liquid, a new substance always forms. Liquids are more reactive than solids.
If the mixture changes color in any way, it always formed a new substance. Color is the only thing that matters in science.
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.
If you stir long enough, any mixture will form a new substance. The main factor is how long you mix it.
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.
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?
Salt + water formed a new substance because the salt disappeared. Sand + water did not because sand is heavier than water.
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.
Both tests formed new substances because the water looked different after mixing. Any change in look means a chemical change.
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.
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?
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.
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.
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.
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.
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.
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.
A new substance forms whenever one substance seems to disappear, because disappearing means it is gone forever.
A new substance forms when the substances react, shown by evidence like gas bubbles, a new smell, or being hard to reverse.
A new substance forms whenever the mixture becomes clear, because clear liquids are always new substances.
A new substance forms only when the mixture is heated, because heat is the only way to cause change.
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'.
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?
Example 2 is a physical change because it happens slowly, while Example 1 is chemical because it happens quickly.
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.
Example 1 is a chemical change because the salt disappears, while Example 2 is physical because the nail stays solid.
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.
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?
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.
Both mixtures formed new substances because both were mixed in a cup. Mixing in a container always causes a chemical change.
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.
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.
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.
Sand and water did not react because sand is heavier, but baking soda and vinegar reacted because they are lighter.
Baking soda and vinegar reacted and made gas, but sand and water only mixed and could be separated again.
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.
Baking soda and vinegar made bubbles because they were stirred, but sand and water were not stirred enough.
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.