- After mixing the substances, Jordan stirred 200 mL of room-temperature water (22°C) with 2 teaspoons of salt. The salt "disappeared," there were no bubbles, the temperature stayed at 22°C, and the water tasted salty. The next day, the teacher left the cup in a warm sunny window and the water evaporated, leaving white salt crystals. Based on this evidence, is this a chemical change or a physical change?
Answer: It is a physical change because the salt dissolved but stayed the same substance. Getting the salt back after evaporation shows no new substance formed.
This question tests a 5th grader's ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically distinguishing chemical change evidence from physical change evidence. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. Dissolving looks dramatic but is physical change because substance still present. For this question, salt dissolved in water showing no temperature change, no bubbles, still tastes salty - physical change. Choice C is correct because it correctly recognizes dissolving is physical change because salt still present and recoverable. This shows the student understands dissolving is physical not chemical and must distinguish reaction-produced changes from external changes. Choice A represents a common error where students think dissolving is chemical change because substance 'disappears' (it's physical - still there in tiny pieces). This typically happens because dissolving seems so dramatic that 5th graders assume it's chemical, but substance is still present and recoverable. To help students: Demonstrate that dissolved substances are still there by evaporating salt water to recover salt, showing dissolving is reversible (physical); Practice Claim-Evidence-Reasoning structure: state conclusion, cite observations, explain how observations support conclusion. Watch for: Students who don't understand dissolving is physical because substance still present and recoverable; Students who confuse their prediction with their evidence-based conclusion.
- After mixing 30 mL of vinegar with 1 teaspoon of baking soda in a clear cup, students made these observations: bubbles formed right away, the mixture foamed up, and the temperature dropped from 22°C to 18°C without adding ice or cold water. Based on the observations, did a new substance form (chemical change) or not (physical change)?
Answer: Yes, a new substance formed because gas bubbles appeared and the temperature changed without an outside heat source. These are strong signs of a chemical change.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically using multiple pieces of evidence together to identify chemical change. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. For this question, baking soda and vinegar mixed showing bubbles, temperature drop (from 22°C to 18°C without adding cold), and fizzing - all chemical indicators working together. Choice B is correct because it correctly identifies that multiple indicators (temperature drop + gas produced + fizzing) together provide strong evidence of new substance formation, and specifically notes the temperature changed without an outside heat source. This shows the student understands that multiple observations provide stronger evidence than one alone and that temperature change must come from the reaction itself. Choice A represents a common error where students dismiss bubbles as just trapped air from stirring, not recognizing that immediate bubble formation with fizzing indicates gas production from a chemical reaction. This typically happens because 5th graders may not distinguish between mechanical bubbles (from stirring) and chemical gas production (immediate upon mixing). To help students: Use side-by-side comparison of mechanical stirring bubbles (temporary, from agitation) versus chemical reaction bubbles (immediate, continuous, with fizzing sound), and emphasize that multiple indicators together (bubbles + temperature change + fizzing) provide conclusive evidence. Watch for: Students who think all bubbles are just trapped air, students who don't recognize that temperature dropping without adding cold substances is strong chemical evidence, or students who focus on one observation while ignoring the pattern of multiple indicators.
- The data shows results from three mixes:
- Mix 1: Sand + water: sand settled to the bottom after 2 minutes; no bubbles; temperature stayed 20°C.
- Mix 2: Sugar + water: sugar dissolved; no bubbles; temperature stayed 20°C; liquid tasted sweet.
- Mix 3: Vinegar + baking soda: lots of bubbles and foam started in 3 seconds; temperature dropped from 20°C to 16°C.
Based on the evidence, which mix most clearly formed a new substance (chemical change)?
Answer: Mix 3, because bubbles formed quickly and the temperature changed without adding hot or cold water. Two strong indicators together show a new substance formed.
This question tests a 5th grader's ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically identifying which observations constitute evidence of chemical change and using multiple pieces of evidence together. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. Multiple indicators together provide stronger evidence than single observation. For this question, baking soda and vinegar mixed showing bubbles, temperature drop, and fizzing - all chemical indicators. Choice C is correct because it correctly identifies that multiple indicators (temperature drop + gas produced + fizzing) together provide strong evidence of new substance. This shows the student understands multiple observations provide stronger evidence than one and certain observations are reliable indicators of chemical change. Choice D represents a common error where students think all visible changes are chemical changes. This typically happens because physical changes can look dramatic (dissolving, color mixing) but are still physical because original substances are still present. To help students: Use side-by-side comparison of chemical (baking soda + vinegar) vs physical (salt + water) so students see difference; Emphasize that good science uses multiple pieces of evidence, not just one. Watch for: Students who think any dramatic change is chemical (including dissolving); Students who make conclusions based on one observation without checking for additional evidence.
- Based on the observations, which situation is MOST likely a physical change (no new substance formed)?
1) 1 tablespoon of sugar mixed into warm water: sugar disappeared; no bubbles; temperature stayed 25°C.
2) Vinegar mixed with baking soda: many bubbles; foam rose; temperature dropped 4°C.
3) Yeast mixed with sugar and warm water: after 10 minutes, bubbles appeared and the smell changed.
Which choice best matches the evidence?
Answer: Situation 1, because dissolving can be reversed by evaporating the water and there were no other reaction signs. No bubbles and no temperature change support a physical change.
This question tests a 5th grader's ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically distinguishing chemical change evidence from physical change evidence. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. Dissolving looks dramatic but is physical change because substance still present. For this question, sugar dissolved in water showing no temperature change, no bubbles - physical change. Choice B is correct because it correctly recognizes dissolving is physical change because substance still present and recoverable. This shows the student understands dissolving is physical not chemical. Choice D represents a common error where students think all visible changes are chemical changes. This typically happens because physical changes can look dramatic (dissolving, color mixing) but are still physical because original substances are still present. To help students: Demonstrate that dissolved substances are still there by evaporating salt water to recover salt, showing dissolving is reversible (physical). Watch for: Students who think any dramatic change is chemical (including dissolving); Students who don't understand dissolving is physical because substance still present and recoverable.
- The data shows that Ella mixed 25 mL of lemon juice with 25 mL of milk in a cup at 22°C. After 1 minute, the mixture became lumpy, and solid clumps formed that could be caught in a coffee filter. The smell changed slightly, and no heat was added. Based on the observations, which evidence best supports that a new substance formed?
Answer: Solid clumps formed from two liquids, which is strong evidence of a chemical change.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically identifying which observations constitute evidence of chemical change. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. For this question, lemon juice + milk producing solid clumps (curdling) that can be filtered out - a form of precipitate indicating chemical change. Choice C is correct because it correctly identifies that solid clumps forming from two liquids is strong evidence of chemical change (precipitate formation), showing the student understands that when liquids combine to form solids, new substances have formed. Choice D represents a common error where students think absence of bubbles means no chemical change, not recognizing that precipitate formation is equally strong evidence - this typically happens because students may overfocus on bubbles as the main indicator and not recognize other forms of evidence like precipitate. To help students: Teach that chemical changes have multiple possible indicators (not just bubbles) including precipitate formation, and demonstrate milk curdling as real-world example of chemical change producing new substances (curds). Watch for: Students who think only bubbling reactions are chemical changes, or who don't recognize that solid formation from liquids is a key indicator of new substance formation.
- The evidence from this investigation includes these observations after mixing two liquids: the mixture turned cloudy and a white solid appeared that sank to the bottom. No one added heat or cold. Based on the observations, which statement is the best conclusion?
Answer: A new substance formed because a new solid appeared when two liquids were mixed. A solid forming is evidence of a chemical change.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically identifying which observations constitute evidence of chemical change. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. For this question, two liquids mixed showing cloudiness and white solid forming (precipitate) - key chemical indicator. Choice A is correct because it correctly identifies that a solid forming from two liquids (precipitate) is strong evidence of new substance. This shows the student understands certain observations are reliable indicators of chemical change. Choice B represents a common error where students make conclusion without using evidence, just guessing. This typically happens because students may not realize that physical changes can look dramatic (dissolving, color mixing) but are still physical because original substances are still present. To help students: Teach the key chemical change indicators explicitly (temperature without external heat, gas produced, unexpected color, precipitate, new smell, hard to reverse) and practice identifying them. Watch for: Students who can identify observations but can't explain WHY they indicate chemical vs. physical change.
- Two groups mixed different substances in cups at room temperature (22°C). Group 1 mixed lemon juice and baking soda. Group 2 mixed sugar and water. Group 1 saw lots of bubbles and the temperature dropped to 19°C. Group 2 saw the sugar disappear, no bubbles, and the temperature stayed 22°C. Based on the data shows, which group most likely formed a new substance?
Answer: Group 1 because bubbles formed and the temperature changed without adding hot or cold. These indicators support a chemical change.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically evaluating whether evidence supports new substance formation. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. Temperature change only counts as chemical evidence if from reaction itself, not from adding hot/cold substance. For this question, Group 1 (lemon juice + baking soda) showed bubbles and temperature drop - chemical indicators, while Group 2 (sugar + water) showed only dissolving - physical change. Choice B is correct because it correctly identifies that Group 1's multiple indicators (bubbles + temperature change) support chemical change while Group 2's dissolving is physical. This shows the student understands to compare evidence between groups. Choice A represents a common error where students think dissolving is chemical change because substance 'disappears' (it's physical - still there in tiny pieces). This typically happens because dissolving seems so dramatic that 5th graders assume it's chemical, but substance is still present and recoverable. To help students: Use side-by-side comparison of chemical (acid + base) vs physical (sugar + water) so students see difference. Practice comparing data tables to identify which group has stronger evidence. Watch for: Students who think dissolving is chemical change. Students who don't compare evidence between groups systematically.
- Students mixed 50 mL of water with 10 drops of blue food coloring. The water slowly became evenly blue. There were no bubbles, no new smell, and the temperature stayed 21°C. Based on the evidence from this investigation, what happened?
Answer: No new substance formed because the food coloring just spread out in the water. The evidence shows mixing, not a chemical change.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically evaluating whether evidence supports new substance formation. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. For this question, food coloring spread in water with no temperature change or bubbles - physical change. Choice B is correct because it correctly identifies that color change alone without other indicators is just mixing (physical), not chemical change. This shows the student understands need clear reasoning connecting evidence to conclusion. Choice A represents a common error where students conclude chemical change from only one weak observation (just color) without checking for stronger evidence. This typically happens because students may focus on most obvious change (color) and not check for more important evidence (temperature from reaction, gas produced). To help students: Emphasize that good science uses multiple pieces of evidence, not just one. Watch for: Students who don't check temperature or gas production, only notice color.
- The evidence from this investigation is incomplete. Students mixed lemon juice and baking soda and saw fizzing bubbles for about 15 seconds. They did not measure temperature or check whether the original substances could be separated again. What additional observation would best help determine if a new substance formed?
Answer: Measure whether the temperature changes without adding hot or cold water. A temperature change would be another strong indicator of a chemical change.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically identifying which additional observations would strengthen evidence for chemical change. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. For this question, students already observed fizzing bubbles (gas production), so temperature measurement would provide a second indicator to strengthen the conclusion. Choice A is correct because it correctly identifies that measuring temperature change without adding hot or cold water would be another strong indicator, showing understanding that multiple indicators strengthen evidence for chemical change. This demonstrates the student knows temperature change from the reaction itself (not external source) is valuable evidence. Choice B represents a common error where students focus on irrelevant factors like container type rather than chemical indicators. This typically happens because students may not yet distinguish between relevant scientific observations and arbitrary details. To help students: Teach students to systematically check for all major chemical indicators (temperature, gas, color, precipitate, smell) when investigating reactions, emphasizing that more indicators mean stronger evidence. Watch for: Students who think container type or stirring amount affects whether reactions occur, students who suggest opinion-based rather than evidence-based observations, or students who don't recognize the value of collecting multiple types of evidence.
- Based on the evidence from this investigation, a student mixed 10 g of salt into 100 mL of room-temperature water (20°C) and stirred for 30 seconds. The water stayed clear, no bubbles formed, and the temperature stayed at 20°C. The salt seemed to disappear, and the water tasted salty. The student evaporated the water overnight and got salt crystals back. Is this a chemical change or a physical change, and what evidence supports it?
Answer: It is a physical change because the salt dissolved and could be recovered by evaporating the water.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically distinguishing chemical change evidence from physical change evidence. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. For this question, salt dissolved in water showing no temperature change, no bubbles, still tastes salty - physical change, and critically, the salt was recovered by evaporation proving it's still the same substance. Choice C is correct because it correctly recognizes dissolving is physical change because salt still present and recoverable, showing the student understands that dissolving is physical not chemical. Choice A represents a common error where students think dissolving is chemical change because substance 'disappears' (it's physical - still there in tiny pieces), which typically happens because elementary students may not yet understand that dissolved substances are still present, just broken into tiny pieces too small to see. To help students: Demonstrate that dissolved substances are still there by evaporating salt water to recover salt, showing dissolving is reversible (physical), and teach explicitly that dissolving breaks substances into tiny pieces but doesn't change what they are. Watch for: Students who think any dramatic change is chemical (including dissolving) or who confuse disappearing with chemical change when the substance is just spread out in tiny pieces.
- A student mixed 100 mL of water with a spoonful of powdered drink mix. The powder dissolved, the water turned bright orange, the temperature stayed 21°C, and there were no bubbles or new smell. Based on the observations, which is the best conclusion?
Answer: No new substance formed because the powder dissolved and simply colored the water. The evidence matches a physical change like dissolving and mixing.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically distinguishing chemical change evidence from physical change evidence. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. Dissolving looks dramatic but is physical change because substance still present. For this question, drink powder dissolved in water with color change but no temperature change or bubbles - physical change. Choice B is correct because it correctly identifies that powder dissolving and coloring water without other indicators is physical change. This shows the student understands dissolving is physical not chemical. Choice A represents a common error where students conclude chemical change from only one weak observation (just color) without checking for stronger evidence. This typically happens because students may focus on most obvious change (color) and not check for more important evidence (temperature from reaction, gas produced). To help students: Teach that dissolving powders (drink mix, sugar) is physical because substance still there, just spread out. Show that color change alone is weak evidence without temperature change or gas. Watch for: Students who think any color change is chemical. Students who don't understand dissolving is physical because substance still present.
- After mixing blue food coloring into water, the student observed: the color spread through the water, there were no bubbles, no new smell, and the temperature stayed at 23°C. Based on the observations, which conclusion is best?
Answer: No new substance formed because the food coloring just mixed and spread out. With no bubbles, smell, or temperature change, it is a physical change.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically distinguishing predictable color mixing (physical) from unexpected color change (chemical). To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. For this question, food coloring spreading in water with no temperature change, no bubbles, and no new smell indicates physical change - the dye simply dispersed. Choice B is correct because it correctly identifies this as physical change, recognizing that food coloring just mixed and spread out without any chemical indicators present. This shows the student understands that predictable color mixing (adding colored substance to clear water) is different from unexpected color change (two clear liquids becoming colored). Choice A represents a common error where students think any color change is chemical change, not distinguishing between adding color (physical) and creating new color (chemical). This typically happens because students focus on the most obvious change (color) without checking for other chemical indicators. To help students: Demonstrate the difference between adding color (food coloring, paint mixing) which is physical, versus creating new color (two clear liquids becoming yellow) which suggests chemical change, emphasizing need for multiple indicators. Watch for: Students who think all color changes are chemical, students who don't check for additional evidence beyond color, or students who think any visible change means new substance formed.
- Students mixed 30 mL of milk with 30 mL of vinegar. After 1 minute, the mixture became clumpy with solid pieces, and the liquid looked more watery. There were no bubbles, and the temperature stayed about 20°C. Based on the observations, which observation is the best evidence that a new substance formed?
Answer: The mixture formed solid clumps even though both started as liquids. A solid forming is strong evidence of a chemical change.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically identifying which observations constitute evidence of chemical change. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. For this question, milk and vinegar forming solid clumps from liquids - chemical indicator (precipitate). Choice A is correct because it correctly identifies that solid forming from two liquids (precipitate) is strong evidence of chemical change. This shows the student understands precipitate formation indicates new substance. Choice B represents a common error where students misunderstand what temperature evidence means - they think no temperature change means slow reaction. This typically happens because students may not understand that not all chemical reactions produce temperature change, and that precipitate formation is strong evidence even without temperature change. To help students: Teach that precipitate (solid from liquids) is strong chemical change evidence even without temperature change. Demonstrate milk + vinegar reaction showing curds forming as new substance. Watch for: Students who think temperature must change for chemical reaction. Students who don't recognize precipitate as strong chemical evidence.
- Based on the observations from this investigation, did a new substance form when Mia mixed 30 mL of vinegar with 1 teaspoon of baking soda in a clear cup? She observed many bubbles and foam starting within 2 seconds, the temperature dropped from 21°C to 17°C after 1 minute (no hot or cold water was added), and the mixture made a new sharp smell. What is the best conclusion using this evidence?
Answer: Yes, a new substance formed because bubbles formed right away and the temperature changed without adding heat or cold. A new smell also appeared, which is strong evidence of a chemical change.
This question tests a 5th grader's ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically evaluating whether evidence supports new substance formation and using multiple pieces of evidence together. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. Multiple indicators together provide stronger evidence than single observation. For this question, baking soda and vinegar mixed showing bubbles, temperature drop, fizzing, and new smell - all chemical indicators. Choice B is correct because it correctly identifies that multiple indicators (temperature drop + gas produced + fizzing + new smell) together provide strong evidence of new substance. This shows the student understands multiple observations provide stronger evidence than one and certain observations are reliable indicators of chemical change. Choice D represents a common error where students think all visible changes are chemical changes. This typically happens because physical changes can look dramatic (like foaming from air bubbles) but are still physical because original substances are still present. To help students: Teach the key chemical change indicators explicitly (temperature without external heat, gas produced, unexpected color, precipitate, new smell, hard to reverse) and practice identifying them; Use side-by-side comparison of chemical (baking soda + vinegar) vs physical (salt + water) so students see difference; Emphasize that good science uses multiple pieces of evidence, not just one. Watch for: Students who think any dramatic change is chemical (including dissolving); Students who make conclusions based on one observation without checking for additional evidence; Students who can identify observations but can't explain WHY they indicate chemical vs. physical change.
- The data shows what happened when two substances were mixed in a sealed plastic bag.
- Before: 2 tablespoons baking soda in one corner, 30 mL vinegar in another corner.
- After the bag was shaken: strong fizzing sound; many bubbles; bag inflated in 10 seconds; temperature dropped from 22°C to 18°C.
Based on the evidence from this investigation, which observation is the strongest evidence that a new substance (a gas) formed?
Answer: The bag inflated in 10 seconds after mixing. The inflation shows gas was produced, which is strong evidence of a chemical change.
This question tests a 5th grader's ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically identifying which observations constitute evidence of chemical change. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. Multiple indicators together provide stronger evidence than single observation. For this question, baking soda and vinegar mixed showing bubbles, fizzing, temperature drop, and gas inflating bag - all chemical indicators. Choice A is correct because it correctly identifies gas production as strong evidence of chemical change. This shows the student understands certain observations are reliable indicators of chemical change. Choice D represents a common error where students think temperature change from adding hot water is evidence of chemical reaction (it's not - must come from reaction itself). This typically happens because elementary students may not yet understand that temperature change must come from reaction itself, not external source. To help students: Teach the key chemical change indicators explicitly (temperature without external heat, gas produced, unexpected color, precipitate, new smell, hard to reverse) and practice identifying them. Watch for: Students who think temperature change from adding hot water is evidence of chemical change; Students who make conclusions based on one observation without checking for additional evidence.
- After mixing two clear liquids, students noticed tiny bubbles only while they were stirring. When they stopped stirring, the bubbles stopped within 3 seconds. The temperature stayed the same, and there was no new smell or color change. Based on the evidence from this investigation, which conclusion is best?
Answer: No new substance formed because the bubbles were likely air mixed in by stirring. There is no other evidence like temperature change or a new smell.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically distinguishing chemical change evidence from physical change evidence. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. For this question, two liquids mixed showing bubbles only during stirring that stop immediately - physical change from trapped air. Choice B is correct because it correctly identifies that bubbles from stirring (not reaction) indicate physical change, especially without other evidence. This shows the student understands certain observations are reliable indicators of chemical change. Choice A represents a common error where students think any bubbles mean chemical change. This typically happens because students may not yet understand that gas must come from reaction itself, not external source like stirring. To help students: Teach the key chemical change indicators explicitly (temperature without external heat, gas produced, unexpected color, precipitate, new smell, hard to reverse) and practice identifying them. Watch for: Students who can identify observations but can't explain WHY they indicate chemical vs. physical change.
- A student mixed two clear liquids. Right after mixing, the cup became cloudy and a solid clump formed at the bottom. There were no bubbles, and the temperature stayed at 19°C. Based on the observations, which statement is best supported?
Answer: A new substance likely formed because a new solid appeared when two liquids were mixed. This is evidence of a chemical change even without bubbles.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically identifying precipitate formation as evidence of chemical change. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. For this question, two clear liquids producing a cloudy mixture with solid clump indicates precipitate formation - a key chemical change indicator. Choice A is correct because it correctly identifies that a new solid appearing when two liquids mix is evidence of chemical change, even without other indicators like bubbles. This shows the student understands that precipitate formation alone is strong evidence of new substance formation. Choice B represents a common error where students think bubbles are required for chemical change, not recognizing that precipitate formation is equally strong evidence. This typically happens because many classroom demonstrations emphasize fizzing reactions, leading students to think all chemical changes must bubble. To help students: Demonstrate various chemical changes including precipitate formation (milk + vinegar), gas production (baking soda + vinegar), and color change reactions, showing that different reactions have different indicators. Watch for: Students who think bubbles are the only evidence of chemical change, students who think temperature must always change in reactions, or students who don't recognize precipitate formation as a key indicator.
- After mixing 200 mL of room-temperature water (20°C) with 1 tablespoon of salt, students observed: the salt "disappeared" after stirring, there were no bubbles, and the temperature stayed 20°C. The mixture tasted salty. Based on the observations, is this a chemical change (new substance formed) or a physical change (no new substance formed)?
Answer: Physical change, because the salt dissolved but is still salt mixed in the water. There were no bubbles or temperature change to show a reaction.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically distinguishing chemical change evidence from physical change evidence. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. Dissolving looks dramatic but is physical change because substance still present. For this question, salt dissolved in water showing no temperature change, no bubbles, still tastes salty - physical change. Choice C is correct because it correctly recognizes dissolving is physical change because salt still present and recoverable. This shows the student understands must distinguish reaction-produced changes from external changes. Choice A represents a common error where students think dissolving is chemical change because substance 'disappears' (it's physical - still there in tiny pieces). This typically happens because dissolving seems so dramatic that 5th graders assume it's chemical, but substance is still present and recoverable. To help students: Demonstrate that dissolved substances are still there by evaporating salt water to recover salt, showing dissolving is reversible (physical). Watch for: Students who think any dramatic change is chemical (including dissolving).
- The evidence from this investigation is incomplete. Lila mixed 1 teaspoon of baking soda into 50 mL of lemon juice. She wrote, "It fizzed a lot," but she did not measure temperature, did not note any smell change, and did not record how long the fizzing lasted. What additional observation would BEST help determine if a new substance formed?
Answer: Measure the temperature before and after mixing without adding hot or cold water. A temperature change from the reaction would be strong evidence of chemical change.
This question tests a 5th grader's ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically identifying which observations constitute evidence of chemical change. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. Physical changes show dissolving (substance breaks up but still there - can recover it), predictable color mixing, separation, or state changes. Temperature change only counts as chemical evidence if from reaction itself, not from adding hot/cold substance. For this question, baking soda and lemon juice mixed showing fizzing - but incomplete without temperature. Choice A is correct because it correctly identifies temperature change without external heat as key chemical change evidence. This shows the student understands certain observations are reliable indicators of chemical change. Choice C represents a common error where students make conclusion without using evidence, just guessing. This typically happens because students may think their prediction is their conclusion rather than using actual evidence. To help students: Practice Claim-Evidence-Reasoning structure: state conclusion, cite observations, explain how observations support conclusion. Watch for: Students who confuse their prediction with their evidence-based conclusion; Students who can identify observations but can't explain WHY they indicate chemical vs. physical change.
- A class did two mixing tests.
Test 1: Sugar + water → sugar seemed to disappear, no bubbles, temperature stayed at 20°C, and the liquid tasted sweet.
Test 2: Vinegar + baking soda → lots of bubbles and foam, and temperature dropped from 21°C to 17°C.
Based on the evidence, which test shows a chemical change (new substance formed)?
Answer: Test 2, because bubbles formed and the temperature changed without an outside source. Using two indicators makes the evidence stronger.
This question tests 5th graders' ability to use evidence to determine whether mixing substances resulted in a new substance forming (NGSS 5-PS1-4), specifically comparing evidence from multiple tests to identify chemical versus physical changes. To determine if a new substance formed (chemical change), students must analyze observations for key indicators: temperature change without external heat source, gas produced (bubbles, fizzing), unexpected color change, solid forming from liquids (precipitate), new smell, or inability to easily reverse. For this question, Test 1 shows sugar dissolving (physical) with no chemical indicators, while Test 2 shows vinegar and baking soda with bubbles and temperature drop - clear chemical indicators. Choice C is correct because it correctly identifies Test 2 as showing chemical change, recognizing that bubbles formed and temperature changed without an outside source, and notes that using two indicators makes evidence stronger. This shows the student can compare different mixtures and identify which has chemical change evidence. Choice A represents a common error where students think dissolving sugar is chemical change because it 'disappears,' even claiming it's stronger evidence than bubbles. This typically happens because dissolving seems so dramatic that students don't recognize it as physical change where sugar remains present unchanged. To help students: Use side-by-side demonstrations comparing dissolving (sugar in water - physical) with reacting (baking soda + vinegar - chemical), highlighting the presence or absence of key indicators in each. Watch for: Students who think dissolving is chemical change, students who value 'disappearing' over actual chemical indicators like gas production, or students who think all mixing creates new substances.
