Compare Properties Before and After - 5th Grade Science

1. Comparing the substances before and after mixing, a student mixed yeast with warm sugar water in a bottle. Before mixing: - Yeast: tan grains, Solid, 22°C, bread-like smell - Sugar water: clear, Liquid, 35°C, no smell After mixing (after 10 minutes): - Mixture: bubbles rising and foam on top, Liquid with gas bubbles, 35°C, bread-like smell Which observation is the best evidence that a gas was produced?
   Answer: Bubbles rose and foam formed on top of the liquid. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically determining significance of property changes. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change; when multiple properties change in unexpected ways (gas produced without external input), this indicates a new substance formed (chemical change); for this question, yeast and sugar water were mixed, showing bubbles and foam while temperature stayed at 35°C, indicating chemical change via fermentation. Choice B is correct because it correctly uses multiple property changes together as stronger evidence, specifically bubbles and foam indicating gas production, which shows the student understands certain property changes are more significant indicators of new substances. Choice D represents a common error where students focus on before properties without noting the after change, like initial clarity, missing the gas evidence. To help students: Teach chemical change indicators specifically (gas produced, hard to reverse) and emphasize comparing multiple properties, not just one, with examples like yeast reactions. Watch for: Students who miss the temperature stability and focus on less relevant properties, or who don't realize multiple changes together are stronger evidence.
2. The data shows properties before and after mixing cocoa powder into warm milk. Which property changed from before mixing to after mixing?
   Answer: The color changed from white to light brown. This question tests 5th graders' ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically identifying which properties changed during dissolving. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When properties change in predictable ways like color mixing from dissolving, the original substances are still present (physical change). For this question, cocoa powder was mixed into warm milk, showing the color changed from white to light brown - indicating physical change. Choice B is correct because it accurately identifies the property that changed by comparing before and after states - white milk became light brown when cocoa dissolved into it. This shows the student understands must compare before and after to detect change. Choice D represents a common error where students expect bubbles and fizzing with any mixture - cocoa dissolving is physical change without gas production. This typically happens because 5th graders may think all changes should be dramatic like fizzing, not recognizing that simple color change from dissolving is also evidence of change (but physical, not chemical). To help students: Use before/after comparison tables explicitly - have students predict what will happen to each property, then observe. Practice distinguishing physical changes (like dissolving causing color change) from chemical changes (like gas production). Watch for: Students who think any color change means chemical change, not recognizing that predictable color mixing from dissolving is physical.
3. Comparing the substances before and after mixing, a student mixed 50 mL of vinegar (clear liquid, sour smell, 22°C) with 1 spoon of baking soda (white powder, little smell, 22°C). After mixing, the cup had lots of bubbles and foam, the mixture felt cooler at 18°C, and it still smelled sour. Which change suggests a new substance was formed?
   Answer: Bubbles and foam formed even though nothing was boiling. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically using property evidence to conclude chemical vs. physical change. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When multiple properties change in unexpected ways (temperature without external heat + gas produced + color change), this indicates a new substance formed (chemical change). For this question, baking soda and vinegar were mixed, showing temperature drop from 22°C to 18°C, clear to bubbly foam, and bubbles produced - all indicating chemical change. Choice A is correct because it correctly recognizes that bubbles without boiling is key evidence of chemical change. This shows the student understands certain property changes are more significant indicators of new substances. Choice B represents a common error where students ignore that some properties stayed same while others changed. This typically happens because 5th graders may focus on one dramatic property (bubbles) and miss more significant one (temperature or gas). To help students: Teach chemical change indicators specifically (temperature without external heat, gas produced, unexpected color, precipitate, new smell, hard to reverse) vs. physical change indicators (dissolving, state change, predictable color mixing, easy to reverse). Watch for: Students who think all changes mean new substance.
4. The table compares properties of two original substances before mixing and the mixture after mixing (salt + water). Which property changed when the substances were mixed? Before mixing: - Salt: white, Solid, no smell, grainy - Water: clear, Liquid, no smell, 22°C After mixing (salt water): clear, Liquid, no smell, 22°C, no visible salt grains​
   Answer: Visible particles changed from salt grains you could see to no grains you could see. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically identifying which properties changed. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When properties change in predictable, reversible ways (dissolving, color mixing, layering), the original substances are still present (physical change). For this question, salt and water were mixed, showing dissolving and clear color maintained - indicating physical change. Choice B is correct because it accurately identifies the property that changed by comparing before and after states. This shows the student understands must compare before and after to detect change. Choice D represents a common error where students misidentify physical change as chemical because saw change, not recognizing change type matters. This typically happens because 5th graders may think any visible change is chemical. To help students: Use before/after comparison tables explicitly - have students fill in properties before mixing, predict, then observe after and compare. Watch for: Students who think dissolving is chemical change (it's physical - substance still there).
5. The table compares properties before and after mixing oil and water in a jar. Before mixing: - Water: clear, Liquid, 22°C - Vegetable oil: pale yellow, Liquid, 22°C After mixing (after shaking, then waiting 2 minutes): - Mixture: two layers formed (yellow oil on top, clear water on bottom), still Liquid overall, 22°C Based on the property changes, what can you conclude?
   Answer: This is a physical change because the liquids separated into layers. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically determining significance of property changes. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change; when properties change in predictable, reversible ways (layering), the original substances are still present (physical change); for this question, oil and water were mixed, showing separation into layers while temperature stayed the same, indicating physical change. Choice B is correct because it accurately distinguishes this property change pattern as chemical vs. physical, specifically recognizing layering as reversible physical separation, which shows the student understands property evidence is more reliable than guessing. Choice C represents a common error where students think any visible change is chemical, not recognizing change type matters, and invent details like temperature increase. To help students: Practice with multiple examples of both types of changes, like shaking oil-water vs. reactive mixtures, and show that separated substances can be recovered to demonstrate physical change. Watch for: Students who think all changes mean new substance or ignore that some properties stayed same, like temperature.
6. Comparing the substances before and after mixing, a student mixed lemon juice (Liquid) with milk (Liquid). Which observation is evidence that a chemical change may have happened?
   Answer: The mixture formed clumps and became thicker than either liquid was before. This question tests 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically using property evidence to conclude chemical vs. physical change. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When lemon juice (acid) mixes with milk (protein), the acid causes milk proteins to clump together (curdle) - this is a chemical change forming new substances. For this question, lemon juice and milk were mixed, and the mixture formed clumps and became thicker than either original liquid. Choice A is correct because it identifies evidence of chemical change - the formation of clumps and thickening shows the milk proteins chemically reacted with the acid to form new substances (curds). This shows the student recognizes that unexpected texture changes can indicate chemical reactions. Choice C represents a common error where students focus on properties that didn't change. This typically happens because 5th graders may think state of matter must change for a chemical reaction, not realizing chemical changes can occur within the same state. To help students: Demonstrate milk curdling with lemon juice or vinegar, explaining that the clumps are new substances formed by chemical reaction. Emphasize that chemical changes can happen while staying in the same state of matter. Watch for: Students who think chemical change requires a state change, or who don't recognize curdling/clumping as evidence of new substance formation.
7. The table compares properties before and after mixing an effervescent tablet with water. Before mixing: - Water: clear, Liquid, no smell, 20°C - Tablet: white, Solid, fizzy smell, 20°C After mixing: - Mixture: clear, Liquid with many bubbles, fizzy smell, 20°C after 2 minutes Which property did NOT change after mixing?​
   Answer: The temperature stayed the same at 20°C. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically recognizing which properties stayed same. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When multiple properties change in unexpected ways (temperature without external heat + gas produced + color change), this indicates a new substance formed (chemical change). For this question, effervescent tablet and water were mixed, showing bubbles and dissolving but temperature stayed 20°C - indicating possible chemical change due to gas production. Choice C is correct because it accurately notes which property stayed the same while others changed. This shows the student understands some properties can stay same while others change. Choice A represents a common error where students only look at after without comparing to before. This typically happens because 5th graders may focus on one dramatic property (bubbles) and ignore more important evidence (temperature change without heat source, gas produced). To help students: Emphasize comparing multiple properties, not just one. Watch for: Students who don't recognize that multiple properties changing together is stronger evidence than one alone.
8. Looking at the before and after data, a student mixed blue food coloring into clear water. What happened to the color?​
   Answer: It changed from clear to blue. This question tests 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically identifying which properties changed. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When food coloring mixes with water, the color changes predictably as the dye spreads throughout - a physical change where the substances are still present but distributed differently. For this question, blue food coloring was mixed into clear water, and the color changed from clear to blue. Choice A is correct because it accurately identifies the property that changed by comparing before and after states - the water was clear before adding food coloring and became blue after mixing. This shows the student understands must compare before and after to detect change. Choice C represents a common error where students make incorrect generalizations about what can or cannot happen. This typically happens because 5th graders may overgeneralize rules they've learned, thinking liquids can never change color, when in fact color change is common in both physical changes (like this one) and chemical changes. To help students: Use concrete examples to show that liquids can change color in both physical changes (food coloring, paint mixing) and chemical changes (indicators changing color). Emphasize observation over assumptions - what actually happened vs. what students think should happen. Watch for: Students who make broad generalizations that contradict their observations, or students who think color change always means chemical change (it can be either).
9. The data shows properties before and after mixing oil and water. Before mixing: - Water: clear, Liquid, no smell, 22°C - Vegetable oil: pale yellow, Liquid, slight smell, 22°C After shaking and letting it sit: - Two layers form again: oil on top and water on bottom - No bubbles, 22°C Based on the property changes, could you separate the mixture back into the original substances?
   Answer: Yes, because the liquids form two layers and can be poured apart carefully. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically determining significance of property changes. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When properties change in predictable, reversible ways (dissolving, color mixing, layering), the original substances are still present (physical change). For this question, oil and water were mixed, showing layering with no temperature or smell change - indicating physical change. Choice A is correct because it accurately distinguishes this property change pattern as chemical vs. physical. This shows the student understands certain property changes are more significant indicators of new substances. Choice B represents a common error where students confuse which property actually changed. This typically happens because 5th graders may not yet understand that comparing before and after is essential, not just noting something changed. To help students: Use before/after comparison tables explicitly - have students fill in properties before mixing, predict, then observe after and compare. Watch for: Students who don't recognize that multiple properties changing together is stronger evidence than one alone.
10. The table compares properties before and after mixing cocoa powder and milk. Before mixing: - Cocoa powder: brown, Solid, powdery, chocolate smell - Milk: white, Liquid, mild smell, 20°C After mixing (stirred well): light brown, Liquid, chocolate smell, 20°C, smooth with no dry powder on top Which statement best describes what happened to the texture/appearance?​
    Answer: It changed from powdery and white to a smooth, light-brown drink. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically identifying which properties changed. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When properties change in predictable, reversible ways (dissolving, color mixing, layering), the original substances are still present (physical change). For this question, cocoa powder and milk were mixed, showing texture from powdery to smooth and color to light brown - indicating physical change. Choice A is correct because it accurately identifies the property that changed by comparing before and after states. This shows the student understands must compare before and after to detect change. Choice D represents a common error where students think all changes mean new substance. This typically happens because 5th graders may not recognize dissolving is physical (substance still there, just in tiny pieces). To help students: Emphasize comparing multiple properties, not just one. Watch for: Students who think dissolving is chemical change (it's physical - substance still there).
11. The data shows properties before and after mixing two clear liquids in a cup. After mixing, the liquid became cloudy and a white solid formed at the bottom. Which statement best describes what happened?​
    Answer: A chemical change may have happened because a new solid formed from two liquids. This question tests 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically using property evidence to conclude chemical vs. physical change. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When two clear liquids mix to form a cloudy mixture with a solid precipitate, this unexpected result indicates a chemical reaction producing a new substance. For this question, two clear liquids were mixed, showing the liquid became cloudy and a white solid formed at the bottom - indicating chemical change. Choice B is correct because it accurately uses the evidence that a new solid formed from two liquids to conclude a chemical change may have happened - this is unexpected and indicates new substance formation. This shows the student understands property evidence is more reliable than assumptions. Choice A represents a common error where students misinterpret the evidence, thinking cloudiness means no real mixing occurred. This typically happens because 5th graders may not understand that precipitate formation (solid from liquids) is strong evidence of chemical change - they might think cloudiness means the substances are just suspended, not reacted. To help students: Demonstrate precipitate reactions (like Epsom salt + ammonia) to show how new solids can form from clear liquids in chemical changes. Emphasize that forming a solid from liquids is very different from dissolving (solid to liquid) and usually indicates chemical change. Watch for: Students who think cloudiness means incomplete mixing rather than chemical reaction, or students who don't recognize precipitate formation as strong evidence of new substance creation.
12. Looking at the before and after properties, a student mixed lemon juice with milk. Before mixing: - Lemon juice: pale yellow, Liquid, 22°C, sour smell - Milk: white, Liquid, 22°C, mild smell After mixing (after 3 minutes): - Mixture: white liquid with small solid clumps, Liquid + Solid, 22°C, sour smell Which property change is evidence of a chemical change?
    Answer: Solid clumps formed in the mixture. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically connecting property changes to new substance formation. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change; when properties change in unexpected ways (formation of solid clumps without adding solid), this indicates a new substance formed (chemical change); for this question, lemon juice and milk were mixed, showing solid clumps forming while temperature stayed the same, indicating chemical change through curdling. Choice B is correct because it correctly recognizes that solid clumps forming is key evidence of chemical change, which shows the student understands multiple simultaneous property changes indicate chemical change. Choice A represents a common error where students overlook changes and focus on properties that stayed the same, like temperature, missing the significance of new solids. To help students: Teach chemical change indicators specifically (precipitate, hard to reverse) vs. physical, and practice with examples like acid-milk curdling. Watch for: Students who don't recognize that multiple properties changing together is stronger evidence than one alone, or who think all changes are physical if temperature doesn't shift.
13. The table compares properties before and after mixing sugar and water. Before mixing: - Sugar: white crystals, Solid, 22°C, no smell - Water: clear, Liquid, 22°C, no smell After mixing: - Sugar water mixture: clear, Liquid, 22°C, no smell, no visible crystals How can you tell this is a physical change and not a chemical change?
    Answer: The sugar dissolved, and you could separate it by evaporating the water. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically using property evidence to conclude chemical vs. physical change. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change; when properties change in predictable, reversible ways (dissolving), the original substances are still present (physical change); for this question, sugar and water were mixed, showing crystals disappearing but recoverable by evaporation, indicating physical change. Choice C is correct because it accurately distinguishes this property change pattern as chemical vs. physical, specifically noting reversibility of dissolving, which shows the student understands property evidence is more reliable than guessing. Choice A represents a common error where students think dissolving is chemical because the solid 'disappeared,' not recognizing it's physical (substance still there, just in tiny pieces). To help students: Show that dissolved substances can be recovered (evaporate sugar water to get sugar back) to demonstrate physical change, and use T-charts for comparisons. Watch for: Students who think any change is chemical change or think dissolving is chemical (it's physical).
14. The table compares properties of two original substances before mixing and the mixture after mixing. Which observation is the best evidence that a new substance formed when baking soda and vinegar were mixed?
    Answer: Bubbles of gas formed and the mixture fizzed. This question tests 5th graders' ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically identifying which properties changed to indicate new substance formation. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When multiple properties change in unexpected ways (temperature without external heat + gas produced + color change), this indicates a new substance formed (chemical change). For this question, baking soda and vinegar were mixed, showing bubbles of gas formed and the mixture fizzed - indicating chemical change. Choice B is correct because it accurately identifies the property that changed by comparing before and after states - gas bubbles forming where none existed before is key evidence of chemical change. This shows the student understands certain property changes are more significant indicators of new substances. Choice A represents a common error where students confuse which property actually changed - the temperature likely did change (usually drops) when baking soda and vinegar react, making this misleading. This typically happens because 5th graders may focus on familiar properties like temperature and miss more significant evidence like gas production. To help students: Use before/after comparison tables explicitly - have students fill in properties before mixing, predict, then observe after and compare. Teach chemical change indicators specifically (temperature without external heat, gas produced, unexpected color, precipitate, new smell, hard to reverse) vs. physical change indicators (dissolving, state change, predictable color mixing, easy to reverse). Watch for: Students who think any change is chemical change without recognizing specific indicators like gas production are stronger evidence than others.
15. The table compares properties before and after mixing sugar and warm water. Which property stayed the same after mixing?
    Answer: The state of matter stayed Liquid after the sugar dissolved. This question tests 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically recognizing which properties stayed the same. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When sugar dissolves in warm water, it breaks into tiny pieces but remains sugar dissolved in water - a physical change where the state stays liquid. For this question, sugar and warm water were mixed, and while the sugar dissolved (disappeared), the state of matter stayed liquid. Choice C is correct because it accurately identifies that the state of matter stayed liquid after the sugar dissolved - the water was liquid before and the sugar-water solution is still liquid after. This shows the student understands that dissolving doesn't change the state of matter. Choice D represents a common error where students confuse stirring bubbles with gas production. This typically happens because 5th graders may see any bubbles as evidence of chemical change, not recognizing that stirring can trap air bubbles without producing new gas. To help students: Clarify the difference between air bubbles from stirring (physical) and gas bubbles from reactions (chemical). Show that sugar water can be evaporated to get sugar back, proving it's still there. Watch for: Students who think dissolving changes state of matter, or who mistake stirring bubbles for chemical gas production.
16. The data shows properties before and after mixing baking soda and vinegar in a cup. Before mixing: - Baking soda: white powder, Solid, 22°C, no smell - Vinegar: clear liquid, Liquid, 22°C, sour smell After mixing: - Mixture: lots of bubbles and foam, Liquid with gas bubbles, temperature dropped to 19°C, sour smell still present Which change suggests a new substance was formed?
    Answer: Bubbles and foam appeared without shaking. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically using property evidence to conclude chemical vs. physical change. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change; when multiple properties change in unexpected ways (temperature without external heat + gas produced), this indicates a new substance formed (chemical change); for this question, baking soda and vinegar were mixed, showing temperature drop from 22°C to 19°C, bubbles produced, and foam - all indicating chemical change. Choice B is correct because it correctly uses multiple property changes together as stronger evidence, specifically bubbles and foam indicating gas production, which shows the student understands certain property changes are more significant indicators of new substances. Choice A represents a common error where students ignore that some properties stayed same, like state partially remaining liquid, and miss the significance of gas formation. To help students: Teach chemical change indicators specifically (temperature without external heat, gas produced, unexpected color, precipitate, new smell, hard to reverse) and emphasize comparing multiple properties, not just one. Watch for: Students who can identify that properties changed but can't use that to determine chemical vs. physical, or who think all changes mean new substance.
17. The data shows properties before and after mixing two clear liquids in a classroom (Epsom salt solution + dish soap solution). Before mixing: - Cup 1 (Epsom salt in water): clear, Liquid, 22°C, no strong smell - Cup 2 (dish soap in water): clear, Liquid, 22°C, soapy smell After mixing: - Mixture: cloudy white, Liquid, 22°C, soapy smell Which property changed from before mixing to after mixing?
    Answer: The appearance changed from clear to cloudy white. This question tests a 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically identifying which properties changed. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change; for this question, Epsom salt solution and dish soap solution were mixed, showing appearance change from clear to cloudy white while temperature and smell stayed mostly the same, possibly indicating a physical or chemical change via precipitate. Choice C is correct because it accurately identifies the property that changed by comparing before and after states, specifically appearance to cloudy white, which shows the student understands must compare before and after to detect change. Choice B represents a common error where students invent changes like temperature drop, missing the actual observed property shift. To help students: Use before/after comparison tables explicitly - have students fill in properties before mixing, predict, then observe after and compare, emphasizing multiple properties. Watch for: Students who focus on one dramatic property (like cloudiness) but ignore that others stayed same, or who think any visible change is always chemical.
18. The table compares properties before and after mixing powdered drink mix into water. Which property stayed the same after mixing?
    Answer: The state of matter stayed Liquid. This question tests 5th graders' ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically recognizing which properties stayed the same during dissolving. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When properties change in predictable, reversible ways (dissolving, color from powder), the original substances are still present (physical change). For this question, powdered drink mix was mixed into water, and while the powder dissolved and added color/flavor, the state of matter stayed liquid - indicating physical change. Choice A is correct because it accurately notes which property stayed the same - both water before and the drink after remain in liquid state. This shows the student understands some properties can stay same while others change. Choice C represents a common error where students misunderstand dissolving - powder doesn't stay as dry clumps but dissolves throughout the liquid. This typically happens because 5th graders may not yet understand that dissolving spreads particles throughout the liquid rather than leaving them clumped. To help students: Use clear containers to show how colored powder spreads throughout water when dissolving. Emphasize that state of matter staying the same is common in physical changes. Watch for: Students who think dissolved substances should still be visible as clumps, not understanding that dissolving spreads particles too small to see.
19. The table compares properties before and after mixing sand and water. Which observation shows this was most likely a physical change?​
    Answer: The sand grains stayed visible and later settled to the bottom. This question tests 5th grader's ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically determining significance of property changes to identify physical vs. chemical change. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When properties change in predictable, reversible ways without forming new substances, this indicates physical change. For this question, sand and water were mixed, and the sand grains stayed visible and later settled to the bottom - indicating physical change. Choice C is correct because it accurately identifies evidence of physical change - the sand grains remaining visible and settling shows the sand is still sand, just mixed with water, not chemically changed into something new. This shows the student understands property evidence is more reliable than guessing. Choice B represents a common error where students confuse indicators of chemical change with those of physical change. This typically happens because 5th graders may memorize that temperature change indicates chemical change, not realizing this only applies to temperature change without an external heat source - if sand and water warmed without heating, that would suggest chemical change, but this didn't happen. To help students: Teach the difference between temperature change from external sources (physical) vs. spontaneous temperature change (often chemical). Practice identifying physical change indicators: substances can be separated, properties are predictable, original substances still present. Watch for: Students who incorrectly apply chemical change indicators to physical situations, or students who think any mixture must involve chemical change.
20. The table compares properties of two original substances before mixing and the mixture after mixing. Which property is evidence that mixing yeast with warm sugar water produced a gas?
    Answer: Bubbles and foam appeared on top after 10 minutes. This question tests 5th graders' ability to compare properties before and after mixing to look for evidence of change (NGSS 5-PS1-4), specifically identifying which properties changed to show gas production. Comparing properties before and after mixing is the key method for determining if change occurred and what type of change. When gas is produced (bubbles and foam appearing), this indicates a new substance formed (chemical change). For this question, yeast was mixed with warm sugar water, showing bubbles and foam appeared on top after 10 minutes - indicating chemical change as yeast converts sugar to gas. Choice C is correct because it accurately identifies the property that provides evidence of gas production - bubbles and foam forming where none existed before. This shows the student understands certain property changes are more significant indicators of new substances. Choice D represents a common error where students make assumptions - the smell likely did change as yeast produces gas and alcohol, making this incorrect. This typically happens because 5th graders may not realize that yeast is alive and causes chemical changes, producing gas as it consumes sugar. To help students: Demonstrate yeast experiments explicitly, showing the time delay before bubbles appear. Teach that living things like yeast can cause chemical changes by producing new substances (gas). Watch for: Students who don't recognize that bubbles and foam are evidence of gas production, or who think yeast mixing is just physical change.

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