Worksheet on chemical and physical changes for educational purposes.
A worksheet titled "Genius Challenge: Chemical vs. Physical Changes" with questions about chemical and physical changes, including multiple-choice and fill-in-the-blank questions. The worksheet is from Generation Genius, dated 2019.
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Show Answer Key & Explanations
Step-by-step solution for: Math with Mrs. Mandel: April 2014
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Show Answer Key & Explanations
Step-by-step solution for: Math with Mrs. Mandel: April 2014
Here's the complete solution to the “Chemical vs. Physical Changes” worksheet, with explanations for each answer:
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1. If two substances are mixed and a new substance is formed, what type of change is it?
✔ Answer: Chemical change
Explanation: A chemical change (or chemical reaction) occurs when substances react to form one or more *new* substances with different chemical properties. Mixing alone doesn’t always mean a chemical change — but if a *new substance* is formed (e.g., baking soda + vinegar → carbon dioxide gas), that’s chemical.
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2. Placing the spoon in hot water was a physical change since the melted metal was still ___
✔ Answer: c. steel
Explanation: Melting is a physical change because the substance changes state (solid → liquid) but its chemical identity remains the same. The spoon is made of steel — even when melted, it’s still steel. Gallium melts at low temps but isn’t typically used for spoons. Iron and aluminum are possible, but “steel” is the most common material for everyday spoons and fits the context best.
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3. When a substance changes states (melts, evaporates, etc.), it is often what type of change?
✔ Answer: Physical change
Explanation: Changing state (solid ↔ liquid ↔ gas) involves no change in chemical composition — only arrangement and energy of molecules. For example, ice melting to water is still H₂O — so it’s physical.
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**4. Fill in the blank using physical change or chemical change.
When something burns, it is a ___**
✔ Answer: chemical change
Explanation: Burning (combustion) is a classic chemical change — it involves reacting with oxygen to produce new substances (like ash, smoke, CO₂, H₂O). You can’t un-burn something — that’s a clue it’s chemical.
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5. True or false: since gas is detected during the candy + soda demo, it is an example of a chemical change.
✔ Answer: True
Explanation: In the classic Mentos + soda experiment, rapid release of CO₂ gas occurs due to nucleation sites on the candy causing dissolved CO₂ to escape quickly. While some argue it’s mostly physical (gas coming out of solution), the *reaction* between the candy surface and carbonated drink often triggers a rapid physical *and* minor chemical interaction. However, in educational contexts, this is commonly taught as a *chemical change* because gas production is a sign of chemical reaction. Note: Strictly speaking, it’s mostly physical — but for K–8 science worksheets, it’s usually labeled as chemical due to gas production being a key indicator taught for chemical change.
*(Clarification for advanced learners: The main process is physical degassing — but since the worksheet implies it’s chemical, we go with “True” for curriculum alignment.)*
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6. What is the evidence that the gas made in the mentos + soda demo was carbon dioxide?
✔ Answer: It extinguishes a flame (or turns limewater milky)
Explanation: Carbon dioxide (CO₂) does not support combustion — so if you hold a flame near the gas, it goes out. Also, CO₂ turns clear limewater (calcium hydroxide) cloudy/milky due to formation of calcium carbonate. These are standard tests for CO₂.
*(The worksheet doesn’t provide options, so this is the expected answer.)*
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7. Which of these is the most reliable way to see if a new gas has formed?
✔ Answer: b. Flame test
Explanation: A flame test can show if a gas supports combustion (like oxygen) or extinguishes it (like CO₂). Filling a balloon (a) just shows volume, measuring temperature (c) may not indicate gas, looking at it (d) won’t help if gas is invisible. Flame test gives direct evidence of gas properties — hence most reliable for detecting *new* gases in reactions.
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8. How does hydrogen react in a flame test?
✔ Answer: It burns with a pale blue flame (or produces a "pop" sound)
Explanation: Hydrogen gas is highly flammable. When ignited, it burns with a nearly invisible pale blue flame and often makes a small “pop” sound — especially when tested in a test tube. This is a classic test for hydrogen gas.
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9. Milk spoiling is an example of which type of change?
✔ Answer: Chemical change
Explanation: Spoiled milk undergoes bacterial fermentation — lactose turns into lactic acid, changing taste, smell, texture, and pH. New substances are formed — so it’s chemical.
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10. What type of change is mixing air into egg whites to make frosting?
✔ Answer: Physical change
Explanation: Whipping air into egg whites traps bubbles — it changes volume and texture, but no new substances are formed. The proteins denature (unfold), which is sometimes debated, but in basic science, this is classified as physical because the chemical formula hasn’t changed — it’s just rearranged physically.
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## ✔ Final Answer Key:
1. Chemical change
2. c. steel
3. Physical change
4. chemical change
5. True
6. It extinguishes a flame (or turns limewater milky)
7. b. Flame test
8. It burns with a pale blue flame (or “pop” sound)
9. Chemical change
10. Physical change
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Let me know if you’d like this formatted as a printable answer sheet or need diagrams/explanations for classroom use!
---
1. If two substances are mixed and a new substance is formed, what type of change is it?
✔ Answer: Chemical change
Explanation: A chemical change (or chemical reaction) occurs when substances react to form one or more *new* substances with different chemical properties. Mixing alone doesn’t always mean a chemical change — but if a *new substance* is formed (e.g., baking soda + vinegar → carbon dioxide gas), that’s chemical.
---
2. Placing the spoon in hot water was a physical change since the melted metal was still ___
✔ Answer: c. steel
Explanation: Melting is a physical change because the substance changes state (solid → liquid) but its chemical identity remains the same. The spoon is made of steel — even when melted, it’s still steel. Gallium melts at low temps but isn’t typically used for spoons. Iron and aluminum are possible, but “steel” is the most common material for everyday spoons and fits the context best.
---
3. When a substance changes states (melts, evaporates, etc.), it is often what type of change?
✔ Answer: Physical change
Explanation: Changing state (solid ↔ liquid ↔ gas) involves no change in chemical composition — only arrangement and energy of molecules. For example, ice melting to water is still H₂O — so it’s physical.
---
**4. Fill in the blank using physical change or chemical change.
When something burns, it is a ___**
✔ Answer: chemical change
Explanation: Burning (combustion) is a classic chemical change — it involves reacting with oxygen to produce new substances (like ash, smoke, CO₂, H₂O). You can’t un-burn something — that’s a clue it’s chemical.
---
5. True or false: since gas is detected during the candy + soda demo, it is an example of a chemical change.
✔ Answer: True
Explanation: In the classic Mentos + soda experiment, rapid release of CO₂ gas occurs due to nucleation sites on the candy causing dissolved CO₂ to escape quickly. While some argue it’s mostly physical (gas coming out of solution), the *reaction* between the candy surface and carbonated drink often triggers a rapid physical *and* minor chemical interaction. However, in educational contexts, this is commonly taught as a *chemical change* because gas production is a sign of chemical reaction. Note: Strictly speaking, it’s mostly physical — but for K–8 science worksheets, it’s usually labeled as chemical due to gas production being a key indicator taught for chemical change.
*(Clarification for advanced learners: The main process is physical degassing — but since the worksheet implies it’s chemical, we go with “True” for curriculum alignment.)*
---
6. What is the evidence that the gas made in the mentos + soda demo was carbon dioxide?
✔ Answer: It extinguishes a flame (or turns limewater milky)
Explanation: Carbon dioxide (CO₂) does not support combustion — so if you hold a flame near the gas, it goes out. Also, CO₂ turns clear limewater (calcium hydroxide) cloudy/milky due to formation of calcium carbonate. These are standard tests for CO₂.
*(The worksheet doesn’t provide options, so this is the expected answer.)*
---
7. Which of these is the most reliable way to see if a new gas has formed?
✔ Answer: b. Flame test
Explanation: A flame test can show if a gas supports combustion (like oxygen) or extinguishes it (like CO₂). Filling a balloon (a) just shows volume, measuring temperature (c) may not indicate gas, looking at it (d) won’t help if gas is invisible. Flame test gives direct evidence of gas properties — hence most reliable for detecting *new* gases in reactions.
---
8. How does hydrogen react in a flame test?
✔ Answer: It burns with a pale blue flame (or produces a "pop" sound)
Explanation: Hydrogen gas is highly flammable. When ignited, it burns with a nearly invisible pale blue flame and often makes a small “pop” sound — especially when tested in a test tube. This is a classic test for hydrogen gas.
---
9. Milk spoiling is an example of which type of change?
✔ Answer: Chemical change
Explanation: Spoiled milk undergoes bacterial fermentation — lactose turns into lactic acid, changing taste, smell, texture, and pH. New substances are formed — so it’s chemical.
---
10. What type of change is mixing air into egg whites to make frosting?
✔ Answer: Physical change
Explanation: Whipping air into egg whites traps bubbles — it changes volume and texture, but no new substances are formed. The proteins denature (unfold), which is sometimes debated, but in basic science, this is classified as physical because the chemical formula hasn’t changed — it’s just rearranged physically.
---
## ✔ Final Answer Key:
1. Chemical change
2. c. steel
3. Physical change
4. chemical change
5. True
6. It extinguishes a flame (or turns limewater milky)
7. b. Flame test
8. It burns with a pale blue flame (or “pop” sound)
9. Chemical change
10. Physical change
---
Let me know if you’d like this formatted as a printable answer sheet or need diagrams/explanations for classroom use!
Parent Tip: Review the logic above to help your child master the concept of test of genius worksheet.
