Physical and Chemical Changes True or False Worksheet for students to assess statements about matter transformations.

To solve the worksheet, we need to determine whether each statement is true or false based on the definitions of physical and chemical changes:

- Physical Change: A change in which the substance's physical properties (e.g., size, shape, state) are altered, but its chemical composition remains the same.
- Chemical Change: A change in which the substance's chemical composition is altered, resulting in the formation of new substances with different properties.

Let's analyze each statement:

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1. If a substance changes in size or shape, the change is physical.

- True: Changing the size or shape of a substance does not alter its chemical composition. For example, cutting a piece of paper or melting ice into water involves only physical changes.

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2. Water freezing and becoming ice is a chemical change.

- False: Freezing water into ice is a physical change because the chemical composition of water (H₂O) remains the same. Only the state (liquid to solid) changes.

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3. A chemical change leads to a new substance with new properties forming.

- True: In a chemical change, the original substance undergoes a reaction that produces one or more new substances with different properties. For example, rusting iron forms iron oxide, which has different properties than iron.

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4. If platinum is heated and cooled to its original state, it is a physical change.

- True: Heating and cooling platinum do not alter its chemical composition; they only change its temperature and possibly its state (e.g., from solid to liquid and back). This is a physical change.

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5. Water breaking into oxygen and hydrogen is a physical change.

- False: Breaking water (H₂O) into oxygen (O₂) and hydrogen (H₂) requires a chemical reaction (e.g., electrolysis). This alters the chemical composition, making it a chemical change.

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6. Milk turning sour is a physical change, as a change in odor is not an indicator of a chemical change.

- False: Milk turning sour involves the fermentation of lactose by bacteria, which produces lactic acid and other compounds. This is a chemical change because new substances are formed.

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7. If citric acid and baking soda mix, they produce carbon dioxide with a drop in temperature. This is a chemical change.

- True: The reaction between citric acid and baking soda produces carbon dioxide gas, water, and sodium citrate. This is a chemical change because new substances are formed.

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8. Trimming a bush because it has grown too much is a physical change.

- True: Trimming a bush involves cutting off parts of the plant without altering its chemical composition. This is a physical change.

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9. A sugar cube dissolving in water is a chemical change.

- False: Dissolving a sugar cube in water is a physical change because the sugar molecules simply disperse in the water without forming new substances. The chemical composition of sugar (C₁₂H₂₂O₁₁) remains unchanged.

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10. A bicycle rusting in the rain is a chemical change.

- True: Rusting is a chemical reaction where iron reacts with oxygen and water to form iron oxide (rust). This is a chemical change because a new substance (rust) is formed.

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11. Alcohol evaporating is a physical change.

- True: Evaporation of alcohol is a physical change because the alcohol transitions from a liquid to a gas without altering its chemical composition.

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12. Grass growing in the lawn is a chemical change.

- True: Grass growing involves photosynthesis, where plants use sunlight, water, and carbon dioxide to produce glucose and oxygen. This is a chemical change because new substances are formed.

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13. Blow drying hair is a chemical change.

- False: Blow drying hair removes moisture (water) from the hair, changing its physical state (wet to dry). This is a physical change because no new substances are formed.

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14. Food coloring is added to water. This is a physical change.

- True: Adding food coloring to water results in a mixture where the food coloring disperses in the water. No new substances are formed, so this is a physical change.

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15. In a fireworks display, the crackers exploding are undergoing a physical change.

- False: Fireworks involve chemical reactions where chemicals burn and react to produce light, heat, and sound. These reactions create new substances, making it a chemical change.

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Final Answers:

1. True
2. False
3. True
4. True
5. False
6. False
7. True
8. True
9. False
10. True
11. True
12. True
13. False
14. True
15. False

Final Answer:
\boxed{
\begin{array}{ll}
1. \text{True} & 2. \text{False} \\
3. \text{True} & 4. \text{True} \\
5. \text{False} & 6. \text{False} \\
7. \text{True} & 8. \text{True} \\
9. \text{False} & 10. \text{True} \\
11. \text{True} & 12. \text{True} \\
13. \text{False} & 14. \text{True} \\
15. \text{False} &
\end{array}
}