Physical and Chemical Changes (Worksheet) : Name: Surname: School ... - Free Printable

Worksheet: Physical and Chemical Changes

#### Q.1. Define the following terms:

A. Physical Change:
A physical change is a change in the form or appearance of a substance without altering its chemical composition. In other words, the substance remains the same, but its state, shape, size, or phase may change. Examples include melting ice, tearing paper, or dissolving sugar in water.

B. Chemical Change:
A chemical change is a process in which one or more substances are transformed into new substances with different chemical properties. This involves the breaking and forming of chemical bonds, resulting in the creation of new materials. Examples include burning wood, rusting iron, or cooking an egg.

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#### Q.2. Write T (True) or F (False) if the statement is false.

1. A physical change causes the properties of a substance to change.
- Answer: T (True)
- Explanation: During a physical change, the observable properties of a substance (e.g., shape, size, state) change, but the chemical composition remains the same.

2. No new substance is formed with a physical change.
- Answer: T (True)
- Explanation: In a physical change, the substance does not undergo any chemical transformation, so no new substances are created.

3. A chemical change can be easily reversed.
- Answer: F (False)
- Explanation: Chemical changes involve the formation of new substances through the breaking and forming of chemical bonds. These changes are generally irreversible because the original substances cannot be recovered without further chemical processes.

4. Changes in states of matter are physical changes.
- Answer: T (True)
- Explanation: Changes in states of matter (e.g., solid to liquid, liquid to gas) involve only changes in the arrangement and motion of particles, not changes in their chemical composition. Therefore, they are classified as physical changes.

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#### Q.3. Which of the following is not a sign that a chemical reaction has occurred?

- a) Change in temperature
- Explanation: A change in temperature can indicate a chemical reaction, as energy is often absorbed or released during chemical changes.

- b) Change in shape
- Explanation: A change in shape alone does not necessarily indicate a chemical reaction. For example, cutting a piece of paper changes its shape but does not alter its chemical composition. This is a physical change.

- c) Change in color
- Explanation: A change in color is often a sign of a chemical reaction, as it indicates a change in the molecular structure of the substance.

- d) Formation of a gas
- Explanation: The formation of a gas is a common sign of a chemical reaction, as it suggests the production of a new substance.

- Answer: b) Change in shape

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#### Q.4. Identify the following as physical change or chemical change.

1. Glass breaking
- Answer: Physical change
- Explanation: Breaking glass only changes its shape and size but does not alter its chemical composition.

2. Burning wood
- Answer: Chemical change
- Explanation: Burning wood involves the combustion of wood, producing new substances such as carbon dioxide and ash. This is a chemical reaction.

3. Cutting meat
- Answer: Physical change
- Explanation: Cutting meat only changes its shape and size but does not alter its chemical composition.

4. Melting ice cubes
- Answer: Physical change
- Explanation: Melting ice cubes is a change in state from solid to liquid, which is a physical change because the chemical composition of water remains the same.

5. Chopping wood
- Answer: Physical change
- Explanation: Chopping wood only changes its shape and size but does not alter its chemical composition.

6. Fireworks exploding
- Answer: Chemical change
- Explanation: Fireworks exploding involve chemical reactions that produce light, heat, and new substances like gases and smoke.

7. Cooking an egg
- Answer: Chemical change
- Explanation: Cooking an egg involves denaturing proteins, which is a chemical change that alters the chemical structure of the egg.

8. Boiling water
- Answer: Physical change
- Explanation: Boiling water is a change in state from liquid to gas, which is a physical change because the chemical composition of water remains the same.

9. Rusting of iron
- Answer: Chemical change
- Explanation: Rusting of iron involves the reaction of iron with oxygen and water to form iron oxide (rust), which is a new substance. This is a chemical change.

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Final Answers:

1. Physical Change: A change in the form or appearance of a substance without altering its chemical composition.
2. Chemical Change: A process in which one or more substances are transformed into new substances with different chemical properties.
3. Q.2 Answers:
- 1. T
- 2. T
- 3. F
- 4. T
4. Q.3 Answer: b) Change in shape
5. Q.4 Answers:
- Glass breaking: Physical change
- Burning wood: Chemical change
- Cutting meat: Physical change
- Melting ice cubes: Physical change
- Chopping wood: Physical change
- Fireworks exploding: Chemical change
- Cooking an egg: Chemical change
- Boiling water: Physical change
- Rusting of iron: Chemical change

Final Boxed Answers:
\[
\boxed{
\text{Q.3: b) Change in shape}
}
\]