Grade-7-Science-Olympiad - Physical & Chemical Changes Magazine - Free Printable

Worksheet: Physical and Chemical Changes

#### Multiple-Choice Questions

Let's solve each question step by step:

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#### Question 1: Which change can be easily reversed?
- (A) Chemical Change
- (B) Physical Change
- (C) Both a physical and chemical change
- (D) Neither a physical nor chemical change

Explanation:
- Physical Change: A physical change involves a change in the state or form of matter without altering its chemical composition. Examples include melting ice, boiling water, or tearing paper. These changes are usually reversible.
- Chemical Change: A chemical change involves a transformation of one substance into a new substance with different chemical properties. Examples include burning wood, rusting iron, or cooking food. These changes are generally irreversible.

Answer:
(B) Physical Change

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#### Question 2: If the chemical properties of a substance remain unchanged and the appearance or shape of a substance changes, it is called a
- (A) Physical change
- (B) Chemical change
- (C) Neither a physical nor chemical change
- (D) Both a physical and chemical change

Explanation:
- In a physical change, the chemical properties of the substance remain the same, but there is a change in its physical appearance, such as its shape, size, or state (e.g., solid to liquid). Examples include cutting a piece of wood or dissolving sugar in water.
- In a chemical change, the chemical properties of the substance change, resulting in the formation of new substances with different properties. Examples include burning paper or rusting metal.

Since the question specifies that the chemical properties remain unchanged but the appearance or shape changes, this describes a physical change.

Answer:
(A) Physical change

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#### Question 3: Which of the following characteristic best describes a physical change?
- (A) Composition changes
- (B) Composition remains the same
- (C) State of the matter remains the same
- (D) Loss of mass

Explanation:
- Physical Change: During a physical change, the composition of the substance does not change. The substance retains its original chemical identity, but its physical properties (such as state, shape, or size) may change.
- Chemical Change: During a chemical change, the composition of the substance changes, resulting in the formation of new substances with different chemical properties.

The key characteristic of a physical change is that the composition remains the same.

Answer:
(B) Composition remains the same

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#### Question 4: Which of the following property remains same during physical as well as chemical changes?
- (A) Density
- (B) Shape
- (C) Mass
- (D) Arrangement of particle

Explanation:
- Mass: According to the Law of Conservation of Mass, the total mass of the reactants in a chemical reaction must equal the total mass of the products. This means that mass is conserved during both physical and chemical changes.
- Density: Density can change during both physical and chemical changes. For example, when ice melts into water, its density changes. Similarly, in a chemical reaction, the density of the products may differ from the reactants.
- Shape: Shape can change during physical changes (e.g., bending a piece of metal) and chemical changes (e.g., burning paper).
- Arrangement of particles: The arrangement of particles can change during both physical and chemical changes. For example, in a phase change (a physical change), the arrangement of particles changes. In a chemical reaction, the arrangement of atoms in molecules changes.

The property that remains constant during both physical and chemical changes is mass.

Answer:
(C) Mass

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Final Answers:

1. (B) Physical Change
2. (A) Physical change
3. (B) Composition remains the same
4. (C) Mass

Boxed Final Answer:
\[
\boxed{(B), (A), (B), (C)}
\]