Physical and Chemical Changes

What is the main difference between physical and chemical changes?

• Physical changes involve a change in the form or appearance of a substance, while chemical changes involve a change in the chemical composition of a substance.

• Physical changes involve a change in size, while chemical changes involve a change in weight.

• Physical changes involve a change in state, while chemical changes involve a change in texture.

• Physical changes involve a change in color, while chemical changes involve a change in temperature.

Give an example of a physical change.

• Melting ice

• Rusting iron

• Burning wood

• Boiling water

Give an example of a chemical change.

• Burning of wood

• Cutting paper

• Mixing salt and water

• Melting ice

Explain the role of energy in physical and chemical changes.

• Energy has no role in physical and chemical changes

• Energy only affects the color of the substances involved

• Energy provides activation energy and influences the speed and direction of the change.

• Energy is only important in physical changes, not chemical changes

How can you reverse a physical change?

• By ignoring the change and leaving it as it is

• By applying the same conditions or forces that caused the change

• By adding more of the substance that caused the change

• By applying opposite conditions or forces that caused the change

How can you reverse a chemical change?

• By using a chemical reaction that can reverse the original reaction.

• By heating the substance even more

• By adding more of the original chemicals

• By diluting the substance with water

What happens to the composition of a substance during a physical change?

• It turns into a completely different substance

• It remains the same

• It becomes a gas

• It becomes a solid

What happens to the composition of a substance during a chemical change?

• The composition of the substance becomes invisible

• The composition of the substance remains the same

• The composition of the substance disappears

• The composition of the substance changes

Why is it important to understand the differences between physical and chemical changes?

• To identify and predict the behavior of substances in various situations.

• To learn how to cook different recipes

• To improve physical fitness

• To understand the history of chemistry

Example for physical change

• melting of ice

• Burning crakers

• Burning ppaper