Intro to physical & chemical change

Melting ice

• physical change

• chemical change

Answer explanation

Melting ice is a physical change because it involves a change in state from solid to liquid without altering the chemical composition of water. The molecules remain H2O before and after melting.

Burning wood

• physical change

• chemical change

Answer explanation

Burning wood is a chemical change because it transforms the wood into new substances (ash, smoke, gases) through a reaction with oxygen, releasing energy. This process cannot be reversed, distinguishing it from a physical change.

Burning coal

• physical change

• chemical change

Answer explanation

Burning coal is a chemical change because it involves a reaction with oxygen, producing new substances like carbon dioxide and ash, which cannot be reversed. This distinguishes it from a physical change, where no new substances are formed.

Melting ice

• physical change

• chemical change

Answer explanation

Melting ice is a physical change because it involves a change in state from solid to liquid without altering the chemical composition of water. The molecules remain H2O before and after melting.

Burning wood

• physical change

• chemical change

Answer explanation

Burning wood is a chemical change because it transforms the wood into new substances (ash, smoke, gases) through a reaction with oxygen, releasing energy. This process cannot be reversed, distinguishing it from a physical change.

Burning coal

• physical change

• chemical change

Answer explanation

Burning coal is a chemical change because it involves a reaction with oxygen, producing new substances like carbon dioxide and ash, which cannot be reversed. This distinguishes it from a physical change, where the substance remains the same.

Which change describes a substance that changes shape, form, or appearance but is still the same substance?

• physical change

• chemical change

Answer explanation

A physical change occurs when a substance changes its shape, form, or appearance without altering its chemical composition. Therefore, the correct answer is a physical change, as the substance remains the same.

What happens when a new substance is produced during a reaction?

• physical change

• chemical change

Answer explanation

When a new substance is produced during a reaction, it indicates a chemical change. This contrasts with a physical change, where no new substances are formed.

rusty nail

• physical change

• chemical change

Answer explanation

A rusty nail undergoes a chemical change as iron reacts with oxygen and moisture, forming iron oxide (rust). This process alters the nail's chemical composition, distinguishing it from a physical change, which does not affect composition.

broken glass

• physical change

• chemical change

Answer explanation

Broken glass is a physical change because it alters the form of the glass without changing its chemical composition. The glass can be reformed, which is characteristic of physical changes.