Question

chemistry quiz #2 - physical and chemical pro...
water reacts with sodium metal
a solid is crushed into a powder.
mixing salt and pepper
two chemicals are mixed together and a gas is produced.
an ice cube is placed in the sun. later there is a puddle of water. later the puddle is gone.
a marshmallow is cut in half
two substances are mixed and light is produced.
a bicycle changes colour as it rusts.
chocolate syrup is dissolved in milk
a marshmallow is toasted over a campfire

1. physical change
2. chemical change

Explanation:

• Water reacting with sodium metal forms new substances (sodium hydroxide and hydrogen), so it's a chemical change.
• Crushing a solid into powder only changes the physical form, not the substance itself, so it's a physical change.
• Mixing salt and pepper is just a physical combination without forming new substances, so it's a physical change.
• Two chemicals reacting to produce a gas means new substances are formed, so it's a chemical change.
• Ice - cube melting and then evaporating are physical state changes without new substances, so it's a physical change.
• Cutting a marshmallow in half only changes its physical shape, so it's a physical change.
• Two substances producing light likely means a chemical reaction is occurring, so it's a chemical change.
• A bicycle rusting is a chemical reaction between iron in the bicycle and oxygen in the air, so it's a chemical change.
• Dissolving chocolate syrup in milk is a physical process of mixing without new chemical substances formed, so it's a physical change.
• Toasting a marshmallow over a camp - fire causes a chemical reaction due to heat, so it's a chemical change.

Answer:

• Water reacts with sodium metal: 2. Chemical Change
• A solid is crushed into a powder: 1. Physical Change
• Mixing salt and pepper: 1. Physical Change
• Two chemicals are mixed together and a gas is produced: 2. Chemical Change
• An ice cube is placed in the sun. Later there is a puddle of water. Later the puddle is gone: 1. Physical Change
• A marshmallow is cut in half: 1. Physical Change
• Two substances are mixed and light is produced: 2. Chemical Change
• A bicycle changes colour as it rusts: 2. Chemical Change
• Chocolate syrup is dissolved in milk: 1. Physical Change
• A marshmallow is toasted over a campfire: 2. Chemical Change