State four different properties of a compound and a mixture. With reference to the stated properties give reasons why air is considered a mixture and not a compound.

Four Properties of compounds:

1. It has a fixed composition.
2. It has definite set of properties.
3. It cannot be separated by physical means.
4. Chemical Formula possible.

Four Properties of mixture:

1. It has a variable composition.
2. It has no definite properties.
3. It cannot be separated by physical means.
4. No chemical formula possible.

Air is considered a mixture and not a compound because:

1. Composition — Air has a variable composition
2. Properties — Air has no specific set of properties
3. Separation of components — Air can be separated into its components by physical means
4. Chemical formula — No chemical formula is possible for air.