Physical or Chemical Change?

For our homework we were asked to identify if the following were Physical or Chemical change and explain why.
1. Chocolate has a brown color.
2. Nail polish evaporates if left open.
3. An energy drink will supply one with stamina.
4. Insect can walk on the surface of the water.
( I hope you could help me find my answers ) :D

Anonymous2015-01-10T01:01:03Z

1. chemical. to do with which wavelengths the chemicals will absorb / reflect.
2. chemical because of entropy.
3. chemical energy from the sugar in the drink
4. chemical. due to h-bonding which causes surface tension i water