Quiz results

My answers to Richard Banks' quiz:

1. Classify the following as either a chemical or physical change.
Burning wood : physical
Crushing a rock : physical
Dissolving sugar in water : physical
The rusting of iron: chemical

2. Classify the following as to whether or not they are pure substances or mixtures.
milk: mixture
table salt : mixture
sugar : pure
steel : mixture

3. A cup of black coffee is considered to be __?__ and a/an __?__ substance.
(a) homogeneous…..pure
(b) homogeneous…..impure
(c) non-homogeneous…pure
(d) non-homogeneous…impure

I chose non-homogenous impure first. Apparently, that is not necessarily correct, but I can't say that I understand why. Perhaps I assumed a cup of brewed coffee and the question referred to a cup of coffee beans? Is that the difference?

4. The boiling of water is considered to be a __?__ change and the temperature at which water boils is considered to be a __?__ property. Answer: (d)
(a) chemical…..chemical
(b) chemical…..physical
(c) physical…..chemical
(d) physical…..physical