Question

Please help with at least one of these questions! I have about 15-20 mins left :(

1. Name 2 examples of a physical change and tell why they are physical changes and not chemical changes.

2. Name 2 examples of a chemical change and tell why they are chemical changes and not physical changes.

3. Gold and pyrite (fool's gold) cannot easily be distinguished by color? What other physical property/properties can be used to tell the 2 metals apart from one another?

Answer 1

1. Melting ice does not change the composition of the water or ice, as the ice is only changing its state from solid to liquid. Boiling water also does not change the composition of the water or gas, as the water is only changing its state from liquid to gas.

2. Burning paper turns the paper fibres to ashes. Making yoghurt from milk is making something new out from milk, where there is fermentation going on to turn the lactose into an acid, resulting in a chemical change and not a physical change.

Step-by-step explanation:

A chemical change is when a new substance is formed from the old thing due to a chemical process such as burning where energy is given off or absorbed, while a physical change is basically changing the state of a substance but its composition does not change, unlike a chemical change.