Answer:
A
Explanation:
When molecules speed up, they become excited and create friction that is transformed into heat, do when an abject cools, the molecules slow down and thus for have less friction.
Yes magnesium is a pure substance and it is a element.
Mixture. Mixtures can be separated into their component parts, while substances are chemically bonded atoms that can't be separated by physical means.
A. Adding a catalyst. A catalyst by definition is a compound that speeds up reaction rates.
