Why are bottles of chemicals kept tightly closed except when a quantity of chemical is being removed

What are the 4 phases of matter in order of increasing engery content?

This classification of drug typically changes the brain's chemistry and reduces its ability to create its own endorphins.

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.