Calculate (a) the number of methane molecules in
120 cm3 of methane at r. t.p.;
(b) the mass of 42 dm3 of chlorine at r. t.p.

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.

What is the ph of a solution that has a hydrogen ion concentration of 1.0 * 10 -9 m?