What is a good high school level science experiment?

The half-life of a certain element is 100 days. how many half-lives will it be before only one eighth of this elementremains?

Sodium azide is a substance that can be used to inflate airbags. an electrical impulse causes the sodium azide to decompose, producing elemental sodium and nirtogen gas. write the balanced chemical equation for this reaction. plzzz

How many moles of nitrogen would react with excess hydrogen to produce 520 ml of ammonia?