Test for oxygen and carbon dioxide gases

To test for oxygen gas, use a glowing splinter.

Observation: If oxygen gas is present, it will rekindle / relight.

To test for carbon dioxide gas, use limewater (calcium hydroxide)

Observation: If carbon dioxide gas is present, it will give a white precipitate with limewater. 

Reactions of metals with hydrochloric acid

Zinc, aluminium and iron will form metal chlorides and hydrogen gas.

Copper does not react with hydrochloric acid because it is unreactive. Copper is below hydrogen in the reactivity series, therefore it is unable to displace the hydrogen ions.