Which is a substance that is made up of only one type of atom?

How do i complete this electrolysis of water lab? i’m at home, so i don’t have the materials, and the lab didn’t properly work and was incomplete at school.

The diagrams show objects’ gravitational pull toward each other. which statement describes the relationship between diagram x and y? gravity attracts only larger objects toward one another. gravity attracts larger objects only if they are close to one another. if the masses of the objects increase, then the force between them also increases. if distance between the objects increases, then the amount of force also increases.

In which reaction is precipitation occurring?