density

Why do ice cubes float in a  glass of water?

• the ice cubes are more dense than the water
• the water is more dense than the ice cubes
• the water is more dense than the glass
• the ice is more dense than the glass

A brick sinks in water while a wooden block of the same size floats.  This is because the brick has a

• lower volume than the wooden block
• lower density than the wooden block
• higher volume than the wooden block
• higher density than the wooden block

Helium balloons rise on earth because

• helium is less dense than air
• helium is more dense than air
• helium is cooler than air
• helium is warmer than air