The paper starts to spin because the heat of your hand heats up the air. This sets up a convection current in the air which...

At home 5-11 11-14

Hot water is less dense than cold water so it rises into the top bottle while the cold water sinks into the bottom bottle...

At home 5-11 11-14

The spiral should start to spin slowly. The radiator raises the temperature of the air around it, so the particles move more...

At home 5-11 11-14