This simple, visual activity is great for starting to understand why rain falls.
What is a cloud?
Clouds are droplets of water and crystals of ice, the exact composition depends on the temperature. Clouds form when warm air rises, expands and cools. Water molecules then attach to dust, pollution and smoke particles, when these molecules come together they form a cloud. Clouds float because the water droplets forming them are warmed up by the heat from the sun and warm air rises.
The altitude at which clouds form depends on lots of factors such as air temperature, wind and size of the cloud.
Make a rain cloud in a jar
What you need
Dropper or pipette
Fill the jar about 3/4 full with water
Cover with shaving cream to completely cover the surface of the water
Drip water over the shaving foam using a pipette
Drop food colouring over the shaving foam and watch what happens?
Can you see the food colouring falling to the bottom of the jar?
Why does this happen?
When a rain cloud reaches a certain mass the water needs to escape and so breaks through the cloud to fall as rain. As you drip the water over your shaving cream cloud the water starts to fall through the cloud.
Why are rain clouds grey?
When the clouds become full of water droplets the are so thick that light cannot go all the way though, making the cloud look grey.
Inspiration Laboratories has a great cloud in a bottle activity.