A barometer is a device that measures air pressure.
What You Need:
- Food colouring
- Plastic cup
- Plastic bottle
- Pour a few inches of water and add a couple of drops of food colouring into a plastic cup.
- ¨Set a plastic bottle upside down inside the cup. It should fit snugly but not be airtight. The mouth of the bottle should be well below the waterline but not touch the bottom of the cup. This is your barometer.
- Mark the water level on the outside of the cup with a marker, then set the barometer where it won’t be
- ¸Look at the barometer after a day or two. If the weather is warm, you will notice that the water level in the cup has dropped, while the water in the neck of the bottle has actually risen.
When the air pressure increases, as it usually does when monsoon weather clears up and it is less muggy, the hot air presses down on the water in the cup, forcing it up into the neck of the bottle.