If you’re in the middle of a heatwave or just generally need to cool off, I’ve got five easy hacks to help. When the temperatures soar, and you don’t have air con, it can get pretty uncomfortable. I currently have a fan pointed at me, the curtains closed, and a big, icy drink, and I’m still sweating. It’s time to hack the thermodynamics! Get ready to find out how to use science to keep everyone cool and happy this summer.
Frozen Water and a Fan Hack
If you find that a fan is just pushing warm air around, try putting a bottle of frozen water in front of it. There are two cool reasons this science hack works.
- The Heat Sponge
As hot air from the fan passes over the frozen water bottle, the bottle absorbs some of the heat, causing the ice to start melting. As the air has lost heat to the ice, it cools down.
- 2. The Convection Current
The frozen water bottle cools the air around it. If you just left the bottle on a table, you wouldn’t really notice the effect, but the fan creates a convection current in which hot air is constantly pushed towards the bottle and cooled air is spread around the room.
Frozen Water and Fan Extension Task
Try again, but this time add 3 tablespoons of salt to the water bottle before freezing. Salt lowers the freezing point of water, so the bottle will feel much cooler than plain frozen water. When you place the salty water bottle in front of the fan, it should cool the room much faster than the plain water did.
Wear Cool Colours
White and light-coloured clothes help you stay cool as they reflect sunlight away from you, while dark colours absorb light and heat, warming you up.
You can investigate this by placing ice on light and dark coloured plates and observing where it melts first.
Cool a Room with the Bernoulli Principle
In the evening, when it’s cooler outside than inside, point your fan out of one window, a few feet back, and open the other windows. This blows warm indoor air outside, creating a low-pressure area inside the room and forcing cooler outdoor air through other open windows, creating a lovely cooling breeze.
How does it work?
The fan blows warm air outside. Bernoulli’s Principle states that fast-moving air has lower pressure than still air.
The warm air leaving the room creates a low pressure zone inside the window, but the still air in the rest of the room is at higher pressure. To create a balance again, the high pressure air inside moves towards the low pressure window area to even things up.
As hot air is forced out of the window with the fan, cooler air rushes in from outside to fill the gap.
Keep a Room Cool with Aluminium Foil
It’s not a pretty solution, but in a heatwave we do what we can. A room where the sun enters through a window can get hot quickly. When sunlight lands on indoor surfaces and floors, they absorb the light and radiate it out as heat, which warms your room.
Aluminium foil reflects most of the light that hits it, and doesn’t easily absorb heat, so instead of sunlight entering a room, the foil reflects most of the energy back outside.
The best way to set this up is to cut a thick sheet of cardboard (like from a box) to the size of your window. Cover one side with foil, making sure the shiny side faces outwards.
Place the foil covered cardboard on the outside of the window. If you can’t get to the outside, you can put it on the inside, but you must use the cardboard too, or the window could crack due to it getting too hot.
The foil reflects the light and heat away from the window, and the cardboard acts as an insulator, blocking the heat.
Sponge Fight
Swap the water balloons for sponges! Soak clean small sponges in cold water and use as an alternative to water balloons. There’s no plastic mess to clean up, and sponges hold a lot more water than a standard water balloon, so they stay cold for longer.
More cool science ideas for kids
Cool a drink fast with ice and salt. This easy hack works in about 5 minutes, giving you a lovely cold drink much faster than putting it in a freezer.
Use the same salt and ice trick to make a magic fruit slushy.
Set up a selection of ice excavations. These are inexpensive, easy to set up and keep kids busy for a long time on a hot day.
Last Updated on July 7, 2026 by Emma Vanstone
