Curious Experiments

Fiery Skies

As the autumn evenings draw in and you’re using your reflective tags to stay bright and seen, you might notice some spectacular sunsets on the way home!

But have you ever wondered why the sky is brilliantly blue during the day, but then turns into magical oranges and reds in the evening? It all comes down to how light travels and scatters!

In the same way the retroreflective tags on your backpack bounce light back to cars, the gases and particles in our sky bounce sunlight in different directions. Here’s how we can build a sunset in a jar to see how it works.

What you need
– A clear container with flat, straight sides
– Water
– A splash of milk
– A torch
– A dark room
– A helpful adult

What to do
1. Find a nicely darkened room to become your science lab.
2. Fill your clear container with water.
3. Shine the torch directly through the water. You might see a tiny glint as the light reflects off a stray dust particle, but probably not much else!
4. Add a small amount of milk and try again. This time, look at the container from the side, across the beam of the torch. The water will suddenly have a magical blue tint to it.
5. Now, carefully look at the torch head-on through the container. You will be able to see a glowing yellow, orange, and red “sunset” shining through the milky water!

What’s happening?
White light is actually a secret mix of the whole rainbow! When it hits the milk particles, the blue light easily scatters to the sides (which is why our daytime sky is blue). But the longer red and orange lightwaves scatter less, and move straight through the cloudy water, creating a glowing sunset right in your kitchen.

Take it further!
Experiment with your atmosphere!
– Add a few extra drops of milk. Does your sunset get deeper, redder, or disappear completely?
– Look at the jar from directly above, and then from the side. How many different colours can you spot?

Balloon Racers

Ever wondered how giant rockets make it all the way to space? It all comes down to mass and force! The more mass an object has, the more force it needs to move. Because real space rockets are extremely heavy, they need a massive amount of fuel to generate enough force to escape Earth!

You might not have rocket fuel at home, but you can explore this concept right in your living room or garden. Set up a track, race these balloon rockets with your friends, and see exactly how changing the mass affects how far your rocket travels!

What you need
– A balloon
– Some thin string (thread or even tooth floss work well)
– A straw
– Sticky tape
– A clothes peg

What to do
1. Thread the string through the straw.
2. Set up your string racing tracks. Tie the string to an object (maybe a door handle or a tree), thread the straw onto the string, attach the other end of the string to another object, so the string is parallel.
3. Blow up the balloon. Don’t tie it – but twist and peg the end with your clothes peg, so the air doesn’t come out (yet!).
4. Using a few pieces of sticky tape, attach the balloon to the straw (that has the string through it, from step 1).
5. Get ready!
6. Release the peg and watch the rocket take off!
7. Get your friends to set up their own rockets and race!!

What’s happening?
It’s all about action and reaction! When you let go, the air trapped inside the balloon rushes out backwards. Thanks to a famous rule of physics (Newton’s Third Law), that backward push creates an equal and opposite push forward, zooming your racer across the room. This forward push is called thrust – and it’s exactly the same science that blasts real rockets into space!

Take it further!
Scientists love to test things out. Can you design a faster rocket?
– What happens if you only blow the balloon up halfway?
– What if you tape a coin to your racer to make it heavier?
– Does the rocket travel faster on a smooth string or a bumpy piece of wool?

Custard Armour

Did you know that custard has inspired protective clothing and materials… even things like bullet-proof vests, snowboards and firefighters gear!

You may usually have it with your pudding, but custard is a great example of a non-Newtonian material. These are materials that are soft or bendy, but go stiff or hard when hit, because they absorb energy.

But don’t just take our word for it. Here’s a curious experiment you can try at home to prove the theory!

What you need
– A large plastic sandwich bag
– A raw egg
– Custard powder
– Water
– A helpful adult

What to do
1. Make up the custard by mixing 1 part custard and 1 part water. It needs to be really thick, so it might be good to get an adult to help.
2. Put your egg in the large sandwich bag.
3. Pour the custard into the sandwich bag, making sure to fully surround the egg. Seal the bag (double check it’s sealed really well – get your helpful adult to check!)
4. Drop the sandwich bag from different heights. The custard should protect the egg so it reaches the floor unharmed!

What’s happening?
Custard is a non-Newtonian fluid. It usually acts like a liquid, but the moment it hits the floor, it instantly hardens into armour – saving your egg from a splatty end!

Take it further!
– Try rolling a handful of the custard into a solid ball in your palms. What happens the second you stop squeezing it?
– Rest a spoon gently on the surface, then try tapping it quickly and firmly. How does the liquid react differently?

Make a Quadrat

Biodiversity is all about the different types of living things that you find in an environment, from fungi and teeny tiny bugs to huge trees, and even humans!

There are over 70,000 species living in the UK! Here’s how you can become a back-garden biologist and find some of them, by making your own quadrat and going on a search for biodiversity where you live!

You can even share what you find with Cambridge Science Centre as part of their summer Ecological Survey!

What you need
– 8 bendy straws
– String or wool
– Scissors
– Patches of grass in a garden, park or field
– Paper and a pencil to record your findings

What to do
1. Join two straws together. Do this four times.
2. On each ‘double straw’, fold one at the bendy bit.
3. Lay the straws out in a square.
4. Join the square together with tape.
5. Tie four pieces of string across the square, from left to right and top to bottom, so the square is split into nine smaller squares. Your quadrat is now finished!
6. In a garden, park or field, place the quadrat on the ground and use the record sheet to mark down the plants and creatures you find inside each square of the quadrat. Write them down on your piece of paper.
7. Move the quadrat around to see which areas are more biodiverse. Are there more species in the sun or shade? Near the edge of the grass or in the middle? Write down what you find.

Take it further!
When you have your findings, get a grown up from your family to help you fill our one of our ecologist reports, as part of Cambridge Science Centre’s summer Ecological Survey (click below to get this!).