Junior Scientists Experiments

How does the trumbone work? Why do bigger drums sound deeper? Make a musical instrument and find out by changing the pitch of its sound.

What you need:

• Pieces of A4 card
• Empty Pringles Tube or something similar covered in white paper
• Sticky Tape

What you do:

Step 1

Make a tube by rolling the card over the Pringles container so it’s a nice snug fit but can slide up and down the tube. Secure with sticky tape. Repeat with the second card to fit on the end of the first.

Step 2

Make the tubes as long as possible and tap the tin. Make the tubes shorter and tap again.

What happens?

The more extended the tubes are, the deeper the sound.

How and why

When you tap the tube, you make the air inside it vibrate. These vibrations travel through the air to your ear when you hear them as sound. By making the tube longer or shorter you change the amount of air you vibrate, which changes the sound. This is how trumbones work: When you blow into them the air vibrates in the column; the longer it is the lower the pitch.

Some substances sometimes just can’t make up their mind whether they’re a liquid or a solid! See what we mean with this messy experiment

What you need:

• Cornflower
• Water
• A Wooden Spoon
• A bowl

What you do:

Step 1

Pour half a box of cornflower into a bowl. Then gradually pour water over and mix until it looks and feels like custard.

Step 2

Run your fingers through the liquid.

Step 3

Now try and punch the mixture with your fist.

What happens?

When you run your fingers through it, it acts like a liquid. But when you punch it, it becomes hard and behaves like a solid. (If it doesn’t try adding some more cornflower.)

How and why

The cornflower particles aer suspended in water, so it flows like a liquid. But when you apply force to it, the particles lock together, acting like a solid. As soon as the force stops, the slime goes back to being runny. Now roll some up and see if you can throw it to your friend before it turns back into slime!

You can’t walk through a wall, so you’d think that sound would travel through air more easily than through  something solid. Not so!

What you need:

• Wire coathanger
• Two peices of string

What you do:

Step 1

Tie a peice of string on to both ends of the coathanger.

Step 2

Twist the ends of the string around your fingers and press them to your ears (but don’t put your finger’s in your ears).

Step 3

Tap the coathanger gently with a metal spoon.

What Happens?

You hear a gong-like sound – but only when your fingers are pressed against your ears.

How and why

Sound vibrations travel through most materials better than through air. So when a coat hanger vibrates, the sound vibration travels up the string, along your finger and straight into your ear. The sound travels less well through air, so without your fingers pressed against your ears all you’ll hear is a faint tapping sound.

Gas just doesn’t like to be cramped into small spaces, and here’s a brilliant way to prove it. Just don’t do it indoors its guaranteed to be messy!

What you need:

• Mint Mentos (a type of sweet)
• A bottle of diet cola
• A thin plastic tube e.g. a vitamin C container, to tip the sweets into the bottle with.

What you do

Step 1

Load the Mentos into the tube.

Step 2

Pour the mentos from the tube straight into the diet cola bottle – you need to do this FAST!

Step 3

Stand back – quickly!

What Happens?

The cola shoots out like a fountain.

How and why

When you add the Mentos to the diet cola, a chemical reaction takes place between the two, and thousands of tiny bubbles are produced. These take up loads more space than the liquid alone did, so the pressure increases rapidly and…. Whoosh! Out comes all the foam. Try this experiment with other fizzy drinks – does it work better with full sugar versions? Or with fizzy water?