Wimbledon Common Preparatory School Assembly

Workshop - Reception


What’s the science behind (or inside) a bubble? Bubbles provide the opportunity to study science concepts such as elasticity, surface tension, chemistry, light, and even geometry.

What is a bubble?

A bubble is air wrapped in “film”. Can you blow bubbles just with water? Yes you can but water bubbles will only live for very short time due to strong water surface tension.

Real bubble is air wrapped in soap film. Soap film is made from soap and water (or other liquid). The outside and inside surfaces of a bubble consist of soap molecules. A thin layer of water lies between the two layers of soap molecules, sort of like a water sandwich with soap molecules for bread. They work together to hold air inside. Washing up liquid lowers the surface tension of water. It makes the water stretchy and wibbly-wobbly so that you can blow bubbles.

Why is a bubble round?

Bubbles can stretch and become all kinds of crazy looking shapes. But if you seal a bubble by flipping it off your wand, the tension in the bubble skin shrinks to the smallest possible shape for the volume of air it contains. That’s why even if it had a goofy shape before you sealed it, once sealed shut, the bubble will shrink into a sphere shape. Compared to any other shape, a sphere has the smallest surface area for the amount of volume.

Why do bubbles pop?

Other than being poked or landing on something sharp, bubbles pop when the water between the soap film surfaces evaporates. To note, when it’s cold, those molecules take longer to leave. If you blow a bubble on a calm winter day, a bubble can even freeze and last for several minutes before it wisps away. Also, the colder the outside temperature is, the higher a bubble might fly. That’s because the warm air from your breath is lighter than cold air.

A bubble gets its colour from light waves reflecting between the soap film’s outer and inner surfaces. The distance between the layers gets smaller as the water evaporates, making the colours change. Bubbles can also reflect what’s around them, like the faces peering at them.

Why do bubbles stick together? Since a bubble tends to minimize its surface area, bubbles will join together to share one common wall. Three bubbles will meet at the centre, always at an angle of 120 degrees. When bubbles are about the same size, they form perfect hexagons. Bees do the same thing when they build a beehive. Bees, like bubbles, are also very efficient with their spaces. They use the minimum amount of wax to create their spaces.

Exercise 1

Equipment: Each class will need:

1 squeezy bottle of fairy liquid

1 squeezy bottle of glycerine

Small Measuring cups

Large bowls (one per pair)



Make a bubble solution

Give out one plastic bowl to every pair of children. Make sure each child is wearing a blue apron provided

Use the small plastic cups to add 2 cups of water to their large plastic bowl.

Next add ½ cup of washing up liquid and 3 ½ tsp of glycerine----Glycerine stops bubbles from drying out so they don’t pop as quickly.

Now each child will spoon some mixture onto their plate with their spoon. Have a go at blowing with different types of straws – do some work better than others? See if you can try and blow a bubble inside a bubble!

Exercise 2

Cut off plastic bottles

Muslin squares

Rubber bands

Get your plastic bottle with the base cut off. On the base end, cover with the piece of muslin provided and secure with an elastic band. Pour some bubble mixture on your plate and with the muslin end of the bottle touching the surface of the plate, blow down into the smaller neck of the bottle and move your head up so you create a bubble tower. MAKE SURE YOU DO NOT SUCK IN. IF YOU NEED A BREATH, TAKE YOUR MOUTH AWAY FROM THE BOTTLE!

Workshop - Year 1

Optional video to watch - "About energy " - play first 7.35 minutes!

Making Flip Cards


This workshop is all about the release of stored energy. The energy is stored inside the rubber band when it is stretched, and when it is released, the band transfers its energy making the cards flip in the air.


Equipment Needed:

2 plastic cards with holes in

Cloth Tape

Rubber band

Paper clip

  1. Place 2 cards horizontally next to each other. Make sure that the holes are at OPPOSITE ends from each other.

  2. Tear (with your hands) 10-15cm of cloth tape and lay it flat on your surface sticky side up.

  3. Place the cards slowly and carefully on top of the tape so that it creates a ‘hinge’ down the centre. Flip the excess tape over the other sides of the cards connecting them together. NB: there should be a couple of mm between each card so they are not completely touching.

  4. Take an elastic band and thread it through one of the holes. Loop one end through the other so you are knotting it around. With the other end, thread it across to the other hole on the other card.

  5. To test, fold the cards back on themselves until they touch and then let go – they should flip high into the air as the stored energy is released.

  6. When you know your flip card works, you can attach the loose end of the rubber band to a paper clip and fasten down with a small piece of cloth tape.

Workshop - Year 2

Optional video to watch - "About energy " - play first 7.35 minutes!

Making Catapults


This workshop is all about the release of stored energy. The energy is stored inside the spring of the peg. When the spring is released, it transfers its energy making the catapult flip and the ball rocket into the air.


Equipment Needed:

1 wooden peg

1 and ½ lolly sticks

Bottle cap


Double sided sticky tape

  1. Attach two pieces of double sided sticky tape to both outside lengths of the wooden peg.

  2. Attach the longer lolly stick to one side and the shorter lolly stick to the other side.

  3. On the side with the shorter lolly stick, attach a small square of double sided tape and stick your bottle cap on top. Make sure you leave space (around an inch) for your thumb to press down on the peg. This is your ball holder.

  4. Have fun launching your ball!