Activities to Try at Home
Here are some try-at-home demonstrations from the Shell Questacon Science Circus.
- Balancing broomsticks
- Balloon party games
- Bouncing superballs
- Collision car
- Levitating water
- Making a good bubble mix
- Musical coathanger
- Plastic straw water pistol
- The best kind of parachute
- There's a balloon in my freezer
- Viscosity race
There's a balloon in my freezer
If you've seen someone from the Science Circus use Liquid Nitrogen in a show, you may think that you can't repeat any of the same “cool” experiments at home. WRONG! Although you won't be able to use liquid nitrogen, you can use your humble freezer to shrink a balloon.
What to do
- Blow and tie up a balloon to a medium/large size and tie a piece of string tightly around it.
- Place the balloon in a freezer for two days (don't remove any food from your freezer to make room for the balloon. We don't want you to starve for science).
- Remove your balloon and see if the string is looser, tighter or the same.
- Leave the balloon on a window sill for two days. Is there any difference in the tightness of the string now?
What happens?
When gas (in the balloon) is cooled down, it has less pressure and the balloon contracts and takes up less space. You should have noticed that the string was loose after being in the freezer. Once the balloon had been warmed up again near the window, the gas pressure inside should have increased and the balloon increased in size and the string should be fitting snugly again.
What would happen to you if you were thrown into outer space? Why is force and area important for pressure (think about a bed of nails or a stiletto shoe heel)? You may have seen the Science Circus perform some demonstrations using air pressure and the possibility of pain...
The following two demonstrations show unbalanced pressures.
Levitating water
You will need
- Drinking glass
- Piece of cardboard
- Water
Fill the glass with water—right up to the very top. Slide the paper card across the top of the glass. Carefully turn the glass upside down, holding the card in place. Gently let go of the card. What happens to the water?
Practice this experiment over a sink or basin until you have mastered it.
What happens?
The atmospheric pressure pushing up on the cardboard (1000 g/cm2) is greater than the weight of the water pushing down on the cardboard (1 g/cm3), so the water stays in place.
Plastic straw water pistol
You will need
- Plastic straws
- Glass of water
Cut 1/3 off the end of a straw. Put this into a glass of water. Using the remaining piece of the straw, blow through the straw so that the air passes across the top of the straw in the water. This should produce a spray of water.
What happens?
The air blown out of the straw moves quickly, which makes a low pressure area over the vertical straw. Pressure pushing down on the water in the rest of the glass is stronger than the pressure pushing down on the water in the straw, so the water rises in the straw and can be sprayed like a water pistol.
Balloon party games
Balloons of all shapes and sizes are used to demonstrate pressure, static electricity, forces and air as a fuel. Balloons are great fun because there are so many cool things you can do with them. You can pick up glass jars using just a balloon, make your hair stick on end, and stick cups onto the side of balloons without using glue or sticky tape! An activity you can do at home is to make a balloon kebab!
You will need
- Two balloons
- A wooden skewer
What to do
- Blow up the two balloons to a medium size and tie the top.
- Quickly poke the skewer through the side of the first balloon and see what happens.
- With the second balloon, carefully push the skewer through the dark end of the balloon near the knot where you tied the top. What happened? Can you carefully push the skewer through the other dark patch without bursting the balloon?
What happens?
When you skewer a balloon through the side it pops, but when you push a skewer carefully through the top of the balloon it doesn't pop! This is because the rubber on the side of a balloon is stretched very tightly and will pull away rapidly when the balloon is pierced, hence popping the balloon. At the top or the bottom of the balloon, the rubber is much thicker and not stretched enough to cause the rubber to pull away when a small hole is made by the skewer. In fact, the skewer acts as a plug for the hole, preventing any air from escaping the balloon, hence creating the skewer kebab!
Making a good bubble mix
To make a strong bubble mix solution the following ingredients are recommended:
- 1 part detergent (Morning Fresh works well)
- 2 parts water
- 10% glycerine (in this case, 0.3 parts)
Making bubbles
To make bubbles stronger, you can add a little more glycerine and leave the bubble mix for a while. The longer you leave the mixture, the stronger and better the bubbles will be. Give the mix a good stir before use and remove any froth before making your bubbles. Bubble making works best on cooler, moist days, otherwise they dry out and pop too fast.
To clean bubble mix from surfaces, spray vinegar over the area and wipe up.
Wash and dry metal bubble frames after each use or they will rust.
The best kind of parachute
So you want to drop toy soldiers from high places. Well, as long as you DON'T JUMP AFTER THEM, here is the best way to make a toy parachute.
What to do
- The trick is to use something light and strong for the parachute canopy. The Science Circus recommends a large, square piece cut out of a big garbage bin liner.
- Fishing line is best for the harness. Cut four pieces of line to the same length.
- Tie one end of each piece to the four corners of the parachute. (You might need to use sticky tape to stop the plastic ripping.)
- Tie the other ends to the soldier, or Barbie doll, or whatever. (Actually, the whole doll is probably too heavy, maybe you should just use her head).
- Holding the parachute in the middle, drop it from a dizzying height. (Try standing on a chair.)
What happens?
Air gets caught under any large, flat surface. The trapped air creates aerodynamic drag, slowing the parachute's fall. Some seeds and animals also glide (fall more slowly) because their wings act a bit like a parachute.
Bouncing superballs
Colliding balls, superballs and putty help to show how the surface of an object and energy are important in how it behaves.
Superballs can be a lot of fun because they are different to a normal rubber ball.
Try throwing your superball so that it bounces from the floor to the underside of a table or flat piece of board held by someone else. Try the same thing with another type of ball, such as a golf ball.
What happens?
The superball behaves a little strangely! Instead of bouncing all the way through to the other side, the superball will bounce back to you!
Why?
To help answer this, try holding the superball in your fingertips and rubbing it along a smooth, dry surface such as a glass table top. Did you find that the superball strongly grips the surface?
Although the surface of the superball looks smooth, the rubber molecules which make up the superball show a large amount of friction when the ball contacts another surface. This makes the superball behave as if it has a very rough surface. The superball is also very elastic. This means that when it collides with something most of the energy is converted into the rebound movement, and so superballs are very bouncy!
Collision car
Another interesting demonstration in the collisions show is the car crash. The car crash car is one that can be made by anyone at home.
You will need
- 1 shoe box
- 4 flat cardboard wheels
- 6 pieces of wire
- 1 marker
- some aluminium foil
- some cling wrap
- some sticky tape
What to do
The shoe box will be the car body. Read steps 1-3 before beginning.
- On the front of the box wrap around a piece of aluminium foil which will be the crumple zone for the front of the car.
- Fold the foil over at the front so the front of the car looks solid, but leave the underbelly open so that you can put your fingers under this and push the foil back out after a crash.
- The foil should stick out about 8 cm when it is folded. Using some sticky tape to hold the foil together.
- Repeat this for the back of the car.
- On the top of the car draw a 10 x 10 cm square. Place wires about 10 cm high in each corner of the square. Make these stable by sticky taping the bottom of the wire to the underside of the box.
- Wrap the wire with aluminium foil to make it stronger. Over the top tape a sheet of foil which will be the roof.
- Around the side of the wires wrap cling wrap which will be the windows.
- Run two longer pieces of wire through the sides of the car, which are the axles for the car. Attach to each side a cardboard wheel which has a hole in the centre for the wire to be threaded through. Bend the wire over so that it will not come back out of the wheels.
- Draw on a licence plate and windows with the marker, also add some headlights if you like.
You now have your own crash car, which can be increased and used again after each crash.
Balancing broomsticks
It's something we do every day and take for granted—balance!
This is an easy experiment you can do by yourself. All you need is a long object like a broomstick, mop, ruler, golf club or an ordinary stick.
Hold your hands out in front of yourself with your palms facing each other and your thumbs pointing towards the sky. Balance the object between your thumb and index finger, making sure you are not holding the object with your thumb. At this stage your hands should be spread apart so they are supporting the object at its ends. Now move your hands showly together as if you were clapping in slow motion. Try not to move your hands quickly.
Where your hands meet is the object's balance point—the point at which the object can be balanced. Try balancing it using only one finger.
Did you notice that your hands did not move together? First one hand slides then it comes to rest then the other moves. This is because of a force called friction. Friction acts between the skin of your fingers and the object.
To see this effect better, start with both hands at the balance point with your thumbs up and palms touching each other. Now try and move your hands away from each other towards the ends of the object. Did only one hand move? The hand that does not move is closer to or at the balance point and so is carrying most of the object's weight. This hand is harder to move because there is more friction. It is like when you press your hands together really hard and then try to slide one over the other—it's very hard to do because there is more friction between your hands than if you only had your hands pressed lightly together.
Viscosity race
Sometimes the Science Circus conduct a thought experiment to demonstrate the viscosity of normal fluids. Imagine a glass of water in one hand and a glass of honey in the other. Pour them at the same time to see which one lands first. You can also have a real race between different fluids.
WARNING! this is a messy experiment. Do it outside or make sure that the work area is covered with newspaper.
You will need
- 3 drinking glasses
- 3 dinner plates
- 3 people
- pencil or whiteboard marker
- water
- cooking oil
- honey
What to do
- With the pencil or whiteboard marker, mark a starting line on one side and a finish line on the other side of each plate.
- Place a tablespoon (20 ml) of water, cooking oil and honey in separate glasses.
- Give 3 people a glass each. Tip the glass onto its side on the dinner plate, making sure that the rim of the glass is on the starting line. Which fluid wins the race?
What happens?
Viscosity is a measure of how easily a fluid flows. The word comes from the Latin for ‘sticky’. The three fluids have different viscosities. The viscosity of a normal fluid can change according to temperature. Try heating or cooling the fluid before the race! You should find that the viscosity decreases when you increase the temperature.
Musical coathanger
This demonstration shows how sound travels differently through solids compared to air.
You will need
- a wire coathanger
- two 1m long pieces of string
- a ruler
What to do
- Tie a piece of string to each corner of the coathanger.
- Tie the other end of each string to the index finger of each hand.
- Lean over and (carefully!) place the fingers with the string on them into your ears. Let the coathanger swing freely.
- Get someone else to tap the coathanger with the ruler.
- Listen for the loudness and length of the sound.
- Now get someone else to try it and listen to the sound.
What happens?
With the musical coathanger in your ears the sound you hear is much louder and longer than without it in your ears. The sound made when you hit the coathanger travels through the string and your fingers to your ears much better than it travels through the air. Try placing your ear on a table and hitting the table and you will notice that sound travels much better through solids than through air.
