Place the outside box of the match box upright on a table.
Put the inner box upright on top of the outside box.
Try to smash the construction from the top using your fist. What happens?
Now, place only the inner box of the match box upright on a table.
Try to smash the inner box with your fist. What happens now?
When hitting only the inner box, it will smash. However, if inner and outer box are placed on top of each other, they do not smash, but fly off undamaged in a high curve.
The reason is that the inner box can divert pressure to the outer box when both are placed on top of each other. The boxes fly off because their edges are not rigid, but flexible. The elastic energy from the edges is transferred to kinetic energy.
If one box is placed by itself, pressure cannot be diverted and the box is smashed.
When objects are not moving or moving at a constant speed, the forces on them are balanced. We are going to try and balance the force of gravity and the force from a hair dryer’s air stream on a table tennis ball.
You will need
1 Table tennis ball
1 Hair dryer
What to do
Point the hair dryer upwards and turn it on.
Carefully place the table tennis ball in the air stream.
The table tennis ball should float in the hair dryer’s air stream.
You might have to play with the strength of the air flow to get things exactly right.
If you get it to work, try to tilt the hair dryer and see how far you can tilt it, before the ball falls off.
When the table tennis ball is floating the forces of the hair drier’s air stream and gravity are exactly balanced.
Our eyes can only see a certain amount of pictures per second. They are actually quite slow. This is why we cannot see objects that are moving extremely fast. In this experiment we are going to use the slowness of our eyes.
You will need
Pens or colouring pencils to draw a picture
What to do
From the paper cut two pieces with the same shape and size.
Draw two different pictures on the two pieces of paper that can also go together, for example a rabbit on one piece of paper and grass on the other. You could also do a bowl of water on one piece and fish on the other one. Or a bird on one piece and a tree on the other one for the bird to sit on.
Tape both pieces of paper on either side at the end of a pencil. The pictures need to face outside.
Now rub the pencils between your hands as if it was a stick that you want to light a fire with.
Look at the pictures.
You will see both pictures combined together, for example the rabbit sitting on the grass or the fish in the bowl.
The reason this works is that our eyes are too slow to follow the fast movement of the pictures and can only see a limited amount of pictures per second.
When a balloon is rubbed against hair, a towel or a jumper, it gains more electrons which have a negative charge. This gives the balloon an overall negative charge. Objects with a positive charge or no overall charge like a tin can will now be attracted (= be drawn) to the balloon. We call this “static electricity”.
You will need
Towel, jumper or your hair
Empty soda can
A smooth surface, e.g. a table
What to do
Blow up the balloon.
Put the empty soda can on its side on a smooth surface.
Rub the balloon on a towel, jumper or your hair to create static electricity.
Hold the balloon close to the side of the soda can, but do not let them touch.
Slowly move the balloon away from the soda can along the surface.
Observe what happens.
Rub the balloon again on a towel, jumper or your hair.
Open the water tap, so that only very little water is running. It should be almost dripping.
Hold the balloon close to the water, but do not let the balloon touch the water.
Density tells you how heavy a certain volume of a substance is. It decides which materials can float on water and which sink. For example, a rock will sink because its density is higher that the density of water. However, wood floats because its density is lower than that of water.
The same is true for liquids. Liquids with high densities sink, while liquids with lower densities float. We are going to use this to make a rainbow in a glass. Chocolate sauce has a highest density of the four liquids and will stay at the bottom. However, water has the lowest density and will, therefore, float on top.
You will need
Washing up liquid
Red food colouring
What to do
Start by pouring chocolate sauce into your glass until it is one quarter full.
Use the spoon to carefully add the honey until your glass is half full. Do NOT stir!
Now add the washing up liquid slowly and until your glass is three quarters full.
In a separate glass mix water with red food colouring.
Carefully add the water dropwise until your glass is full. Do NOT stir!
Air is made from gas particles. They constantly move around at a high speed. When speeding around like this, the particles often collide with the walls of their containers. For example, the air particles in a balloon move around and hit the balloon’s walls. These collisions cause the balloon to stay inflated. We call this gas pressure.
There are two ways to affect gas pressure. One is to change the number of air particles. When you blow up a party balloon, you add more air particles to it. More gas particles hit the walls more often and the balloon’s pressure increases.
The second method to increase pressure is by raising the temperature. When it is warmer, the gas particles have more energy and move faster. If the particles move faster, they hit with the walls more often and the pressure increases. When decreasing the temperature by cooling, the gas pressure will decrease.
In this experiment we are going to look at what happens to the pressure inside a plastic bottle when you cool down the temperature.
What you will need
1 empty plastic bottle (a small bottle is enough, 500 ml or even smaller)
What to do
Remove the lid and put the empty plastic bottle in the sun or on the radiator to heat up a bit.
Close the lid tightly, so nor more air can move in or out of the bottle.
Put the bottle in the freezer and wait for one hour.
Collect the bottle from the freezer. What has happened to it? Take notes.
Now observe the bottle for a couple of minutes after taking it out of the freezer.
1. What happened to the bottle in the freezer?
2. Why did this happen? Look back at the introduction to find some clues.
3. What happened to the bottle after you took it out from the freezer?
4. Why did this happen? Look back at the introduction to find some clues.
5. Why was it important to close the lid tightly before putting the bottle into the freezer?
In a gas, the particles move around at high speed. By doing this they collide with the sides of their container and produce a force. This is the force that keeps balloons and tires inflated. We call it gas pressure.
There are two ways to increase gas pressure. The first is to add more gas particles. More gas particles can collide with the walls more often which increases the pressure. This is what happens when you blow up a balloon or pump up your bike tire. You add more air particles.
The second way to increase gas pressure is to increase the temperature. When it is warmer, gas particles gain more energy and can move around faster. At a higher speed the particles collide with the walls more often and the pressure increases.
If you reduce the temperature, the opposite happens. The gas particles move slower and collide with the walls less frequently. This decreases the gas pressure.
What causes gas pressure?
How can you increase gas pressure? Describe both ways.
How can you decrease gas pressure?
What would happen if I put a party balloon into the sun on a hot day? Why?
What would happen if I put a party balloon in a freezer? Why?
Some pieces of chocolate (dark chocolate works best, but you can use milk chocolate too)
What to do:
Put water in the pan and place it on the hob.
Break the chocolate into small pieces and place it in a bowl over the pan with the water. (See image above.) Be careful not to mix any water with the chocolate.
Turn on the hob and gently heat the water with the chocolate and bowl on top.
Once the chocolate has melted, turn off the hob.
Place half of the molten chocolate in a freezer to cool. If you do not have a freezer, you can use the fridge.
Let the rest of the chocolate cool slowly at room temperature.
Once both chocolates have frozen, compare what they look like. In addition, test how they taste differently and how they feel to the touch.
Although both chocolates freeze and become solid again, they will be very different depending which temperature they are freezing at.
A) Draw a diagram showing the arrangement of the chocolate particles in a solid. B) Draw a diagram showing the arrangement of the chocolate particles in a liquid.
What happens to the energy of the chocolate particles when it melts?
What happens to the energy of the chocolate particles when it freezes?
How is the chocolate that was cooled in the freezer different from the chocolate cooled at room temperature? Compare how they look, taste and feel when you touch them.
The process of melting and freezing chocolate is quite important in food industry and chocolate making. Based on your experiment which temperature do you think is better for freezing chocolate, room temperature or the freezer/fridge? Why?