Make paper windmills.
You can make your windmill go round and round by blowing it. But you could also make it go round by holding it over the top of a boiling kettle. [demonstrate] You should never play with kettles, though, ask an adult to help you if you need to use one for an experiment. Today we are going to look at how power stations work – particularly nuclear power stations. Does anyone know what power stations are for?
Most power stations use generators to make electricity. A generator takes a round and round movement and turns it into electricity. In nuclear power stations the round and round movement comes from steam, just like the kettle I used to make my windmill spin. You can turn round and round movements into electricity by using magnets. Faraday’s Law tells us that when you move a magnet inside a coil of wire you create an electric current. I can demonstrate this with a multimeter, if I move the magnet in and out of the coil of wire, the number on the screen shows that I create a current. A generator, however, has a big magnet around the edge and a coil that spins very fast inside it. I’ve got some simple models here. If you spin the axles very fast the LEDs will light up, showing that you have made electricity flow. To make the axles spin very fast, you need to wrap some string around tightly then pull it away hard. [demonstrate, then give out motors so the children can have a go.]
You do need to be patient with this experiment. We found that some attempts didn’t quite work, but after a few goes all the children managed to succeed at least once.
This week we are focussing on Nuclear Power stations.In power stations steam spin turbines that spin generators to generate electricity. Nuclear power stations use nuclear fission to heat water and make steam.
Some atoms are radioactive.
As we have mentioned before, atoms are made up of protons, neutrons and electrons. Every element contains these same basic ingredients, but different amounts of these ingredients forms different elements.
If you have lots of protons and lots of electrons you end up with a less stable element.
It’s sort of like this. If I pour a little bit of sand, it makes a neat pile, but if I keep pouring and put lots of sand grains in my pile, I end up with an unstable pile and grains start to tumble off.
Elements with lots of protons and electrons are unstable, they have a tendency to break apart and we call this being radioactive. When parts of the Uranium atom break away, you end up with different elements and every break releases energy in the form of heat. It’s that heat that is used to boil the water.
Uranium is a radioactive element. It has 92 Protons and 92 Electrons and 143 or 146 Neutrons. That’s a lot!
Now, when I poured the sand, I didn’t know how the big pile was going to collapse, or exactly when it would happen. And it’s like that with Uranium. We don’t know when any single Uranium atom is going to decay. If we have enough atoms, however, we can make a pretty good guess as to how long they will take to decay. We’re going to demonstrate this with some M&Ms. [give out M&M experiment sheets.]
Break for drink and snack and put away the tables.
When we did our M&M’s experiment, all the sweets fell independently. But that’s not exactly what happens in a nuclear reactor. Inside a nuclear reactor something called a chain reaction takes place. When a uranium atom decays, it breaks down into fission products and loose neutrons. These loose neutrons hit other uranium atoms, causing them to decay, emitting more loose neutrons, which hit more uranium atoms and so on and so on.
Though there are plenty of people online who can do this, we found it very tricky!
Luckily, I also took along some packets of dominoes and the children had a lot of fun making chain reactions with those!