5 experiments for kids using eggs

Each of these 'eggsperiments' comes recommended by the people behind British Science Week and can be done from the comfort of your kitchen, using things you'll already have.

1 Egg in a bottle

Can you get a milk bottle to suck an egg in without you touching it? Kids never cease to be amazed by this little trick, no matter how many times you show it to them.

What you'll need: one hard boiled egg, peeled; boiling water; a heat-proof glass bottle with a neck slightly smaller than the egg (e.g. milk bottle).

1. Set the egg on the neck of the bottle to demonstrate that the egg simply won't fit in the bottle. Tell the child that you know a trick to make that egg go down into the bottle without touching or breaking it.

2. Remove the egg from the bottle and pour the boiling water into the bottle. Carefully roll the water around in the bottle and then pour it out.

3. Quickly put the egg back on the neck of the bottle and wait for it to get sucked down into the bottle.

When you put the hot water into the bottle and then pour it out, the hot water leaves steam behind in the bottle. The steam forces out some of the air that was already in the bottle.

As the steam in the bottle cools down, it converts into tiny droplets of water. The drops of water require less space and this reduces the amount of air pressure in the bottle. The pressure on the outside of the bottle is greater than the pressure on the inside, and that is what forces the egg into the bottle.

2 Hardboiled or raw?

What you'll need: two eggs, one hardboiled and one raw; a flat surface.

Can't remember which egg is which? The answer is only a spin away. Simply spin the egg and pay close attention to how well it spins. If the egg spins well, it's hardboiled. However, if the egg wobbles and spins slowly, it's raw. A hardboiled egg is solid inside, whereas a raw egg is fluid.

When you spin the raw egg, its centre of gravity changes as the fluid inside the egg moves around. This results in the wobbling motion you noticed in the raw egg. As soon as the raw egg starts spinning, touch it briefly with your finger just long enough to stop it. When you take your finger away, the egg will continue to spin for a while, but a hard-boiled egg will stop dead.

This is due to the inertia of the fluid inside the raw egg. When the hardboiled egg is spun, the solid centre immediately moves with the shell, causing little resistance to the spinning motion.

3 Soft-shelled eggs

What you'll need: one egg (hard boiled is less messy if you accidentally break it, but you can use a raw one); one cup vinegar; clear jar or glass.

Pour one cup of vinegar into your jar. Add the egg. Record what you see (bubbles rising from the egg.) Leave the egg in the vinegar for one day. Remove the egg and feel it. Record your observations (the egg shell will be soft.)

Eggs contain something called 'calcium carbonate'. This is what makes them hard. Vinegar is an acid known as acetic acid. When calcium carbonate (the egg) and acetic acid (the vinegar) combine, a chemical reaction takes place and carbon dioxide (a gas) is released. This is what the bubbles are made of.

The chemical reaction keeps happening until all of the carbon in the egg is used up - it takes about a day. When you take the egg out of the vinegar, it's soft because all the carbon floated out of the egg in those little bubbles.

Now try this

Leave the same egg sitting out on the table for another day. Now feel it again. It's hard! The calcium left in the egg shell stole the carbon back from the carbon dioxide that's in the air we breathe.

OR: If you were using a raw egg, once the shell has softened, you can place the egg in water and it'll absorb and expand via osmosis until the shell finally bursts.

4 Can you make an egg float?

This experiment will be too difficult for younger kids to grasp, but school-age children should be able to do it. The idea is to demonstrate buoyancy and how the density of water affects it.

What you'll need: three tall, clear drinking glasses (identical ones are best); three eggs; a tablespoon; something to stir the water gently (e.g. a straw); water; salt.

1. Fill each of the glasses halfway up with water. Put one egg in each glass. Choose one of the glasses to be the control glass (Glass 1). That means that you won't do anything to it and it will give the child something to compare the other glass to.

2. Now, begin adding salt to one of the non-control glasses (Glass 2). Start by adding three tablespoons of salt to Glass 2 and gently mixing it up in the water with a stir stick. Get the kids to tell you what happens…

3. Add ten tablespoons of salt to the other non-control glass (Glass 3) and gently stir it up. Slowly pour water into the glass until it is full, but don't stir it, so that you try to keep as much of the salty water at the bottom as you can.

What you should observe:

Glass 1: This glass simulates a fresh water environment. The egg will sink to the bottom in fresh water.

Glass 2: This glass simulates a salt water environment. The egg should rise to the top of the water and float in this glass.

Glass 3: This glass shows what happens when you add fresh water to salty water. The egg should be suspended in the middle.

The more dense a liquid is, the greater its buoyancy and the easier it is to float. Salt makes water more dense. When you add fresh water to the denser salt water, it will float also. In fact you can tell exactly where the salt water and the fresh water meet in the glass by where the egg is floating.

5 Boiling water myths

Which egg boils faster: the egg on the intense heat or the egg on the lower heat?

What you'll need: a cooker; two pans of water; two eggs.

Bring two pans of water to the boil. Once they are both boiling, turn the temperature under one pan up to full heat, and keep the other simmering over a low heat. Now pop an egg into each pan.

Which egg do you think will cook the fastest? Wait for 5 minutes then cut the tops off the eggs. You will see that they are both cooked to the same degree.

Once water has reached 100ºC, it doesn’t get hotter, it just evaporates. So turning up the heat on one of the pans doesn’t make any difference. This is a great lesson on boiling points and wasted energy.