8 Simple Chemistry Experiments That Your Kids Can Do at Home

Follow these instructions to make an egg bounce while learning about chemical reactions.

You will need

Equipment needed for this activity includes:

• hard-boiled egg, with shell on
• glass of vinegar.

What to do

To make your eggs bounce you will need to:

1. Put the egg into the vinegar – you should see bubbles start to form on the egg.
2. Leave the egg undisturbed for at least a day. You should see some wonderful scum form.
3. Take the egg out of the vinegar and rinse it with water. The shell will rub off.
4. Give the egg a poke with your finger and squeeze it gently.

What’s happening

Vinegar, or dilute acetic acid, ‘eats up’ the calcium carbonate in the egg shell, just leaving the inner membrane, or skin, of the egg behind. As the calcium carbonate is responsible for making the shell hard, the vinegar soaked egg feels soft and rubbery.

When calcium carbonate (the egg shell) and acetic acid (the vinegar) combine, a chemical reaction takes place and carbon dioxide gas is released. That’s why you see the bubbles.

The chemical reaction keeps happening for about a day until all of the calcium carbonate in the egg is used up. Calcium carbonate is in eggshells, seashells, limestone, and many other materials.

Let’s have a closer look at the chemical reaction. Calcium carbonate’s formula is CaCO₃ and acetic acid is CH₂COOH.

So the reaction is: CaCO₃ + CH₂COOH -> Ca²⁺ (in the form of a salt) + H₂O + 2CO₂.

The calcium ions (Ca²⁺) float free in the solution. Ions are atoms or molecules that have an electric charge due to the loss or gain of electrons.

Applications

Limestone is a sedimentary rock that is largely made of calcium carbonate. It is ordinarily white, but may be coloured by impurities; iron oxide making it brown, yellow, or red and carbon making it blue, black, or grey. The texture varies from coarse to fine.

Most limestones are formed over thousands of years from the skeletons of marine invertebrates. Among the important varieties of limestone are marl, chalk, oolite, travertine, dolomite, and marble.

Acid rain causes reactions like the ones in this activity. One kind of acid rain can come from air pollution caused by burning fuels that have sulfur atoms, which when burnt produce sulphur dioxide gas.

When the sulfur dioxide mixes in with rain, it turns to weak sulfuric acid. When the acid rain hits the limestone it slowly makes it fall apart, like the egg shell did. People use limestone in buildings and statues.

This is why over time, buildings and statues are being damaged by acid rain.

If you collect small rock samples and drop them in vinegar, you may see bubbles appear, like they did on the egg. The presence of bubbles indicates that calcium carbonate may be present in the sample.

Calcium carbonate reacts with acids to produce carbon dioxide gas, which we observe as bubbles. This is called the ‘acid test’. The ‘acid test’ is one of many tests that geologists use to determine the identity of a rock sample.

Creating Crystals

You will need

• Sugar
• Salt
• Bi-carb soda
• Warm water
• 3 eye-droppers
• 3 spoons
• 3 plastic containers or bowls
• Measuring cup
• 3 small plastic cups
• Marker

What to do

1. Label the containers ‘sugar’, ‘salt’ and ‘bi-carb’.
2. Pour half a cup of warm water into the container labelled ‘sugar’.
3. Add a spoonful of sugar to the water and stir until dissolved. Keep adding sugar until no more will dissolve.
4. Repeat Steps 2 and 3, but with the salt instead of sugar.
5. Again repeat Steps 2 and 3, but this time with bi-carb soda instead of sugar or salt.
6. Label the small plastic cups ‘sugar’, ‘salt’ and ‘bi-carb’.
7. Use separate eye-droppers to put a few drops of each container’s solution into the matching cup.
8. Place the cups in a warm, sunny place and leave them until the liquid has evaporated. What do you see?

You can try this activity with other crystalline substances as well.

What’s happening?

When a solid (or ‘solute’) is dissolved in the water until no more dissolves, the solution is ‘saturated’. The amount of substance that dissolves in water increases with temperature. As the solution cools back down to room temperature, there is now more solute in the water than would normally be the case – the solution is ‘supersaturated’.

As the water evaporates, the solute precipitates out of solution in the form of crystals. This is an example of crystallisation. You will notice that each precipitate forms slightly different crystals: they might be different in size and shape. The size and shape of a crystal depend on a number of factors including chemical formula, temperature and pressure. In general, crystals that form slowly tend to be larger than crystals that form quickly.

Slime

You will need

• Cornflour
• Food colouring
• Small mixing bowl
• Plastic spoon
• Water

What to do

1. Pour some cornflour into a mixing bowl.
2. Stir in small amounts of water until the cornflour has become a very thick paste.
3. To make the slime the colour of your choice, thoroughly stir about five drops of food colouring into the mixture.
4. Stir your slime REALLY slowly. This shouldn’t be hard to do.
5. Stir your slime REALLY fast. This should be almost impossible.
6. Now punch your slime REALLY hard and fast. It should feel like you’re punching a solid.

You can keep your cornflour and water mixture covered in a fridge for several days. If the cornflour settles, you need to stir it to make it work well again.

What’s happening

Anything that flows is called a fluid. This means that both gases and liquids are fluids.

Fluids like water which flow easily are said to have low viscosity, whereas fluids like cold honey which do not flow so easily are said to have a high viscosity.

Cornflour slime is a special type of fluid that doesn’t follow the usual rules of fluid behaviour. When a pressure is applied to slime, its viscosity increases and the cornflour slime becomes thicker.

At a certain point, slime actually seems to lose its flow and behave like a solid. Cornflour slime is an example of a shear-thickening fluid.

The opposite happens in shear-thinning fluids; they get runnier when you stir them or shake them up. For example, when toothpaste is sitting on a toothbrush it is pretty thick, so you can turn the toothbrush upside down and the toothpaste doesn’t fall off.

But if it was that thick when you tried to squeeze it out of the tube, there is no way you could manage it. Fortunately, toothpaste gets runnier when you are squeezing it out of the tube. Other shear-thinning fluids include:

• blood
• paint
• ballpoint pen ink
• nail polish.

Although there are lots of shear-thinning and shear-thickening fluids, nobody has a really good idea why they behave the way they do.

The interactions between atoms in the fluids are so complicated that even the world’s most powerful supercomputers can not model what is happening. This can be a real problem for people who design machinery that involves shear-thinning fluids, because it makes it hard to be sure if they will work.

Snot Slime

You will need

• 1 tablespoon of unflavoured gelatine (from supermarkets)
• ½ cup golden syrup or glucose
• 1 tablespoon of salt
• Hot water
• Food colouring
• Heat-proof bowl

What to do

1. Place the gelatine and salt in your bowl.
2. Add ½ cup of syrup.
3. Add ½ cup of hot water. Now is the time to add food colouring if you want icky green or yellow coloured snot.
4. Mix every thing together and cool in a fridge for 30 minutes.
5. Run a fork through the snotty mixture to see what it looks like. Your mucus will get thicker and thicker as it cools, if it is too thick, you can add more water.

What’s happening?

You have just made a realistic model of your very own snot. Mucus is composed of water, epithelial (surface) cells, dead leukocytes (white blood cells), mucins (large proteins), and inorganic salts. Your home made mucus contains water, salt and proteins (gelatine is animal protein, usually made from beef or pig skin and hooves), almost like real mucus.

The gelatine dissolves in hot water making a thick solution, but is insoluble (won’t dissolve) in cold water. When cooled, the particles swell to make jelly-like goo.

Applications

Mucus has an important role to play in your body. In your nose it traps dust and anything else unwanted in the air. Mucus dries around particles which harden and this means it can take a quick exit out of your body when you blow your nose.

It’s your mucous membrane that makes snot, and this lines the inside of your nose and respiratory system. The outermost cells of this membrane produce the thick mucus fluid.

You may think that mucus is only found in your nose, but did you know that you also find it in your mouth, lungs, stomach and intestines!

When you get a common cold, an infection in your upper respiratory tract, your body produces loads more mucus than normal to carry away waste material. When sick, your mucus can change colour to yellow or green because of trapped bacteria, virus particles and white blood cells – the causalities of your body fighting the viral or bacterial infection.

Reference:

These experiments are from our partners at CSIRO.