Tag Archives: experiments

#TryThisTuesday: Rock Candy

This weeks Try This Tuesday takes a while, but you end up with a tasty treat!

You will need:

  • A wooden skewer or chopstick
  • Peg
  • 1 cup of water
  • 2-3 cups of sugar
  • A narrow glass or jar

pic

Clip the wooden skewer into the peg so that it hangs down inside the glass and is a couple of centimetres off the bottom.

Put the water into a pan and bring it to the boil. Pour about a quarter of a cup of the sugar into the boiling water and stir until it dissolves.

Keep adding more and more sugar, each time stirring it until it dissolves, until no more will dissolve. This might take quite a while!

When no more sugar will dissolve remove it from the heat and leave it to cool for about 20 minutes.

Pour the sugar solution into the glass or jar almost to the top. Then put your skewer back into the glass so it hangs down and doesn’t touch the sides.1st

Leave your glass in somewhere it won’t be disturbed. The sugar crystals will grow over 3-7 days. Once these have grown you can eat them!finished-product

The Science

By mixing the sugar and water together when they were really hot, you have created a super saturated solution. This means that the water contains much more sugar than in could in normal circumstances. As the water cools back down the sugar leaves the solution (mixture) and becomes sugar crystals again, forming on the skewer.

Supersaturated solutions are used in real life. In a sealed fizzy drink the drink is saturated (full) with carbon dioxide, as the carbon dioxide is put in using pressure. When you open the drink, the pressure of the carbon dioxide is decreased, which causes your drink to be supersaturated as there is much more carbon dioxide dissolved than there would be at normal pressure. The excess carbon dioxide is given off as bubbles.

#TryThisTuesday: Easter Eggsperiments

As Easter is coming up we’re treating you to four experiments instead of one this week! And a little video showing Ellie and Clare demonstrating each of them (or at least attempting to!)

1. Hard-boiled Egg Test

Our first eggsperiment requires a hard boiled egg so we’re going to show you how you can test if an egg is hard boiled or not.

Lay a hard-boiled and a normal egg flat on their sides and spin them. Put your finger on the eggs to stop spinning them and then let go. The one that starts spinning again is the raw egg.

This is all due to momentum. When you spin the eggs you spin their insides too. In the hard boiled egg, the insides are fixed to the shell so it behaves as you would expect. In the raw egg the insides continue to spin after you’ve stopped the shell. When you let go, the momentum of the spinning yolk carries the shell and the whole egg starts spinning again.

 

2. Egg in a Bottle

Now we know which is our hardboiled egg, we need to peel it for next experiment. This one requires a glass bottle, a match and of course, the egg.

If we place the egg on top of the bottle it doesn’t look like it’s going to fit in. But if we light the match and drop it into the bottle then after a second place the egg on top, the egg will squeeze into the bottle.

The match heats up the air in the bottle, causing it to expand slightly. The egg creates a seal so more air cannot enter. As the air cools inside the bottle it decreases the pressure and forces the egg into the bottle.

 

3. Naked Bouncy Egg

To make a naked bouncy egg you will need an egg, white vinegar and a beaker. Place your egg in the beaker and pour in enough vinegar to cover the egg. Leave you egg here overnight.

The egg shell is made mostly of calcium carbonate, this reacts with the acid in the vinegar and dissolves to leave a naked egg. It also produces carbon dioxide gas, so as your egg is soaking you may see little bubbles of CO2 forming around it.

After a day, carefully remove you egg from the vinegar and wipe away any remaining shell. You should see that it’s now quite rubbery and bouncy as well.

 

4. Bouncy Elastic Egg Drop

For this final eggsperiement you can use your bouncy naked eggs but we’re cheating a little bit and using rubber eggs. For this you will need to take two rubber eggs and join them together with a piece of elastic or a string of elastic bands.

When you hold your eggs next to one another and let go they both hit the floor at the same time as you might expect. But what do you think will happen if we just hold the top egg and let the other hang below it, which will reach the floor first when we let go?

Gravitational acceleration is the same no matter the weight or mass of an object, but when we add elastic between the eggs, this adds an extra force that speeds up the drop of the higher up egg as the elastic pulls them together.

 

#TryThisTuesday: Making coins shiny again

New coins are always bright and shiny but they quickly become dull and tarnished. Today we are going to make our coins shiny again!

You will need 100ml of vinegar, some tarnished copper coins and a bowl.vinegar

Pour the vinegar into the bowl and add the salt. Mix until the salt is dissolved.

img_4336

Try dipping a coin in and holding it there for 5 minutes. See how half becomes really shiny!

half

Put all your coins in and leave for 30 minutes. If you put lots of coins in the vinegar may turn green.img_4337

Make sure you rinse all the coins with clean water.

The Science

Coins become dirty due to oxygen in the air reacting with the metal to form copper oxide. They become darker as they age as the oxide layer increases. Vinegar is an acid (acetic acid) which can be used to clean up surfaces and remove the unwanted oxides. Acids release positively charged hydrogen atoms, also known as Hydrogen ions (H+) which react with the negatively charged oxygen in copper oxide and produce water (H2O). The copper that was linked to the oxygen dissolves leaving a nice shiny surface.

If your vinegar turned green this is due to all the copper dissolving and producing copper acetate.

Real World Applications

Iron that is used to make cars, trucks and boats can also react with the oxygen in the air and oxidise, producing rust. If a car gets rusty, mechanics can use phosphoric acid  to remove it. It reacts with the rust, removing the oxide and replacing it with a layer of iron phosphate. This also protects the metal from rusting further.

Phosphoric acid is also found in coca cola, which is why it is so good at dissolving your teeth!

#TryThisTuesday: Spinning Disk

This Tuesday, you don’t need any equipment to try this experiment at home – you just need to stare at your screen, or more specifically the video clip below:

(don’t worry we aren’t trying to hypnotise you!)

Stare in the dot in the middle of the circle for 20 seconds, you can blink but don’t look away, keep your eyes focused there. After 20 seconds look at someone’s face, if there’s no one around you, get a face up on screen that you can quickly look at.

What did you see?

Hopefully, if it worked you should have seen the face appearing to get bigger. Obviously, it didn’t really grow before your eyes, this is simply an optical illusion playing a trick on your brain.

You see things because your eyes send messages to your brain about different types of light, shapes and movement and your brain makes up an image of the world around you. When you stare at the spinning disk for so long, your eyes continually send messages to you brain to say its spinning. Your brain gets a bit bored of hearing the same message over and over again so kind of stops listening, tunes out the messages and just assumes from now on, this is how it is – everything is spinning.

So when you look away at a face or your hands or anything really, your brain thinks it should be spinning so gets confused and spins the image in the opposite direction, making it appear to grow. After a few seconds, your brain will hopefully catch up and everything will go back to normal.

#TryThisTuesday Mini Fire Extinguisher

You will need: large tall glass, bicarbonate of soda (baking soda), vinegar, a candle and some matches

image11. Add 4 teaspoons of bicarbonate of soda to the glass

2. Pour in roughly 150ml of vinegar, the mixture will fizz.

3. Light the candle.

4. Once the mixture has stopped fizzing, pick up the glass. Without pouring out the vinegar, gently tip the glass from a few centimeters above the candle. Imagine that there is an invisible liquid inside above the mixture. The candle will go out!

The Science

You have produced a gas, carbon dioxide, by mixing the bicarbonate of soda with vinegar (also known as acetic acid). Bicarbonate of soda contains carbon dioxide, but it is attached to other molecules. When you mix it with vinegar the bicarbonate breaks down and releases carbon dioxide as a gas.

The following reaction takes place:

bicarbonate of soda + vinegar → sodium acetate + water + carbon dioxide

NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2

Carbon dioxide is heavier than air so stays in the glass until you tip it over the candle. When you pour carbon dioxide on a candle it stops the flow of oxygen which is needed for a flame to burn, and the candle is extinguished.

Real fire extinguishers also use carbon dioxide to put out fires, it is compressed (squashed) into cylinders and sprayed at fires.

Why Perfumes are not the Perfect Christmas Present…

Many animals rely heavily on their sense of smell for finding food, getting a whiff of the competition and even sniffing potential mates. You might not often see humans checking the scent of their partners, but scientists have found it does play a subtle role in helping us chose mates – as do perfumes.

All animals are made up of a collection of genes that are inherited from parents, these code for all sorts of things like eye colour and taste buds. All mammals, including us, have a section of genes called the major histocompatibility complex (MHC) which affects how well your immune system fights diseases. It is also linked to your natural scent.

There have been experiments on mice, mandrills, meerkats and many other animals showing that females tend to mate with males that have a different MHC to their own. This ensures that their offspring have a more varied set of genes and so will likely have a better immune system and survive for longer – which is what every parent wants for their child.

When tested in humans, the usual method is to get a group of men to wear a t-shirt for several days to get it nice and sweaty and smelly. Women will then smell each of the t-shirts and rate the odours in order of which they find the most pleasant. These experiments have consistently found that women tend to prefer the scent of men with MHC genes different to their own.

So what happens when you wear perfume and cover up that lovely natural odour of yours? Two researchers, Wedekind and Milinski wanted to find out. They asked over 100 people to rate a selection of perfumes based on whether they would like to smell like that. They found a correlation between the type of MHC and the scents selected, suggesting that we choose perfumes for ourselves that will enhance our natural odour. However, when asked to rate perfumes based on whether they would like their partner to smell like that, they found no significant link.

It appears that we are great a picking out odours for ourselves, but not so much at selecting the perfect perfume for others. Maybe a gift card would be better this year…

perfume

 

 

#TryThisTuesday: Making Snow

We’re feeling very festive this Tuesday so we thought it was the perfect time to make snow with science. All you need for this one is some shaving foam and bicarbonate of soda.

image3

Simply mix the bicarbonate of soda and shaving foam together in a bowl until you get a powdery consistency.

image4

Pick it up and have a play – you might notice that your fake snow actually feels cold too. This is due to the reaction between the bicarbonate of soda and the shaving foam. The reaction is endothermic meaning that it requires heat to occur, it takes this from the environment and so decreases the temperature around it.

image6

The Science of Shaving Foam

Do you think shaving foam is a liquid or a solid? It’s actually a colloid. A colloid is a substance which has droplets of one state surrounded by another state. There are lots of different types of colloids with different combinations of states making up the droplets and the surrounding. In the case of shaving foam, the droplets are gas and the surrounding is liquid making it a foam colloid.

colloids1

#TryThisTuesday: Pop or not?

Today we will be experimenting to see what happens when you put a lighter or a flame underneath a balloon filled with two different states of matter: air and water.

popornot

You will need two balloons, some water and a lighter

  1. Blow up one of the balloons with air and tie it up.
  2. Fill the other balloon with a little bit of water, blow it up the rest of the way and tie it up.
  3. Hold the lighter under the balloon with the air in it and see what happens. Be careful as it should pop!

    Balloon with air in
  4. Light the lighter under the balloon with some water in it, be careful to hold the lighter under the part of the balloon where the water is. The balloon won’t pop!

    Balloon with water in

The Science

This happens because water can absorb heat a lot easier than air and is a better conductor of heat. Water keeps the heat away from the balloon. This is called its ‘heat capacity’ and is why water is often used to cool things down in places such as power plants. The air is not very good at absorbing the heat, so the balloon heats up and pops!

 

#TryThisTuesday: Lava Lamp

This week’s experiment will show you how to create the 1960’s invention – the lava lamp – at home!

You can create your lava lamp in a beaker, a glass or a plastic bottle, whatever you have lying around that you can see through.

  1. Start by filling your container 1/4 full with water and add some food colouring of your choice.20161108_160122
  2. Add oil until its nearly full to the top. Wait a minute or two and the oil should separate out and sit above the water.20161108_160212
  3. Drop in a Alka-Seltzer or any other effervescent (fizzy) tablet and watch the bubbles rise.

The Science

Oil floats on top of water because it is less dense and water molecules stick closely together due to their hydrogen bonds, making it difficult for the oil to mix in.

The tablet is more dense than the oil and the water so sinks directly to the bottom. There it reacts with the water to produce the gas, carbon dioxide (CO2). CO2 is less dense than both the water and oil so it rises to the top, carrying some water molecules with it, these are the bubbles that you can see. The bits dropping back down are the water molecules sinking again once the gas has escaped.

A real lava lamp uses wax that is heated by a bulb. The hot wax expands, becomes less dense than the water and so rises. When it cools, it shrinks, becomes denser and sinks.

World Egg Day: Eggsellent Experiments

egg-carton-628x363

Happy world egg day! Here are some cracking eggsperiment that you can at home on this very important day:

Egg in a Bottle

For this experiment you will need a hard boiled egg, an empty plastic bottle, a scrap of paper and a lighter.

Light the paper and drop it into the bottle. After a second place the egg on top of the bottle and observe the results.

The lit paper heats up the air in the bottle, causing it to expand slightly and for some air to escape. The egg creates a seal so more air cannot enter. As the air cools inside the bottle it decreases the pressure and forces the egg into the bottle.

Floating Egg

All you need to try this one is an egg, a glass, water and salt.

Fill you glass half full with tap water and carefully place the egg inside. It should sink. Add some salt until the egg floats. The salt increases the density of the water, when you add enough the egg becomes less dense than the water so floats to the top.

Next dribble spoonfuls of tap water down the side of the glass until it is full. The egg should appear to float in the middle of the glass, it is actually floating on top of the salt water with a layer of fresh water above it.

Hard boiled Spin

Lay a hard boiled egg flat on its side and spin it. Put your finger on it to stop and then let go, nothing remarkably happens there. Try the same with a raw egg and when you let go it will start spinning again on its own accord.

This is all due to momentum. When you spin the eggs you spin their insides too. In the hard boiled egg, the insides are fixed to the shell so it behaves as you would expect. In the raw egg the insides continue to spin after you’ve stopped the shell. When you let go, the momentum of the spinning yolk carries the shell and the whole egg starts spinning again.