Category Archives: Try This Tuesday

#TryThisTuesday: Invisibility Cloak

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Glass is transparent (see through) but we can still see it. In this experiment we will show you how to make it vanish!
1. Fill a large glass bowl or container with cooking oil.

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2. Put a smaller glass bowl inside the large one.


3. Look from the side, can you see it?

The Science

This happens due to the refraction of light and how the speed of light changes when it passes from one state of matter to the other.

Light travels through different objects at different speeds. It travels faster in air than in water or glass. We can see glass normally as light passes from air to glass and slows down and changes direction. This distorts (changes) how we see other objects through the glass, telling the brain there must be a transparent object in the way.

The bowl disappears when we put it in cooking oil, as light travels at the same speed in cooking oil and glass. The light doesn’t change direction so your brain doesn’t know that the light has traveled through the glass, making it disappear!

#TryThisTuesday: Submarine

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This week’s experiment will show you how a submarine works using just a water bottle and a ketchup sachet.

  1. Take a large (2 litre) plastic bottle and fill it with water
  2. Test a few ketchup sachets in a bowl of water to see if they float, not all of them will have an air pocket in.
  3. Add an unopened sachet of ketchup to the bottle. The sachet should float, but if it doesn’t, try adding some salt to the water. Salt increases the density of water, making the sachet float better.
  4. Make sure the bottle is full of water to the top.
  5. Screw on the top very tightly and squeeze the bottle hard.

The sauce submarine will sink to the bottom. If you let go it will float back up.

You can challenge other people to get the sachet to the bottom, lots of people will try and shake it or turn it upside down!

The Science

This experiment is all to do with how things float, or the buoyancy of an object. Water pushes up on the ketchup packet with the force equal to the weight of the water that the ketchup packet pushes out the way.  If the displaced water is heavier than the sachet, then it will float because it is less dense than the water.

When you squeeze the bottle you apply pressure to the liquid inside. Liquids cant be compressed (squashed) so the pressure is transmitted to the sachet. The ketchup sachet has some nitrogen gas in (to keep it fresh). The gas is compressed and the sachet sinks and therefore displaces less water and sinks. As soon as you let go the sachet expands again and floats.

Submarines use similar systems to allow them to sink and float easily.

 

#TryThisTuesday: Lava Lamp

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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.

#TryThisTuesday: Honeycomb

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honeycomb

Honeycomb or Cinder Toffee not only makes a great Bonfire Night snack, it’s also a fun and quick science experiment! Here’s our simple recipe for the honeycomb reaction:
1. Grease a baking tray with butter and set aside.
2. Mix 100g sugar with 2.5 tablespoons of golden syrup in a pan. Mix the two well before you heat the pan.


3. Gently heat the pan, try not to stir the mixture at this point just let it gently begin to melt.
4. Once you can see the sugar start to melt you can push the sugar around to ensure in melts evenly and doesn’t burn.
5. When all the sugar has melted turn up the heat so the sugar begins to boil and forms an amber coloured caramel
6. Turn off the heat and add one teaspoon of bicarbonate of soda, beat the mixture quickly as it begins to bubble up to incorporated all the bicarb then tip onto the greased baking tray.


7. Leave to set for 30-60 minutes then enjoy!

The Science

The heat causes the bicarbonate of soda (NaHCO3) to break down and release the gas, carbon dioxide (CO2). The gas gets trapped within the sugar, this results in the bubbles in your honeycomb.

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#TryThisTuesday: Slime!

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slime

With Halloween coming up, what better time to make some of your very own slime?

It’s super easy and quick to make – you just need to mix water and cornflour! Start with a little bit of both, if it seems too runny you can add more cornflour and if it becomes a solid then add more water.

You can also add food colouring and glitter if you want to add some sparkle to your slime.

The slime should become a consistency that appears to be a liquid but if you hit it or try to stir it quickly it becomes a solid – so which is it?

Liquid or Solid?

Slime isn’t actually a solid or a liquid – it is a non-Newtonian fluid, this is a fluid that changes its properties when a stress or force is applied.

The slime we’ve made is a particular non-Newtonian fluid called oobleck (yes it’s a funny sounding word – that’s because it is derived from a Dr. Seuss book). The particles of cornflour don’t dissolve in the water, they become suspended in the water and repel each other. Mechanical stress, such as stirring quickly provides energy that overwhelms the repulsive forces, causing the particles of cornflour to temporarily stick together. When the stress is removed, the repulsion returns and the slime becomes liquidy again.

More Non-Newtonian Fluids

1. Custard behaves just like oobleck, in fact if you filled an entire swimming pool with custard, you would be able to walk across it!

2. Ketchup is almost the opposite of oobleck – it become thinner and runnier under impact, that’s why it helps to bang the end of a ketchup bottle when you’re struggling the get some out.

3. Whipping cream acts differently when under a constant and prolonged stress, such as whipping. If you whip cream for long enough it will appear to go from liquid to solid as it becomes whipped cream.

4. Honey similarly needs prolonged stress to change it’s properties. When you stir honey, it will become more like a liquid than a solid.

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World Egg Day: Eggsellent Experiments

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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.

 

#TryThisTuesday: Making Plastic from Milk and Vinegar

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plastic

Yes – you really can make plastic from just milk and vinegar!

First of all just measure out 120ml of milk (it can be any type, we used semi-skimmed). Either heat your milk in your microwave or in a pan on the hob. It needs to get to around 50 degrees C so 1 or 2 minutes in the microwave should do it.

Next add 2 tablespoons of white distilled vinegar to the hot milk and stir – you should see clumps start to form.

Sieve the mixture to remove the excess liquid. Remove even more liquid with a paper towel or piece of kitchen roll.

You should be left with a clump of plastic which you can mould and shape as you please. It should begin to set in an hour.

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The Science

Plastics are polymers meaning they are made up of long chains of repeated molecules (called monomers). The monomer that we have used is called casein and is found in the milk. When the milk is heated the casein molecules unfold. Adding the vinegar causes them to reorganise into a long chain polymer – making it a plastic.

It might look quite different to the plastics you’re used to today but up until the end of World War II in 1945, casein plastics were commonly found.

#TryThisTuesday: Make your own Sherbet

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sherbet

This week we’re taking on the science of sweets! Here is a super easy way to make your own sherbet powder at home.

All you will need is:

  • 7 teaspoons of sugar (either caster sugar or icing sugar)
  • 1 teaspoon of bicarbonate of soda
  • 3 teaspoons of citric acid in powder form

Mix your ingredients in a bowl and then take a small amount on a teaspoon and have a taste. It should fizz in your mouth.

Where does the fizz come from?

When you place the mixture on your tongue it reacts with the water in your mouth and produces carbon dioxide, this causes the fizzy feeling.

sherbet-equation

The reaction occurs because  acids, like the citric acid used here, release charged hydrogen particles when added to water. These particles will attack an alkaline (the opposite of an acid) such as bicarbonate of soda. The reaction produces more stable molecules – water and carbon dioxide.

If you pour water onto your mixture you should be able to see the reaction that’s happening in your mouth. You can actually feel the carbon dioxide gas being released if you hold your hand close to the surface.

#TryThisTuesday: Floating Paperclip

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Can you make a paperclip float in water? Your standard metal paperclip isn’t very buoyant and as you would expect, tends to sink in water. But with just a piece of tissue paper and a pencil you can make a paperclip float…

  1. Place a small piece of tissue paper in the water so it floats
  2. Carefully put your paperclip on the tissue paper without you touching the paper
  3. Slowly use the pencil to push the paper down so it sinks – try not to touch the paperclip.
  4. You should be left with a floating paperclip – but is it really floating?


The science

Technically, the paperclip isn’t actually floating. It is held on the surface of the water by surface tension. Water molecules tend to attract one another and this forms a ‘skin’ on top where the water particles hold tightly together. This surface tension is strong enough to hold the paperclip. But if you poke the paperclip or shake the bowl, you break the surface tension and the paperclip will sink.

Pond skaters also use water tension to walk on water. They have evolved legs that distribute their weight evenly and so are adapted to life on the water’s surface.

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#TryThisTuesday: Balloon Kebab

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Your challenge this week is to pierce a skewer through a balloon without popping it.

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Share your attempts with us on Facebook, Instagram or Twitter  – just use the hashtag #TryThisTuesday

How we did it:


Pierce the balloon at the bottom near the knot, then slowly pass the skewer through and piece it through the darkest part at the far end. These points are where the rubber is under the least stress so is less likely to tear and pop under impact.

Did you manage it?