Tag Archives: chemistry

#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.

honeycomb

The Chemistry of Being Scared

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Happy Halloween! We all like being scared sometimes, whether it’s scary movies or a rollercoaster, but why do we get scared?

We feel fear when we see or hear something that makes us anticipate harm. If you are walking through a haunted house this Halloween and a skeleton jumps out at you, the skeleton is a stimulus that triggers a signal in your brain.

The hypothalamus is part of your brain that activates the ‘fight or flight’ response. When you are scared molecules of glutamate (a neurotransmitter) travel to the hypothalamus. This then triggers the autonomic nervous system, a response that you can’t control.

brain

Nerves from the brain carry impulses to glands which produce adrenaline, released into the blood. Adrenaline causes our heart rate and blood pressure to increase making us ready to run away quickly.

When we get scared we also get goosebumps. This is a trait that evolved in our hairier ancestors. When our hair stands up on end it makes us look bigger and more threatening to whoever is scaring us. This is seen in other animals too, such as cats.

However, we aren’t scared forever. Eventually our body realises that there is nothing to be worried about.  Sensory data of what we have seen and heard is sent to the hippocampus in the brain which can store and retrieve conscious memories. It gives context to what we have seen and asks questions such as have I seen this before and what happened last time?

If a skeleton jumps out, we will realise that it isn’t real and is probably just someone dressed up! The hippocampus will determine that there is no danger and sends a message to the hypothalamus. Adrenaline production stops and our heart rate goes back to normal.

thinking

We have evolved to feel fear to allow us to survive. People and animals who feared the right things survived and passed on their genes. This makes sure we don’t do stupid things like picking up poisonous snakes or walking off buildings.

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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.

nonnewtonian

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.