This week’s experiment is quick and simple but sure to amaze!
You will need:
An indoor tap
Clean dry hair
Turn the tap on so there is a very thin but constant stream of water flowing
Rub the balloon on your hair until you form static (about 10 seconds, until your hair begins to stand on end)
Slowly bring the balloon close to the flowing water while being careful not to actually touch the water
Watch the water bend towards the balloon!
When you rub the balloon on your hair, tiny electrons are collected on the balloon. These electrons have a negative charge. This causes the balloon itself to have an overall negative charge, therefore it is attracted to things with a positive charge (opposites attract!). The flow of water has a positive charge, therefore the attraction is strong enough to pull the water towards the balloon.
This weeks Try This Tuesday takes a while, but you end up with a tasty treat!
You will need:
A wooden skewer or chopstick
1 cup of water
2-3 cups of sugar
A narrow glass or jar
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.
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!
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.
For this week’s experiment you will need to raid your fridge and kitchen cupboards to get some milk, food colouring and washing up liquid.
Pour some milk into a dish or bowl, this works better with full fat milk (we’ll tell you why later!). Add small drops of your food colouring wherever you like in the milk.
Get some washing up liquid on the end of a spoon or cotton bud and gently tap the spots of food colouring with it.
The food colouring should burst out into colourful stars and wavy shapes. This happens because the washing up liquid molecules have a hydrophobic tail, these means that they don’t like water so try to get away from it by seeking fat molecules. The milk (especially if it is full fat milk) contains lots of fat molecules. So the washing up liquid moves around in the milk seeking out this fat and takes the food colouring along with it, creating these funky patterns.
This is why we use washing up liquid to clean our dishes. The hydrophobic, fat-loving parts cling to grease and fat. The head of the washing up molecules are hydrophilic, meaning they love water. The heads cling to the water and the tails cling to the grease, this pulls the grease and dirt from your plates and washes them away with the water, giving you sparkly clean dishes.
During our time as STEM Ambassadors, we’ve visited several beaches together. From Newcastle in Northern Ireland to Clear Water Bay in Hong Kong and even beaches closer to home in Whitley Bay and Tynemouth, we always ended up skipping rocks somewhere!
But how do we do it!? Why don’t the rocks just fall into the water?
The key is to get a nice flat rock and throw it quickly at the right angle. The large surface area allows the stone to bounce off the water’s surface.
You need to throw it fairly hard to give it enough speed to gain momentum before it hits the water. When the rock hits the surface of the water it pushes the water down whilst the water pushes the rock up. If the force pushing the stone up from the water is greater than or balances the weight of the stone then it will bounce on for another skip rather than sinking. This is why it helps to have a nice small stone.
It is also important to get the right velocity. Velocity is the speed of something in a give direction. So we have the speed covered, now for the direction. Scientists have discovered that the optimal angle at which the stone should hit the water should be around 20 degrees. As you probably won’t be able to measure this on a causal day trip to the beach, just aim to throw the stone sideways rather than up or down.
Hopefully you’ll manage more than my measly two skips. Try beating the world record of 88 skips in a row!
Today we are looking at the science behind curly potato fries. First, let’s talk about how we make them.
Carefully chop up a potato into straight thick chips.
Boil around 250ml of water and stir salt into this water until no more salt will dissolve.
Fill a bowl with tap water and place half of your chips into this bowl.
When the salty water has cooled pour it into another bowl and add the rest of your chips to this.
Leave both bowls of chips out overnight.
The next day you should have one bowl of chips that are still hard and straight and the other bowl (with salty water in) will be full of chips that are more flexible, that you can shape into curls.
The addition of salt to the water allows you to make curly fries due to osmosis. Osmosis is the movement of water from an area that has few molecules in the water to an area that has more molecules in it to try to even things out and create a balance.
Plants like our potato here are made up of millions of cells that have a cell membrane around its edge which allows some things in and not others. Water can easily flow through this but the salt we dissolved in it can’t. Cells are filled with lots of little molecules so water usually flows into the cells and fills them to dilute the liquid. But when we have lots of salt in the water, there are more particles in the water outside of the potato cells than inside so the water leaves the cells.
When cells are filled with water they are quite rigid and packed closely together making a fairly sturdy chip. When the cells are dehydrated, they are smaller leaving space between cells, allowing the chip to bend without snapping.
Osmosis is used in all plants – not just when you cut them up and put them in a bowl of water! Plants use osmosis in their roots to allow water to move from the soil into their roots.
This week we’re making ice cream but instead of using an ice cream machine, we’re going to make it using science!
You will need:
Two Ziploc bags – one small, one large
100ml double cream
Measure out the milk, cream and sugar and place them into the smaller Ziploc bag.
Add a dash of vanilla extract then zip up the bag.
Fill the larger bag 2/3 full with ice.
Pour a generous amount of salt onto the ice.
Making sure the small bag is tightly zipped up, place it inside the bigger bag with the salt and ice.
Gently shake the bag for 5-10 minutes, be careful not to rip the bag!
Leave the ice cream to sit inside the ice and salt bag for another 10 minutes
Open up your bag and enjoy!
Try making different flavours of ice cream by swapping the vanilla extract for strawberry or mint extract or even cocoa powder for chocolate ice cream. You could also try adding chocolate chips.
How does this work?
Water, as I’m sure you know, freezes to make ice at 0oC. But your freezer at home is around -18oC, so how are we making the ice cold enough to freeze your creamy mixture? The secret is in the salt.
Ice is in a constant state of melting and refreezing and melting and refreezing. When we add salt, the salt particles block the path of the melted ice, stopping it from freezing back on to the rest of the ice but ice can still melt. Therefore more ice is melting that freezing.
Now you may be thinking that surely if the ice is melting that means it is getting warmer? It’s actually the opposite. For ice to melt it needs to break the bonds that are formed between the H2O molecules. This breaking requires energy which it gets in the form of heat. When a molecule melts away a bond is broken, taking heat away from the surrounding, causing the temperature to drop.
This is also the reason that salt is put on icy roads – it stops water forming ice.
For this experiment all you will need is a clear bottle or jar with a lid, water, cooking oil and some washing up liquid.
Fill the water bottle half full with water.
Pour about 100ml of oil in to the bottle and observe what happens.
The oil should float on the water. Try and mix them together or challenge other people to mix them! It is impossible, the oil and water always separate out again.
Add a squeeze of washing up liquid to the bottle and shake. The oil and water now mix together.
Oil is less dense than water so floats on top. Oil and water don’t mix together as the water molecules are more attracted to each other than the oil molecules. Oil molecules are hydrophobic or ‘water-fearing’.
Washing up liquid molecules are attracted to both water and oil. When you add a squirt in, one end of the washing up liquid molecule attaches to a water molecule and the other end attaches to an oil molecule. This creates a mix of water with oil droplets spread throughout it. This is because one end of the washing up liquid molecule is hydrophobic (water fearing) and one is hydrophilic (water loving).
The washing up liquid acts as a stabiliser and creates an emulsion. This is a mixture of two liquids that wouldn’t normally mix.
Real Life Applications
We use washing up liquid when we are washing up as it attaches to the oil on the dirty dishes and lifts it off into the water.
Animals that live in the ocean also stay warm by producing an oily substance on their fur or feathers which keeps the cold water away from their skin.
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.
You will need two balloons, some water and a lighter
Blow up one of the balloons with air and tie it up.
Fill the other balloon with a little bit of water, blow it up the rest of the way and tie it up.
Hold the lighter under the balloon with the air in it and see what happens. Be careful as it should pop!
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!
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!
This week’s experiment will show you how a submarine works using just a water bottle and a ketchup sachet.
Take a large (2 litre) plastic bottle and fill it with water
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.
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.
Make sure the bottle is full of water to the top.
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!
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.
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.
Start by filling your container 1/4 full with water and add some food colouring of your choice.
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.
Drop in a Alka-Seltzer or any other effervescent (fizzy) tablet and watch the bubbles rise.
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.