Have you ever heard of the water cycle? The water that falls down to earth as rain or snow actually came from lakes or the sea or even perhaps from a cup of water left out on a hot day!
When water on Earth is heated up by the sun it does something called ‘evaporating’. This is when it turns into water vapour and starts to float up towards the clouds. When you boil a kettle you get steam which is a type of water vapour.
Up in the sky it is very cold! When the water vapour floats high enough it does something called ‘condensing’. This is where it turns back to liquid water again. Condensed water droplets clump together into a cloud. Eventually the cloud gets too big and water starts to pour down, back towards the ground – this is called rain! The rain goes into puddles, rivers, lakes and seas and then the whole cycle starts again.
You are going to making your own mini water cycle in a bag so that you can see this happening in your own home and teach your grownups all about it!
Get your sandwich bag and place it in front of you so that the opening is at the top.
Find your sun sticker and stick it on the outside of the bag in the the top right hand corner. You can use this picture to help if you need to.
Find your cloud sticker and stick it on the outside of the bag in the the top left hand corner.
Take one of your arrows and stick it so that it is pointing from the bottom of the bag, up to the sun. This will show us that, when the sun heats up water on the earth, it evaporates and floats from the ground up to the sky
Take your other arrow and stick it so that it is pointing from the cloud down to the bottom of the bag. This will show us that, when the cloud gets too big, rain falls down to the ground!
Next, carefully fill your bag with roughly a cup of water – just enough to cover the bottom of the bag. You can pretend that this is like a lake or sea.
Close the bag up and find a window that you can stick it to. Make sure it’s the right way up and that you ask a grownup first!
Keep an eye on your bag of water. On a hot sunny day the water will be heated by the sun and will evaporate and float to the top of the bag – just like in the water cycle!
When the water reaches the top of the bag it will condense back into water droplets – you may even be able to see some water droplets on the insides of the bag
These water droplets will eventually clump together and when they are too heavy they will fall back down to the bottom of the bag – just like rain!
Here is Edward to tell you something a bit gross about the water cycle…
Making a volcano
Did you know, the Earth is made up of four different layers? Right in the middle of the Earth is the inner core and it is very hot! Outside this is the outer core then the mantle then the layer we walk on – the crust. Sometimes, the mantle gets very hot – so hot that it gets really big and eventually explodes through the crust. We call this a volcano! Lava is just the mantle of the earth, bursting up through the crust. You are going to make your own volcano. You can either follow the instructions below or scroll down to the video.
Take your orange fizzy tablet and place it on a plate – right in the middle. This is going to be your mantle.
Use your clay to build a volcano shape around your fizzy tablet. Your tablet should be on the plate with the volcano on top of it. Try and make sure your volcano goes all the way around the fizzy tablet so you can’t see it anymore The volcano is the crust of the earth. Make sure you leave a little hole in the top of your volcano. It should look something like this…
Get yourself a cup of warm water. This is going to represent the mantle heating up.
Pour a little bit of warm water through the hole in the top of your volcano. Keep pouring until your volcano explodes! Don’t worry if some explodes out of the sides – that happens in real volcanoes too.
Here is Chemical Cress to demonstrate this experiment.
Have you ever seen a rock that looks like it has lots of layers? This is called a sedimentary rock. Sedimentary rocks are made out of lots of different types of rock that have been squashed together. This happens when rocks are broken into lots of little pieces by rivers or extreme weather. The broken pieces settle at the bottom of the sea or river. Later, little pieces of a different type of rock settle on top of them. This keeps happening until there are lots of layers of different rock, all on top of each other. Eventually, the rocks on the top get so heavy that the rocks on the bottom get squashed together! Sedimentary rocks can take millions of years to be made.
You are going to be using your starburst sweets to make your own edible sedimentary rock.
Unwrap your first sweet and put it in the middle of your piece of foil.
Next, unwrap your second sweet and put it on top of the first.
Unwrap the last sweet and put it on top of the second so that you have a starburst tower. Each flavour of sweet will be repesenting a different type of rock.
Wrap the whole tower up in the foil and then push really hard on the tower. You are going to try and squash the different sweets together like in a sedimentary rock. Here are a few different things you may want to do to help you.
Use both hands to push down on the tower whilst jumping so that you can use all your body weight.
Get a heavy book and put it on top of the tower.
Put the tower under the leg of a chair and sit on it (be very careful not to lose your balance).
Sit on the tower
Squash the tower between two hands.
When you have done this, open up the foil. Do your sweets look like a sedimentary rock?