Ice and light

So since December 1st we have gone all out Christmassy in our house. The tree is up and decorated. And although this was an activity to keep a (slightly) sick child entertained while we had an unplanned morning at home, we were going to put it up in early December anyway. We have also been dancing lots to Christmas songs. I am a big fan of pretty much all the Christmas hits but I think my daughter may out do me with her tolerance for them as she really can’t get enough of Mariah. So I thought I’d start on some Christmas science activities. As the temperature has dropped and we have had our first frosts we decided to have a look at ice. And to make it a bit more Christmassy we tried to do some pretty things with colours and light, but as you will see from my photos it wasn’t quite as beautiful as hoped!

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This activity requires some night before preparation.

What you need:

  • dish/Tupperware box to make ice in (essential – you just want to make a thin block so anything that holds about a cm of water. Ideally with a flat bottom so your block is all the same thickness but this isn’t essential as one of ours wasn’t).
  • water (essential – just good ol’ h20 from the tap will do).
  • salt (essential – just table salt or ground rock salt – whatever you have to hand).
  • food colouring or ink (essential – helps to visualise the melting).
  • Big plate or tray (not essential but helps to keep mess to minimum)

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The night before:

  • Pour water into your container and pop into freezer.

Activity with a child:

  • Pop your ice block out onto a tray or plate. Doesn’t matter if it breaks (as one of ours did).
  • Sprinkle salt over the ice.
  • Add the food colouring or ink to the ice and watch the melting occur!
  • Hold up to a light for stain glass effect (this actually is more difficult than it sounds as you have a slightly slippery bit of ice dripping with salty water and food colouring, however if you manage to do it then it does look pretty!)

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The science bit

Salt makes ice melt faster by lowering the melting point. The food colouring or ink show the channels in the ice that have melted faster due to the salt. Holding it up to the light just allows you to see this more clearly (and is meant to look pretty too!).

Explaining it to children

They probably know when you put water in the freezer it turns to ice, and that when you hold an ice cube in your warm hand it melts but good to talk about this to get them thinking about freezing and melting (and if they don’t then you can do these activities). Then just explain the salt makes the ice melt faster (it doesn’t melt the ice though!). You can also explain that when it gets cold in the UK and there is a risk of ice, that the roads get gritted with salt. Get them to think about would happen if the roads were all icy and cars drove on them (talk about slipping on ice  or snow such as ice skating, skiing, sledging – they may have done it themselves or seen it on tv/a film if they haven’t).

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Experiment based on an activity from the fantastic Usborne Activities: 365 Science Activities book.

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