Take a deep breath and come with us on a journey to the nether world of low temperature as we discover just how low we can go with a series of science facts so cool, they’re absolutely freezing!
The Concept of Cold
Cold is an interesting concept. Technically speaking, it doesn’t exist. You see, we sometimes use words to describe things by what they are not. Darkness for example, is really just the absence of light. And cold, as you have probably guessed, is just a lack of heat. It’s a word we use to describe the lower end of the temperature scale. Cold is relative, heat is quantifiable. The lowest temperature possible is 273.15⁰C. It’s also known as ‘zero K’ law of the universe and the K stands for Kelvin. The discovery of absolute zero you see, was made by William Thomson, a giant of 19thCentury science who pioneered the study of electromagnetism and thermodynamics. In 1892 Thomson became Lord Kelvin. He is buried in Westminster Abbey near to Sir Isaac Newton. Pretty impressive. The really cool bit though is this: William Thomson was from Belfast and you can see his statue in Botanic Gardens, just in front of the Ulster Museum. If you don’t believe me, go see it for yourself. But wrap up warm, it gets cold in the park this time of year.
Why Does it Snow ?
You may have noticed that it only snows in cold weather! It needs certain weather conditions before it can fall. Snow is a type of precipitation which falls when the air temperature is below 2°C. It is a myth that it needs to be below zero to snow. In fact, in this country, the heaviest snow falls tend to occur when the air temperature is between zero and 2°C. The falling snow does begin to melt as soon as the temperature rises above freezing, but as the melting process begins, the air around the snowflake is cooled.Snow forms high in the Earth’s atmosphere within clouds but it isn’t just frozen water, it is actually frozen water vapour, the stuff that clouds are really made from!
Nitrogen is a very common element and here on Earth it normally takes the form of a gas. It is colourless, odourless and non-toxic and makes up around 78% of the air we breathe (oxygen is around 20%). That means that every breath you take contains a lot of nitrogen but it goes in and out of your lungs without a problem. The blood in your lungs mixes with your breath and absorbs the oxygen that you need but the nitrogen comes right back out again.
All gases will turn into a liquid when they get cold. Oxygen is a liquid at -183°C Nitrogen is even colder: -196°C. That means that above -196°C it starts to boil. If it gets really cold it will of course turn into a solid. That happens at -210°C. If you want to find solid nitrogen in its natural state you will need to go to Pluto at Christmas. The snow there is made of nitrogen! (okay, we’re not sure if they have Christmas on Pluto but it’s a nice thought!).
The Wonders of Water
It’s a law of the universe that things shrink when they get cold and expand when they get warm. All elements and substances behave like this. But there are a few minor exceptions to this rule and one of those is a very special exception indeed. Any ideas? Water!
When water freezes it expands about 9% and also becomes less dense. That’s why ice floats on water even though it’s made of the same thing. Try this at home – put water in a clear plastic cup. Draw a line with a marker at the water level. Put it in the freezer and after it has frozen you will see that the level of the ice is higher (9%) than the water!
Find out more cool science facts, touch a cloud, make it snow and meet the W5 Bubble Monster at Winter Freeze, FREE with admission to W5 on various dates until Sunday 5 January 2020. Check out the website for details W5online.co.uk