The 31st element, Gallium is an unusual material. It is not found in nature but can be extracted from minerals.
Gallium, which comes under Aluminium in the periodic table, is a metal. Most metals have high melting points but there are a few exceptions and Gallium is one of those exceptions. You might already know that Mercury, another metal, is liquid at room temperature. Gallium is normally solid at room temperature but it melts at 29 degrees centigrade. This means that its melting point is similar to that of chocolate and any of you who eat chocolate and especially those of you who came to Anyone 4 Science summer camps this year will know that you can melt chocolate in your hand. Well it is exactly the same for Gallium - hold a piece in your hand, which is at 37 degrees centigrade and it will melt! Fairly cool don't you think.
Because aluminium and Gallium look similar a chemistry trick is to make a teaspoon out or gallium instead of aluminium and offer this to your victim to stir their coffee, tea or hot chocolate. Guess what happens to their spoon? - It melts and goes to the bottom of the cup. Check out this disappearing spoon video - http://www.youtube.com/watch?v=QaJ_Yxj9bG8
Gallium also has a big range between its melting and its boiling temperature. This means it is suitable to use in a thermometer.
Another interesting property of Gallium is that is expands as it solidifies. It is unusual for this to happen as most materials contract as they cool. Another exception to this contracting as it cools rule is water. As water freezes it also expands. It is this property that causes pipes to burst when water freezes. If you stored Gallium in a glass container it would crack the container as it cooled.
Check out this cool video made by scientists at Nottingham University showing how to make Gallium beat like a heart. http://www.youtube.com/watch?v=N6ccRvKKwZQ&feature=player_embedded
Experiments of the Week
To show that water expands as it freezes
You will need:
Empty 500 ml PET bottle
water
measuring cylinder
marker
What to do:
Measure 400 mls water into the measuring cylinder and transfer it into the 500ml bottle.
Mark the line showing where the water comes to in the bottle.
Put the bottle of water in the freezer and leave overnight.
Take the bottle our of the freezer and mark the new level of the ice in the bottle.
Allow the liquid to melt.
Fill the bottle to the new mark.
Pour all the water into the measuring cylinder.
Calculate by how much the ice expands.
Experiment 2
Make your own Thermometer
You will need:
Glass bottle.
Water
Food colour
Drinking Straw
modelling clay / blu tack
cold water
basin with hot water
What to do:
Colour some cold water with a few drops of food dye.
Fill the glass bottle with coloured cold water.
Using the modeling clay fix the straw so that it is sealed into but sticking out of the bottle.
Stand the bottle in the basin of hot water
What happens? Leave your comments below.
No comments:
Post a Comment