From Hydrogen to Tellurium - CALCIUM

Calcium


Positioned next to Potassium and under Magnesium is Calcium. With the chemical symbol Ca and 20 electrons, Calcium is an element most children have heard about.


It is not naturally found in its elemental state - in other words you don't find lumps of calcium atoms on their own but when scientists remove the other elements leaving just Calcium they are left with a soft, grey / silver metal.


Calcium is grouped with Beryllium and Magnesium in the group known as the Alkali Earth Metals.

You may well have heard your parents encouraging you to drink milk, telling you that milk will give you strong teeth and bones. Milk is one of the foods that is rich in Calcium and Calcium is needed by the body. In fact our bodies are 5 per cent Calcium so for every 100g of our bodies 5 g are Calcium, and most of this Calcium is in our banes and teeth. It is the presence of Calcium in our bones that makes them opaque to x-rays. This characteristic is widely used to check to see if bones have been broken.

                    

Calcium is also the fifth most abundant element in the earth's crust. Many rocks contain Calcium  - limestone and chalk are both made from the Calcium containing compound Calcium Carbonate CaCO3. In caves, stalactites and stalagmites are Calcium containing compounds which have dissolved in water and moved through the rocks.
           


The mortar builders use to stick bricks together is a mixture of Calcium Hydroxide, known as lime, Sand and Water.

Cement is also made fromCalcium containing compounds.


Many Calcium containing compounds are not soluble in water but dissolve in other solvents such as acids. This means that buildings do not dissolve in rain but if you get acid rain which is caused by pollution then this acid rain can dissolve buildings. This can cause serious damage to old decorative buildings




Experiment of the Week
Dissolving egg shells


You will need
adult supervision
2 jam jars or jars with lids that seal
Water
Vinegar
2 eggs
Hot water
Basin containing cold water
bottle with a large neck such as the one in this picture - 
 




What to do
Carefully place a raw egg into each of the 2 jam jars.
Cover one with water and put on the lid.
Cover the other with vinegar and put on the lid.
After 24 hours remove the lids and carefully pour off the liquids. Compare the 2 eggs. The one which was in the vinegar should be soft - its shell dissolved in the vinegar.
Fill the large necked bottle with hot water and then pour the water out.
Sit the rubbery egg on top of the bottle.
Cool the bottle by immersing it in the cold water.
Your egg should be sucked into the bottle.