What are all substaces made from?
All substances are made from atoms.
A substance made from only one type of atom is called an element. There are about 100 of these which are all shown on the periodic table. The groups in the peroidic table contain elemnts with similar properties.
They are represented by chemical symbols.
They have a small central nucleus around which are electrons.
What happens when elements react?
When elements react, their atoms join with other atoms to form compounds. This involves giving, sharing and taking electrons. The atoms are held together to make the compound.
Transfer of electrons - ionic bond - metal + non-metal
Sharing of electrons - covalent bond - two non-metals
Atoms and symbols are used to represent and explain what is happening to the substances in chemical reactions.
The formula of a compound shows the number and type of atoms that are joined together to make the compound.
No atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants and we can write balanced equations showing the atoms involved.
What is Limestone?
Limestone is a grey/white coloured rock containing calcium carbonate (CaCO3).
It is made out of fossilised and crushed sea shells.
It is quarried out of the ground which causes enviromental problems.
It is great for making building blocks, however, it can be dissolved by acid rain. It is used for statues and cathedrals and also crushed to be used in road surfacing.
1. Limestone + thermal decomposition = calcium oxide(quicklime) + CO2
2. Calcium oxide (quicklime) + water = calcium hydroxide (slaked lime)
Carbonates of other metals decompose on heating in a similar way.
Products of Limestone
Slaked lime: calcium oxide and water
Cement: Limestone and powdered clay heated
Mortar: Cement ad sand and water
Concrete : Mortar and gravel
Glass: Limestone and sand and sodium carbonate heated