C1a Products from rocks

Key Points:

• All substances are made of atoms
• Elements are substances made of only one type of atom
• Symbols are used for atoms to show what happens in chemical reactions

• Elements are listed in the periodic table
• Atoms form chemical bonds by losing, gaining or sharing a small number of electronsCompounds contain the atoms of two or more elements bonded together

Key points:

• Limestone is used as a buliding material and make quicklime, cement and glass
• Thermal decomposition of limestone makes quicklime and carbon dioxide
• The formula for a substance shows the number of atoms of each element that have joined together

Limestone is made up of mainly of calcium carbonate; formula CaCO3

When heated strongly, calcium carbonate decomposes to make quicklime (calcium oxide, CaO) and carbon dioxide (CO2)

Word equation:

calcium carbonate---->calcium oxide + carbon dioxide

Key words:

• Carbonates of metals are decompose when heated to produce the metal oxide and carbon dioxide 
• We can represent chemical reastions by balanced equations
• In a chemical reastion the mass of the reactants is equal to the mass of the products 

• Symbol equation should be balanced with the same number of each type of atom on both sides
• Atoms are not created or destroyed in chemical reactions. So the mass of the products is always the same as the mass of the reactants 

Key points:

• Adding water to quicklime produces slaked lime
• Lime water is used as a test for carbon dioxide
• Mortar can be made by mixing slaked lime, sand and water

• Mortar is used to hold stone or bricks together in buildings
• When carbon dioxide in the air reacts with calcium hydroxide in the mortar it forms calcium carbonate and sets hard

Key points:

• Cement is made by heating a mixture of limstone and clay
• Concrete is made by mixing cement with sand, stones or crushed rocks and water
• Glass can be made from limestone, sand and sodium carbonate

• Mortar made with cement and sand is stronger and sets faster than lime mortar. It will set in wet conditions, even under water
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