1. Chemical reactions +  reactantsproducts A chemical reaction is a change that takes place when one or more substances (called reactants) form one or more new substances (called products).

2. Bonding and electrons When elements react, their atoms join with other atoms to form molecules and/or compounds. This is Bonding. Bonding involves giving, taking or sharing electrons to form ions or molecules

3. Metals bonding with Non-metals Compounds formed from metals and non metals consist of ions. Metals lose electrons to form positive ions. Non metals gain electrons to form negative ions

4. Word and symbol equations Chemical reactions can be represented by word equations or by symbol equations No atoms are lost or made during a chemical reaction so the mass of products equals the mass of the reactants +  Symbol equation: C (s) + O 2 (g)  CO 2 (g) carboncarbon dioxideoxygen +  Word equation:

5. HT candidates should be able to balance symbol equations A symbol equation must be balanced to give the correct ratio of reactants and products.

6. Limestone = calcium carbonate Limestone is mainly composed of the compound calcium carbonate (CaCO 3) Limestone is quarried (dug up) and can be used as a building material

7. Heating calcium carbonate Calcium carbonate can be decomposed by heating (thermal decomposition) to make calcium oxide and carbon dioxide The carbonates of magnesium, copper, zinc, calcium and sodium decompose on heating in a similar way

8. Limestone cycle

9. Limestone and its products can be involved in various useful chemical reactions: Summary of limestone chemistry calcium oxide water calcium hydroxide  + calcium carbonate calcium oxide carbon dioxide  + thermal decomposition of limestone production of calcium hydroxide using limewater to test for carbon dioxide. calcium carbonate calcium hydroxide (aq) carbon dioxide  ++ water

10. Making building materials Limestone is heated with clay to make cement. Cement is mixed with sand to make mortar and with sand and aggregates to make concrete Limestone+ClayCement +SandMortar Cement+ Sand and aggregates Concrete

11. Carbonates and acid Carbonates react with acids to produce carbon dioxide. Limestone is damaged by acid rain

12. Pros and cons of quarrying