Hypothesis: some metal carbonates decompose more easily than others when they are heated.

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Thermal decomposition of carbonates

Introduction:

Carbonates decompose when they are heated, producing calcium oxide and carbon dioxide. Carbon dioxide can be detected using lime water.

Calcium carbonate  calcium oxide + carbon dioxide

CaCO3 CaO + CO2

Other metal carbonates decompose in the same way. Here are the equations for the thermal decomposition of copper carbonate:

copper carbonate  copper oxide + carbon dioxide

CuCO3 CuO + CO2

Hypothesis: some metal carbonates decompose more easily than others when they are heated.

Aim: The times taken for a chemical reaction to take place metals high up in the reactivity series (such as calcium) have carbonates that take a lot of energy to decompose them. Metals low down in the reactivity series (such as copper) have carbonates that are easily composed. This is why copper carbonate is often used at school to show these reactions. It is easily decomposed and its colour change, from green copper carbonate to black copper oxide, it is easy to see.

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Variables

Independent variables (what I will change)

The carbonates

Dependant variables (what I will measure and observe)

The time taken for a reaction to take place

Control variables (what I will keep the same)

The amount of carbonate (1g)

The amount of lime water (2ml)

Use Bunsen burner in the same way in each experiment.

Put 1g of the carbonate in a boiling tube.

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A reasonable write up which has a good beginning and method. It however loses momentum in the last section and does not give suggestions how the method could be improved. 3 Stars.