A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).
These lessons look at the thermal decomposition of calcium carbonate.
Limestone is a common rock that is a very useful material. For example, it is used for building and road making, and also as a starting material for making many other products. This activity illustrates some of the chemistry of limestone (calcium carbonate) and other materials made from it.
Calcium carbonate is heated strongly until it undergoes thermal decomposition to form calcium oxide and carbon dioxide. The calcium oxide (unslaked lime) is dissolved in water to form calcium hydroxide (limewater). Bubbling carbon dioxide through this forms a milky suspension of calcium carbonate.
The following diagram shows the Limestone Cycle: Calcium Carbonate, Calcium Oxide, Calcium Hydroxide. Scroll down the page for activities to demonstrate the Limestone Cycle.
Questions 1 Why does the chalk crumble slightly on strong heating? 2 What type of reaction is taking place during the heating process? Write an equation for the reaction. 3 Why is steam evolved when drops of water are added? Write an equation for the reaction occurring. 4 Why does the limewater turn cloudy? Write an equation for the reaction which is occurring. 5 What is the colour change when Universal Indicator is added? What does it tell you about the pH of the solution? Explain why the pH would be expected to have this value.
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