1. 1Bunsen burner
2. 2Magnesium ribbon
3. 3Tongs
4. 4Watch glass
5. 5Magnesium oxide

Figure 1.1 Burning of a magnesium ribbon in air and collection of magnesium oxide in a watch-glass.

Activity 1.2 Lead nitrate and potassium iodide

1. Take lead nitrate solution in a test tube.
2. Add potassium iodide solution.
3. Observe the colour and physical state of the substance formed.

Observation: A yellow insoluble solid, lead iodide, forms. This solid is called a precipitate.

Activity 1.3 Zinc and dilute acid

Caution: Handle the acid with care.

1. Take a few zinc granules in a conical flask or test tube.
2. Add dilute hydrochloric acid or dilute sulphuric acid.
3. Observe what happens around the zinc granules.
4. Touch the outside of the container carefully and note any temperature change.

Observation: Hydrogen gas bubbles form and the container becomes warm. The evolution of a gas and rise in temperature show that a chemical reaction has occurred.

Figure 1.2 Formation of hydrogen gas by the action of dilute sulphuric acid on zinc.

From Activities 1.1-1.3, these observations help us recognise a chemical reaction:

• change in state
• change in colour
• evolution of a gas
• change in temperature

27 min