CHEMICAL CHANGES

One of the most important topics in Chemistry is chemical changes.  Students find it interesting because they get what they see; and learning is enhanced when they love what they are doing.

Teachers and students alike could try this simple yet relevant activity for chemical changes. It is always recommended that teachers are around to supervise when students are allowed to do this practical.

Theory:

            There are signs if chemical change has taken place. When one or more substances are formed out of a reaction then chemical change has occurred. In chemical change, the change is usually difficult to reverse. For example, when you cook food, chemical change happens and there is no way you could get back the original substance if you wish to. In chemical change, energy is taken out or given in. Just like, when iron reacts with sulphur; heat is produced. When there is a chemical reaction, the atoms are rearranged so they mixed in an entirely different way.

Materials/Equipment/Solutions

Lead nitrate solution

potassium iodide

Barium chloride

Sulphuric acid

Hydrogen peroxide ( 15 % solution)

Hydrochloric acid

Manganese oxide (test powder)

Copper carbonate

Test tubes

Wooden splints

Spatula/laboratory spoon

Note: All solutions must be diluted to 0.1M unless specified otherwise.

Precipitation Activity

1. Get one test tube and half-fill it with dilute lead nitrate. Half-fill another test tube with dilute potassium iodide. Pour one solution into the other. Put the test tube with the mixture in a test tube rack and observe what happens. Is it a chemical change? WHY? Wait for 10 minutes and record any observations.

2. With new set of test tubes, prepare the same amount as in procedure 1 the dilute solutions of barium chloride and sulphuric acid. Pour one into the other. Is it a chemical change? Explain.

Fizzing Activity

1. Prepare a quarter of hydrogen peroxide into a test tube. Get a wooden splint and dip into the manganese oxide. Now dip the splint into the test tube with hydrogen peroxide and put your thumb to cover the test tube’s opening. What do you observe? What can you feel?
2. Half-fill a new test tube placed on the test tube rack with dilute hydrochloric acid and put a spatula of copper carbonate into the solution.  Record any observations.