Science Demonstrations

SCIENCE  DEMONSTRATIONS

As a science teacher, we should have knowledge from all branches of science. Also, we should be able to teach students all the branches of science effectively. By keeping this idea in mind, I have performed 3 demonstrations from three different branches of science: Physics, Chemistry, Biology.

PHYSICS  DEMONSTRATION

"HERO'S ENGINE"

Aim: To explore Newton’s third law of motion using ‘Hero’s engine’

Materials Required: Plastic cup, 2 plastic bendable straws, String, Craft knife, Water and tray, Modeling clay.

Procedure:

1. Take plastic cups and poke two small holes near the top rim on opposite sides from one another.
2. Thread string through the holes and tie a knot so that the cup can be suspended from the string.
3. Make two holes near the bottom of the cup.
4. Slide two bendable straws into the holes and fix it using modeling clay. Make sure that they both point in a clockwise direction.
5. Pour water into the cup and observe.

Result: Gravity draws the water downward and out through each straw. This causes the engine to spin in a clockwise direction.

Conclusion: The water being forced by gravity to leave the cup in a clockwise direction pushes back on the cup in a counterclockwise direction, causing the cup to turn. This is an example of Newton’s third law of motion; that is ‘every action has equal and opposite reaction’.

CHEMISTRY  DEMONSTRATION

"DISAPPEARING WHITE"

Aim: To study the effect of sodium hydroxide on zinc sulphate

Materials Required: ZnSO₄, NaOH, H₂O, 2 beakers, stirrer, dropper.        

Procedure:

1. Prepare the aqueous solution of Sodium hydroxide by dissolving NaOH in water.
2. Prepare the aqueous solution of zinc sulphate by dissolving ZnSO₄ in water.
3. Using dropper pour a little amount of NaOH solution in ZnSO₄ solution.
4. A white precipitate of zinc hydroxide will form. This test is used to detect the presence of Zn in water.
5. Now add excess of NaOH solution to it. At one point the white precipitate disappears.

Result: 

1. When we add NaOH to ZnSO₄ , it reacts and a white gelatinous precipitate Zn(OH)2 is formed.

2. When we add NaOH in excess, the precipitate gets dissolved in excess NaOH. Thus, the white precipitate disappears.

Conclusion:

The reaction between ZnSO₄ and NaOH is used to test for presence of Zn.

The Zn(OH)₂ is used widely in calamine creams, ointments, baby powder, skin lotions and cosmetics.

BIOLOGY DEMONSTRATION

"FERMENTATION"

Aim: To study the fermentation of varying amount of sugar using yeast.

Materials Required: 3 bottles, yeast, sugar, 3 balloons, warm water.

Procedure:

1. Add 2 spoons of yeast in each bottle.
2. Add 1 cup of warm water in each bottle.
3. In first bottle add 2 spoons of sugar, in second add 1 spoon and don’t add any sugar in the last bottle.
4. Shake all three bottles so that they mix well.
5. Now tie balloon at the top of each of the bottle and wait for around 24 hours.

Result: 
The balloon covered on a bottle having more amount of sugar in it grows bigger in size as compared to the balloon covered on a bottle having less amount of sugar.

The balloon covered on the bottle having no sugar doesn’t blow at all.

Conclusion:

Fermentation is a metabolic process that converts sugars to acids, gases and/or alcohol. It occurs in yeast, bacteria and other microorganisms as well as oxygen starved muscle cells.

The yeast consumes sugar and converts it into carbon dioxide and ethanol. CO₂ gas tries to come out of the bottle causing the balloon to blow.