Demonstrations

CHEMISTRY DEMONSTRATION

Title: pH scale

Requirements: pH scale, pH papers, beakers, HCL, lemon juice, baking soda solution, milk, NaOH.

Procedure:

1)   Take 6 beakers.

2)   Take HCl in first beaker, lemon juice in second beaker, baking soda solution in third beaker, milk in fourth beaker, water in fifth beaker and NaOH in sixth beaker. Label the beakers.

3)   Immerse pH papers in each of the six beakers and match the colour on the pH scale.

4)   Note down the pH number corresponding to the colour of the pH paper.

5)   Keep the beakers in increasing order of pH numbers.

Observation:

Beaker No.	Name of the solution	Colour on pH paper	pH value
1
2
3
4
5
6

Theory: pH scale has numbers from 1 – 14. Solutions with pH numbers 1 – 6 are acids. Solutions with pH numbers 8 – 14 are bases and pH number 7 is neutral. Smaller the pH number of acids, stronger is the acid. Larger the pH number of acids, weaker is the acid. Smaller the pH number of bases, weaker is the base. Greater the pH number of bases, stronger is the base.

Indicator only tell whether a solution is an acid or base or neutral. Whereas a pH scale tells us how strong or how weak an acid or a base is. 

                                                                                       

PHYSICS DEMONSTRATION

Title: Bottle Fountain

Requirements: Plastic bottle, balloon, straw, M-seal, coloured water.

Procedure:

1)   Take a plastic bottle and drill a hole in the bottle a little above half level.

2)   Insert a straw in the hole and fix it with M-seal so that air wont escape through the hole.

3)   Fill the bottle with coloured water a little above half of the bottle.

4)   Blow the balloon and put it at the mouth of the bottle.

Observation:

When the inflated balloon is put at the mouth of the bottle, water flows out of the straw. Only the water below the straw remains in the bottle.

Theory: The air trapped inside the balloon, pushes the coloured water downwards. The water has no other passage to move out but through the straw. The water moves against gravity.

BIOLOGY DEMONSTRATION

Title: Diffusion and Osmosis

Requirements: Beaker, starch solution, iodine solution, zipper plastic bag.

Procedure:

1)   Take a 500mL beaker.

2)   Pour starch solution in the beaker.

3)   Pour iodine solution in the zipper plastic bag. Make sure that the iodine solution does not move out.

4)   Insert the zipper plastic bag in the starch solution and leave for 20-30 minutes.

Observation: The brown iodine solution in the zipper plastic bag turns blue.

Theory:

Osmosis is the net movement of solvent molecules through a partially permeable membrane into a region of higher solute concentration, in order to equalize the solute concentration on the two sides.

Diffusion  is that physical process in which any solvent moves, without input of energy, across a semi-permeable membrane separating two solutions of different concentrations.

In the demonstration, iodine solution moves out of the plastic bag into the starch solution. Therefore the colour of the iodine solution changes to blue due to reaction between iodine and starch.