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Wednesday, June 24, 2009

Chemistry Week - Laboratory Experience

We attended a series of laboratory sessions at the Singapore Science Centre during their Chemistry Week. Most of the workshops used concepts in Chemistry learnt at the Secondary 3/4 level. Of course, my 8 year-olds don't get it all! But they had fun just "playing" with the apparatus. ;-)

For the sake of future reference, I will go ahead with noting down the specifics of what was done.

Workshop 1 - Sulfur Dioxide and its Role in Preserving Food

What we did :- We tested for the presences of SO2. Hydrogen peroxide was added to food samples (preserved mango, dried sour plum, preserved papaya, raisins, potato chips, fruit juice). This causes SO2 to be oxidised to form sulphates. This sulphate will precipitate out as barium sulphate when barium chloride is added.

My observation :- Boys got the droppers all mixed up and in the process contaminated the solutions!

Workshop 2 - Recycle Paper - Transform Newspaper to New Paper

What we did :- We blended newspaper shreds in a blender with some water. The resultant pulp was gently laid on a mesh that is submerged in a tray of water. The pulp is spread evenly to dry.

Some dried flowers were sprinkled throughout.

We had some leftover pulp, so we made a smaller circular shaped paper.

My observation :- This is the most straight forward of all the workshops. The boys needed to learn that "more doesn't mean better"... I had to remove most of the dried flower they "dumped" onto the paper.

Workshop 3 - Hydrogen Fuel Cell

What we did :- We produced hydrogen gas by reacting magnesium with hydrochloric acid. Hydrogen gas was tested using a glowing splinter.

Too slow in preparing the glowing splint. Ops... fingers too small to stopper over test-tube opening, so most of the hydrogen escaped! ... Managed to get a soft "pop"sound (positive test for hydrogen). Phew!

The set up here was used to electrolyse water.

Green solution of Universal Indicator was added into the water. We observe that the colours at the two graphite electrodes were different. The indicator cahnged to orange (acidic) on the anode (left arm) and violet on the cathode (right arm).

The electrode reactions are as follows:
at the anode:
2H2O(l) → O2(g) + 4H+(aq) + 4e–
at the cathode:
4H2O(l) + 4e– → 2H2(g) + 4OH–(aq)
2H2O(l) → O2(g) + 2H2(g)

The aim of showing the children the electrolysis of water is to show the working principles of a hydrogen fuel cell. The electron gradient produced can be be channelled through an electrical circuit.

Workshop 4 - Green Chemistry - Balance with Nature

What we did :- We investigated the greenhouse effect of carbon dioxide. Two identical set up like this was set up.

Carbon dioxide was put in one of the boxes. The thermometer poked into the box allowed temperature in there to be taken over a period of 8 minutes after the lamp above it has been switched on. The temperature gradient was significantly higher in the box with carbon dioxide.

This was another experiment where we investigated on the effects of various solution on shells. You can see that there is a hole in the middle of the shell on the left. That is the result of submerging it in hydrochloric acid. This experiment aims to show the effect of acid rain.

Conclusion : I realized that my boys had a lot to learn about basic laboratory skills! These include measuring, planning and general apparatus handling. I found a simple lab sheet on Laboratory Safety and Measurement that we can work through at home. Alright, more hands-on session at home from now on...

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