chemistry

Making slime without borax

Made the simplest slime with the P3s using 3 ingredients only.

Watch the tutorial below:

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Egg membrane paper ball

Egg membrane paper ball (my students said it looks like ping pong ball and they can toss it around.

1. Poke thru 2 holes using optical pin, one at the top and another at the bottom
2. Students chip off for a slighlty bigger hole (not too big!)

3. Remove egg content by draining it through the hoke or blowing thru it using a straw (straw need not be thru the hole, can place it just above.

4. Place egg in a beaker containing HCl. Use glass rod to ensure egg doesn’t float.

5. After 5min, discard off HCl. Place egg on petri dish. Gently tap the shell to crack it.
6. Pick up the membrane and rinse it.

7. Blow through it using straw so it inflate. Simply place the straw above the hole.
8. Roll it in talcum powder.
9. Allow it to dry.

Red cabbage indicator

My favourite demo for the chapter on acid and alkali is…

red cabbage indicator

Add a pieces few leaves of red cabbage into a beaker of hot water. The leaves will decolourise and the solution will eventually turn purple. We will use this solution as the indicator. Add 2 drops into different samples and observe for colour change.

red-cabbage-indicator

Colourful results from red cabbage indicator

Here’s my colourful result using these samples (from yellow, clockwise)
Lye water, bicarbonate of soda, sprite, detergent, lemon

Best used with samples that are colourless.

You can encourage students’ participation by allowing them to bring their own samples. Students generally are more excited to work on stuff that they contributed.

You can also extend this activity by giving them time to make their own indicator paper which they can bring home. Simply cut strips of filter paper, soak it in red cabbage juice and let it air dry. Students can then use them by dipping it into samples.

Flying rocket experiment

Students had fun today with flying rocket experiment. Conducted this activity to introduce reaction of acid with carbonate.

Add sprite in film canister, to about 3/4.
Add 3 spatulaful of baking soda on the cap.
Place the cap over the film canister and shut it tight.
Invert the film canister.
Step away and watch it launch!

Sprite can be replaced with coke or vinegar.
Baking soda can be replaced with antacid tablet.

What’s happening?
Reaction of acid and carbonate produce carbon dioxide gas. Carbon dioxide produced is trapped in the film canister provide a force for it to propel upwards.

Simple titration

Conducted a simple titration for a lesson on Acid Rain. Parts of lesson is scenario-based to provide solution for acidic soil.

Level: Sec 2 Normal Technical
Topic: Air Pollution (Effects of Air Pollution – Acid Rain)
Objectives:
Students should be able to:
– test for pH of solution using universal indicator
– test for acidity or alkalinity of solution using pH paper
– conduct simple titration and determine the end-point for neutralisation

Materials:

acid rain – titration activity (student)

acid rain – titration activity (teacher)

Water pollution at Whampoa River

Earlier this year, whitish discharged was reported at Whampoa River.

whampoa-river-whitish

There was no update about it about until today. Investigations by National Environment Agency (NEA) shows that the source of the water pollution is chemical illegally discharged by a construction firm, Singbuild. The firm was fned a total of $7,000 for illegal dumping industrial waste and debris into drains.

This news can be used as materials for lessons on water pollution.

Archived news articles for lesson materials:
Clean-up in Whampoa River after whitish discharge discovered
Singbuild fined $3,000 for pollution Whampoa River
Construction company Singbuild fined $7,000 for illegal dumping and pollution