acid

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.

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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.