Demonstration for surface area to volume ratio

So, surface area to volume ratio is a common concept in Science…

In digestion, they learnt that food are broken into small pieces so that it has larger surface area to volume ratio for enzymes to work on.

But, it’s hard to student to grasp the concept. They don’t get it how food in smaller pieces have larger exposed surface area to volume ratio.

So, here’s a simple demonstration.

First, make 2 jelly using red cabbage (reason being it’s a natural pH indicator) with identical moulds. Cut only 1 of the jelly into quarters. Then, add them into container of equal volume of lye water (alkaline solution).

Due to red cabbage being natural pH indicator, the jelly will change colour in alkaline solution (yellow in strong alkaline). As seen, the jellies cut in quarter turned yellow faster than the larger jelly because it has larger surface area to volume ratio.

2 jellies using identical mould. Only 1 jelly is cut into quarters.
The results of the demonstration.

Broken heart

The blue piece had always been loose. And drops easily. Didn’t noticed it drop as I was on my way to class yesterday. Unfortunately, couldn’t find the piece as I retrace my step.

RIP. Had it since my practicum days… time to buy a new one.
Bought this years ago… with other tools for this chapter is a stethoscope (which really works!) and an oxymeter (clipped to finger to measure oxygen level and pulse rate). Those were the days being a young, enthusiastic teacher ūüėõ

Oh, btw this model is the same size of a typical child’s heart.

Flower- Model making with show & tell

Artifacts from a project years ago¬†after I taught them parts of a flower and adaptation of insect and wind pollinated plants. So proud that quite a number of them actually put in so much effort for it. The final products were so good that I placed them on display at the back of the Bio lab. The Bio lab is one of the venue for guests whenever we have school visits, so it’s definitely a good idea to put them on display there.

Their task was to design their own flower using any materials. Then, we had show and tell for them to describe the features of the flower they had created, using ideas of pollination.

Model for respiratory system

This is an activity I usually carry out for lesson on part of respiratory system- Model making using straws.

Straws of various sizes and Q-tips are provided foe them to make the model. Straws that I use are bubble tea straw, regular straw and coffee stirrer.

They simply cut the items and tape them to a large piece of white paper provided.

Here’s a sample of the final product.

Water pollution at Whampoa River

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


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