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.

Break the Code themed lessons

I started this year figuring out use of google forms for Break the Code themed lessons. I’ve been seeing such lessons by fellow teachers on IG/ FB and I guess it’s finally time for me to try in class. Better late than never, right?

One of the advantages of gamification of lessons is that it increases students’ motivation. This was the most evident during my lessons, because students took much faster time to complete the questions compared to paper-pen approach. I mean naturally most of us are competitive, right?

Having an interesting storyline helps too, for example by having role play for students to be on a challenge or mission. With this students are motivated to work towards the end goal.

The downside of this is time for planning such lessons. It is quite time consuming, but once you get the hang of it and everything comes together, trust me, it’ll be worth it. Especially after hearing from your students how they enjoyed it very much and when’s the next escape room/ break the code lesson 😉

Here are the 2 escape room/ break the code themed lessons I’ve done:

Save the animals

Let’s Discover Plants

Steady hand game

Currently doing electricity with Sec 3 NT and here’s throwback of a bonus activity I did with them last year for the chapter on Electricity. Each pair received a kit of battery, chopstick, straw, lightbulb, wire and index card to make their own steady hand game.

The video shows my first prototype 👏

It was not that difficult. They managed to get it done within 1hr lesson.

They designed their own loop and had fun challenging each other. A player is out if the bulb lights up.

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 😛

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.

Heat demonstration

Kids were amazed with convection demonstration today.

They went “wow” when they saw the red dye reversed its direction. Love their expression! If only I could snap a photo of their wide-eyed reaction. hahaa.. This is why I enjoy doing demonstration 🙂

The kids also had fun with a “magic liquid”.

They kept asking me where to buy it and I was like… I don’t even know what this “toy” is called to google to buy it.

Also did metal ball and metal ring, but not much excitement as these two demo.

Teaching of density using case study.

One of my favourite lesson package to carry out for lesson on density is “Gold Ingot Scam”. It’s in the form of a case study in which students role-play as police officers. This is based on a real crime in Singapore in 2011.

I like this activity because there are videos from Crimewatch that can be used for pre and post lesson. In fact, in the part 2 of the video, it shows the detective carrying out the experiment.

I did this as a group work with my students.

Each group receive an electronic balance, a pendulum bob wrapped with Ferero Roche gold foil and a measuring cylinder.

The pendulum bob is kinda tricky though. The small one will not show much increase in water level, but the medium bob might get stuck in the cylinder. They kinda vary slightly in size, so you have to check beforehand. I was blessed with a lab tech who was willing to check that the medium bobs used did not get stuck in the cylinder. Luckily it was only 10 sets needed for him to check *phew*

I provided for the students a mock police report and a template for them to complete their report.

I did not provide instructions as I wanted the students to figure out on their own. Most generally got it that they have to measure mass and volume. But, while they’re were carrying out the experiment, I did spot some mistakes though.. such as

  1. Measuring volume, then mass (with water droplets still on sample!!)
  2. Not releasing the sample completely in the measuring cylinder. Some held on to the string, with the sample in the middle of the cylinder filled with water.

In the next lesson, I discussed these with them and elicit response from them on how those steps can affect the results.

For those keen for the lesson materials, you can get the materials here.