Boost Your Child's Thinking Skills Through Making Simple Toys


Through play, children cultivate curiosity and interest in Science, Technology, Engineering and Mathematics. Rather than getting children to just play with toys, a great way to spark critical and creative thinking skills is by guiding them to make toys that work on scientific principles. You can even make toys from household items!

Tap on your child's sense of playfulness, kinesthetic learning skills and appeal factors to create toys that generate their interest in science. One such toy is the Cartesian Diver. It allows your child to understand the scientific concept of buoyancy and density and it provides a way for them to be inquisitive into the scientific principles of operating the toy in a fun manner.

Here are the steps to create a basic Cartesian Diver toy!



A ketchup packet
1.5 litre bottle filled with water to its brim
Bucket (optional)
Salt (optional)


Step 1: Fill the bottle to its brim.
Step 2: Insert the ketchup packet into the bottle.
Step 3: Challenge your child to bring the ketchup packet down.

Learning Points

Young children can be challenged to bring the ketchup packet down and will often turn the bottle upside down, causing the packet to still float upwards. Parents can introduce children to the idea of buoyancy - things float when there is air in them. Hence, turning the bottle upside-down will not work because of the presence of air in the packet.

It is important for children to be given time to keep trying and playing (experimenting!) ways of bringing the packet down.

Parents can eventually demonstrate that a way to make the ketchup sink would be to squeeze the bottle. Squeezing the bottle causes the air in the packet to be compressed. This makes the packet less buoyant, and thus sink!



Step 1: Fill the bucket with water.
Step 2: Place the ketchup packet into the bucket.
Step 3: Challenge your child to make these packets float! (tip: use salt)
Step 4: Keep adding salt into the water and stirring it, creating a salt solution!

Learning Points

A number of ketchup packets (from fast food outlets) do not float because there is little air in them. Parents can engage with children on ways to make these packets float.

A way to make these packets float would be to place them in salt water. Children would see the ketchup packet rising up in salt water. The science phenomena behind this lies in the concept of density - a concept they will come to appreciate in their primary and secondary years.


There are many fun variations of this toy that can be made through simple materials! Watch the video for the steps to making this toy variation!


Dr Muhammad Nazir Amir from the workshop "Boost your Child's Thinking Skills with Toys" held on 30 July 2016.

The video was inspired by the 'Hook Cartesian Diver', a toy invented by three students from Greenview Secondary School (Singapore), and won the Raffles Junior College Toy Inventors' Challenge 2006.


Click here for more recommended books from the National Library Board on how to 'boost your child's thinking through toys'!