During my internship at Science Centre Singapore, I was given the opportunity to look through issues of Science Spy (a science magazine for children aged 9-12).
It enlightened me on many different topics relating to life sciences and physical sciences, which inspired me to share something of my own – about friction!
Friction is an unsung hero! It keeps us from falling, and if applied rightly, even allows just one pencil to lift an entire container of rice. Sounds cool, right? Let’s try it out!
- Floating Rice
All you need for this experiment is:
- 1x small container
- Some uncooked rice grains
- 1x pencil
- Fill ¾ of the container with uncooked rice.
- Slowly insert the pencil into the rice and take it out fully.
- Repeat step 2 – making sure to poke the rice at different spots to increase friction between the rice and the pencil.
- Eventually you won’t be able to remove the pencil.
- Pick up the bottle with the pencil!
Amazing isn’t it? Show this newfound trick to your friends!
The science behind this experiment is friction. As the pencil pokes through the rice at various spots, it forces air to move out of the spaces between the rice grains. This allows greater surface contact between the pencil and the rice grains with subsequent insertions. Eventually, the frictional force between the rice and pencil overcomes the weight of both the container and the rice grains!
Next, do oil and water mix? We’ll explore this in the next experiment, Abyss in a Bottle. This activity can be done both indoors and outdoors. Let’s dive right in!
2. Abyss in a Bottle
- 1x Bottle with a cap
- Small bowl
- Vegetable Oil
- Some food colouring
- Warm Plate wrapped with Aluminum foil
- Fill ⅓ of the bottle with water.
- Fill the other ⅓ of the bottle with vegetable oil.
- Cap the bottle and shake the mixture.
- In a separate container, add food colouring to some detergent, and mix.
- Use the syringe to drip some of the coloured detergent into the bottle of water and oil.
- Watch as bubbles of coloured oil fall through the mixture!
For cool effect:
- Place the bottle on a warm plate covered with aluminum foil, and watch the coloured oil rise and fall in the bottle!
Do the oil and water mix? Oil and water do not mix because of polarity. Water molecules are positively charged at one end, and negatively charged at the other, making it a polar liquid.
Polar liquids mix, because the positive and negative ends of the molecules attract each other. Water molecules will always attract other water molecules, thus forming water.
Oil is a non-polar liquid and therefore it does not not mix with water. The oil floats on top of the water because water has a higher density than oil.
Detergent adheres to both water and oil molecules, making the oil droplets float on the water. When you drip the coloured detergent into the bottle, the detergent causes an emulsion of oil and water to form – a scenario that would otherwise not occur.
Try it out for yourself!
These experiments make use of household items, making it easy to do! So, what are you waiting for? Gather your family and friends and try these activities out!
Authored by: Eu Jiayu Kelly & Hezekiah
Reviewed by: Danny