Surface Tension

Water drop on a coin

 
We started off  by observing a drop of water on a coin and how it holds the shape of a dome. It holds the shape unless the drop is bigger than the coin. We tried adding few more drops to this drop. And this is due to cohesion and surface tension properties of water.




Cohesion is the attraction of one molecule to the other molecule. Surface tension is the cohesion between water molecules.

There are few science experiments that you can do to show the surface tension property of the water.

1. Allow a steady flow of water.
2. Hold one finger under and observe that water flow becomes like water droplets due to surface tension in the steady flowing water.



The  second experiment would be

1. Take a bowl of water .
2. Take  materials such as hair clip, safety pins, coins .
3. Drop them into the bowl.
4. Observe that they all sink to the bottom.

Pin and the coin sank to the bottom




Now , take a small sheet of paper and put in the water. slowly place the hair clip, safety pin, coin on top of the paper. You will note that they don't sink to the bottom and float for a long time till the paper soaks.

Coin , pin floating on the paper


This is due to the paper not breaking up the surface tension of the water .

Kids also tried their hands on dropping coins in a full cup of water and observed the surface tension holding it together without spilling.


Comments

Post a Comment

Share your thoughts here:

Popular posts from this blog

Osmosis in potato

Image
After checking out my plants in the balcony, the young girl in my class had a curious question "Aunty, how do the roots know when to absorb water?".  "You mean, how does water get into roots ..right?" asked my daughter walking towards the girl.  "Yes, thats what I don't understand " replied the girl. Listening to their conversation I said "water enters the root hair cells by 'osmosis' and we will do an experiment to understand osmosis today".  And that's how we decided to do an experiment on osmosis.   What is Osmosis? Plants absorb water from the soil by 'osmosis'. Osmosis is the movement of water through a semi permeable membrane. Water moves into plant cells through osmosis by making them turgid or stiff to hold the plants upright. Osmosis is passive transport, meaning it does not require energy to be applied.   We also discussed about how osmosis is helpful for photosynthesis as well. Otherwise the plan
Read more

Why cut apples turn brown in color?

Image
I was cutting the apples into pieces when kids entered the science class. Noticing that, they all assumed I was going to give it to them to eat :-) which I didn't. So, one of them asked me " Aunty, you had left the cut apple pieces out. Will they not turn brown in color?". I was glad that they had initiated the discussion for the day. Further, I asked them to think about things that turn brown when left outside. That triggered them to wonder 1. Why cut apple pieces  turn brown in colour? 2. Why copper vessels change color from pink to brown when kept out? 3. Why does Iron rust when exposed to moisture? Let us first check out why do cut apples turn brown in colour? Have you ever bitten into an apple, left it for sometime to find that it had turned brown in colour. When apple is cut or bruised, oxygen is introduced into the cells which then reacts with the enzyme (polyphenol oxidase) in the chloroplast to turn into brown colour. The fru
Read more

The hoop glider!!!

Image
Our activity started with kids imagining to go to school  by a car, that is environmental friendly and flies in the air. One of them said , if he lived on a mountain and the school was in a valley he would do paragliding. So, we talked about gliders and how they fly without motors.Gliders always descend relative to the air in which they are flying. Para gliders, hand gliders are some of the gliders that we see these days. What are Gliders? Gliders are a type of aircraft which do not have engine, but use the wing design and air flow to fly around. Now, it was time for them to build one themselves, but using a different design and shape that they had seen. I gave them a straw to throw, which did not go very far. As they were brain storming, the idea of adding loops instead of the wings came to them. They were quick to decide that they would need 2 hoops instead of one to make it fly for some time. That is how kids made a hoop glider. It worked really well. design for mak
Read more