January 19, 2018

HOW WATER GETS FROM HERE TO THERE

Have you ever wondered why water is considered so vital to life? Well we all know it is useful as rain to grow plants, as a medium to cook food and essential in the manufacturing process of many everyday items. It is also very important for many of your bodily functions, but have you ever wondered why?

One quick answer to that is; Osmosis. You may have heard of osmosis before and your textbooks would have defined it something like this: “the spontaneous net movement of water molecules from a region of high concentration to a region of low concentration through a semi-permeable membrane”. That’s a great definition which will give you marks in an exam, but what does osmosis look like? Well, follow the steps below and you can see for yourself

 

Materials 2 small containers (cups or glasses will do) Tap water Distilled water (boiled water that has cooled down will also do) Salt Small set of scales Cucumber (or another vegetable such as carrots)

Method

  1. Fill one glass with about 250ml of tap water (that is half of a pure water sachet).
  2. Add five tablespoons of salt and stir
  3. Fill the second glass also with 250ml of boiled water that has cooled down (Don’t add any salt)
  4. Peel the cucumber or your other choice of vegetable (It works best with cucumber)
  5. Cut two big chunks about the size of your little finger
  6. Use the scale to weigh each chunk that you cut
  7. Put one in the salt water and the other in the boiled water that has cooled down
  8. Leave the glasses to stand in a corner where no one will disturb them and come back to weigh the pieces again after 2hrs and after 12-14hrs

You can use the picture below as a guide for your experiments

Adapted from Open University

 

What do you notice about your results?

 

Osmosis in action

You should find that the cucumber in the salt water would have lost some weight and will now appear floppy. On the other hand, the piece in the boiled water that has cooled down should have gained weight and feel very strong/turgid. The observations you make are because the cucumber in the salty water lost some water while the piece in the boiled water gained some water, all through osmosis. The skin of the cucumber acts as the semi-permeable membrane just like the definition.

Now that you have seen what osmosis looks like in action, here are some examples of how osmosis is relevant in everyday life. Osmosis allows plants to draw water and nutrients into their roots. It is also the reason your skin gets wrinkly if you keep it in soapy water for too long, for example when washing clothes or dishes. A more important function of osmosis is that it allows your intestines to absorb water from the food you eat into your body. When cholera infects the body, it causes osmosis in the intestines to work in the opposite direction, this is why the body loses water and can lead to death.

So the next time you want an excuse to tell your parents why you cannot do all the washing at once, think science and think osmosis. Even if it doesn’t get you out of doing household chores, it will definitely impress them.

Fun fact: Water makes up about 60% of your body content and about 70% of the Earth’s surface.