Measure the minimum amount of salt your are able to detect in water.

If you do this experiment with others, you can do a "blind tasting" and measure the detection threshold of each one of you as if you were laboratory instruments.

The human body is extremely sensitive to certain environmental variables. We can detect some odours and flavours in very low concentrations. You can start pouring 0.1 g of salt in 10 litres of water. Can you detect the salt? Test now 0.1 g in 1 litter. Not yet?

Why fingers wrinkle during the bath – Osmosis

When we bath in freshwater, fingers wrinkle when we emerge from the water, but when we bathe in salt water, fingers wrinkle while we are bathing. The reason is due to a physical process known as osmosis which is the transfer of liquid through two solutions separated by a semi-porous membrane.

In the example chosen, the skin of the fingers is the semipermeable membrane. The skin pores are large enough to let water molecules go through, but they are too small to let sea salt pass. So, in the bath, the water tends to flow towards the interior of the skin swelling it. When we leave the bath the inner layer of the skin loses that water and it wrinkles. The process in salt water is the reverse. The inner layers of the skin tend to lose water to equal the salinity of the seawater.    

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