Film title: Separation by evaporation
Why does bottled spring water taste different to tap water?
The water molecules in both liquids are identical.
The difference is that spring water contains a different mix of minerals.
minerals
Spring water usually contains more calcium and magnesium than tap water.
calcium
magnesium
So where do the minerals in spring water come from?
As water flows from a spring, downhill, it passes over many rocks.
The minerals in the rock dissolve in the water.
dissolve
This means they form a mixture with the water molecules.
The minerals break into tiny particles and move so far apart that they can't be seen in the water.
Substances such as minerals, sugar or instant coffee, that dissolve in a liquid like water are known as soluble.
The mixture is called a solution.
soluble substances
dissolve in a liquid
form a solution
So spring water is a solution of minerals and water.
Soluble substances can be separated back out from their solution by a process called evaporation.
When spring water is heated to 100 degrees Celsius the water molecules gain so much energy that they can escape as the gas, steam.
We say the water evaporates.
If the steam is collected and allowed to cool, it will condense back into liquid water that no longer contains minerals.
The solid minerals are left behind.
Evaporation is a way of separating soluble substances from their solution.
evaporation
separates soluble substances
from a solution
So the reason spring water has a different flavour to tap water is because of the dissolved minerals it contains.
You might not be able to see them, but you can certainly taste them.
soluble
dissolve
solution
evaporation
Learn how to find out the difference between tap water and spring water.
Learning points
Embed this film
Copy and paste the embed code above to include this film on other websites.