The properties and functions of water
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Summary
The properties and functions of water
In a nutshell
Water is an incredibly important molecule with essential functions inside and outside of cells. These include acting as a metabolite and solvent; being cohesive; and allowing for temperature control.
Structure
Water is made up of one atom of oxygen joined to two atoms of hydrogen by shared electrons.
The shared negative hydrogen electrons are pulled towards the oxygen atom. This leaves the other side of each hydrogen atom with a slight positive charge. As oxygen has unshared electrons, it has a slight negative charge.
This is why water is a polar molecule with a partial negative (δ−) and partial positive (δ+) charge. The δ− of the oxygen attracts the δ+ of the hydrogens on other water molecules. This is known as hydrogen bonding.
Functions of water
Function | Description | Example |
| Metabolite | Water is involved in many metabolic reactions. | Condensation reactions release a molecule of water as a bond is formed. Hydrolysis reactions use a molecule of water to break a bond. |
| Solvent | Substances can dissolve in water. As water is polar, the positive side will attract negative ions and the negative side will attract positive ions. | Most metabolic reactions take place in a cell's cytoplasm (solution), so substances are dissolved. |
| Temperature control | Water has a high latent heat of vaporisation, which means a lot of energy is required for water to evaporate as it takes a lot of energy to break hydrogen bonds. | This is helpful as it allows humans to sweat and cool down. |
| Water has a high specific heat capacity. This means it can buffer changes in temperature. This is because hydrogen bonds can absorb a lot of energy. | This is useful inside organisms as it means water doesn't experience rapid temperature changes and allows a constant internal body temperature to be maintained. | |
| Cohesion | Water molecules stick together due to their polarity. This also means water has high surface tension. | This helps water transport in plants through the xylem. |
FAQs - Frequently Asked Questions
Why is water polar?
Water is polar because the shared negative hydrogen electrons are pulled towards the oxygen atom. This leaves the other side of each hydrogen atom with a slight positive charge. As oxygen has unshared electrons, it has a slight negative charge.
What is cohesion of water molecules?
Cohesion is when molecules of water stick together due to their polarity.
What is the structure of water?
Water is made up of one atom of oxygen joined to two atoms of hydrogen by shared electrons.