A - IB Biology

Properties of hydrogen atoms

• Polar covalent bonds

• Partial negative O and partial positive H due to uneven electron sharing

Hydrogen bonds

Form between the partially negative and positive sides of hydrogen atoms, very weak and form and break quickly.

Cohesion

• Possible because of hydrogen bonds

• When water sticks together, which allows water to move up the xylem with a continuous water column

• Helps water bugs stay on the water by making surface tension, so the pressure exerted by the bug is too weak to break the water bonds

Adhesion

• When water bonds to other things

• Helps to move water through plants and soil through capillary action

Universal solvent

• Water is considered the universal solvent because it can dissolve almost anything

• This is because water is polar and bonds with the solutes easily

• Helps transport; examples include water in the xylem and ions, glucose and amino acids in the blood

Buoyancy

• Force exerted upon an object

• Water is very buoyant. Most aquatic animals have similar buoyancy to water and some can adjust their buoyancy

Viscosity

Resistance to flow. Water is somewhat viscous.

Thermal conductivity

Ability to conduct heat. Water does so very easily, which can be good or bad. It means heat can spread through our body easily, but we also lose body heat quickly.

Specific heat capacity

Water has a high specific heat capacity, so it needs more energy to change temperature, giving animals a more stable environment.

Ringed seal

Has lots of blubber that helps it resist water’s thermal capacity and resist losing body heat.

Arctic loon

Air isn’t buoyant, so it’s more difficult to stay afloat but easier to move due to the low viscosity of air.