Water

Question 1

What type of bonding is there within a water molecule?

Answer 1

Covalent bonding

Question 2

What type of bonding is there between water molecules?

Answer 2

Hydrogen bonding

Question 3

Why is water a polar molecule?

Answer 3

There is an unequal distribution of charge:

• Oxygen negatively charged
• Hydrogens positively charged

Question 4

What are the 8 properties of water?

Answer 4

• temperature
• cohesion
• adhesion
• solvent
• density
• low viscosity
• transparent
• produces upthrust

Question 5

What components of temepeature make it a useful property?

Answer 5

• High specific latent heat - a lot of energy required to change the state of a kilo of water without changing its temperature.
• High specific heat capacity - a lot of energy required to raise a kilo of water by 1 degrees.

Question 6

Why is a high specific latent heat useful?

Give an example in biological circumstances

Answer 6

A lot of energy energy needed to break hydrogen bonds, which means a lot of energy required for evapouration.

Biological advantage - water in sweat on the skin absorbs heat energy from the body as it evapourates, causing cooling.

Question 7

Why is a high specific heat capacity useful?

Give an example in biological circumstances

Answer 7

A lot of energy is needed to break hydrogen bonds, therefore little energy left to raise the temperature.

Biological advantage - stops rapid changes of temperature, keeping it fairly constant within the body.

Question 8

What is different with water’s density compared to all other known substances?

Answer 8

Water expands by 9% when it freezes, meaning water in its solid state is less dense than in its liquid state.

Question 9

What is the biological advantage of water’s density? (2 answers)

Answer 9

• Icebergs can float on oceans, which provides habitats for animals.
• Ice doesn’t freeze from the bottom up, meaning soil remains fertile, as well as meaning that glaciers and other ice masses remain on land, which massively lowers sea level.

Question 10

Why is water a solvent?

Answer 10

It is a polar molecule, meaning it attracts other charged molecules. As a result, the substance is likely to spread out, dissolving the substance, therefore making water a solvent.

Question 11

What is the biological advantage of water being a solvent? (3 answers)

Answer 11

• Ions being carried in plasma
• Sucrose in phloem sap
• Urea in urine

Question 12

What is the biological advantage of water being transparent?

Answer 12

• Essential for aquatic plants, as sunlight is essential to plants for photosynthesis, which can only be reached as a result of water being transparent.

Question 13

What is the biological advantage of water providing upthrust? (Expand)

Answer 13

Provides a habitat for animals (aquatic animals)
- These can animals can be much larger due to upthrust e.g. the blue whale at 135 tonnes, compared to the largest animal on land which is the elephant at 7 tonnes.

Question 14

What levels of viscosity does water have?

- what does this mean?

Answer 14

Water has a low viscosity.

It can flow easily, with low levels of resistance, which important for the flow of water.

Question 15

What is the biological advantage of water having a low viscoisty?

Answer 15

Its lubricating nature is useful in synovial fluid - which is the fluid between joins.

Question 16

Why does surface tension occur? (Cohesion)

Answer 16

Cohesion between water molecules:
Oxygen atoms in water molecules are attracted to other hydrogen molecules.
- this means that water molecules “stick together”
- It is a pulling force that draws water molecules closer together forming a strong surface layer.

Question 17

What is the biological advantage of water having cohesive qualities?

Answer 17

Surface tension - provides habitat for animals e.g. pond skater, which utilises the surface tension of water.

Question 18

Explain water’s adhesive quailities?

Answer 18

Water molecules are attracted to other materials, as it is a polar molecule.

Question 19

What is the biological advantage to water having adhesive quailities?

Answer 19

Allows water to rise through the xylem tubes e.g. up to 100m in redwood trees.