Biological Molecules (water)

Question 1

What is special about water

Answer 1

Water is the only molecule that can be present in all states at one time

Question 2

What is the structure of water

Answer 2

Each hydrogen shares a pair of electrons with the oxygen

Question 3

What does oxygen have a higher affinity for

Answer 3

The oxygen has a greater affinity for electrons than the hydrogens, so it pulls them closer.

Question 4

What does oxygen having a higher affinity mean

Answer 4

The oxygen becomes slightly negative and the hydrogen slightly positive. This creates different charged regions making it a polar molecule.

Question 5

What do the different charges in water result in

Answer 5

The slightly negative charged oxygen on one water molecule attracts the slightly positive hydrogen of another water molecule.

Question 6

Draw 2 water molecules together

Answer 6

DRAW IT

Question 7

What is water at room temperature

Answer 7

Water is a liquid at room temperature not a gas.

Question 8

Why is water being a liquid at room temperature useful for organisms

Answer 8

It’s a habitat for aquatic organisms - oxygen/nutrients can circulate, organisms can float as water is a similar density to living organisms
It’s an effective transport medium
It’s a medium for chemical reactions

Question 9

What happens when a polar molecule is dissolved in water

Answer 9

The water molecules form a layer around the ions and breaks the ionic substance apart.

Question 10

What are lipids an example of

Answer 10

Non polar molecules

Question 11

Why do non polar molecules not dissolve in water

Answer 11

They don’t dissolve in the water because they don’t attract to the water molecules.

Question 12

What do the different parts of the water molecules do to the ions

Answer 12

The slightly positively charged hydrogen attracts to the negatively charged ions and the slightly negative charged oxygen attracts to the positively charged ions.

Question 13

What does the attraction between ions and water molecules do

Answer 13

Separates the molecules forming a solution

Question 14

What does the property allow water to be

Answer 14

To act as a medium for chemical reactions in cells transporting dissolved molecules around living organisms.

Question 15

What happens to the density of water as it freezes

Answer 15

It decreases

Question 16

Why does the density of water decrease when it freezes

Answer 16

Because the hydrogen bonds fix the position of the molecules slightly further apart than the average distance in the liquid state, producing a giant open structure, with every oxygen at the centre of a tetrahedral arrangement.

Question 17

Why is ice being less dense than water an important property

Answer 17

Animals such as polar bears can live on ice and ice forms a protective layer on ponds which insulates the water below, reducing the rate of heat loss and making the environment more stable for aquatic organisms.

Question 18

What is cohesion in terms of water

Answer 18

At the surface the water molecules are all hydrogen bonded to the molecules below them which gives the surface of the water an ability to resist force applied to it.

Question 19

What does cohesion mean for water

Answer 19

It means that the molecules stick together.

Question 20

What does the hydrogen bonding lead to in terms of temperature

Answer 20

It has a high specific heat capacity.
This means that a large amount of heat energy is needed to alter its temperature.
This prevents large fluctuations in temperature.

Question 21

What does this mean for aquatic organisms

Answer 21

It provides a constant environment allowing them to survive

Question 22

What is adhesion for water molecules

Answer 22

Adhesion is the attraction between a water molecule and another polar molecule due to hydrogen bonding.

Question 23

What do cohesion and adhesion allow for

Answer 23

Together with cohesion, this is what enables water to move up xylem tissue from roots to the leaves (capillary action).

Question 24

What is the last property of water (liquid-gas)

Answer 24

It has a high latent heat of vaporisation.
This is because energy is needed to overcome the hydrogen bonding between water molecules.

Question 25

What does a high latent heat of vaporisation make water

Answer 25

An excellent coolant

Question 26

How do plants and animals make use of this

Answer 26

Mammals are cooled when sweat evaporates and plants are cooled when water evaporates from mesophyll cells in leaves.