Module 2 Section 2 - Water

Question 1

Why is water important

Answer 1

• it is a reactant and solvent
• it transport substances
• it helps with temperature control
• it is a habitat

Question 2

What is meant by water is a reactant

Answer 2

It is important in loads of chemical reactions, including hydrolysis reactions

Question 3

What is meant by water is a solvent

Answer 3

Substances can dissolve in it. Most biological reactions take place in solution

Question 4

What is meant by water transport substances

Answer 4

It is a liquid and a solvent meaning it can easily transport all sorts of materials like glucose and oxygen around plants and animals

Question 5

What is meant by water helps with temperature control

Answer 5

Has a high specific heat capacity and a high latent heat of evaporation

Question 6

What is meant by water is a habitat

Answer 6

many organisms can survive and reproduce in it because, it helps with temperature control, is a solvent and is less dense when it freezes

Question 7

A molecule of water is….

Answer 7

One atom of oxygen joined by 2 atoms of hydrogen - joined by shared electrons

Question 8

Why is the other side of each hydrogen left with a slight charge

Answer 8

Because the shared negative hydrogen electrons are pulled towards the one oxygen atom

Question 9

Why is the oxygen atom slightly charged

Answer 9

Because the unshared negative electrons give it a slight charge

Question 10

Is water a polar molecule

Answer 10

Yes - it has a partial negative charge on one side and a partial positive charge on the other

Question 11

What is meant by hydrogen bonding

Answer 11

The slightly negatively charged oxygen atoms attract the slightly positive charged hydrogen atoms of the other water molecules

Question 12

What is specific heat capacity

Answer 12

The amount of energy needed to raise the temperature of 1 gram of a substance by 1°c

Question 13

Why do hydrogen bonds allow water to have high Specific heat capacity

Answer 13

The hydrogen bonds between the water molecules can absorb a lot of energy

Question 14

Because water has a high SHC (Specific Heat Capacity) it means water doesn’t experience what

Answer 14

It means water doesn’t experience rapid temperature changes - this also makes it a good habitat because the temperature under water is likely to be more stable than it is on land

Question 15

What also does hydrogen bonds give water what

Answer 15

A high latent heat of evaporation

Question 16

What does high latent heat of evaporation mean

Answer 16

It takes a lot of energy to break hydrogen bonds between water molecules so a lot of energy is used up when water evaporates

Question 17

What does high latent of evaporation mean for water

Answer 17

Means water is great for cooling things down e.g. we sweat when we too hot when sweat evaporates it cools the surface of our skin

Question 18

What does water’s polarity make it

Answer 18

Very cohesive

Question 19

What is cohesion

Answer 19

The attraction between molecules of the same type - water molecules are cohesive because they are polar

Question 20

What does water’s cohesiveness mean for the properties of water

Answer 20

The cohesiveness means it helps water flow making it great for transporting substances

Question 21

What does waters polarity also make it

Answer 21

A good solvent

Question 22

A lot of important substances in biological reactions are ….

Answer 22

Ionic

Question 23

What does ionic mean

Answer 23

They’re made from one positively charged atom or molecule and one negatively charged atom or molecule

Question 24

How is water ionic

Answer 24

Because water is polar, the slightly positively charged end of a water molecule will be attracted to the negative ion and the slightly negative end of a water molecule will be attracted to the positive ion

Question 25

Why will water dissolve other substances

Answer 25

Because the ions will totally get surrounded by water molecules

Question 26

Water is what when it is a solid

Answer 26

Less dense

Question 27

What happens to water at low temperatures

Answer 27

It freezes

Question 28

What does freezing mean for the water molecules

Answer 28

Water molecules are held further apart in ice than they are in liquid water because each water molecule forms 4 hydrogen bonds to other water molecules making a lattice shape

Question 29

Why is water as a solid beneficial for organisms such as fish

Answer 29

In cold temperatures ice forms an insulating layer on top of water - the water below the ice doesn’t freeze. Meaning fish don’t freeze and can still move around