Water

Question 1

What is H20 made up of?

Answer 1

1 atom of oxygen joined to 2 atoms of hydrogen by a shared pair of electrons in a covalent bond

Question 2

How is water a polar molecule/a dipole? 2

Answer 2

• Oxygen is more electronegative than hydrogen

- The shared negative electrons are pulled towards the oxygen atom

Question 3

What charge is on the hydrogen atoms in water?

Answer 3

A slightly positive charge - delta positive

Question 4

What charge is on the oxygen atoms in water?

Answer 4

A slightly negative charge - delta negative

Question 5

What type of molecule is water?

Answer 5

A dipole/polar

Question 6

What is hydrogen bonding in water?

Answer 6

The delta hydrogen atoms are attracted to the lone pair of other oxygen atoms of the water molecules

Question 7

What are the useful properties of water? 4

Answer 7

• Cohesive
• Solvent
• High specific heat capacity
• High boiling point

Question 8

What does cohesive mean?

Answer 8

Molecules stick together

Question 9

Why is water being cohesive useful? 3

Answer 9

• Helps water flow well
• Useful for transporting substances
• Makes it possible to pull water uphill e.g in xylem

Question 10

Define solvent.

Answer 10

A liquid that other substances dissolve in

Question 11

What types of substances dissolve in water? 2

Answer 11

• Ionic

- Polar

Question 12

What type of substances don’t dissolve in water?

Answer 12

Non polar

Question 13

Why is water being a solvent useful?

Answer 13

Substances for important reactions can dissolve in it to be transported

Question 14

Why do ionic substances dissolve in water? 6

Answer 14

• Water is polar
• The hydrogen delta positive end of the water molecule is attracted to the negative ion [e.g Cl-]
• The oxygen delta negative end of the water molecule is attracted to the positive ion [e.g Na+]
• All the small charges in water add up together to equal the charge of the ion
• The ion breaks free
• Ions are hydrated, completely surrounded by water molecules and have dissolved

Question 15

Give a useful ionic substance dissolved in water

Answer 15

NaCl - salt

Question 16

What reactions is water important in?

Answer 16

Metabolic reactions e.g condensation/hydrolysis

Question 17

Why is water cohesive?

Answer 17

Due to hydrogen bonds

Question 18

What polar molecules are useful to dissolve in water and what makes them polar?

Answer 18

• Sugars - OH group

- Amino acids - NH2 group

Question 19

Give a type of non polar molecule that doesn’t dissolve in water.

Answer 19

Lipids

Question 20

How is water useful in allowing biochemical reactions to occur in cell cytoplasm?

Answer 20

Substances it transports are free to move around and react because they are dissolved

Question 21

What do lipids require to be transported?

Answer 21

Proteins - they form lipoproteins

Question 22

What does water having a high specific heat capacity mean? 2

Answer 22

• A large amount of energy causes only a small increase in temperature
• Water cools and heats up slowly

Question 23

Why does water have a high specific heat capacity and a high boiling point?

Answer 23

Large amount of energy needed to break hydrogen bonds

Question 24

Why is water having a large specific heat capacity useful for organisms? 2

Answer 24

• Helps them avoid rapid changes in internal temperature and maintain a steady one
• Even when external temperature varies considerably

Question 25

Why is water having a high specific heat capacity useful for aquatic organisms?

Answer 25

The large bodies of water they live in do not change temperature rapidly