Water

Question 1

Which atoms make up water?

Answer 1

1 oxygen atom
2 hydrogen atoms

Question 2

What charge does the oxygen atom have?

Answer 2

Slightly negative (delta negative)

Question 3

What charge do the hydrogen atoms have?

Answer 3

Slightly positive (delta positive)

Question 4

What is the overall charge of water?

Answer 4

Slightly positive (delta positive)

Question 5

What type of molecule is water?

Answer 5

Dipolar molecule (2 charges)

Question 6

What kind of bond joins atoms within a water molecule?

Answer 6

Covalent bond

Question 7

What kind of bond joins water molecules loosely together?

Answer 7

Hydrogen bonds

Question 8

What is water known as and why?

Answer 8

• A universal solvent
• Because it is charged, it is a good solvent
• Useful as almost all chemical reactions of life take place in aqueous solutions

Question 9

What type of molecule can dissolve in water, and what name is given to them?

Answer 9

Polar molecules (charged), called hydrophilic (water-loving)

Question 10

What is an example of a hydrophilic molecule?

Answer 10

Salts, sugars and amino acids

Question 11

What type of molecule can’t dissolve in water, and what name is given to them?

Answer 11

Non-polar molecules (uncharged), called hydrophobic (water-hating)

Question 12

What is an example of a hydrophobic molecule?

Answer 12

Lipids

Question 13

What are the bonds between water molecules doing when water is in a liquid state?

Answer 13

Hydrogen bonds being constantly being broken and unbroken

Question 14

What are the bonds between water molecules doing when water is in a gaseous state?

Answer 14

Hydrogen bonds aren’t there

Question 15

What are the bonds between water molecules doing when water is in a solid state (ice)?

Answer 15

Hydrogen bonds are fixed and permanent

Question 16

How are atoms arranged when a positively charged polar molecule (Na+) dissolves in water?

Answer 16

Oxygen (d-) is attracted to Na+, and the hydrogen atoms stick out

Question 17

How are atoms arranged when a negatively charged polar molecule (Cl-) dissolves in water?

Answer 17

Hydrogen (d+) is attracted to Cl-, and the oxygen atoms stick out

Question 18

What is latent heat of vaporisation?

Answer 18

How much heat energy it takes to turn a liquid into a gas

Question 19

Is the latent heat of vaporisation of water high or low?

Answer 19

High (lots of heat energy is needed)

Question 20

Which natural process uses latent heat of vaporisation?

Answer 20

Sweating

Question 21

How does sweating cool us down?

Answer 21

• When we sweat, water evaporates from the skin surface
• A lot of heat energy is needed to change the liquid to a vapour
• So a lot of heat energy is taken away from the skin (and blood)
• Acting as a coolant

Question 22

What is heat capacity?

Answer 22

• How much heat energy is required to increase the temperature of a liquid by 1·c
  AND
• How much heat energy is lost when a liquid drops in temperature by 1·c

Question 23

Does water have a high or low heat capacity?

Answer 23

High (a lot of heat energy is needed/is lost)