`Outcome 1- Water/ Ionic equations

Question 1

Properties of water

Answer 1

• High melting and boiling points of water compared wit h similarly sized molecular substances.
• Expands when frozen
• Relatively high latent heat value for fusion and evaporation
• High specific heat capacity
• Ability to dissolve other substances

Question 2

Explain how the properties of water can be explained by the nature of the intermolecular forces between water molecules

Answer 2

The existence of hydrogen bonding between water molecules allows it be a good solvent for other polar substances as well as many ionic substances

Question 3

Why is water different from most liquids with respect to its density in the solid and liqud states

Answer 3

Its solid form is less dense than its liquid form. The molecules are arranged in a more structured hexagonal way. This means ice floats on water and that water freezes from the surface down.

Question 4

What is latent heat

Answer 4

Measures the amount of energy required to change the state of a given amount of substance

Question 5

What is specific heat capacity

Answer 5

The amount of energy needed to raise the temperture of one gram of the substance by one degree celcius.

Question 6

How is water unique to latent heat and SHC

Answer 6

it has the ability to absorb large amounts of heat energy with only a minimal increase in temperture. The higher the SHC is the more energy it must absorb to raise its temp

Question 7

Why would life not exist if ice was denser than water

Answer 7

If Ice were denser than water, bodies of water would freeze solid during winter and the aquatic life would die.

Question 8

How does “like dissolves like” explain that- Potassium chloride dissolves in water

Answer 8

Potassium chloride is ionic and water is Polar

Question 9

How does “like dissolves like” explain that- Ammonia dissolves in water

Answer 9

Ammonia and water are both polar

Question 10

How does “like dissolves like” explain that- Methane is insoluble in water

Answer 10

Methane is non polar where as water is polar

Question 11

Latent heat of fusion

Answer 11

The change from solid to liquid

Question 12

Latent heat of vaporisation

Answer 12

The change from liquid to gaseous

Question 13

Symbol for latent heat is

Answer 13

l and units are kjmol-1 and jkg-1

Question 14

Latent heat of fusion of water is

Answer 14

6.02kj mol-1

Question 15

How much energy is needed to raise 250ml of water from 20C to 100C?

Answer 15

250x 4.18x (100-20)

=83 kj or 8300j or 4.2x 10^3 j

Question 16

Specific heat capacity of water

Answer 16

4.18jg-1

Question 17

Is water electrically neutral?

Answer 17

Pure does conduct electricity very slightly, however the amount is so tiny, it is still viewed as a non conductor.
Water molecules can react with each other. this is called SELF IONISATION OF WATER

Question 18

Hydrophillic

Answer 18

They are polar compounds so they are strong enough to break the cohesive hydrogen bonds. This dissolves with the water

Question 19

Hyrdro phobic

Answer 19

Cannot overcome the cohesive nature of water.

These molecules are non polar and cannot dissolve

Question 20

Capillary action

Answer 20

When water molecules are molecules are attracted to other water molecules by cohesion (Attraction of water) This causes water molecule to go up a glass straw

Question 21

Using water a solvent

Answer 21

Industrial Applications
Biological Applications
Domestic Applications

Question 22

Two reactions when mixing solutions

Answer 22

Nuetralisation and precipation

Question 23

Dissociation is

Answer 23

Ionic compounds dissolving in water

Question 24

Ionisation is

Answer 24

Covelant compounds dissolving in water

Question 25

Equation for self ionisation of water

Answer 25

H2O + H2O -> H3O+ + OH-