U2 AOS 1 Chapter 9

Question 1

condensation

Answer 1

state change from gas to liquid (opposite to vapourisation)

Question 2

group 16 hydride

Answer 2

Group 16 element covalently bonded to hydrogen, all group 16 hydrides are V-shaped

Question 3

specific heat capacity definition

Answer 3

the amount of energy required to raise the temperature of 1g of a substance by 1 degree C

Question 4

latent heat of vapourisation definition

Answer 4

the amount of energy that needs to be absorbed by 1 mol of a substance to convert it from liquid to gaseous state at its boiling point

Question 5

transition of a substance between states

Answer 5

phase change

Question 6

potable water

Answer 6

drinkable; low salt content, free from contaminants

Question 7

brackish water (+ eg.)

Answer 7

more salinity than freshwater, less than seawater eg. swamps, lakes, estuaries

Question 8

uses of water

Answer 8

solvent (polarity), coolant (heat absorption), means to convert thermal to mechanical energy

Question 9

water vs potable water (statistics on earth)

Answer 9

more than 70% of Earth’s surface is water (97% salt, 3% fresh), vast majority is not drinkable

Question 10

freshwater eg

Answer 10

eg. lakes, rivers, streams

Question 11

water vapour eg.

Answer 11

air

Question 12

What is the structure of water?

Answer 12

each water molecule can form up to 4 hydrogen bonds

Question 13

specific heat capacity formula (+ constants)

Answer 13

q=mc∆T where heat capacity of water is 4.18J/g/C

Question 14

mL to g

Answer 14

x 0.997

Question 15

ice structure

Answer 15

less than water, molecules move slowly, form hydrogen bonds w/ 4 water molecules, tetrahedral lattice structure, molecules further apart

Question 16

liquid water structure (vs ice)

Answer 16

more dense than ice, molecules move fast, form hydrogen bonds w/ 4 water molecules randomly, random arrangement, molecules closer together

Question 17

latent heat formula (+ constant)

Answer 17

q=n x kJ/mol where LHV of water is 44.0kJ/mol

Question 18

significance of thermal properties of water

Answer 18

1. heat is absorbed (coolant)
2. high specific heat temp ensures constant biological temp
3. SHC prevents solar energy raising temp of ocean - rising global temp combats thermal properties of water

Question 19

Why does water have a high latent and specific heat?

Answer 19

strong IMFs, absorbs large amount of energy in bonds before it changes state or temp

Question 20

Why does water act as a coolant?

Answer 20

high specific heat capacity, stores large amounts of energy before temp increases (efficient)

Question 21

Why is water able to form 4 hydrogen bonds?

Answer 21

polar bonds between oxygen and two hydrogens

water = oxygen (two partially negative lone pairs), two hydrogens (partially positive)

opposite partial charges on seperate water molecules attract, 4 hydrogen bonds can be made

Question 22

How does water’s high latent heat of vapourisation allow the temperature of water to remain stable?

in relation to ocean

Answer 22

large amount of energy is removed from ocean when it evaporates

allows heat to be released reducing the amount of heat stored in the water = maintaining stable, relatively cool temperature (like sweating)