Principles of Chemistry

Question 1

What are the properties of solids?

Answer 1

• fixed shape
• fixed volume
• cannot be compressed

Question 2

What are the properties of liquids?

Answer 2

• no fixed shape, take shape of their container
• fixed volume
• can flow
• cannot be compressed

Question 3

What are the properties of gases?

Answer 3

• no fixed shape, take shape of their container
• no fixed volume, take up volume of their container
• can flow
• can be compressed

Question 4

Describe the structure of solids.

Answer 4

• regular arrangement
• particles tightly packed (touching each other)
• vibrate about their fixed position

Question 5

Describe the structure of liquids.

Answer 5

• no regular arrangement
• tightly packed particles (less than solid)
• particles further apart
• move randomly at different speeds, not far as they frequently collide with other particles

Question 6

Describe the structure of gases.

Answer 6

• no regular arrangement
• particles move randomly at different speeds, much faster than liquids
• particles separated

Question 7

solid to liquid

Answer 7

melting

Question 8

solid to gas

Answer 8

sublimation

Question 9

liquid to solid

Answer 9

freezing

Question 10

liquid to gas

Answer 10

evaporating/boiling

Question 11

gas to solid

Answer 11

deposition

Question 12

gas to liquid

Answer 12

condensing

Question 13

Explain changes of state in terms of the kinetic theory.

Answer 13

temperature of a substance increases, the average KE of particles rises, gain enough energy to overcome forces of attraction
vice-versa for temperature drop

Question 14

Describe the effects of temperature on the volume of a gas.

Answer 14

temperature of gas increases, particles move faster and further (still randomly), increasing distance between particles, so the volume of the gas increases

Question 15

Describe the effects of pressure on the volume of a gas.

Answer 15

• increase the pressure of a gas, volume decreases
• same number of particles, less volume.
• same number of particles will exert more collisions on the sides of the container, increasing pressure

Question 16

Define diffusion.

Answer 16

movement of particles from an area of high concentration to an area of low concentration, until the concentrations are even throughout

Question 17

State factors which affect diffusion rate.

Answer 17

• temperature
• concentration gradient
• molecular mass

Question 18

What is a concentration gradient?

Answer 18

The difference in concentration of a fluid between two connected areas

Question 19

What is the effect of molecular mass on rate of diffusion?

Answer 19

the greater the molecular mass, the slower the molecules move, decreasing RoD

Question 20

Explain the dependence of rate of diffusion on molecular mass.

Answer 20

larger molecules carry more mass, need more KE than smaller molecules to move the same distance

Question 21

What is an element?

Answer 21

chemical substance that cannot be broken down into simpler substances and is composed of only one type of atom

Question 22

What is a compound?

Answer 22

substance made of two or more elements chemically bonded together

Question 23

What is a mixture?

Answer 23

two or more chemical substances found together but not chemically bonded

Question 24

Describe the properties of metals.

Answer 24

• good electrical and thermal conductors
• high melting and boiling points
• most are malleable
• ductile

Question 25

Describe the properties of non- metals.

Answer 25

- good electrical and thermal insulators - usually have low melting and boiling points - not malleable - not ductile

Question 26

Apparatus for the measurement of time.

Answer 26

stopwatch

Question 27

Apparatus for the measurement of temperature.

Answer 27

thermometer

Question 28

Apparatus for the measurement of mass.

Answer 28

mass balance

Question 29

Apparatus for the measurement of volume.

Answer 29

burettes, volumetric pipettes, measuring cylinders

Question 30

Burettes are used to measure...

Answer 30

volume

Question 31

What are pipettes are used to measure?

Answer 31

volume

Question 32

What is a solvent?

Answer 32

a substance that dissolves a solute

Question 33

a substance that dissolves a solute

Answer 33

solvent

Question 34

What is a solute?

Answer 34

a substance that is dissolved in a solvent

Question 35

a substance that is dissolved in a solvent

Answer 35

solute

Question 36

What is a solution?

Answer 36

a mixture of one or more solutes dissolved in a solvent

Question 37

What is a saturated solution?

Answer 37

a solution containing the maximum concentration of a solute dissolved in the solvent at a specified temperature

Question 38

What is residue?

Answer 38

a substance that remains after evaporation, distillation, filtration or any similar process

Question 39

What is a filtrate?

Answer 39

a liquid or solution that has passed through a filter

Question 40

Why is paper chromatography used?

Answer 40

to separate mixtures of soluble coloured substances, using a suitable solvent

Question 41

Equation for Rf

Answer 41

distance travelled by substance/distance travelled by solvent

Question 42

What are some examples of purification?

Answer 42

suitable solvent, filtration, crystallisation and distillation

Question 43

Purification with a solvent:

Answer 43

mixtures of solid substances are separated using solvents to create a suspension that can be filtered

Question 44

Filtration:

Answer 44

removes an insoluble solid from liquids by pouring through a filter, such as filter paper

Question 45

Crystallisation:

Answer 45

used to obtain solid dissolved in a solution; as the liquid part of the solution cools + becomes denser, there's less space for solid particles to occupy. These particles are excluded from the liquid and form crystal arrangements on the side of the vessel.

Question 46

In which condition does crystallisation work best?

Answer 46

when there is a large difference between the solubilities of a given soluble solid at high and low temperatures

Question 47

Distillation:

Answer 47

separates liquids by temporarily transforming one of the liquids into a gas

Question 48

How can you assess a substance's purity using melting and boiling point information?

Answer 48

Impurities within a substance alter the temperature at which the bonds between them form/break, changing melting and boiling points

Question 49

In chromatography, what are the unknown substances?

Answer 49

solutes

Question 50

What happens during paper chromatography?

Answer 50

- unknown substances (solutes) carried up a sheet of filter paper by a solvent - solutes move at different rates - spread out and are deposited at different positions along the filter paper

Question 51

In paper chromatography, why do solutes move at different rates?

Answer 51

according to their mass and solubility

Question 52

What is Rf?

Answer 52

retardation factor value: distance a substance travels from the reference line

Question 53

How can you identify substances in chromatography?

Answer 53

Assuming that the Rf value of a pure substance has previously been established, Rf values of each unknown solute can be found and the substance identified by comparison

Question 54

How can paper chromatography be used to separate mixtures of soluble colourless substances?

Answer 54

using a suitable solvent and a locating agent

Question 55

What is a locating agent and what is it used for?

Answer 55

- chemical substance that reacts with solute(s) separated in chromatography, to produce a coloured substance - used to identify colourless compounds separated in chromatography