CHEMISTRY REVISION GUIDE

Question 1

what does the state depend on?

Answer 1

It depends on the forces of attraction between the particles. These forces depend on the material, temperature and pressure.

Question 2

Describe solids

Answer 2

In solids, there are…

• strong forces of attraction holding it together in a fixed regular lattice arangement
• definite shape and volume
• their particles vibrate in their positions
• when heated, their particles vibrate faster and allow the to expand

Question 3

describe liquids

Answer 3

in liquids, there are…

• weak forces of attraction between the the particles
• randomly arranged (but they tend to stay closely together.
• the dont have a fixed shape but do have a fixed volume.
• their particles are constantly moving but when heated the expand

Question 4

describe gases …

Answer 4

in gases, there are…

• very weak forces of attraction
• move far apart from each other
• travel in straight lines between collisions
• constantly moving randomly
• don’t have definite shape of volume (they fill any container)
• when heated their particles move faster which means they expand or their pressure increases

Question 5

what is solid -> liquid

Answer 5

melting

Question 6

what is liquid -> gas

Answer 6

evaporating

Question 7

what is gas -> liquid

Answer 7

condensing

Question 8

what is liquid -> solid

Answer 8

condensing

Question 9

what is solid -> gas

Answer 9

subliming

Question 10

define diffusion

Answer 10

the gradual net movement of particles moving from areas of high concentration to areas of low concentration until a uniform concentration is achieved

Question 11

what experiment is used to demonstrate diffusion through liquids

Answer 11

1) potassium manganate (vii) + water

Question 12

what are your observations in the experiment to test diffusion in liquids.

Answer 12

1) the potassium manganate is placed at the bottom of the beaker
2) the particles are slowly diffusing out a,ong the particles in the water
3) it’s the random motion of particles in the liquid which cause it to eventually spread out.

(if you were to add more water, the particles could spread out even further making it less purple . This is called dilution.)

Question 13

what are the 2experiments to show diffusion between gases

Answer 13

ammonia + hydrogen chloride

and

bromine gas and air

Question 14

describe what is observed in the diffusion experiment- ammonia and hydrogen chloride

Answer 14

1) the aqueous ammonia (cotton wool soaked in NH3) gives off ammonia gas and the hydrochloric acid gives off hydrogen chloride gas.
2) the NH3 gas diffuses from one end of the tube and the HCl on the other
3) A white ring of ammonium chloride will form at the end closer to HCl as is diffuses faster (ammonia is lighter)

Question 15

describe what you observe in the experiment: bro kng gas and air

Answer 15

1) fill a jar full of bromine gas and the other with air (separated by a glass plate)
2) remove and watch the diffusion take place
3) the random movement of particles mean it will completely fill the jar.

Question 16

key features of the nucleus

Answer 16

contains protons and neutrons

has positive charge (because of protons)

almost its entire mass is concentrated here

Question 17

describe the key feature of electrons

Answer 17

they move around the nucleus in energy levels, called shells

negatively charged

their size of their orbits determines the size of the atom

the has virtually no mass

Question 18

protons :

relative mass and charge

Answer 18

they are heavy with a R.M of 1

positively charged (+1)

Question 19

neutrons:

relative mass and charge

Answer 19

heavy - rm 1

no charge (0)

Question 20

electrons:

relative mass and charge

Answer 20

tiny - 1/2000

negatively charged (-1)

Question 21

describe the neutral charge of atoms

Answer 21

they have no charge overall. this means that the charge on the electrons is the same size as the protons. the number of electrons will be equal to the number of protons . if protons are added or removed, the atom will become and ion

Question 22

a
X
b

Answer 22

a=mass number (p+n)
b=atomic number (p)
X=atom

Question 23

describe molecules

Answer 23

molecules are groups of atoms e.g. O2

atoms can form together to make molecules, some can be made from one or more than one element e.g. H2O. molecules are held together by covalent bonds

Question 24

definition of an element

Answer 24

An element consists of one type of atom. They cannot be broken down into simpler substances by chemical means (heat or electricity). An example is O2- elements can also be molecules.

Question 25

definition of a compound

Answer 25

a compound is a substance made of two or more atoms chemically bonded together by heat or electricity. they can be separated by a chemical reaction. an example of this is CO2

Question 26

definition of mixture

Answer 26

a mixture is a substance made up of to or more atoms which have not been bonded together through chemical means. they can be separated through physical methods e.g. distillation. an example of this is air.

Question 27

what type of separation is filtration and crystallisation?

Answer 27

a form of separation where the substance is not chemically bonded together- the physical method to separate mixtures.

Question 28

filtration experiment

Answer 28

it is used to separate insoluble solids from a liquid reaction mixture. it is also a type of purification, for example, solid impurities in the reaction mixture are separated out using filtration.

apparatus: filter paper, filter and beaker

the filter paper is folded into a cone shape and the solid remains in the filter paper while the liquid can get through the tiny holes.

Question 29

crystallisation experiment

Answer 29

it is used to separate an insoluble solid from a solution.

apparatus: evaporating dish, tripod and Bunsen burner

method:
pour solution in dish

slowly heat - some of the solvent will evaporate and the solution will become more concentrated

stop heating when crystals start to form

remove fish and leave in a warm place to allow the rest of the solvent to evaporate

place the dry product in a drying oven

Question 30

method to separate rock salt

Answer 30

rock salt is a mixture made up of salt and sand. salt and sand are compounds however sand is insoluble in water.

the 4 steps of separation

grinding: grind up with pestle and mortar
dissolving: dissolve in a beaker and stir (sand is insoluble)

filter (collection of sand) : filter through filter paper with funnel ( the sand grains won’t get through the tiny holes)

crystallisation(collection of salt): evaporate in evaporating dish ( water will evaporate leaving the salt ).

Question 31

what are materials made of?

Answer 31

materials come in 3states of matter ; solid, liquid and gases