introduction

Question 1

observations made when describing substances:

Answer 1

• solid, liquid or gas
• coloured of colourless
• crystalline or powdered (solids)
• clear or cloudy (liquids)

Question 2

observations made when describing changes:

Answer 2

• fizzing
• solid appeared/ disappeared
• colour change
• unusual sound/ smell

Question 3

signs of a physical change:

Answer 3

• no new substances
• easy to reverse
• absorb/ release small amounts of energy

Question 4

example test of a physical change:

Answer 4

melting ice in a beaker:
- particles are still water particles but move around more
- easy to reverse (freeze)
- beaker does not get much hotter/ colder

Question 5

signs of a chemical change:

Answer 5

• creates new substance
• difficult to reverse
• absorb/ release large amounts of energy

Question 6

example test of a chemical change:

Answer 6

burning wood on the floor:
- oxygen and wood particles turn into soot and ash
- impossible to reverse
- floor gets hotter

Question 7

chemical test for water:

Answer 7

anhydrous copper (II) sulphate: turns white to blue
-> shows that water is present, but not how pure it is

Question 8

physical test for water:

Answer 8

melting point (MP) = 0C
boiling point (BP) = 100C
-> pure water matches these properties more closely

Question 9

define ‘element’

Answer 9

substance that contains only one type of atom

Question 10

how can elements be categorised?

Answer 10

metal or non metal (according to their properties)

Question 11

metal properties of an element:

Answer 11

high melting/ boiling point
malleable
shiny
electrical conductors

Question 12

non metal properties of an element:

Answer 12

low melting/ boiling point
brittle
dull
electrical insulators

Question 13

where are metals based on a periodic table?

Answer 13

left-hand side

Question 14

where are non metals based on a periodic table?

Answer 14

right-hand side

Question 15

what are the 8 diatomic molecules?

Answer 15

hydrogen (H2), nitrogen (N2), oxygen (O2), fluorine (F2), chlorine (Cl2), bromine (Br2), iodine (I2), astatine (At2)

Question 16

define ‘compound’

Answer 16

substance containing more than 1 type of atom, chemically bound together

Question 17

how are compounds often formed?

Answer 17

by heating the elements together

Question 18

what are the 3 different compounds

Answer 18

metallic bonding (metals)
ionic bonding (both)
covalent bonding (non metals)

Question 19

what happens when ammonia and hydrogen chloride meet in a sealed tube?

Answer 19

ammonium chloride forms as a white smoke

Question 20

how can you speed up an experiment?

Answer 20

heat, stirring

Question 21

define ‘solute’

Answer 21

substance that dissolves in the solvent

Question 22

define ‘solvent’

Answer 22

the liquid that dissolves solute

Question 23

define ‘solution’

Answer 23

mixture of solute and solvent

Question 24

define ‘saturated’

Answer 24

a solution where no more solute can be dissolved

Question 25

define ‘suspension’

Answer 25

solid floating in a liquid because it cannot dissolve

Question 26

define ‘soluble’

Answer 26

a substance which can be dissolved

Question 27

define ‘insoluble’

Answer 27

a substance which cannot be dissolved

Question 28

how do you measure solubility

Answer 28

g per 100g of solvent

Question 29

what happens when you heat up ammonium chloride in a tube

Answer 29

white smoke forms faster because the particles move faster and collide more often. It still forms in the same place because both gases diffuse faster

Question 30

what does the line show on a solubility curve

Answer 30

saturated

Question 31

what does below the line show on a solubility curve

Answer 31

soluble

Question 32

what does above the line show on a solubility curve

Answer 32

insoluble

Question 33

fill in the blank: solubility ______ with temperature

Answer 33

varies