paper 1

Question 1

compound

Answer 1

A compound is a substance made up of two or more different types of atoms chemically bonded together in fixed proportions.

e.g. water (H₂O), carbon dioxide (CO₂), and sodium chloride (NaCl).

Question 2

element

Answer 2

An element is a substance that consists of only one type of atom

e.g. oxygen (O), carbon (C), and hydrogen (H).

Question 3

mixture

Answer 3

a substance with different elements or compounds not chemically combined together.

e.g. air (a mixture of gases), sand and salt, and salad (a mix of vegetables and dressing).

Question 4

name 4 physical separation techniques

Answer 4

can only be used to separate mixtures.

filtration
distillation
crystallisation
chromatography

Question 5

molecule

Answer 5

has any elements chemically combined even if they are the same element

e.g. CH₄

Question 6

filtration

Answer 6

a physical separation technique

used to separate an insoluble solid from a liquid

we need…
- filter paper
- filter funnel
- conical flask

Question 7

insoluble

Answer 7

the solid wont dissolve in the water

Question 8

crystallisation

Answer 8

a physical separation technique

is used to separate a soluble solid from a liquid
e.g. salt and water

Question 9

aq meaning

Answer 9

aq stands for aqueous, meaning a substance is dissolved in water.

Question 10

why is it better to let the water evaporate in it’s own during crystallization?

Answer 10

certain chemicals will break down if we heat them

Question 11

simple distillation

Answer 11

a physical separation technique

used when we want to separate a dissolved solid from a liquid but we want to keep the liquid

Question 12

simple distillation method

Answer 12

• Heat the solution in a flask.
• The liquid with the lower boiling point evaporates.
• Vapour rises into a condenser, where it cools and turns back into liquid.
• The liquid is collected in a separate container, leaving the solute *behind.

Question 13

fractional distillation

Answer 13

when we want to separate a mixture of different liquids

will only work if the liquids have different boiling points

Question 14

fractional distillation method

Answer 14

• Heat the mixture in a flask.
• The liquid with the lowest boiling point evaporates first.
• Vapour passes through a fractionating column, which helps separate the components.
• The vapour cools in a condenser and turns back into liquid.
• Collect the liquids one by one as they condense at their specific boiling points.

Question 15

paper chromatography

Answer 15

a physical separation technique

a process which allows us to separate substances based on their different solubilities.

Question 16

process of paper chromatography

Answer 16

Preparation:
Draw a pencil line near the bottom of a sheet of chromatography paper and place small spots of the mixture on the line.

Stationary Phase:
Place the paper in a container with a small amount of solvent, ensuring the solvent is below the pencil line.

Movement:
The solvent (mobile phase) travels up the paper, carrying the mixture.

Separation:
Different substances move at different speeds and separate as they travel.

Result:
The separated substances appear as spots at various heights on the paper, forming a chromatogram.

Question 17

why do we use pencil when drawing the starting line for paper chromatography?

Answer 17

because if we drew it with pen the pen ink could dissolve in the solvent and move up the paper

Question 18

alpha scattering experiment method

Answer 18

took a piece of gold foil because we can hammer gold into very thin foil - just a few atoms thick

scientists then fired tiny alpha particles (positively charged) at the gold foil

found out that most of the particles passed straight through the gold foil without change in direction.

results
However sometimes an alpha particle was deflected (change in direction) as it passed through the gold foil.

Some even bounced straight back from the gold foil

Question 19

what did the alpha scattering experiment method tell us

Answer 19

• the fact that most of the AP went straight through the GF meant that atoms are mainly empty space
• since some were deflected this meant that the centre of the atom must have a positive charge (++=REPELLED)
• Finally since some bounced back this told us that the centre of an atom must contain a great deal of mass

Question 20

what did the alpha scattering experiment lead to?

Answer 20

it led to the plum pudding model being replaced by the nuclear model of atomic structure

Question 21

who discovered the plum pudding model?

Answer 21

J.J. Thomson in 1904

he also discovered electrons in 1897

Question 22

who discovered the nuclear model

Answer 22

Ernest Rutherford in 1911 after his alpha scattering experiment

he also discovered protons and the nucleus

Question 23

who discovered the nucleus

Answer 23

Ernest Rutherford

Question 24

who discovered neutrons

Answer 24

James Chadwick

Question 25

what did James Chadwick discover?

Answer 25

discovered the neutron in 1932. and that the nucleus also contains neutral particles

Question 26

what is the charge of an atom and why

Answer 26

atoms have no overall charge since they have the same number of protons and electrons so they cancel each other out

Question 27

what are isotopes

Answer 27

Isotopes are atoms of the same element with different numbers of neutrons. e.g. carbon

Question 28

what are ions?

Answer 28

ions are atoms which have an overall charge. that is because ions have lost or gained electrons. - gained = negative - lost = positive e.g. Sodium ion (Na⁺) and Oxygen ion (O²⁻)

Question 29

what is the relative atomic mass

Answer 29

The relative atomic mass is the average mass of an element's atoms, weighted according to the relative abundances of its naturally occurring isotopes. It reflects the average mass of all isotopes

Question 30

what do we call the elements that aren't in a group?

Answer 30

we call them transition elements

Question 31

why do all the elements in the same group have similar chemical properties (react in the same way)

Answer 31

because they all have the same number of electrons in their outer energy level

Question 32

describe the arrangement, movement and energy of particles in solids

Answer 32

Arrangement: Particles are closely packed in a regular, fixed pattern. Movement: Particles vibrate in place but do not move freely. Energy: They have low energy, only enough to vibrate in their fixed positions.

Question 33

describe the arrangement, movement and energy of particles in liquids

Answer 33

Arrangement: Particles are still close together but are not in a fixed pattern, allowing them to move around each other. Movement: Particles can slide past one another, allowing the liquid to flow. Energy: They have more energy than solids, enough to move more freely within the liquid.

Question 34

describe the arrangement, movement and energy of particles in gases.

Answer 34

Arrangement: Particles are far apart and move randomly and independently. Movement: Particles move quickly in all directions. Energy: They have high energy, allowing them to move freely and fill any container they are in.

Question 35

name the interconversions between solids, liquids and gases. (6)

Answer 35

- Melting: Solid → Liquid - Freezing: Liquid → Solid - Evaporation: Liquid → Gas - Condensation: Gas → Liquid - Sublimation: Solid → Gas - Deposition: Gas → Solid

Question 36

what's a boiling point

Answer 36

A boiling point is the temperature at which a substance changes from a liquid to a gas. At this point, the substance has enough thermal energy for the particles to break free from the liquid phase and form a gas.

Question 37

what's a melting point

Answer 37

A melting point is the temperature at which a solid turns into a liquid. At this temperature, the solid absorbs enough heat energy to break the bonds holding its particles in a fixed position, causing it to melt.

Question 38

what's an atom

Answer 38

is the smallest unit of an element that retains the chemical properties of that element consists of a nucleus made up of protons and neutrons, and surrounded by electrons.

Question 39

describe how the periodic table is arranged in

Answer 39

increasing atomic number

Question 40

explain why the noble gases do not readily react using their electronic configurations.

Answer 40

they have full outer electron shells, making them stable and unreactive. they don't need to loose or gain an electron to be complete

Question 41

write a word equation to represent the chemical reaction for salt

Answer 41

Sodium + Chlorine → Sodium Chloride (NaCl - table salt)

Question 42

write a chemical equation to represent the chemical reaction for salt

Answer 42

2 Na (s) + Cl₂ (g) → 2 NaCl (s)

Question 43

explain why carbon monoxide is poisonous.

Answer 43

it binds to haemoglobin in the blood more strongly than oxygen, reducing the blood's ability to transport oxygen to cells and tissues.

Question 44

describe how sulfur dioxide is formed in combustion reactions.

Answer 44

Sulfur dioxide (SO₂) is formed during combustion when fuels containing sulfur impurities burn. The sulfur reacts with oxygen in the air to produce SO₂: S + O₂ → SO₂.

Question 45

what's the difference between short and long chains of hydrocarbons

Answer 45

long chains are less flammable and the boiling point increases opposite for short ones

Question 46

exothermic reactions

Answer 46

An exothermic reaction releases energy, usually in the form of heat, to the surroundings. Examples include combustion and respiration.

Question 47

Endothermic reactions

Answer 47

takes in energy from the surroundings. so temperature of the surroundings decreases (colder)

Question 48

what makes things acidic

Answer 48

Substances are acidic if they release hydrogen ions (H⁺) when dissolved in water. The higher the concentration of H⁺ ions, the stronger the acid.