Paper 1 Chemistry

Question 1

Diffusion

Answer 1

The movement of particles from an area of high concentration to an area of low concentration (2)

Question 2

Pure

Answer 2

A substance that has only one type of atom or compound (2)

Question 3

Mixture

Answer 3

Contains elements and/or compounds that are not chemically bonded, and have no fixed composition (2)

Question 4

Filtration

Answer 4

The separation of a soluble substance from an insoluble substance, by dissolving, filtering and evaporating (2)

Question 5

Saturated solution

Answer 5

When the maximum mass of solute that can dissolve in that volume of that particular temperature (2)

Question 6

Crystallisation Point

Answer 6

When some of the solution is evaporated and the crystals start to form; shows that a saturated solution has formed (2)

Question 7

Simple distillation

Answer 7

The separation of two liquids with very different boiling points (2)

Question 8

Fractional distillation

Answer 8

The separation of miscible liquids with different boiling points (2)

Question 9

Chromatography

Answer 9

The use of parts of a mixture’s solubility to identify components in the mixture (2)

Question 10

Desalination

Answer 10

The removal of salt (2)

Question 11

Atom

Answer 11

The smallest complete part of any element (1)

Question 12

Describe the arrangement, movement, and relative energy of particles in solids and liquids.

Answer 12

In solids, the particles are very rigid and are arranged in a fixed lattice structure.
They cannot move freely but can only vibrate in place.
In liquids, the particles are close together but can move more freely and flow.
They still maintain contact with one another.
The energy of particles in solids is low, while in liquids, it is higher, allowing for movement. (2)

Question 13

Explain the difference between a pure substance and an impure substance.

Answer 13

A pure substance consists of only one type of atom, molecule, element, or compound, meaning it has uniform composition.
This results in a sharp, fixed boiling point.
In contrast, impure substances contain a mixture of different atoms or molecules.
This causes them to have a range of boiling points, leading to a broader melting range.
The presence of different components affects the physical properties, such as boiling point and melting point. (2)

Question 14

Describe the process of simple distillation.

Answer 14

An impure solution is placed in a round-bottomed flask connected to a condenser.
The solution is heated using a Bunsen burner.
The liquid with the lower boiling point evaporates first.
This vapour then travels through the condenser, where it cools and condenses back into liquid form.
The condensed liquid is collected in a separate container (beaker).
This method effectively separates components based on their boiling points. (2)

Question 15

Explain the differences between simple and fractional distillation.

Answer 15

Simple distillation is used for separating liquids with significantly different boiling points, typically greater than 25°C apart.
Fractional distillation employs a fractionating column, which provides a larger surface area for multiple condensation and vapourisation cycles.
This allows it to separate liquids with closer boiling points, often within 25°C.
Simple distillation does not prevent other components from evaporating with the desired liquid, while fractional distillation does.
Therefore, fractional distillation is more efficient for complex mixtures. (2)

Question 16

Describe how wastewater is treated to make it potable.

Answer 16

Wastewater treatment begins with screening to remove larger particles like twigs and leaves using a sieve.
The water then enters a sedimentation tank where smaller solid particles settle out.
After sedimentation, the water is filtered through layers of gravel and sand to remove finer particles.
Finally, it is chlorinated to kill harmful bacteria, ensuring it is safe for drinking. (2)

Question 17

Explain the process of paper chromatography.

Answer 17

A pencil line is drawn on the chromatography paper to ensure it does not travel with the inks.
The inks are placed on the line with some space apart to prevent them from mixing together.
The paper is then submerged in water, ensuring the pencil line does not touch the water.
Over time, different solubilities of the dyes will travel up different distances in the paper, showing the various components.
(2)

Question 18

How can Rf values be used to identify components in a mixture?

Answer 18

The Rf values from an experiment can be compared to values collected from other experiments using the same paper and solvent.
This comparison helps identify the specific components present in the mixture based on their known Rf values.
If the Rf values match those of known substances, their presence in the mixture is confirmed. (2)

Question 19

Describe the changes that occur during the melting of a solid.

Answer 19

When a substance is solid, the particles are rigid and in a fixed lattice structure, vibrating in place.
As it is heated, thermal energy is transferred to the kinetic energy of the particles.
This energy allows the particles to break intermolecular forces and move more freely, resulting in a change to the liquid state.
The flat line on a heating curve indicates that energy is being used to break forces rather than increasing temperature. (2)

Question 20

Screening

Answer 20

using a sieve to remove twigs and leaves; a stage to purify wastewater (2)

Question 21

Sedimentation

Answer 21

when the wastewater without any leaves or twigs is placed in a reservoir where small particles are allowed to settle out; a stage of purifying wastewater (2)

Question 22

Filtration

Answer 22

using bags of sand and gravel in a filtration tower to remove finer particles; a stage to purify wastewater (2)

Question 23

Chlorination

Answer 23

when chlorine is bubbled through the water to kill harmful bacteria; a stage to purify wastewater (2)