Year 9 Chemistry End Of Year Assessment (Purity, Formulations & Chromatography, Global Reserves & Potable Water 1-28, Life Cycle Analysis & Recycling and Using Materials 27-41)

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What is a pure substance?

A pure substance is a single element or compound that contains no other substances.

What is the difference between a pure substance and a mixture?

A pure substance consists of only one substance (an element or a compound), while a mixture contains two or more different substances not chemically combined.

True or False? Salt dissolved in water is a pure substance.

False. A solution of salt dissolved in water is a mixture.

State what is meant by the term melting point.

The melting point is the temperature at which a solid turns into a liquid.

What is a boiling point?

The boiling point is the temperature at which a liquid turns into a gas.

What property can be used to distinguish a pure substance from a mixture?

Melting point and boiling point can be used to distinguish a pure substance from a mixture.

True or False? Pure substances have a range of melting and boiling points.

False. Pure substances have sharp, specific melting and boiling points, while mixtures have a range.

How can melting and boiling points distinguish between pure substances and mixtures?

Pure substances have specific and sharp melting and boiling points, while mixtures have a range.

Define a formulation.

A formulation is a mixture designed as a useful product.

Give an example of a formulation.

Examples include fuels, cleaning agents, paints, medicines, alloys, fertilisers, and foods.

True or False? Many products are complex mixtures in which each chemical has a particular purpose.

True. Many products are mixtures where each chemical serves a specific function.

How is a formulation made?

By mixing components in carefully measured quantities to ensure desired properties.

True or False? Formulations are compounds.

False. Formulations are mixtures.

What is paper chromatography used for?

To separate substances with different solubilities in a solvent and identify components of a mixture.

What does a single spot on a chromatogram indicate?

That the substance is pure.

What should the base line on a chromatogram be drawn with?

A pencil.

True or False? The solvent level should start above the pencil line on a chromatogram.

False. The solvent should not start above the line to avoid ruining the chromatogram.

How many substances are in sample D?

There are 3 substances in D.

True or False? Multiple spots on a chromatogram indicate a pure substance.

False. Multiple spots indicate a mixture.

True or False? If two substances are the same, they will produce identical chromatograms.

True. Identical substances yield identical chromatograms.

Which colours from A–E does black food colouring contain?

It contains A, E and an unknown.

Why should the baseline in chromatography be drawn in pencil?

Because pencil won't contaminate or run, unlike ink.

State the equation to calculate the retention factor (Rf value).

Rf = distance travelled by sample ÷ distance travelled by solvent front.

What does an Rf value closer to 1 indicate?

That the component is highly soluble in the solvent used.

True or False? The Rf value of a compound is always the same, regardless of the solvent used.

False. Rf value depends on the solvent used.

What is the purpose of calculating Rf values in paper chromatography?

To help chemists identify unknown substances.

Why does an Rf value have no units?

Because it is a ratio.

What does the Rf value range between?

Between 0 and 1.

Identify the mobile and stationary phase in chromatography.

Mobile = water; Stationary = chromatography paper.

True or False? If two substances are the same, they will produce identical chromatograms.

True. Identical substances give identical chromatograms.

What do humans use the Earth's resources for?

Humans use the Earth's resources for shelter, food, warmth, and transport.

What is meant by a finite resource?

A finite resource is one which cannot be replaced, so it will eventually run out.

Define the term sustainable development.

Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

Give an example of a natural product that can be replaced by a synthetic product.

Examples include rubber and fertilisers.

What is meant by a renewable resource?

Renewable resources are those which can be replenished or replaced.

True or False? Wood is an example of a renewable resource.

True. Wood is an example of a renewable resource.

True or False? Rubber is an example of a synthetic product.

False. Rubber is a natural resource as it is extracted from the sap of trees.

Define the term potable water.

Potable water is water that is safe to drink.

True or False? Potable water is pure water.

False. Potable water contains dissolved substances like salts and chlorine.

Describe the two main steps used to produce potable water in the UK.

Filtration and sterilising.

Why is chlorine added to water?

To kill bacteria.

Name three sterilising agents used to treat water.

Chlorine, UV light, and ozone.

Why is water filtered when producing potable water?

To remove insoluble solids.

Define the term desalination.

Desalination is the removal of salt from water.

True or False? Distillation and reverse osmosis can remove salt from water.

True. Distillation and reverse osmosis can remove salt from water.

Why is distillation expensive?

Because it requires large amounts of energy.

True or False? Potable water contains low levels of salts and microbes.

True. Potable water contains low levels of salts and microbes.

Give the main source of fresh water in the UK.

Rainwater collected in the ground, rivers, and lakes.

Give two sources of waste water.

Industrial processes, sewage, and agriculture.

Give the main steps involved in treating sewage.

Screening and grit removal, sedimentation, anaerobic digestion of sewage sludge, and aerobic digestion of the effluent.

Why does sewage need to be treated?

To remove organic matter and harmful microbes.

Describe what happens during the sedimentation of sewage.

The water stands in a tank, and heavier solids sink to the bottom to form sewage sludge.

True or False? Aerobic digestion of the effluent requires oxygen.

True. Aerobic digestion of the effluent requires oxygen.

True or False? The effluent is treated by anaerobic digestion.

False. The effluent is treated by aerobic digestion.

Why happens to the effluent once it has undergone aerobic digestion?

The treated water is released back into the environment.

Why does sewage need to be screened?

To remove large solid materials.

What can the by-products of anaerobic digestion of sewage sludge be used for?

As fertiliser and methane as an energy source.

Why does industrial waste water need to be treated?

To remove organic matter and harmful chemicals.

Why are lifecycle assessments carried out?

Lifecycle assessments are carried out to assess the environmental impact of a product.

Name the four main stages of a life cycle assessment.

Extraction and processing of raw materials, manufacturing and packaging, use of product, and disposal of product.

True or False? It is fairly easy to quantify the use of water, resources, energy sources and production of some waste.

True. It is fairly easy to quantify the use of water, resources, energy sources and production of some waste.

True or False? It is easy to allocate a numerical value to the polluting effect of a product when carrying out a LCA.

False. It is not easy to allocate a numerical value to the polluting effect of a product when carrying out a LCA.

True or False? A life cycle assessment is not an objective process.

True. A life cycle assessment is not an objective process.

Why do materials such as glass and metal need to be recycled and reused?

Because they are made from natural but finite sources.

State two advantages of recycling materials.

Reducing energy use, conserving raw materials, and reducing the amount of waste sent to landfill.

State two disadvantages of recycling metals.

Collection and transportation require energy and fuel, sorting is needed, and final products may be of lower quality.

How does recycling impact the use of fossil fuels?

Recycling reduces the use of fossil fuels.

Describe how a glass bottle can be recycled.

It can be crushed, melted, and remoulded into a different shape.

Describe the process of recycling metals.

Metals are heated until they melt and are then recast into a new shape.

True or False? It is much more energy efficient to recycle metals than it is to extract them as melting and re-moulding requires less energy.

True. Recycling metals is more energy-efficient than extracting them.

Give two factors that determine the amount of separation required for recycling.

The material being recycled and the properties required in the final product.

True or False? Most of the energy needed to produce raw materials, such as glass, comes from limited resources.

True. Most energy used in raw material production comes from limited resources.

True or False? Glass is separated by colour and size before being recycled.

False. Glass is separated by colour and chemical composition before recycling.

Why do thermosetting polymers have high melting points?

Thermosetting polymers have high melting points because there are strong cross-links between polymer chains that need lots of energy to overcome.

Name the monomer used to produce high density and low density poly(ethene).

The monomer used to produce high density and low density poly(ethene) is ethene.

Why do high density and low density poly(ethene) have different properties?

Because they are made under different conditions.

The properties of a polymer depend on which two factors?

The monomers they are made from and the conditions under which they are made.

Describe the structure of a thermosoftening polymer.

A thermosoftening polymer consists of individual, tangled chains with no cross-links between them.

True or False? Thermosoftening polymers can be melted and remoulded to form different shapes.

True. Thermosoftening polymers can be melted and remoulded to form different shapes.

Name the two components of a composite.

Reinforcement and matrix.

True or False? In a composite, the matrix is surrounded by a reinforcement.

False. In a composite, the reinforcement is surrounded by a matrix.

Name the reinforcement and matrix used to make concrete.

Reinforcement: Aggregate (sand and gravel), Matrix: Cement.

True or False? The matrix in carbon fibres is a polymer.

True. The matrix in carbon fibres is a polymer.

True or False? Wood is a natural composite.

True. Wood is a natural composite.

Give two examples of composites.

Concrete, fibreglass, carbon fibre, and wood.

How is soda-lime glass made?

By heating a mixture of sand, sodium carbonate and limestone.

True or False? Borosilicate glass has a lower melting point than soda-lime glass.

False. Borosilicate glass has a higher melting point than soda-lime glass.

Describe how clay ceramics, such as bricks, are made.

Clay ceramics are made by shaping or moulding wet clay and then heating them in a furnace.