Chemistry Questions (Common)

Define the term ‘hydrocarbon’.

(molecules) made up of carbon and hydrogen (atoms only)

Explain how crude oil is separated into fractions.

(crude oil) is heated

(so some of the hydrocarbons) vaporise

the column gets cooler going up

(so) the fractions / hydrocarbons condense at different heights (in the column)

the hydrocarbons condense at their boiling points (bc they have different BPs)

Describe the test for alkenes.

add bromine (water)

(bromine water) changes (from orange) to colourless

Explain the effect of increasing the temperature on the rate of a reaction.

(increasing the temperature) increases the rate of reaction

(because) particles have more energy

(so) the frequency of collisions increases

What is meant by a ‘catalyst’?

increases the rate of reaction

and is not used up during the reaction

Describe how crude oil was formed.

plankton (died)

and were buried (in mud)

and were compressed

over millions of years

• Peat Bogs Came Man

Plankton

Buried

Compressed

Million years

Suggest how sulfur dioxide can be produced by transport.

(some) fuels contain sulfur

(which) reacts with oxygen to produce sulfur dioxide

Give two problems caused by sulfur dioxide as an atmospheric pollutant.

acid rain

respiratory problems (in humans)

Describe how carbon monoxide can be produced by transport.

fuels are burnt

produced by incomplete combustion

Give one disadvantage of using distillation to produce potable water.

large amounts of energy required

Describe one other method to produce potable water from sea water.

reverse osmosis using membranes

Give two methods that can be used to extract copper from leachate solutions.

displacement using (scrap) iron

electrolysis

Describe how metal compounds are obtained from the plants.

plants are harvested

and burned

to produce ash (that contains metal compounds)

Where does the nitrogen come from?

air / volcano

What environmental effect do particulates from burning diesel cause?

global dimming

Explain why water vapour and not liquid water is produced when diesel burns.

diesel) burns at a high temperature

above the boiling point of water

Explain why sulfur being an impurity in diesel causes an environmental problem.

sulfur dioxide (is produced when diesel is burnt)

(which causes) acid rain

(which results in) • damage to buildings / statues / bridges

Why do the substances in a mixture separate in the mobile phase of chromatography?

the substances: • move at different speeds

• have different solubilities

• have different attractions for the (chromatography) paper

Give two reasons why crude oil is not a formulation.

(crude oil is a mixture but) not a useful product

(and) not mixed in carefully measured quantities

crude oil is not designed for a specific purpose

not the same composition all the time

Explain why potable water contains dissolved solids after filtering.

the dissolved solids pass through filter paper

(because) the dissolved solid (particles) are very small

Explain how greenhouse gases cause global warming.

(greenhouse gases) allow short wavelength radiation to enter the atmosphere

(which are) absorbed by the earth and re-emitted as longer wavelength radiation

(which is) absorbed by (greenhouse gases in) the atmosphere

(this) increases the temperature leading to global warming

What are the errors which can be faced during chromatography'?

(start) line drawn in ink

(so ink) will mix with solvent (1)

the solvent is above the (start) line (1)

(so) colours / ink will dissolve (1)

no lid on tank (1) (so) solvent will evaporate (1)

What is more easier to get potable water from: Ground Water or Waste Water?

You should be able to reinforce with infomation

Ground water: Easier to obtain since there are fewer processes and takes less time.

You filter through filter beds to remove insolube solids.

Then you sterilise via ozone, uv, chlorine; since it kills bacteria

Waste water: More harder since there are more processes which takes more time.

You would screen and grit removal to remove any large particales

You then sediment to produce sewage sludge and effluent

Aerobic biological treatement to reduce solid waste

Then you sterilise using uv, chlroine, ozone to kill bacteria

Sludge is then anaerobically digested by specific bacteria, to remove organic matter

Explain the main changes in the amounts of nitrogen and oxygen in the Earth’s atmosphere.

nitrogen increased

(because of) emission from volcanoes

oxygen increased (because of) photosynthesis

Describe how coal was formed from the carbon dioxide present in the Earth’s early atmosphere.

carbon dioxide is used during photosynthesis in trees

(which) die

and are compressed

over millions of years

Describe how bioleaching is used to extract a metal from low grade ores

uses bacteria

to produce leachate solutions

from which copper is obtained by displacement / electrolysis

Explain how a catalyst increases the rate of a reaction.

provides a different reaction pathway

(which) has a lower activation energy

What can scientists predict using Le Chatelier’s Principle?

the effects of changing conditions on the position of an equilibrium

Describe how a reversible chemical reaction is able to reach equilibrium.

the forward and reverse reactions have the same rate

in apparatus which prevents the escape of reactants and products

How is waste water treated?

• Waste water passes through screens to remove large objects and debris

• The water is left in sedimentation tanks so solid sludge sinks to the bottom

• Liquid effluent remains at the top

• Anaerobic bacteria digest the sludge

• Biogas is produced during anaerobic digestion

• Aerobic bacteria break down dissolved organic matter in the effluent

SSEABA

(Sam So Excellent All B’s Ate)

Screen the water to remove objects

Sediment it so sludge sinks to bottom

Effluent remains on top

Anaerobic bacteria digests sludge

Bio gas is produced in result

Aerobic bacteria digests organic matter in effluent

Describe how potable water is produced from water sources.

• Some water is first treated by sedimentation

• Water is passed through filter beds to remove insoluble solids

• Filtration removes suspended particles

• The water is sterilised using chlorine or ozone

• This kills harmful microorganisms

• The clean water is then supplied to homes

SFFSKS

(So Flipping Freaky Sam Killed Sam)

Some water is first treated by sedimentation

Filter beds used to remove large objects

Filtiration removes suspended particles

Sterilise using Ozone, UV or Chlorine

Kills micro-organisms

Supply to homes

How does phytomining work?

• Plants are grown in soil that contains low concentrations of metal compounds

• The plants absorb metal ions through their roots

• The metal ions accumulate inside the plant tissues

• The plants are harvested once they have grown

• The plants are then burned to produce ash containing metal compounds

• The metal is extracted from the ash (often using displacement or electrolysis)

GAAHBE

(Great Andrew Always Helps Big Elliot)

Grow plants in soil with low conc of metal compounds

Absorbs metal ions - plants

Accumulate in plant tissue - the metal ions

Harvest the plants

Burn these plants to produce ash with the metal compounds

Extract metal using electrolysis / displacement

How does bioleaching work?

• Low-grade ore is mixed with bacteria

• The bacteria break down the ore and produce solutions containing metal compounds

• The metal becomes dissolved in solution forming a leachate

• The leachate is collected

• The metal is extracted from the solution (often by displacement using scrap iron or by electrolysis)

• This method is used because it works for low-grade ores and is more environmentally friendly than mining large amounts of rock

BBLCE

(Big Bad Ladies Come England)

Bacteria is mixed with low grade metal ore

Bacteria breaks low grade ore down and produces solution with metal compounds

Leachate is formed

Collect the Leachate

Extract using electrolysis / displacement

What is Quarrying?

• Quarrying is the extraction of rock (e.g. limestone) from large open pits near the Earth’s surface

• Vegetation and soil are removed to expose the rock

• Explosives are used to break up the rock into smaller pieces

• Heavy machinery is used to dig up and load the rock

• Rock is transported away by trucks for use in construction (e.g. roads, cement)

• It can cause environmental impacts such as habitat destruction, noise, dust, and visual pollution

QVEEHTE

(Queen Vineet Eats Everyday, Houses Turn Elite)

Quarrying is extraction of rock

Vegetation removed from plant

Exposes the rock

Explosives used to break down rocks

Heavy Machinery used to dig and load rock onto truck

Transported for use in construction

Environmental impacts such as habitat destruction, dust, noise, visual pollution

What is Mining?

• Mining is the extraction of metals or coal from the Earth

• It can be surface mining (open-cast) or deep mining (underground shafts/tunnels)

• Explosives and machinery are used to access and break up the ore

• The ore is dug out and transported to a processing plant

• The useful metal is extracted from the ore at the processing stage

• It can cause environmental impacts such as habitat destruction, land instability, and pollution (dust/noise/spoil heaps)

MSSEOEE

(Mine So Silly Everday, Opening Every Evening)

Mining is extraction of metals or coal from the Earth

Surface / deep mining

Strip overburden

Explosives to break ore

Ore removed

Extract the ore

Environmental impacts - Habitat destruction, etc