Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

chemistry > lastmin > Flashcards

lastmin Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

Fractional Distillation stages

A

1-Crude Oil is heated to a very high temperature causing the crude oil to boil so all the Hydrocarbons evaporate and turn into a gas

2-Crude Oil Vapour is then fed into the fractional distillation column , the column is hotter at the bottom and cooler at the top .

3- Hydrocarbon vapours now rise up the column, the hydrocarbons condense when they reach their boiling point and then the liquid fractions are removed. The remaining hydrocarbons continue moving up the column and these condense when they reach their boiling point.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Fractions contain hydrocarbons with a similar number if carbon atoms. Some fractions are used as fuels. What is petrol and diesel use to do

A

fuel cars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Fractions contain hydrocarbons with a similar number if carbon atoms. Some fractions are used as fuels. What is kerosene used as

A

jet fuel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Fractions contain hydrocarbons with a similar number if carbon atoms. Some fractions are used as fuels. What is heavy fuel oil

A

to power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Fractions contain hydrocarbons with a similar number if carbon atoms. Some fractions are used as fuels. What is liquified petroleum gases used in

A

camping stoves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Some fractions are used as Feedstock for the petrochemical industry. What chemicals are feedstock used to make?…(4)

A

Solvents
Lubricants
Detergents
Polymers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is cracking

A

Cracking is a process in which long chain alkanes are broken down (cracked) to produce smaller, more useful molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Long chain Hydrocarbons are not very flammable and this is one reason why they do not make good fuels. Why is this a problem

A

Because there is a high demand for short-chain hydrocarbons to be used as fuels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

name the two ways to carry out cracking

A

Catalytic Cracking and Stream Cracking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what we use in catalytic cracking

A

We use high temperatures and a catalyst.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what we use in steam cracking

A

We use high temperature and steam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what does cracking make

A

Cracking makes hydrocarbons called alkenes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Alkenes are very useful molecules, why?

A

Used to make chemicals called polymers

also used as the starting material for other useful chemicals as well

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Well, alkenes are MORE reactive than alkanes and we can use this idea to test for alkenes…how do you test for alkenes?

A

We test for alkenes using bromine water which is orange. If we shake our alkene with bromine water then bromine water turns colourless

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how to calculate the mean rate of reaction

A

mean rate of reaction = quantity of product formed/time taken

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is a pure substance

A

A pure substance is a substance not mixed with any other substance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the simplest way to determine if a substance is pure or not

A

To simply measure its melting point and boiling point.

A pure substance melts at a specific fixed temperature.

A pure substance also has a specific fixed boiling point.

Impure substances melt and boil over a range of temperatures.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a formulation

A

A formulation is a complex mixture that has been designed as a useful product

In a formulation, the quantity of each component is carefully measured so that the product has the properties we need.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Formulations include…(name 7)

A 
FUELS
CLEANING PRODUCTS
PAINTS
MEDICINES
ALLOYS
FERTILISERS
FOODS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are 4 ways to separate mixtures/physical separation techniques

A

FILTRATION
CRYSTALLISATION
DISTILLATION
CHROMATOGRAPHY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Gases in the atmosphere?

A

78 percent nitrogen
21 percent oxygen
small proportions of other gases eg carbon dioxide, water vapour and noble gases such as argon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is carbon footprint

A

The total amount of C02 and other greenhouse gases emitted over the full life cycle of a product, service or event

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what do we use resources for

A

For warmth, shelter, food and transport.

In many cases these resources are produced by agriculture (farming) eg cotton is produced from a plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what i s Potable water

A

Potable water is water that is safe to drink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

why is potable water not the same as pure water?

A

Because pure water in the chemical sense contains no dissolved substances at all but potable. water dies - but in small amounts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

where crude oil found

A

in rocks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what kind of resource is crude oil

A

finite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is crude oil

A

a mixture of molecules called hydrocarbons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what are hydrocarbons

A

molecules made of hydrogen and carbon atoms only

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

alkanes

A

hydrocarbons with the general formula C2H2n+2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

List Alkanes in order

A

Methane
Ethane
Propane
Butane

MEPB

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What are alkanes and why

plus ps what does saturated mean

A

Alkanes are saturated molecules because the carbon atoms are fully bonded to hydrogen atoms

Because the carbon atoms are fully bonded to the hydrogen atoms

Saturated on general means something has bonded as many times as possible aka no more (C-C can be made)

In specific here, saturated means the carbons atoms are fully bonded to the hydrogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

3 properties of hydrocarbons

A

Viscosity - tells us thickness of a fluid

Size of HC molecules increases, Viscosity increase

Flammability - tells us how easily a hydrocarbon combusts

Increases decreases

Boiling point - the temperature at which a liquid turns to a gas

Increases increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Examples of where hydrocarbons can be used as fules

A

ships
planes
cars

these all run on Hydrocarbon fules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

when do Hydrocarbons release energy and how

A

When combusted (burnt).

During combustion, Carbon and Hydrogen atoms in fuel react with oxygen . The carbon and hydrogen are oxidised.
If oxygen is unlimited, the reaction produces carbon dioxide and water - this is Complete combustion.

Complete combustion =

Hydrocarbon + oxygen —-> carbon dioxide + water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

for hydrocarbons in crude oil ( a naturally occurring petroleum product) to be useful, what must we do?

A

Separate them - to do that we use a technique called fractional distillation

In Fractional distillation, crude oil is separated into fractions. Fractions contain hydrocarbons with a similar number of carbon atoms.

Fractional distillation separates crude oil into simpler, more useful mixtures. The method can be used because different hydrocarbons have different boiling points.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

long chain hydrocarbons have long chain boiling points. Where are these removed in fractional distillation?

A

From the bottom of the column.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Very short chain hydrocarbons have low boiling points and these do not condense - they are removed from where as what in fractional distillation?

A

Removed from the top of the column as gases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

some fractions are used as feedstock for the petrochemical industry, what is a feedstock?

A

A chemical that is used to make other chemicals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

to solve the problem of a demand of shorter chained hydrocarbons, what do we do?

A

We use cracking!!!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what does cracking make

A

Hydrocarbons called alkenes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

alkanes have a single bond between two carbon atoms, what do alkenes have?

A

A double bond between two carbon atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what is petrochemical

A

a substance made from crude oil using chemical reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

When we plot quantity of product formed (grams) on y axis and time in x axis, initially the reaction is fast why?

A

Because we are making a lot of product in a short amount of time. That is because we have a large number of reactant molecules so lots of them are reacting and forming products.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

When we plot quantity of product formed (grams) on y axis and time in x axis, gradually, the slope of the line becomes less steep, telling us that the reaction is slowing down. Why

A

Because the rate of reaction is decreasing, meaning a lot of the reactants have turned into product, meaning there are fewer reactant molecules available to react.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

When we plot quantity of product formed (grams) on y axis and time in x axis, at the end of the line, the slope of the line is now zero - the line is flat so the reaction has stopped… Why?

A

Because all the reactant molecules have already reacted.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

how to calculate mean rate of reaction?

A

Mean rate of reaction = quantity of product formed / time taken

48
Q

what does a forward reaction tell us

A

that the product will not turn back to form the reactants.

49
Q

what does shift mean

A

moving

50
Q

what is a reversible reaction

A

when the products can reform to original reactants

51
Q

how can we change the direction of reversible reactions

A

by changing the conditions

52
Q

magnesium +oxygen —> magnesium oxide (a compound) talk about this

A

Arrow points in one direction only
telling. us reaction only goes forward
magnesium oxide will not turn back to form magnesium and oxygen again

53
Q

ammonium chloride ——-> ammonia + hydrogen chloride

meant to be another arrow

A

When we heat compound ammonium chloride, it reacts to form ammonia and hydrogen chloride….
If we take the products (ammonia and hydrogen chloride) and cool them down, they now react together to reform ammonium chloride
It is a reversible reaction

We can change the direction of the reaction by changing the conditions and in this case we made the reaction go forwards by heating it and backwards by cooling but every reaction is different.

54
Q

Energy changes taking place in a reversible reaction

A

endothermic/heat
hydrated copper sulfate (blue) ——–> hydrous copper sulfate (white)+water
meant to be another arrow
If we heat anhydrous copper sulfate then it reacts to form anhydrous copper sulfate which is white and also produces water
Because we are heating we are putting energy in so the forward reaction is endothermic
If we take our anhydrous copper sulfate and add the water back the reaction reverses and in the reversible reaction the energy os released and the reaction gets hot telling us the reversible reaction is exothermic

If a reversible reaction is exothermic in one direction it is endothermic in the other direction and the same. amount of energy is transferred each time.

55
Q

Equilibrium in a reversible reaction plus example

A

ammonium chloride ——-> ammonia + hydrogen chloride
meant to be another arrow

Imagine we are carrying out this reaction in a sealed container and it stops anyr eactants or products from escaping. At some point, the forward and reverse reactions will take place at the exact same rate - at equilibrium

56
Q

equilibrium definition

A

Equilibrium is when we carry out a reversible reaction in a sealed container none of the reactants or products can escape and when at some point the forward and reverse reactions occur at the same rate. - this point is called equilibrium.

57
Q

what are the effects of changing conditions on equilibrium

A

If a system is at equilibrium and a change is made to the conditions, then the system responds to counteract the change.

This is called Le Chatelier’s Principle

(We use the word system here just to say reaction)

58
Q

what happens if we change the concentration of products plus reaction to remember

A

At equilibrium, the system will counteract any changes we make.
So if we change the concentration of the reactants or products, then the system is no longer at equilibrium.
In other words, the forwards and reverse reactions are not taking place at the same rate.
This means that the concentrations of all the substances will change until equilibrium is reached.
so in this case, because we have increased the concentration of the products , more of the reactants will be formed until equilibrium is reached again.

Example =

2N02 arrows N2O4

59
Q

what happens if we make a change ‘to the temp

A

like we said before if we make any change to a system at equilibrium then the system counteracts the change. So if we increase the temperature of this system then the equilibrium shifts to the left to reduce the temperature
Example =

2N02 arrows N2O4

That is because the reversible reaction is endothermic soo the amount of N2O4 would decrease

If we were to decrease the temperature of this system, equilibrium shifts to the right to increase the temperature that is because forward reactions exothermic so energy is released causing the temperature to increase. So in this case the amount of N2O4 would increase and the amount of NO2 would decrease.

60
Q

Pressure and rate of reactions

A

Pressure affects reactions involving gases
The pressure of a gas depends on the number of molecules
but also other factors too but for gcse we will just look at number of molecules

Nitrogen + hydrogen reverse arrows ammonia

N2 +3H2 goes to RR 2NH3

Rules
If we increase pressure on a rr at equilibrium, the position of equilibrium shifts to the side with the smaller number of molecules
and if we reduce the pressure then the position of the equilibrium shifts to the side with the larger number of molecules

If the number of molecules is the same on both sides then changing the pressure would have no effect of the position of equilibrium

61
Q

REQUIRED PRACTICAL - THE RATE AND EXTENT OF CHEMICAL CHANGE
EFFECT OF CONCENTRATION ON RATE OF REACTIONS

There are 2 different methods and we should know both..

First tell me about the disappearing cross experiment. Use it to explore the effect of concentration on rates of reactions.

A

Sodium thiosulfate solution + hydrochloric acid —–> Sulfur (solid)

If we react those reactants then one of the products is sulfur and sulfur is a solid.
The sulfur makes the solution go cloudy and scientists call this cloudiness TURBIDITY and we can use this to see how long the reaction takes to finish. Here is the method:

1)use measuring cylinder to put 10cm3 of sodium thiosulfate solution into a conical flask
and place a conical flask onto a printed black cross and add 10cm3 of hydrochloric acid into the conical flask

2) swirl the solution and start a stopwatch
and look down through the top of the flask
because After a certain time the solution will turn cloudy so Stop the clock when we no longer see the cross

3) Carry out experiment again using lower concentrations of sodium thiosulfate solution
and repeat whole experiment and calculate mean values for each concentration of sodium thiosulfate solution

Remember not to calculate any anomalous results when calculating a mean
One important idea linked to this practical is reproducibility.

Both this and the second experiment show us that the greater the concentration of a chemical reaction, the faster the reaction takes place

so because this result is shown by two different experiments, we can say that the finding is reproducible

62
Q

what is a hypothesis

A

a proposal that could explain a fact or observation

In science, a hypothesis must be testable

63
Q

REQUIRED PRACTICAL - THE RATE AND EXTENT OF CHEMICAL CHANGE
EFFECT OF CONCENTRATION ON RATE OF REACTIONS

There are 2 different methods and we should know both..

First tell me about the disappearing cross experiment. Use it to explore the effect of concentration on rates of reactions.

One important idea linked to this practical is reproducibility. when is a measurement reproducible and what is the problem with the disappearing cross experiment

A

A measurement is reproducible if it can be repeated by another person or using a different technique or equipment and still get the same result

The problem with the disappearing cross experiment is that different people have different eyesights meaning some can see the cross for longer than others so they may not get the same results
However, because all the students use the same size printed cross, hopefully, this problem may not be too great.

64
Q

REQUIRED PRACTICAL - THE RATE AND EXTENT OF CHEMICAL CHANGE
EFFECT OF CONCENTRATION ON RATE OF REACTIONS

There are 2 different methods and we should know both..

Tell me about the 2nd method - measuring the volume of a gas produced by a reaction

A

Take a look at this reaction :

Magnesium + hydrochloric acid —> magnesium chloride + hydrogen

This reaction produces hydrogen gas
here we are reacting magnesium with hydrochloric acid
This reaction produces hydrogen gas and this allows us to measure the volume of hydrogen gas produced

Method :

1-Use a measuring cylinder to place 50cm3 of hydrochloric acid into a conical flask and Attach the conical flask to a bung and delivery tube

2-Place the delivery tube into a container filled with water and Then place an upturned measuring cylinder also filled with water over the delivery tube

3-Add a 3cm strip of magnesium to the hydrochloric acid and start a stopwatch and The reaction produces hydrogen gas which is trapped in the measuring cylinder

4-Every 10 seconds we measure the volume of hydrogen gas in the measuring cylinder and we continue until no more hydrogen is given off an we should Repeat the experiment using different concentrations of hydrochloric acid

Both this and the first experiment show us that the greater the concentration of a chemical reaction, the faster the reaction takes place

so because this result is shown by two different experiments, we can say that the finding is reproducible

65
Q

All separation techniques including paper chromatography are physical processes meaning what

A

meaning that they do not involve chemical reactions and no new substances are made.

66
Q

What does paper chromatography allow us to do

A

separate substances based on their solubilities

67
Q

what is solubility

A

the degree to which a substance dissolves in a solvent to make a solution

68
Q

what is a solvent

A

Just like an ordinary liquid in which another substance dissolves in to make a solution

69
Q

what do we call paper in paper chromatography and why

A

the stationary phase because it does not move.

70
Q

what do we call the solvent and why in paper chromatography

A

the mobile phase because it does move

71
Q

why does paper chromatography work

A

because each chemical in the mixture will be attracted to the stationary phase (the paper) to a different extent
Chemicals that are strongly attracted to the stationary phase will not move very far but chemicals that are only weakly attracted will move further up the paper

72
Q

in paper chromatography, what will a pure chemical produce but what will chemicals in a mixture produce

A

a pure chemical will produce a single spot in all solvents but the chemicals in a mixture may separate into different spots depending on teh solvent.

73
Q

why do we draw our starting line in pencil for paper chromatography?

A

Because if we drew the line in pen then the pen ink would move up the paper with the solvent

74
Q

Paper chromatography required practical - we have a sample of food colouring which is a mixture of chemicals and we’ll call it U for unknown.
We also have four known food colourings that it could contain and we are going to label these A-D

A

1-First use a ruler to draw a horizontal pencil line on the chromatography paper around 2 cm from the bottom of the paper and Mark five pencil spots at equal spaces across the line, leaving at least 1 cm clear at each side

2- Use a capillary tube to put a small spot of each of the known food colours and the unknown colour on the pencil spots and It is important that we keep the spots relatively small as this prevents the colours from spreading onto each other later

3-Now pour water into a beaker to a depth of 1 cm (water is the solvent in this case) and Attach the paper to a glass rod using tape and lower the paper into the beaker

pencil line with the spots of ink must be above the surface of the water otherwise the water will wash the ink off the line.

The sides of the paper must not touch the side walls of the beaker, if that happens then it will interfere with the way that the water moves

We usually put a lid on the beaker to reduce evaporation of the solvent

4-At this stage, the water will move up the paper and the colours will be carried up, during this time, we need to be careful not to move the beaker but Remove the paper when the water has travelled around three quarters up
and Here use a pencil. to mark the point where the water has reached then finally hang the paper to dry

75
Q

what should we do in paper chromatography if we want to identify the chemicals in the colours

A

calculate the RF value

76
Q

how to calculate the RF value

A

RF value = distance moved by chemical / distance moved by solvent

ANSWER SHOULD ALWAYS BE LESS THAN 1

77
Q

Gases in the atmosphere have stayed pretty constant for the last 200 million years but before that there were huge changes:

A

First billion years was intense volcanic activity
volcanoes releases the gases that formed the atmosphere, one of these was water vapour
As earth cooled, water vapour condensed to form oceans
volcanoes also released huge amounts of carbon dioxide
so in this early stage, the earth’s atmosphere consisted mainly of carbon dioxide with little or no oxygen - very much like Mars/Venus atmosphere today, volcanoes also released other gases including nitrogen which gradually built up in the atmosphere eg small amounts of methane and ammonia

Water vapour from volcanoes condensed to form the oceans
Some of the CO2 dissolved in the oceans to form a weak acid
These reacted with minerals in the sea to form precipitates
Over time, this formed sediments of carbonate rock on the sea bed
Some of the CO2 in the sea was used to make corals and shells of organisms eg mussels

When these died they formed sedimentary rock limestone, this removed CO2 from the atmosphere

Also photosynthetic algae first evolved in the oceans and photosynthesis produced oxygen which entered the atmosphere
Over following billion years, plants evolved, increasing amount of oxygen in the atmosphere and at some point , the level of oxygen reached the point where animals could evolve.

As well as producing oxygen, photosynthesis also takes in carbon dioxide

The carbon dioxide can be trapped in fossil fuels and again that caused the level of CO2 in atmosphere to fall

78
Q

fossil fuels definition plus examples

A

non renewable resource formed over millions of years
coal
oil
gas

All fossil fuels contain trapped carbon
That carbon is part of the carbon dioxide taken in by photosynthesis

79
Q

how coal formed

A

from remains of ferns and trees
if these die in marshy wetlands then they do not decompose and that can be due to lack of oxygen or acidic conditions these both prevent bacteria from carrying out decomposition
Over time the plant remains are covered with sediment and compressed

High temp and pressure creates coal

80
Q

how oil formed

A

crude oil formed from plankton
when they died they settle in mud near sea bed
if oxygen is not present then they do not decompose and over time are compressed by sediment
Heat and pressure then convert them to crude oil

81
Q

how natural gas formed

A

Mainly in the hydrocarbon methane

Often find near deposits of oil because natrual gas is formed from plankton in a similar way to oil

82
Q

greenhouse gases

A

water vapour
co2
methane

83
Q

greenhouse effect

A

1- energy from sun travels to earth as short wavelength radiation eg ultraviolet // uv and visible light

some reflects back to space but most passes easily through atmosphere because short wavelength radiation does not interact strongly with the gas molecules in the atmosphere; the energy of the radiation is absorbed when it reaches the surface of the earth
surface of earth the radiates as long wavelength radiation eg infrared

some long wavelength radiation interacts with the greenhouse gas molecules in the atmosphere ie the energy in the long wavelength radiation is absorbed because energy is trapped, temp increases

Greenhouse effect keeps warmth for life, without, would be too cold for most organisms to survive.

84
Q

Resources - modern agriculture lets us do what

A

to grow enough cotton to meet the needs of the world

Also agriculture helps us use Earths resources more efficiently

85
Q

resources - humans plant trees which can be used for what

A

for timber or fuel eg powerstations run on biofuels like woodhsip

86
Q

In some cases, chemistry has let us replace natural resources with a synthetic alternative eg rubber talk about rubber

A

natural rubber comes from tree sap

Synthetic rubber is produced from crude oil

87
Q

what resource is metal

A

finite

88
Q

what resource is wood

A

renewable

89
Q

important that out activities are sustainable what does this mean

A

we can meet our needs without preventing future generations from meeting theirs

90
Q

chemistry is important for how we use resources give examples

A

eg artificial fertilisers allow us to grow more food with the land available

Chemistry also helps provide water safe to drink

Processes like phytomining and bioleaching help us extract metals more efficiently

91
Q

humans do not just drink any water….water must be sufficiently low in levels of dissolved salt like what?////
drinking water cannot have high levels of microbes eg what?

A

sodium chloride

bacteria

92
Q

in UK what provides most of our potable water

A

rain water - it contains low levels of dissolved substances

we collect it in the ground in aquifers and in lakes rivers and reservoirs, all these are good sources of freshwater

93
Q

to produce potable water steps

A

first choose a good source of fresh water eg river

Then pass the water through filter beds to remove materials like leaves or suspended particles

Finally water is sterilised to kill microbes. In UK we use chlorine to sterilise potable water but some parts of the world ozone or UV light is used instead.

94
Q

In UK there is a huge access to fresh water eg rivers and we already know they have low levels of dissolved minerals but in other places, fresh water is scarce eg too salty to drink like sea water which has high levels of dissolved minerals. In this case, potable water is produced by desalination. whAT DOES THIS MEAN?

A

It means reducing the levels of dissolved minerals down to an acceptable level for potable water

95
Q

what are the two ways of doing desalination

A

to use distillation

to pass water through membranes, this is called reversible osmosis

Both these reduce levels of dissolved minerals but both require great energy so are expensive.

96
Q

how we use a great deal of water and only a bit to drink ie what else do we use for

A

personal hygene - baths and showers
flush toilets, wash clothes
for agriculture

97
Q

why does all waster water have to be carefully treated before being released back to environement

A

because all the waste contains large amounts of organic molecules eg urine and faeces and harmful microorganisms like bacteria.

98
Q

how to treat water stages

A

1’ - sewage is screened by passing through a mesh which removes solids and pieces of grit

2-Sewage is allowed to settle in large sedimentation tanks producing a liquid effluent and a semi solid sludge which sinks

3-Sludge is taken away and digested by anaerobic bacteria

In absence of oxygen, these bacteria produce biogas which can be burned for electricity

4-At the end, the digested sludge can be used as fertilisers for farming

99
Q

what is liquid effluent

A

liquid waste

100
Q

talk about treatment of liquid effluent

A

liquid effluent contains a large amount of organic molecules and harmful microorganisms that both must be reduced before returning to the environment.
So air is bubbles through the liquid effluent allowing anaerobic bacteria to multiply.

In presence of oxygen, anaerobic bacteria digest the organic molecules and harmful microorganisms

After this, the liquid effluent can be safely discharged into nearby rivers or the sea .

101
Q

a lot of water is used by industry give two examples

A

in making paper and chemicals

102
Q

when water is treated before water can safely enter the general sewage system, what needs to happen?

A

any harmful chemicals first need tobe removed

103
Q

In some parts of the world, treated sewage is used directly to produce potable water but not in where

A

not in UK

104
Q

Comment on how potable water can be produced (not in UK) 3 ways - compare

A

easiest way to produce potable water is to use ground 3 other ways :

1) From aquifers :

water from aquifers- usually this is safe to drink once it has been treated with chlorine

Can sometimes be polluted with fertilizer from farms though so the water from aquifers needs to be tested carefully

2)Directly from wastewater :

We can make potable water directly from waste water eg sewage but this takes many purification steps so only happens when water is scarce

3)Salt water:

salt water needs to be desalinated to produce potable water it required much energy and is expensive

105
Q

most metals are found where

A

in earths crust and already reacted with otehr elements eg oxygen

106
Q

worldwide demand for metals is going up…what is a really important metal and what is it used in

A

copper, used in electronic equipment such as phones

107
Q

Each year millions of tons of metal are extracted from Earth’s crust in where

A

in mines

108
Q

what is a metal ore

A

a metal ore contains enough metal to make it economical to extract the metal

109
Q

problem is that unlike a metal ore usually is, copper ores are becoming scarce so we will need to extract from low-grade ores containing a small amount of copper and so it is harder to extract the copper economically from the ores. How this is done (2 methods plus explain them)

A

PHYTOMINING - plants are grown on land containing the metal compound we want

plants absorb the metal compound and concentrate it in their tissue

plants are then harvested and burned

at end, the ash contains a high concentration of metal compound

BIOLEACHING- uses bacteria as bacteria are mixed with the low grade ore. Bacteria carry out chemical reactions and produce a solution called leachate (which contains the metal copper we want)

At the end of both these the metal cccccoper we wanted has been extracted from the low grade ore.

110
Q

After extracting from ore we want to extract metal from copper….explain how to do that 2 ways and the goods about them

A

We can displace the copper using iron. iron is more reactive than copper. We usually use scrap iron which is more reactive than copper and is usually cheap. We can also extract the copper using electrolysis.

1-both allow us to economically extract metals from low grade ores - important since earth’s resources of metal ores are limited

2-these methods do not involve digging transporting and disposing of large amounts of rock unlike in traditional mining.

111
Q

why do scientists believe climate change is real

A

due to evidence for it being shared between scientists can then criticise the evidence and decide if it is valid , this is then peer reviewed and allows scientists to detect false claims eg based on poor evidence or bias

112
Q

why is it hard understanding climate change

A

since climate change is complex

since. climate change is difficult to model - at times we hear stories about it in media that are simplified or bias or speculation absed on only parts of the evidence

113
Q

why are there uncertainties with climate change

A

since we cannot predict with certainty how much temperature of the atmosphere will increase - this can lead to speculation in the media.

114
Q

talk about the combustion of the hydrocarbon methane

A

methane + oxygen —-> carbon dioxide + water

CH4 + 2O2. CO2 +2H2O

methane is. found in natural gas and is used to heat homes

carbon atom in methane molecule has been oxidised to form gas CO2 and hydrocarbon oxidised to form water vapour
this process is complete combustion and we can tell that because we have made co2

FOR COMPLETE COMBUSTION TO HAPPEN WE NEED PLENTY OF oxygen

CO2 is a greenhouse gas so when we burn fuels and release CO2 it contributes to climate change

115
Q

iF THE amount of oxygen is reduced from combustion of the hydrocarbon methane, we can make carbon monoxide instead of dioxide….describe it

A

toxic gas
no colour
no smell

so have many detectors at home

116
Q

3 products of combustion summary

A

co2, water vapour, carbon monoxide

chemistry (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions