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Revision FlashcardsChemistry – Module C1b

Discover the Earth

78%

21% 1%

Nitrogen

Oxygen

Other

Gases in the Modern Atmosphere

Only 0.03% of the atmosphere is carbon dioxide

OXYGEN

O2 – a diatomic

molecule (2 atoms stuck together)

Used in hospitals to

help with anaesthetic

The most reactive

gas in the air

Supports Combustion

NITROGEN

N2 – a diatomic

molecule (2 atoms stuck together)

Used in the form of a liquid to

keep food frozen

A VERY unreactive

gas

Makes up more than ¾ of the

atmosphere

Used to make

ammonia

NH3

Separating the Gases in the Air

SALT

In this country salt comes from

ROCKSALT mined in Cheshire

Salt is SODIUM

CHLORIDE NaCl

From Salt Solution (BRINE) we get

HYDROGEN, CHLORINE and SODIUM

HYDROXIDE (caustic soda)

Products from SALT are made by passing electricity through BRINE

Cl22Cl- - + 2e-

Chlorine gas is made

Negative ions

• Salt is made of sodium IONS (Na+) and chloride IONS (Cl-).

• Chloride ions go to the positive electrode (anode) where they lose an electron to make a chlorine ATOM.

• The chlorine atoms produced join up into pairs to make a MOLECULE of chlorine

ANODE

What about the Positive IONS?

Positive ions

• Na+ are not the only positive ions present in brine (sodium chloride SOLUTION).

• There are also H+ ions because water molecules split up into H+ and OH- ions.

Na+Cl-

HHO

HO-

H+

How is HYDROGEN gas made?

• Na+ ions move to the cathode but then they just stay there.

• Hydrogen ions H+ pick up electrons from the cathode to make hydrogen ions.

• The hydrogen ions join together to make hydrogen atoms H.

• Hydrogen gas H2 is formed at the cathode (negative electrode).

2H+ + 2e- H2

CATHODE

Na+Cl-

H

O-H+

So what happens to all of the ions?

Stays in the

solution and makes

SODIUM HYDROXID

E NaOH

Na+ + OH- NaOH

Makes chlorine

Cl2

Cl- + Cl- Cl2

Makes hydroge

n H2

H+ + H+ H2

Check your Understanding

Uses of Chlorine

Sterilising Water BleachBleaching newspaper

Making chemicals

PlasticsAntiseptics

Dyes

Biofuels

Are made from plants such as oil seed rape

Can be burned on their own or

mixed with other fuels

Are RENEWABLE

Will biodegrade

Still burn to give out carbon dioxide

Use land to grow which

could be used for growing food crops

Crude Oil

cool

hot

•Crude oil is a mixture of thousands of different chemicals called HYDROCARBONS

•Hydrocarbons contain HYDROGEN and CARBON ONLY

•Crude oil is separated out into groups of hydrocarbons in a FRACTIONATING COLUMN

Hot crude oil vapour in

Fractions out

cool

hot

Fuel gas

Petroleum

Kerosine

Diesel

Lub. Oil

Bitumen

Fraction Boiling Range

(oC)

Kerosine 150 - 240

Diesel 220 – 275

Petroleum 40 - 175

Bitumen >350

Fuel gas Below 40

Lubricating oil

250-350

Arrange the fractions in the right order next to the arrows.

Separating the Fractions Out

Why do the fractions separate out?

Increasing size of molecules

Small hydrocarbon molecules are gases or transparent liquids.As the molecules get larger the colour becomes increasingly yellow through to the brown/black colour of bitumen used on roads and roof repairs

Hydrocarbons

0

50

100

150

200

250

300

350

0 5 10 15 20

No. Carbon atoms

B.Pt

(oC)

The bigger the hydrocarbon chain, the higher the boiling point.

Boiling Points of Hydrocarbons

As the carbon chains get longer and longer, the boiling points of the hydrocarbons increases. This is

because there are more INTERMOLECULAR forces to overcome before the molecules can escape as

gases.BOILING POINT INCREASES AS MORE CARBON ATOMS

Hydrocarbon Formula

Structure

Methane CH4

Ethane C2H6

Propane C3H8

Butane C4H10

Alkanes carbon

hydrogen

The simplest hydrocarbons form a series of compounds known as ALKANES.These all consist of carbon and hydrogen only and every carbon has four single covalent bonds.

C

H

H

H H methane, CH4

C

H

H

H C

H

H

H ethane, C2H6

C

H

H

H C

H

H

C

H

H

H propane, C3H8

More Alkanes

Methane + oxygen water + carbon dioxide

CH4 + 2O2 2H2O + CO2

Alkanes are not especially reactive but they do have one very important reaction: combustion.With an adequate supply of air they react to form carbon dioxide and water.

Combustion of Hydrocarbons

A carbon monoxide detector

Methane + oxygen water + carbon monoxide

2CH4 + 3O2 4H2O + 2CO

Carbon Monoxide

If there isn’t enough oxygen around for complete

combustion, INCOMPLETE COMBUSTION happens. This makes CARBON MONOXIDE

gas which can take the place of oxygen in your

bloodstream and is very poisonous.

Air Pollution

Acid Rain is caused by SO2 in the air from burning impurities in fossil fuels. This dissolves in the rain to make acid.

CFCs – chlorofluorocarbons

have destroyed part of the ozone

layer which protects the earth from harmful UV

rays

Increased levels of CARBON DIOXIDE in the air are though to be causing the earth to warm up.

Scientists disagree about whether

increased levels of ASTHMA are

caused by more chemicals in the

air.

The Carbon Cycle

The amount of CO2 in the

environment has always

been a balance between the

gas being used up during

photosynthesis and

produced during burning

and respiration.

Why Is there a problem?

Human activities are thought to have caused an imbalance in the carbon cycle.

Too much CO2 is being made.

200ppmCO2

300ppmCO2

From air trapped in Antarctic ice, we have a good idea of CO2 concentrations going back

160,000 years. We know the temperatures over the same period.During the very warm period of 130,000 years ago

we had CO2 levels of around 300 ppm. During the previous great Ice Age we had CO2

levels around 200 ppm. Are we heading back to a greenhouse age?

Global Warming

Heat from sun

Heat loss

Earth

More CO2

Earth

Heat loss

Heat from sun

WARMING UP

Normally the Earth absorbs heat from the sun and gives it out at the same rate. Because of this the temperature on Earth stays the same.

Some gases, like carbon dioxide, CO2 and methane, CH4, act like a greenhouse. They let heat in but don’t let it out again.This means: the more CO2 and CH4 there is, the hotter planet Earth is!

The Greenhouse

Effect

Mars Venus

During the first billion years on Earth there was a lot of volcanic activity. This produced the first early atmosphere. It would have contained large quantities of carbon dioxide (CO2), along with methane (CH4) ,and ammonia (NH3).This is rather like the atmosphere on Mars and Venus today. The Earth’s atmosphere also have contained water vapour which condensed to form the oceans.

How the Atmosphere Formed

Earth

Photosynthesis increased

oxygen levels

Carbon dioxide reacted with rocks and was trapped in carbonate rocks like

limestone. Algae started to grow 3000 million years ago, and plants successfully

colonised the Earth’s surface, leading us to the atmosphere we have today.

These plants photosynthesized, taking

carbon dioxide out of the air and making oxygen.

Over a period of time billions of tonnes of carbon dioxide became locked up in fossil

fuels.

Where Did Oxygen Come From?

78%

21% 1%

Nitrogen

Oxygen

Other

As oxygen levels rose, the ammonia (NH3) in the air reacted with oxygen(O2) to form water(H2O) and nitrogen (N2)Living organisms, including denitrifying bacteria, broke down nitrogen compounds which released more nitrogen into the atmosphere. The composition of the atmosphere has remained fairly constant for the last 200 million years.

Where Did Nitrogen Come From?

4500 million

3000 million

2000 million

1000 million

500 million

200 million

NOW

NO GASES VOLCANOES ALGAE PLANTS

O2 AND N2 INCREASING

CO2 DECREASING

SOME H2

and He

NH3 and CH4 DECREASING

ATMOSPHERE TIMELINE

RECYCLING

REDUCES

WASTE

REDUCES

ENERGY USE

CONSERVES NATURAL

RESOURCES

FREES UP LANDFILL

PAPER METAL

GLASS

One of the most exciting developments in modern technology is SMART MATERIALS

‘Smart materials’ are materials which have been designed to be ‘clever’ and respond to different circumstances

These tiny, microscopic sensors are used to detect sudden deceleration in a car’s motion. They send a surge of electricity to the car’s air-bag, telling it to go off.

SMART MATERIALS

Other examples of smart materials are:Lycra – this fabric can be stretched in all directions, but always ‘remembers’ its original shape and returns to it afterwards.

You might have gloves or a hat made out of Thinsulate. This is a very light material which has very thin fibres which trap a lot of air. This layer of air around your body prevents the heat from escaping.Smart Polymers –

mobile phones and PCs are made of ‘smart’ plastics (polymers). When they are placed in hot water, the plastic springs back into its original shape and all of the different components fall apart. This makes them very easy to recycle.

This breathable fabric has a hydrophilic coating.It absorbs moisture from the warm humid air around your body.It pushes the sweat out through your clothing to keep your skin comfortable.

BREATHABLE FABRICS

ELECTRONIC TEXTILES

TV REMOTE CONTROLS

KEYBOARDS ON T SHIRTS

MOBILES ON THE MOVE

Soon soldiers will be able to:

•use an intelligent glove to see if water is safe to drink•communicate using a fabric keyboard sewn to a sleeve•be warned of chemical hazards by their clothing•have their vital signs (e.g. pulse, heart rate) monitored and reported back to command points•have wounds treated on the battlefield by clothes that release antiseptics.•Have clothes which change colour to camouflage them.

Military Applications

Medical Applications

A ‘LIFE SHIRT’ can be worn to check vital

signs in a sick person.

Baby smart material:•is made from coated wool fibres• can detect movement as well monitor temperature• can be linked to an alarm that sounds if movement stops• is non-invasive – it isn’t actually fixed to the baby so it doesn’t feel uncomfortable•can be used at home or in hospital.

NanotechnologyNanotechnology is already

being used in CDs and mobile phones and scientists are having great fun finding out what the possibilities are for the future.

This picture shows a dust mite next to a set of gear wheels! This gives you an idea of how small, small is!

This picture shows a pair of molecular robots, designed to carry out tasks on a ridiculously small scale.

Here, scientists have had fun making a buggy out of atoms, complete

with a set of wheels. While this seems to be just a bit of fun, it gives an idea of the kinds of things which could be achieved by this technology.

The possibilities for the future of this area of Science is what makes nanotechnology so exciting.

This molecular robot is being used to inject microscopic amounts of drugs directly into the cells which need them, in this case into white blood cells.

This robot could be programmed to inject a tiny amount of drug every day for months. The advantages are huge:

•The patient doesn’t need to remember to take his or her drugs, they will just be administered automatically.

•No other cells are damaged by the drugs – they are sent exactly where they are needed.

Medical Advances

Glucose ethanol + carbon dioxideC6H12O6 2C2H5OH + 2CO2

Alcohol from Sugar

YEAST acts as the

catalyst in fermentatio

n

ETHANOL is also used as a biofuel in countries where a lot of cane sugar is grown,

and as a solvent.

YEAST is an ENZYME

Emulsions

This end is HYDROPHOBIC

this means water-hating

This end is HYDROPHILIC

this means water-loving

The molecule looks like

this

OIL

DROP

WATER

HYDROPHOBIC parts of the molecule stay out of the water

HYDROPHILIC parts of the molecule stay in the water

Emulsion molecules

Emulsion molecule

s