Revision Flashcards Chemistry – Module C1b Discover the Earth
Gases in the Modern Atmosphere Only 0.03% of the atmosphere is carbon dioxide
OXYGEN O 2 – a diatomic molecule (2 atoms stuck together) Used in hospitals to help with anaesthetic The most reactive gas in the air Supports Combustion
NITROGEN N 2 – 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 NH 3
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
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
Cl 2 2Cl - - + 2e- Chlorine gas is made ANODE
What about the 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.
H+ Na+ Cl- H H O H O-
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 H 2 is formed at the cathode (negative electrode) .
2H + + 2e- H 2 CATHODE
So what happens to all of the ions? Stays in the solution and makes SODIUM HYDROXIDE NaOH Na + + OH - NaOH Makes chlorine Cl 2 Cl - + Cl - Cl 2 Makes hydrogen H 2 H + + H + H 2 Na+ Cl- H O- H+
Check your Understanding
Uses of Chlorine Sterilising Water Bleach Bleaching newspaper Making chemicals Plastics Antiseptics 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 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 Arrange the fractions in the right order next to the arrows. Separating the Fractions Out cool hot 250-350 Lubricating oil Below 40 Fuel gas >350 Bitumen 40 - 175 Petroleum 220 – 275 Diesel 150 - 240 Kerosine Boiling Range ( o C) Fraction
Why do the fractions separate out?
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 Increasing size of molecules
The bigger the hydrocarbon chain, the higher the boiling point. No. Carbon atoms B.Pt ( o C)
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
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 4 H 10 Butane C 3 H 8 Propane C 2 H 6 Ethane CH 4 Methane Structure Formula Hydrocarbon
More Alkanes C H H H H methane, CH 4 C H H H C H H H ethane, C 2 H 6 C H H H C H H C H H H propane, C 3 H 8
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 Methane + oxygen water + carbon dioxide CH 4 + 2O 2 2H 2 O + CO 2
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. A carbon monoxide detector Methane + oxygen water + carbon monoxide 2CH 4 + 3O 2 4H 2 O + 2CO
Air Pollution Acid Rain is caused by SO 2 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 CO 2 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.
From air trapped in Antarctic ice, we have a good idea of CO 2 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 CO 2 levels of around 300 ppm. During the previous great Ice Age we had CO 2 levels around 200 ppm. Are we heading back to a greenhouse age? Global Warming 200ppm CO 2 300ppm CO 2
Heat from sun Heat loss 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, CO 2 and methane, CH 4 , act like a greenhouse. They let heat in but don’t let it out again. This means: the more CO 2 and CH 4 there is, the hotter planet Earth is! The Greenhouse Effect Earth More CO 2 Earth
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 (CO 2 ), along with methane (CH 4 ) ,and ammonia (NH 3 ). 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 Mars Venus
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? Earth Photosynthesis increased oxygen levels
As oxygen levels rose, the ammonia (NH 3 ) in the air reacted with oxygen(O 2 ) to form water(H 2 O) and nitrogen (N 2 ) 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 O 2 AND N 2 INCREASING CO 2 DECREASING SOME H 2 and He NH 3 and CH 4 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.
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.
Nanotechnology Nanotechnology 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.
Glucose ethanol + carbon dioxide C 6 H 12 O 6 2C 2 H 5 OH + 2CO 2 Alcohol from Sugar YEAST acts as the catalyst in fermentation 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 molecules