Main air pollutants

The main air pollutants in the atmosphere which are harmful are: sulphur dioxide, carbon monoxide, nitrogen dioxide and carbon/particulates. They are harmful because they cause problems for human beings and the welfare of the planet.

- Sulphur dioxide causes acid rain which can cause erosion and kill certain species in lakes, rivers and other various wildlife.

- Carbon monoxide is a poisonous gas that reacts with blood and if taken in copious amounts can amount to death.

- Nitrogen dioxide, causes again, acid rain however also causes breathing problems and can make asthma worse.

- Lastly, particulates will make things dirty and if breathed in by your lungs can give you a lung infection or make asthma worse.

(Please note that the colours are only to help with memory and do NOT represent colours of the gases as most are colourless)

Getting rid of some of these pollutants

There are different methods of reducing these harmful pollutants in the atmosphere. One of the main contributors to carbon monoxide emissions, was once, cars and engines. Since this, catalytic converters have been designed which turn carbon monoxide into carbon dioxide, equally a pollutant, but ultimately less harmful. In the converter, the carbon monoxide is made to react with another oxygen molecule (CO + O), this results to the product of carbon dioxide.

Notes about the catalytic converter:

- The waste gases pass through a honeycomb structure.

- Honeycomb structures have a large surface area coated by platinum.

(May be worth acknowledging that it is platinum which is un-reactive. Any other elements used could well react with the carbon monoxide forming other undesired elements.)

- The platinum acts as a catalyst also which speeds up the reaction by doesn't use itself up.

Also in the converter... Nitrogen monoxide + carbon monoxide --> nitrogen + carbon dioxide

If you count the number of atoms on each side, you will find that there are four aluminium atoms on each side and six oxygen atoms. Sorted!

Crude Oil

Crude oil is made from dead animals under the sea which were compressed between layers of impermeable rock in sedimentary rock.

Fractional Distillation

Fractional distillation takes place at an oil refinery. The process separates the many hydrocarbons in crude oil into useful mixtures. Hydrocarbons that are separated include refinery gas which is used for gas cookers, and kerosine used for aircraft fuel

Properties of fractions at the top

• Low boiling point
• Burn with a clear flame
• Light coloured
• More runny
• Burn readily
• Are smaller molecules

Properties of fractions at the bottom

• Have a high melting point
• Are darker in colour
• Are thicker
• Less likely to burn
• Are larger molecules
• These hydrocarbons have a high boiling point and have longer carbon chains.

alkaneformulachemical structureball-and-stick model methane CH₄
ethane C₂H₆
propane C₃H₈
butane C₄H₁₀

Uses of additives

type of additiveexamplereason for adding it colouring Tartrazine (E102) orange colouring for soft drinks, sweets and sauces emulsifier Lecithin (E322) allows oil and water to mix to make margarine, ice-cream and salad cream antioxidant Ascorbic acid (E300) stops food from reacting with oxygen flavour enhancer Monosodium glutamate (E621) makes food taste more savoury

Additives with an E number have been licensed by the European Union. Some are natural, some artificial. But they have all been safety tested and passed for use.
You can find additives listed on the ingredients label. Many have E numbers to identify them.

Cooking brings about chemical changes in food. The texture and taste of food changes when it is cooked, and cooking helps to kill harmful microbes.

Baking powder contains sodium hydrogencarbonate. This breaks down when heated, releasing carbon dioxide that helps cake mixtures to rise during baking.

Cooking - how and why

Some food can be eaten raw, such as carrots and apples. But some food is usually cooked before it is eaten, such as meat and fish.

Why do we cook food?

Food may be contaminated with harmful microbes that can cause disease. The high temperatures involved in cooking kill these microbes. Cooking also makes food easier to digest. It can improve the food’s appearance, texture and flavour, too.

Proteins

Eggs and meat are good sources of protein. The protein molecules change shape as a result of the heat energy they absorb. This causes changes in the appearance and texture of the eggs and meat when they are cooked. For example: Egg white solidifies and becomes white instead of transparent. Meat becomes firmer and turns from red to brown.

Carbohydrates

Potatoes are a good source of carbohydrate, mainly as a complex carbohydrate called starch. Raw potato is hard and has an unpleasant taste. Potato becomes softer when is cooked, the starch is converted into simple sugars, and the potato becomes sweeter.