12 recycling

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- GCSE Bitesize - Recycling

//www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/recyclingrev_print.shtml[10/21/2013 8:16:09 PM]

Science

Recycling

The Earths resources are limited and it is important that we

conserve as much as possible. One way to do this is to

recycle waste products. Some forms of recycling happen innature: the carbon cycle and nitrogen cycle allow these

elements to be recycled.

Benefits of recycling

Resources on the Earth are limited, It's important that the way

we behave now does not make life difficult or impossible for

future generations. To achieve sustainable development , we

need to carefully consider:

the need for economic development, where standards of

living improve

the environment and the resources it provides for us.

Recycling is an important way to help us achieve sustainable

development. We can recycle many resources, including:

glassmetal

paper

plastic.

Glass

Glass is easily recycled. It can be melted and remoulded to

make new objects, such as bottles. The energy needed to do

this is less than the energy needed to make new glass from its

raw materials. However, we need to sort different coloured glass

ready for recycling, and transport it to the recycling plant.

Metal

Just like glass, it takes less energy to melt and remould metals

than it does to extract new metals from their ores. Aluminium is a


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valuable metal that melts at a relatively low temperature, and is

particularly attractive for recycling. However, a lot of metals that

we use are mixtures called alloys, and it can be difficult to sort

different metals ready for recycling.

Paper

Paper is not melted when it is recycled. Instead, it is broken upnto small pieces and reformed to make new sheets of paper.

This takes less energy than making paper from trees. However,

paper can only be recycled a few times before its fibres become

too short to be useful, and the recycled paper is often only good

enough for toilet paper or cardboard. But it can be used as a

fuel or compost instead.

Plastic

Plastic can be recycled as fleece clothing so that we use less

crude oil, the raw material required for plastic and a scarce

resource that is running out. Different types of plastics have to

be sorted out and this can be difficult. Recycling plastic also

stops much of it ending up in landfill sites.

The carbon cycle

All cells - whether animal, plant or bacteria - contain carbon ,

because they all contain proteins, fats and carbohydrates. Plant

cell walls, for example, are made of cellulose - a carbohydrate.

Carbon is passed from the atmosphere, as carbon dioxide, to

iving things, passed from one organism to the next in complex

molecules, and returned to the atmosphere as carbon dioxide

again. This is known as the carbon cycle.Removing carbon dioxide from the atmosphere

Green plants remove carbon dioxide from the atmosphere by

photosynthesis [photosynthesis : The chemical change that

occurs in the leaves of green plants. It uses light energy to

convert carbon dioxide and water into glucose. Oxygen is

produced as a by-product of photosynthesis. ]. The carbon


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becomes part of complex molecules such as proteins, fats and

carbohydrates in the plants.

Returning carbon dioxide to the atmosphere

Organisms return carbon dioxide to the atmosphere by

respiration [respiration: Chemical change that takes place

nside living cells, which uses glucose and oxygen to producethe energy organisms need to live. Carbon dioxide is a by-

product of respiration ]. It is not just animals that respire. Plants

and microorganisms do, too.

Passing carbon from one organism to the next

When an animal eats a plant, carbon from the plant becomes

part of the fats and proteins in the animal. Microorganisms and

some animals feed on waste material from animals, and the

remains of dead animals and plants. The carbon then becomes

part of these microorganisms and detritus feeders.

The slideshow should help you to understand how the cycle

works.


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Materials from living things decay because they are digested by

microorganisms. This process happens faster in warm, moist

conditions with plenty of oxygen. Decay can be very slow in

cold, dry conditions, and when there is a shortage of oxygen.

Now try a Test Bite.

Nitrogen cycle - Higher tier

Nitrogen is essential for the formation ofamino acids inproteins. The nitrogen cycle is a model that explains how

nitrogen is recycled.

There's lot of nitrogen in air about 78 percent of the air is

nitrogen. Because nitrogen is so unreactive, it cannot be used

directly by plants to make protein. Only nitrates are useful to

plants, so we are dependent on other processes to convert

nitrogen to nitrates in the soil.
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/recycling/quiz/q67450861/http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/recycling/quiz/q67450861/


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1. Nitrogen gas is converted to nitrate compounds bynitrogen-fixing bacteria in soil or root nodules. Lightning

also converts nitrogen gas to nitrate compounds. The

Haber process converts nitrogen gas into ammonia used

in fertilizers. Ammonia is converted to nitrates by

nitrifying bacteria in the soil.

2. Plants absorb nitrates from the soil and use these to

build up proteins. The plant may be eaten by an animal,and its biomass used to produce animal protein.

3. Urea and egested material is broken down by

decomposersdecomposer:An organism which eats

dead organisms or animal droppings, and breaks them

down into simple materials.. This results in nitrogen being

returned to the soil as ammonia.

4. Decomposers also break down the bodies of dead

organisms resulting in nitrogen being returned to the soil

as ammonia.

5. In some conditions denitrifying bacteria in the soil break

down nitrates and return nitrogen to the air. This is

usually in waterlogged soil. Improving drainage reduces

this effect, making the soil more fertile.


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Now try a Test Bite - Higher tier.

Back to Revision Bite
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/recycling/quiz/q56103256/http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/recyclingrev1.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/recyclingrev1.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/recycling/quiz/q56103256/

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