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7/27/2019 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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- GCSE Bitesize - Recycling
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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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- GCSE Bitesize - Recycling
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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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- GCSE Bitesize - Recycling
//www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/recyclingrev_print.shtml[10/21/2013 8:16:09 PM]
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- GCSE Bitesize - Recycling
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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/q67450861/7/27/2019 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]
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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]
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- GCSE Bitesize - Recycling
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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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- GCSE Bitesize - Recycling
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/