Using Resources Flashcards
Humans use the Earth’s natural resources for a number of purposes, including:
energy and fuels for warmth building materials for shelter food through farming fuels for transport materials for clothing
Finite resources
Resource that can only be used once and is in limited supply. For example, oil is a finite resource.
Renewable resources
Resources which will not run out in the foreseeable future. This could be because the reserves of the resources is huge, or because the current rate of extraction is low.
For water to be potable, it must have sufficiently low levels of dissolved salts and microbes. This is because:
dissolved salts can sometimes be harmful for humans
microbes can cause illnesses`
potable
Water that is safe to drink.
What is a life cycle assessment ?
A life-cycle assessment or LCA is a ‘cradle to grave’ analysis of the impact of a manufactured product on the environment.
What does and LCA include at all stages ?
At all stages, an LCA is likely to include information about the use of energy, transport of materials and the release of waste substances into the environment.
What are the 4 stages of LCA ?
1) Raw materials
2) Manufacture
3) Use
4) Disposal
What happens at the manufacture stage ?
The manufacture of products has an impact on the environment, including:
- using up land for factories
- the use of machines and people
What happens at the use stage ?
The impact of a product on the environment during its use depends on the type product. For example, a wooden chair has very little impact, unless it needs cleaning or repair. On the other hand, using a car will have a significant impact.
What happens at the disposal stage ?
The disposal of old products has an impact on the environment, including:
- using up land for landfill sites
- whether any or all of the product can be recycled or
reused
What happens at the raw materials stage ?
All the raw materials we need come from the Earth’s crust, atmosphere or oceans, or are due to living organisms. Obtaining these materials has an impact on the environment, including:
using up limited resources such as ores and crude oil
damaging habitats through quarrying, mining, or felling trees
Recycling
Reusing materials or reprocessing waste materials to produce new materials.
Advantages of recycling
- fewer quarries and mines are needed to extract finite
reserves of metal ores
-less crude oil needs to be extracted from the crust as
a raw material for making plastics
-less energy is needed for recycling compared with
making a new product from natural resources, so the - - emission of greenhouse gases is reduced
the amount of waste that is disposed of in landfill is
reduced
Disadvantages of recycling
- the collection and transport of used items needs organisation, workers, vehicles and fuel
- it can be difficult to sort different metals from one another
- the sorted metal may need to be transported to where it can be turned into ingots
Phytoextraction
- plants are grown on a low-grade ore
- the plants absorb metal ions through their roots and
concentrate these ions in their cells - the plants are harvested and burnt
- the ash left behind contains metal compounds
Phytoextraction is slow but it:
- reduces the need to obtain new ore by mining
- conserves limited supplies of high-grade ores
- reduces the amount of rock waste that must be
disposed of after traditional mining
Name and advantage and disadvantage of bioleaching…
Bioleaching does not need high temperatures but it produces toxic substances, including sulfuric acid, which damage the environment
Bioleaching
Using bacteria to extract metals from their ores.
WATER LEARN
WATER LEARN
In the Haber process:
- nitrogen (extracted from the air) and hydrogen (obtained from natural gas) are pumped through pipes
- the pressure of the mixture of gases is increased to
200 atmospheres - the pressurised gases are heated to 450°C and
passed through a tank containing an iron catalyst - the reaction mixture is cooled so that ammonia -
liquefies and can be removed - unreacted nitrogen and hydrogen are recycled
- it is reversible !
What are fertilisers ?
Fertilisers provide mineral ions needed for healthy growth in plants. As plants grow, they absorb mineral ions from the water in the soil through their root hair cells. Over time, the concentration of these ions decreases, so farmers and gardeners add fertilisers to the soil.
What do fertilisers contain for them to increase growth ?
Fertilisers are formulations which may contain nitrogen, phosphorus and potassium compounds to promote plant growth.
The importance of ammonia in making fertilisers
…..
The reaction conditions in the Haber process are:
a temperature of 450°C
a pressure of 200 atmospheres
an iron catalyst
How to make ammonia….
….
Effect of increasing pressure on the Haber process
In a reaction involving gases as reactants and/or products, increasing the pressure of the reaction mixture will cause the equilibrium position to move to the side with the fewest moles of gas, to reduce the pressure.
There are fewer molecules on the right-hand side of the equation for the Haber process:
N2(g) + 3H2(g) ⇌ 2NH3(g)
1 + 3 = 4 molecules ⇌ 2 molecules
If the pressure is increased, the equilibrium position moves to the right, so the yield of ammonia increases. The rate of reaction also increases because the gas molecules are closer together, so successful collisions are more frequent.
However, the energy costs increase when higher pressures are used and the equipment becomes more expensive. Therefore, the choice of pressure is a compromise between yield and cost.
Effect of temperature on the Haber process
When the temperature is increased, the position of equilibrium moves in the endothermic direction to reduce the temperature.
In the Haber process, the forwards reaction is exothermic, so the reverse reaction is endothermic.
N2(g) + 3H2(g) ⇌ 2NH3(g) (forwards reaction is exothermic)
This means that as the temperature is increased, the position of equilibrium moves to the left, and the yield of ammonia decreases.
It may seem sensible to use a very low temperature in order to maximise the yield of ammonia but lower temperatures reduce the rate of reaction. The temperature chosen is a compromise between yield and rate.
Using a catalyst in the Haber process
A catalyst speeds up the rate of the forward and reverse reactions equally. This reduces the time taken for the system to reach equilibrium but it does not affect the position of equilibrium or the yield of ammonia.
Using a catalyst in the Haber process means that a lower temperature can be used whilst keeping the rate of reaction high. A lower temperature helps to keep the yield high.
Reducing costs in other ways
Most of the hydrogen and nitrogen which go into the reactor leave unreacted. By recycling them back into the reactor, the cost of making the reactants from raw materials is reduced.
