chem chapter 10 - using resources

explain the process of bioleaching to extract finite metals from low-grade ores

bioleaching : bacteria are used to convert copper compounds in the ore into soluble copper compounds, they produce leachate which contains soluble copper ions which can then be extracted using electrolysis or displacement with a more reactive metals, e.g scrap iron

explain the process of phytomining to extract finite metals from low grade ores

phytomining : plants are grown in soil that contains copper, as the plants can’t use the copper it then gets stored in their leaves, they’re then dried, harvested and burnt, their ashes contain soluble copper compound which can then be extracted using electrolysis or displacement using scrap ion

how do you recycle metals and why is it good?

• by melting them and reshaping them into a new product

• slows the demand for mining, conserving energy and producing less waste

• limits the need for ores

how do you recycle glass?

separate by colours and chemical composition then melt it down and reshape it

what are the 4 stages of a life cycle assessment?

• getting the raw materials

• manufacturing and production

• using the product

• disposal

what is the problem with life cycle assessments?

• they can be biased, as it takes in the values of the person making the assessment

• they can be selective, some companies may hide the negatives of their product to give positive advertising

• effects on the environment are hard to value

explain how freshwater (groundwater, rivers, lakes and resorvoirs) is treated to become potable

• filtration - a wire mesh removes any leaves and twigs then gravel and sandbeds filter out any other solid bits

• sterilisation - kills harmful bacteria and microbes, used by bubbling chlorine gas through it, using ozone or uv light

explain how salt water is treated to become potable

a sample of the water is pH tested, if it’s too high or low it has to be neutralised by adding in some acid (if the sample is alkaline) or some alkaline if the sample is acidic. The pH will then be tested again to ensure it’s at 7. Set up simple distillation, filling a conical flask with your water sample, and placing a condenser in the top, have the conical flask on a tripod on a heatproof mat, with a bunsen burner making it boil. When it’s hot enough, it will evaporate and rise up into the condenser, where cold tap water flows through, cooling it down and condensing it back into liquid water, which is collected in a beaker at the other end. Retest the water of the pH and see if any crystals are left in the conical flask to see the salt has been removed.

how else can saltwater be treated?

reverse osmosis, pass the salty water through a membrane that only allows water molecules to pass through, so the salt and water molecules are seperated

what is a negative for both these processes?

they both use lots of energy, expensive and aren’t practical to create large amounts of potable water

why does the Uk use filtration and sterilisation but not desalieanation?

the UK has an abundance of fresh water sources (lake rivers, reservoirs and groundwater) but dry countries such as Kuwait don’t so they use salty water is it’s in abundance

describe the process of making sewage/waste water potable

• the sewage is put through screening, which is a filtration that removes large solids such as plastic bags, twigs and grit

• it is then undergoes sedimentation in a settlement tank, which seperates the effluent (the lighter substance which floats to the top) from the sludge (the heavier suspenede solids that falls to the bottom)

• the eflluent is aoerobically digested, where air is pumped through it top encourage aerobic bacteria to break down the organic matter, including other microbes

• the sludge is transferred into large tanks anaerobically digested, which produces methane which can be used as an energy source and the remaining waste used as fertiliser

• for waste water containing toxic substances chemicals are added, such as bubbling chloring gas through it, or using ozone or UV light

what are the positives and negatives of treating waste water?

• uses less energy and is cheaper than desalianation, so is a good alternative for countries that don’t have much freshwater, e.g Singapore now recycle their sewage

• some people don’t like the idea of drinking water that used to be sewage

where does waste water come from?

• agricultural systems

• industrial processes

what are 2 things produced by waste water treatment?

methane gas - can be used as an energy source

organic waste - can be used as a fertiliser