Food packaging can be made from plastic or aluminium. Figure one shows the percentage of aluminium cans recycled industrially between 1970
Plot points and draw a line on figure one to show the percentage of aluminium cans
not recycled between 1970 and 2010.
First of all, the percentage of cans not recycled is equal to 100 percent minus the
percentage of cans that are recycled. So the process for this question is to calculate this for each point, plot the data,
and then draw a line through the points.
Let’s start by looking at the data in the graph. In 1970, 15 percent of cans were recycled industrially. 100 percent minus 15 percent is 85 percent. Therefore, in 1970, 85 percent of cans were not industrially recycled.
Be careful when plotting these points that you pay attention to the axis. It only goes up to 90 percent, so make sure that you take your values and measure
them up against the axis rather than going from 100 percent and working your way
Now on to 1975. In 1975, 27 percent of cans were recycled, meaning that 73 percent of cans were not
recycled. In 1980, these values were 40 percent and 60 percent. In 1985, these values were 51 percent and 49 percent, and so on and so forth.
So for each value, you take the percentage of cans that were recycled in that year
and subtract it from 100 percent to get the percentage of cans that weren’t recycled
in that year. Now that we’ve plotted all the points, we can draw the line through them. Bear in mind that this is not a line of best fit. We are simply joining one point to the next.
You may have noticed that something that would have sped up answering this question
was noticing that the percentage of cans that were recycled and the percentage of
cans that weren’t recycled are mirror images of each other in the plane of the 50
percent line. However, doing it point by point by calculation is another perfectly valid way of
Life cycle assessments may be used to compare the suitability of materials for the
production of consumer products. Details for the life cycle assessments of plastic and aluminium food trays are listed
in table one. Values in the table are calculated for trays produced from nonrecycled materials. Use the information in table one and your own knowledge to compare the production,
use, and sustainability of plastic and aluminium food trays. In your answer, evaluate which of the two materials is most suitable for this
The best thing to do with this point is to go through the table in detail and analyse
it and see what we can discover. Let’s start with the plastic trays. Plastic trays are made from crude oil, which is a finite resource. The initial production step, fractional distillation, is in the table to jog your
memory and make you think about the amount of energy required to produce the
Fractional distillation is quite an energy-intensive process, requiring many hundreds
of degrees and large production facilities. However, on the plus side, plastic trays are relatively light, and it requires a
relatively small amount of energy to produce each tray.
Looking at the solid waste and the CO₂ emissions of plastic trays relative to
aluminium trays, we can see that plastic trays are vastly more environmentally
friendly than aluminium, producing roughly a tenth as much solid waste and a fifth
as much CO₂. However, on the plus side for aluminium trays, the percentage of aluminium trays that
are recycled is much greater, approximately three times as much.
However, much more energy is required to produce each aluminium tray than a plastic
tray, approximately seven times. And aluminium trays are relatively heavy. The initial production step for aluminium trays is also energy-intensive, but the raw
materials from which aluminium is derived are relatively abundant and could be said
to be inexhaustible.
Now what we have to do is boil down all this information into sentences. Plastic is made from finite nonrenewable crude oil, whereas aluminium is made from
the abundant ore bauxite, which is unlikely to be depleted. Here a good answer is one that makes comparisons between the plastic and the
aluminium directly, using words like “whereas.”
Aluminium trays are recycled more often, so less raw material is needed. However, aluminium trays are heavier, so they require more energy to transport. Here we’re considering the wider implications of the factors that are included in
table one. And that’s what we’re looking for, a deeper understanding of the material in order to
make a judgement assessment.
Aluminium production creates more environmentally harmful solid waste and has a
higher energy requirement and higher CO₂ emissions, resulting in more fossil fuel
use and greenhouse gas release. This part of the question is particularly good because it sets the context for the
damage caused by using aluminium trays versus plastic trays, discussing fossil fuel
use and greenhouse gas emissions.
Overall, plastic trays are preferable because they can be produced with less waste,
expense, and environmental damage. This section of the answer is the judgement call. It’s a summary of all the results that we’ve discussed, and it makes a recommendation
based on the pros and cons of the two situations. You could’ve argued that the fact that aluminium trays are recycled more and are
derived from a nonexhaustible material may make them better in the long term. You just needed to make sure that the structure of your answer reflected the validity
of your conclusion.