Video: GCSE Chemistry Higher Tier Pack 1 • Paper 2 • Question 4

GCSE Chemistry Higher Tier Pack 1 • Paper 2 • Question 4


Video Transcript

Food packaging can be made from plastic or aluminium. Figure one shows the percentage of aluminium cans recycled industrially between 1970 and 2010.

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 down.

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 doing it.

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 application.

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 material.

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.

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