You are viewing a free preview of this lesson.
Subscribe to unlock all 10 lessons in this course and every other course on LearningBro.
This final lesson covers the AQA GCSE Combined Science Trilogy (8464) topic on using the Earth's resources sustainably. You need to understand natural and synthetic resources, potable water, waste water treatment, and life cycle assessments. These topics link chemistry to real-world environmental issues.
Humans use the Earth's resources to provide:
Resources can be classified as:
| Type | Description | Examples |
|---|---|---|
| Natural | Obtained from the Earth or living organisms | Wood, cotton, rubber, metal ores, crude oil |
| Synthetic | Made by humans through chemical processes | Plastics, nylon, polyester, medicines |
| Type | Description | Examples |
|---|---|---|
| Finite (non-renewable) | Being used up faster than they form; will eventually run out | Fossil fuels, metal ores |
| Renewable | Can be replaced at the same rate as they are used | Timber (managed forests), biofuels, cotton |
Key Point: Sustainable development means meeting the needs of the current generation without compromising the ability of future generations to meet their own needs.
Potable water is water that is safe to drink. It is not pure water in the chemical sense — it contains dissolved minerals and other substances, but at levels that are not harmful.
In the UK, most potable water comes from fresh water sources (rivers, lakes, reservoirs). The process involves:
In countries with limited fresh water, desalination (removing salt from seawater) is used. Methods include:
Key Point: Desalination requires a large amount of energy, making it expensive. This is why it is mainly used in countries where fresh water is scarce.
Waste water from homes (sewage) and industry must be treated before it can be released back into the environment. The treatment process involves:
| Stage | Purpose |
|---|---|
| Screening | Remove large objects (rags, grit, debris) |
| Primary treatment (sedimentation) | Allow suspended solids to settle as sludge |
| Secondary treatment (biological) | Aerobic bacteria break down dissolved organic matter |
| Final treatment | Further filtration or chemical treatment before release |
The sludge from primary treatment is digested anaerobically by bacteria, producing biogas (mainly methane) which can be used as a fuel.
Exam Tip: You need to know the stages of waste water treatment and that the biological stage uses microorganisms. You do not need to know specific bacterial species.
A life cycle assessment (LCA) is a method of assessing the environmental impact of a product from "cradle to grave" — from extracting raw materials to final disposal.
flowchart LR
A["1. Raw Materials
Extracting and processing"] --> B["2. Manufacturing
Making the product"]
B --> C["3. Use
During the product’s lifetime"]
C --> D["4. Disposal
End of life: landfill, recycling, incineration"]
| Stage | Factors Considered |
|---|---|
| Extracting raw materials | Energy used in mining/drilling; environmental damage; transport |
| Manufacturing | Energy used; water used; pollutants released; waste produced |
| Use (during product lifetime) | Energy consumed; emissions; maintenance needed |
| Disposal | Landfill space; recycling energy; incineration emissions; biodegradability |
| Factor | Plastic Bag | Paper Bag |
|---|---|---|
| Raw materials | Crude oil (finite) | Trees (renewable, if managed) |
| Manufacturing energy | Relatively low | Higher |
| Durability | Strong, reusable | Less durable, single use |
| Disposal | Not biodegradable; can be recycled | Biodegradable; recyclable |
| Litter impact | Persists in environment; harms wildlife | Breaks down more quickly |
Key Point: LCAs are not always straightforward. Some factors are easy to quantify (energy use, CO₂ emissions), but others involve value judgements that can be subjective (e.g. how much damage to a landscape is acceptable?).
The three Rs help to reduce our use of finite resources and minimise environmental impact:
| Strategy | Description | Example |
|---|---|---|
| Reduce | Use fewer resources | Buy less packaging; use less energy |
| Reuse | Use items again for the same or different purpose | Refill bottles; donate clothes |
| Recycle | Process used materials into new products | Melt glass, aluminium, or plastic for reuse |
| Advantages | Disadvantages |
|---|---|
| Conserves finite resources | Collection and sorting require energy |
| Reduces landfill waste | Not all materials can be recycled economically |
| Often uses less energy than extracting new materials | Contaminated waste may not be recyclable |
| Reduces greenhouse gas emissions | Requires infrastructure and public participation |
Question: Evaluate the use of a ceramic mug versus a disposable paper cup for drinking coffee.
| Factor | Ceramic Mug | Paper Cup |
|---|---|---|
| Raw materials | Clay (abundant) | Trees + plastic lining (mixed) |
| Manufacturing | High energy (kiln firing at ~1200°C) | Lower energy per cup |
| Use | Washed with water and energy; reused many times | Single use; no washing |
| Disposal | Long-lasting; if broken, goes to landfill | Difficult to recycle (plastic lining); landfill or incineration |
Evaluation: The ceramic mug has a higher initial environmental impact but can be used thousands of times. The paper cup has a lower manufacturing cost but generates more waste over time. If used enough times, the ceramic mug has a lower environmental impact per use.
Subscribe to continue reading
Get full access to this lesson and all 10 lessons in this course.