Introduction: Why Should We Care About Resources?
Welcome to one of the most important chapters in your Chemistry GCSE! In "Using Resources," we look at how humans use the Earth’s natural materials to survive and thrive. We use resources for warmth, shelter, food, and transport. However, we have a big challenge: how do we use what we need today without ruining the planet for people in the future? This is called sustainable development.
In these notes, we will break down how we get clean water, how we deal with our waste, and how we can use "Life Cycle Assessments" to see the true impact of the things we buy.
1. Earth's Resources and Sustainability
The Earth provides us with everything we need, but not all resources are the same. Chemists categorize them into two main types:
- Finite Resources: These are "one-time use" on a human timescale. Once they are used up, they are gone. Examples include fossil fuels (coal, oil, gas) and metals.
- Renewable Resources: These can be replaced as quickly as we use them. Examples include timber (we can plant more trees) and food crops.
Did you know? Many modern materials are now being replaced by synthetic (man-made) alternatives to save natural ones. For example, we used to get all our rubber from trees, but now much of it is made from crude oil in factories!
Key Takeaway
Sustainable development means meeting the needs of people today without compromising the ability of future generations to meet their own needs. We do this by using less finite resources and creating less waste.
2. Potable Water: Making it Safe to Drink
Water is essential, but it must be potable. Don't let that word scare you—potable water simply means water that is safe to drink.
Common Mistake: Students often think potable water is "pure water." It isn't! Pure water contains only \( H_2O \) molecules. Potable water contains low levels of dissolved salts and no dangerous microbes.
How we get Potable Water in the UK
In the UK, we are lucky to have plenty of "fresh water" in rivers and lakes. Here is the step-by-step process to make it safe:
- Choosing a Source: We pick a good source of fresh water (like a river or underground rock).
- Filtration: The water is passed through filter beds (usually wire mesh and sand) to remove solid bits like leaves and dirt.
- Sterilising: We kill harmful microbes (bacteria). This is done using chlorine, ozone, or ultraviolet (UV) light.
What if there is no fresh water? (Desalination)
In very dry countries, they have to use seawater. Removing salt from water is called desalination. This can be done by:
- Distillation: Boiling the water and catching the steam.
- Reverse Osmosis: Pushing water through a special membrane that traps the salt.
The Downside: Both methods require massive amounts of energy, making them very expensive.
Quick Review: The Water Steps
Fresh water -> Filter -> Sterilise -> Potable!
Salty water -> Desalination (Expensive!) -> Potable!
3. Waste Water Treatment
When you flush the toilet or wash your hands, that water becomes "waste water." It contains organic matter and harmful microbes that must be removed before the water goes back into the environment.
The Treatment Process:
- Screening: Removing large objects (like grit or plastic).
- Sedimentation: The water sits in a tank. Heavy solids sink to the bottom to form sludge, while the lighter liquid (effluent) stays on top.
- Aerobic biological treatment: Useful bacteria are added to the effluent. Air is pumped in to help them break down organic matter.
- Anaerobic digestion: The sludge is broken down by different bacteria in a tank without oxygen. This can produce biogas (for energy) and dried sludge (for fertilizer).
Key Takeaway
Cleaning sewage is a complex multi-stage process. It is much harder and more expensive than treating fresh water from a river, but it protects our ecosystems from pollution.
4. Alternative Methods of Extracting Metals (Higher Tier Only)
Don't worry if this seems tricky at first! Basically, we are running out of high-grade copper ores (rocks with lots of metal in them). Scientists have found "Earth-friendly" ways to get copper from low-grade ores or waste.
- Phytomining: We grow plants on soil containing copper. The plants absorb the metal. We then burn the plants, and the ash contains the copper compounds.
- Bioleaching: We use bacteria to produce a liquid called a leachate. This liquid contains the metal compounds.
Once we have the copper compounds from the ash or leachate, we can get the solid metal out using displacement (using scrap iron) or electrolysis.
Memory Aid: Phyto sounds like "photo" (as in photosynthesis). Plants do photosynthesis, so Phytomining uses plants!
5. Life Cycle Assessments (LCAs)
A Life Cycle Assessment is like a "cradle to grave" report for a product. It looks at the environmental impact at every stage of its life.
The 4 Stages of an LCA:
- Extracting and processing raw materials (e.g., mining or drilling for oil).
- Manufacturing and packaging (The energy used in the factory).
- Use and operation during its lifetime (Does it use electricity? Does it cause pollution while being used?).
- Disposal at the end of its life (Does it go to a landfill? Can it be recycled? Does it involve transport?).
Is it perfect? No. While we can easily measure energy and water use, it is hard to put a "number" on things like the visual pollution of a factory. Because of this, LCAs can sometimes be subjective (based on opinion).
Key Takeaway
LCAs help us compare products. For example, comparing a plastic bag to a paper bag might show that paper bags use more energy to make, even though plastic bags stay in the environment longer.
6. The 3 Rs: Reduce, Reuse, and Recycle
To be sustainable, we need to reduce our use of limited resources. This helps save energy and reduces the amount of waste we send to landfills.
- Metals: We can recycle metals by melting them and casting them into new shapes. Analogy: It's like melting down old LEGO bricks to make a new toy—it takes much less energy than making the plastic from scratch!
- Glass: Glass bottles can often be reused (washed and refilled). If they can't be reused, they are crushed and melted to make new glass products.
Did you know? Adding scrap steel to a blast furnace reduces the amount of iron ore we need to mine from the ground!
Key Takeaway
The "3 Rs" save the Earth’s resources, save energy, and reduce the environmental impact of mining and waste disposal.
Final Quick Review Box
Potable: Safe to drink (not necessarily pure).
Desalination: Getting fresh water from the sea (uses lots of energy).
LCA: Checking a product's impact from "birth to death."
Finite: Will run out (Coal, Oil, Metal).
Renewable: Can be replaced (Trees, Solar).