Welcome to "Using Earth's Resources"!

In this chapter, we are going to explore how humans get the things we need to survive—like water, warmth, and materials—from the planet. We'll also look at how we can do this sustainably so that people in the future have resources too. Don't worry if some of the processes sound complicated at first; we will break them down step-by-step!


1. Natural and Finite Resources

Everything we use comes from the Earth's crust, oceans, or atmosphere. We can split these resources into two main groups:

  • Natural Resources: These are things like timber (wood), wool, and cotton. We can often use synthetic (man-made) alternatives to replace them. For example, we might use polyester instead of cotton for clothes.
  • Finite Resources: These are "one-time use" resources. Once we use them, they are gone. Examples include fossil fuels (coal, oil, gas) and metals. They take millions of years to form, so we can't replace them quickly.

What is Sustainable Development?

Sustainable development is a big term that means: "Meeting our needs today without making it impossible for people in the future to meet theirs."

Analogy: Imagine you have a giant tub of cookies. If you eat them all today, there are none for tomorrow. Sustainable development is like baking new cookies at the same speed you eat them!

Quick Review: Finite vs. Renewable

Finite: Will run out (e.g., Crude oil, metal ores).
Renewable: Can be replaced as we use them (e.g., Timber, crops for food).

Key Takeaway: Chemistry helps us find ways to use resources more efficiently and create man-made alternatives to protect our natural world.


2. Obtaining Potable Water

Water is essential for life, but not all water is safe to drink. We use the word potable to describe water that is safe for humans to drink.

Potable vs. Pure Water

It is a common mistake to think potable water and pure water are the same thing. They aren't!

  • Pure Water: Contains 100% \(H_2O\) molecules and nothing else.
  • Potable Water: May contain low levels of dissolved salts and microbes, but it is safe for us.

How we make water potable in the UK:

In the UK, we usually get our water from "fresh water" sources like rivers, lakes, and underground rocks (aquifers). Here is the 3-step process:

  1. Choosing a source: We find a good source of fresh water.
  2. Filtration: The water is passed through filter beds (usually sand and gravel) to remove solid bits like leaves and dirt.
  3. Sterilisation: We kill any harmful microbes (bacteria). We can do this using chlorine, ozone, or ultraviolet (UV) light.

What if there is no fresh water?

In very dry countries, people have to use salty seawater. Removing salt from water is called desalination. This can be done in two ways:

  • Distillation: Boiling the water so it turns to steam, then cooling it back into liquid, leaving the salt behind.
  • Reverse Osmosis: Pushing the water through a special membrane that traps the salt but lets the water through.

Note: These methods require a massive amount of energy, which makes them very expensive!

Key Takeaway: Potable water isn't necessarily "chemically pure," but it must be free of harmful bacteria and have safe levels of dissolved salts.


3. Waste Water Treatment

When you flush the toilet, have a bath, or when rain runs off the streets, that "waste water" needs to be cleaned before it goes back into rivers. If we didn't clean it, it would spread disease and kill fish.

Step-by-Step: The Treatment Process

  1. Screening: The water passes through a metal grid to remove large objects like rags, sticks, and plastic.
  2. Sedimentation: The water sits in a big tank. The heavy bits sink to the bottom to form sludge, while the lighter water (effluent) stays on top.
  3. Aerobic biological treatment: We pump air into the effluent. This encourages "good" bacteria to eat any remaining organic matter and microbes.
  4. Anaerobic digestion: The sludge from the bottom is put in a sealed tank without air. Different bacteria break it down, producing biogas (which can be used for energy) and dried crust that can be used as fertiliser.
Memory Aid: The Two 'A's

Aerobic = Needs Air (Used for the liquid effluent).
Anaerobic = No Air (Used for the solid sludge).

Key Takeaway: Sewage treatment is a clever way of using bacteria to "eat" the waste in our water so it can be safely returned to the environment.


4. Alternative Methods of Extracting Metals (Higher Tier Only)

We are running out of "high-grade" copper ores (rocks with lots of metal in them). Scientists have found two "green" ways to get copper from "low-grade" ores (rocks with very little metal).

Phytomining

This uses plants to do the work! Here’s how:

  1. Plants are grown on soil containing low-grade copper.
  2. The plants absorb the copper and store it in their leaves.
  3. The plants are harvested and burned.
  4. The ash contains copper compounds which can be processed to get the metal.

Bioleaching

This uses bacteria to do the work!

  • Bacteria are mixed with the low-grade ore.
  • The bacteria produce a liquid called leachate, which contains copper compounds.

How do we get the actual copper metal out?

Once we have the copper compounds from the ash or the leachate, we can get the pure metal in two ways:

  • Displacement: We react the solution with scrap iron. Iron is more reactive than copper, so it "pushes" the copper out. Using scrap iron is very sustainable!
  • Electrolysis: Using electricity to pull the copper ions out of the solution.

Key Takeaway: Phytomining and Bioleaching take a long time, but they are better for the environment than traditional mining because they don't involve digging huge holes in the ground.


Quick Review Quiz

1. Name three ways to sterilise water: Chlorine, Ozone, UV Light.
2. Which process treats the solid sludge in sewage? Anaerobic digestion.
3. What is the man-made alternative to timber called? Synthetic polymers (plastics).
4. Why is desalination expensive? It requires a lot of energy.

Don't worry if you didn't get them all right—just go back and re-read that specific section. You've got this!