Using Earth's Resources

Ever wondered where your phone's materials come from or why recycling matters so much? Earth provides everything we need, but we've got to be smart about how we use it.

Finite resources like crude oil and metals will eventually run out because they're extracted from the Earth's crust. On the flip side, renewable resources such as wood, hydroelectric power, and biodiesel won't disappear as they can be replenished naturally.

Recycling isn't just trendy - it's essential. When we recycle, we use less crude oil, reduce landfill waste, cut greenhouse gas emissions, and need fewer quarries and mines. It's basically giving materials a second life instead of constantly digging up new ones.

Life cycle assessments track a product's environmental impact through four stages: extracting and processing raw materials, manufacturing and packaging, use during its lifetime, and disposal. Each stage involves transport and distribution, which adds to the environmental cost.

Key Point: Understanding finite vs renewable resources helps you make better environmental choices in everyday life.

Water Treatment and Safety

Clean water doesn't just magically appear from your tap - it goes through serious processing to make it safe to drink.

Potable water is simply water that's safe to drink, containing minimal harmful impurities. When we need to use seawater, desalination removes salt through distillation or reverse osmosis - think of it as giving seawater a complete makeover.

Fresh water treatment involves four main steps: mesh screens remove large debris, coagulants make tiny particles stick together into clumps, sand filtration removes remaining solids, and sterilisation with chlorine or UV light kills harmful bacteria.

Waste water treatment is more complex. It starts with screening and grit removal, then sedimentation separates human waste. Aerobic treatment uses air and good bacteria to kill harmful microorganisms, while anaerobic treatment breaks down sludge without air, producing useful methane gas as a bonus.

Key Point: Both fresh and waste water treatments use bacteria as natural cleaners - pretty clever chemistry in action!

Rates of Reaction

Chemical reactions happen at different speeds, and understanding why gives you serious chemistry superpowers.

Rate of reaction measures how quickly reactants are used up or products form over time. On graphs, steeper gradients mean faster reactions - it's that simple. You can calculate rates using: rate = quantity/time taken, or find the mean rate using change in y/change in x.

For reactions to happen, particles must collide with enough energy (called activation energy) and in the right way. Think of it like a successful high-five - timing and energy matter! More frequent, successful collisions mean faster reactions.

You can speed up reactions by increasing temperature, concentration, pressure, or surface area, or by using a catalyst. Scientists measure reaction rates by tracking gas volume with syringes, mass changes on balances, or timing colour changes and precipitate formation.

Reversible reactions reach equilibrium where forward and backward reactions balance out. Le Chatelier's Principle explains that if you change conditions, the system fights back to restore balance - increase temperature in an exothermic reaction, and it shifts to counteract the change.

Key Point: Controlling reaction rates is crucial in industry - too slow wastes time, too fast can be dangerous.

Crude Oil and Hydrocarbons

That petrol in cars and plastic in your phone both started as ancient sea creatures - welcome to the world of crude oil and organic chemistry.

Crude oil is a finite resource formed from organisms that died millions of years ago. It's a complex mixture of hydrocarbons found in Earth's crust and serves as our main source of fuels and chemical raw materials.

Fractional distillation separates crude oil by heating it and letting vapours rise through a column that's hot at the bottom and cool at the top. Different hydrocarbons condense at different heights based on their boiling points, giving us petrol, kerosene, diesel, and fuel oil.

Small hydrocarbon molecules $1-4 carbons$ have low boiling points, low viscosity, and are highly flammable - perfect for fuels. Large molecules $35+ carbons$ have high boiling points, high viscosity, and are harder to ignite. Cracking breaks large molecules into smaller, more useful ones using heat and catalysts.

Complete combustion with plenty of oxygen produces carbon dioxide and water, releasing lots of energy. Incomplete combustion with limited oxygen produces dangerous carbon monoxide and less energy. Alkenes are unsaturated hydrocarbons that turn orange bromine water colourless - a handy test to remember.

Key Point: The size of hydrocarbon molecules determines their properties and uses - small equals runny and flammable, large equals thick and less reactive.

Atmospheric Chemistry and Climate Change

Your atmosphere has had quite the makeover over billions of years, and human activities are now writing the latest chapter.

Earth's early atmosphere came from volcanic activity, releasing mainly carbon dioxide with some nitrogen and virtually no oxygen. Stage two saw CO₂ levels drop as water vapour condensed into oceans (dissolving CO₂) and plants evolved to absorb CO₂ through photosynthesis.

Stage three brought the oxygen we breathe today. Photosynthesis released O₂ as a waste product, slowly building up to create our modern atmosphere: roughly 78% nitrogen, 21% oxygen, and small amounts of CO₂, water vapour, and noble gases.

Human activities are now changing atmospheric composition rapidly. Farming cattle releases methane, deforestation removes CO₂-absorbing trees, and burning fossil fuels pumps out CO₂. The greenhouse effect traps long-wavelength radiation from Earth's surface using greenhouse gases like CO₂, methane, and water vapour.

Global warming over the last 200 years is causing glaciers to melt, sea levels to rise, and habitats to change. Your carbon footprint measures total CO₂ emissions over a product's life cycle. We can reduce this through renewable energy, efficient processes, carbon taxes, and CO₂ capture technology.

Key Point: Unlike natural climate changes that took millions of years, human-caused changes are happening in decades - that's why it's such a big deal.