Chemistry in society, technology and the environment

Burning petrol, natural gas or coal emits a gas into the atmosphere that enhances the greenhouse effect. Which gas is it? Explain in a simple sentence what the greenhouse effect is.

A domestic boiler burns methane according to the equation $\text{CH}_4 + 2\ \text{O}_2 \rightarrow \text{CO}_2 + 2\ \text{H}_2\text{O}$.

1. a) Which product of this combustion contributes to the greenhouse effect?
2. b) If the boiler is poorly adjusted and burns the gas incompletely, why is it worse for the environment and also for the bill? Give reasons for both answers.

The greenhouse effect is not bad in itself: without it, the average temperature of the Earth would be well below zero. Explain the difference between the natural greenhouse effect and the "enhanced greenhouse effect" mentioned in the news, indicating which human activity is causing it.

Over the years, balcony railings end up covered in a reddish-brown layer. What is this process and this brown substance called? What two things does iron need in order to rust?

Name two common ways to protect an iron gate from rusting and explain how each one works.

The frame of many bicycles is painted, that is, covered by a thin layer of paint. The figure shows a cross-section of the frame:

1. a) How does this layer protect the iron from contact with air and moisture?
2. b) If the bicycle gets scratched and iron is exposed, why does rust attack precisely at the scratched area? Relate this to the conditions required for corrosion.

Name two acidic substances you have in your kitchen at home and explain how you know they are acidic (from their taste, smell or use).

What is acid rain? Name the gases from combustion in factories and cars that cause it and mention one effect it has on the environment.

Marble statues and limestone facades ($\text{CaCO}_3$) wear away faster in heavily polluted cities than in the countryside.

1. a) Explain what acid rain does to the calcium carbonate in the stone.
2. b) Reason why wear and tear is much lower in rural areas far from factories.
3. c) Propose two measures to slow down this damage to heritage sites and justify them: one short-term measure targeting the buildings and one long-term measure targeting the source of the problem.

What type of energy does a battery store and what type of energy does it transform it into when it lights up a torch? Explain why we say that the chemical reaction occurring inside the battery is a "useful" reaction.

The rechargeable batteries in a games console controller can be used hundreds of times before wearing out.

1. a) What does it mean that the chemical reaction in a rechargeable battery is "reversible"? What does the charger do?
2. b) Why should flat batteries, whether rechargeable or not, not be thrown in the household waste?

In a technology class, a homemade battery is made by inserting a copper electrode and a zinc electrode into a lemon: when a small LED is connected, it lights up faintly. The setup is shown in the figure:

1. a) Where does the energy that lights up the LED come from? What type of reaction supplies it?
2. b) What role does the acidic juice of the lemon play in the setup?
3. c) Predict what would happen if three lemons were connected in series and explain how commercial batteries are similar to these "improved lemons".