Unit 1 Chemistry and society
Key unit competence: Assess the application of chemistry in our daily life and its contribution to our economy today.
Key ideas
- Chemistry is the branch of science that studies matter: its composition, its properties, the changes it undergoes and the energy involved in those changes.
- Chemistry is part of daily life: cooking food, medicines (paracetamol, aspirin), soap and detergents, fertilisers, water treatment, fuels, plastics, glass, paints and cloth.
- Industries that use chemistry include food and beverages, water treatment, soaps and detergents, pharmaceuticals, fuels, fertilisers, cement, paints and plastics.
- Chemistry helps Rwanda's economy: medicines keep people healthy, fertilisers raise farm yields, factories give jobs, exported products and minerals earn foreign currency, and chlorinated water reduces disease.
- Traditional activities also use chemistry: brewing urwagwa (fermentation), making pottery (heating clay), tanning hides and smelting iron.
- Careers that need chemistry: pharmacist, doctor, nurse, chemical engineer, agronomist, food scientist, mining engineer, laboratory technician, teacher and environmental officer.
Common misconceptions
- "Chemistry only happens in laboratories." No: Chemistry happens everywhere: in our bodies, kitchens, farms and factories.
- "Chemicals are always dangerous and unnatural." No: Everything, including water, air and food, is made of chemicals; many are harmless and useful.
- "Chemistry has nothing to do with the economy." No: Chemistry turns raw materials into products that create jobs, exports and healthier workers.
Worked examples
Example 1. Give three ways in which chemistry contributes to the economy of Rwanda.
Solution
1. Medicines and vaccines keep the population healthy, so more people can work.
2. Fertilisers and animal feeds increase agricultural production.
3. Mining and processing of minerals and manufactured goods earn foreign currency and create jobs.
Example 2. Explain why cooking food is an application of chemistry.
Solution
When food is heated, the substances in it (proteins, starch, sugars) react and form new substances.
This changes the taste, colour, smell and texture, and kills germs.
New substances are formed, so cooking involves chemical changes.
Practice questions
Define chemistry.
Show answer
Chemistry is the branch of science that studies matter, its composition, properties and the changes it undergoes.
Common mistake: Writing only 'the study of chemicals', which does not mention properties and changes.
List four household products made using chemistry.
Show answer
Any four: soap, toothpaste, detergent, plastics, paint, medicines, cooking gas, bleach.
Common mistake: Listing natural things such as water from a spring or firewood.
Name two industries in Rwanda that depend on chemistry.
Show answer
For example: a cement factory, a brewery, a dairy (milk processing), a soap factory, a paint factory, a pharmaceutical plant.
Common mistake: Giving service activities (tourism, banking) which are not chemical industries.
State two careers that require chemistry.
Show answer
Pharmacist, doctor, nurse, chemical engineer, agronomist, laboratory technician, food scientist (any two).
Common mistake: Naming careers with no link to matter or its changes.
How does chlorination of water help the government save money?
Show answer
It reduces water-borne diseases, so less money is spent on treating patients and more can go to other sectors.
Common mistake: Saying chlorine makes water cheaper to buy.
Explain how chemistry helps farmers.
Show answer
Chemistry produces fertilisers that add nutrients to the soil and pesticides that protect crops, so yields increase.
Common mistake: Saying chemistry brings rain.
Give one example of chemistry in traditional Rwandan life and explain it.
Show answer
Brewing urwagwa: yeast ferments the sugar in banana juice into alcohol (a new substance).
Common mistake: Giving an example where nothing new is formed, such as weaving.
Why should students study chemistry? Give two reasons.
Show answer
To understand the materials around them and use them safely; to prepare for careers such as medicine, engineering and agriculture.
Common mistake: Saying only 'to pass exams'.
Explain how exporting manufactured goods helps the economy.
Show answer
Exports earn foreign currency, which the country can use to import what it needs and to fund sectors like education and health.
Common mistake: Confusing exports (selling abroad) with imports (buying from abroad).
A student says fertilisers are always good. Evaluate this statement.
Show answer
Fertilisers increase yields, but overuse can wash into rivers and lakes and pollute them; they must be used in correct amounts.
Common mistake: Giving only the advantage or only the disadvantage.
Matching and drag-and-drop
Matching
Match each item in column A with the correct answer in column B. Write the letter next to each number.
Column A Column B 1. When food is cooked, its taste, colour and texture change because: a. Petrol 2. Why is it important for citizens to know some chemistry? b. chemical reactions take place in the food 3. Which product is made from crude oil by chemical processing? c. more people are able to work in farms and industries 4. A healthy population helps the economy because: d. To use products such as medicines, fertilisers and cleaners safely Show answer
1 → b (chemical reactions take place in the food) · 2 → d (To use products such as medicines, fertilisers and cleaners safely) · 3 → a (Petrol) · 4 → c (more people are able to work in farms and industries)
- Heat causes chemical changes in proteins, starch and sugars, which changes taste, colour and texture.
- Knowing chemistry helps people use and store chemicals safely and choose better products.
- Crude oil is refined into fuels such as petrol, diesel and kerosene.
- Medicines made with chemistry keep people healthy, so the labour force is bigger and more productive.
Drag and drop
Choose the correct word or phrase from the box for each gap. One word in the box is not needed.
medicine · producing fuels and road materials · adding nutrients that increase crop yields · killing all insects in the soil- Fertilisers help farmers mainly by .
- Chemistry helps the transport sector mainly through .
- Paracetamol and aspirin are examples of chemical products used in .
Show answer
1: adding nutrients that increase crop yields · 2: producing fuels and road materials · 3: medicine
- Fertilisers supply nutrients such as nitrogen, phosphorus and potassium that plants need to grow.
- Fuels power vehicles and materials such as bitumen and cement build roads.
- They are drugs made by chemists to reduce pain and fever.
Matching
Match each item in column A with the correct answer in column B. Write the letter next to each number.
Column A Column B 1. Which activity shows chemistry protecting the environment? a. Treating factory waste water before releasing it 2. Which traditional Rwandan activity is an application of chemistry? b. Brewing urwagwa from bananas 3. A factory turns local raw materials into finished goods. This mostly helps the economy by: c. Vaccines and fertilisers 4. Which pair shows chemistry helping both health and agriculture? d. creating jobs and adding value to raw materials Show answer
1 → a (Treating factory waste water before releasing it) · 2 → b (Brewing urwagwa from bananas) · 3 → d (creating jobs and adding value to raw materials) · 4 → c (Vaccines and fertilisers)
- Treatment removes harmful substances so rivers and lakes are not polluted.
- Brewing uses fermentation: yeast changes the sugars in banana juice into alcohol, a chemical change.
- Processing raw materials locally creates jobs and earns more than exporting raw materials.
- Vaccines protect health; fertilisers increase farm production.
Drag and drop
Choose the correct word or phrase from the box for each gap. One word in the box is not needed.
earning foreign currency · Agronomist and laboratory technician · kill germs that cause disease · making the soil acidic- Adding chlorine to drinking water is done to .
- Exporting minerals such as cassiterite and coltan helps Rwanda by .
- Which pair of careers BOTH need chemistry? →
Show answer
1: kill germs that cause disease · 2: earning foreign currency · 3: Agronomist and laboratory technician
- Chlorine kills micro-organisms, so treated water reduces diseases like cholera and typhoid.
- Minerals sold abroad bring foreign currency that can be used for other sectors like education.
- Agronomists use knowledge of soils and fertilisers; laboratory technicians carry out chemical tests.