Chemistry and Society
Senior 1 · Chemistry
Chemistry and Society
Lesson 4 of 4
22 min
Before tap water reaches your home, someone has checked that it is safe to drink. Before a new medicine is sold in a pharmacy, someone has checked that it contains what the label says. Before maize flour is exported, someone has tested it for mould poisons. These people are chemists and laboratory technicians, and much of their work starts with a simple question: what is in this sample, and how much?
Collect three water samples in clean test tubes: A, tap water; B, rainwater from a clean container; C, water from a stream or pond. For each sample, dip a clean glass rod in the water and touch it onto a small piece of universal indicator paper on a white tile. Match the colour to the chart and record the pH (Figure 4.1). Rinse the rod with distilled water between samples.
Figure 4.1: Testing the pH of water samples with universal indicator paper. The numbers on the chart help if some colours look alike to you.
Warning
Safety and good practice. Treat stream and pond water as if it carries germs: do not touch your face, and wash your hands with soap afterwards. Never drink a sample. Rinse the glass rod between samples, or you will carry one sample into the next and spoil the result.
Definition
pH: a number from 0 to 14 that shows how acidic or alkaline a solution is. Below 7 is acidic, exactly 7 is neutral, and above 7 is alkaline. Example: pure water has a pH of 7; lemon juice is about 2.
Definition
Universal indicator: a mixture of dyes that turns a different colour at each pH, from red (strongly acidic) through green (neutral) to purple (strongly alkaline).
Worked example
Problem. Drinking-water standards used in East Africa ask for a pH between 6.5 and 8.5. A student records these results:
| Sample | Colour | pH |
|---|---|---|
| A: tap water | green | 7 |
| B: rainwater | yellow | 5 |
| C: stream water | light blue | 9 |
Which samples meet the standard for pH?
Solution. Compare each value with the range .
Answer: only sample A. pH is only one test: a water analyst also checks for germs, mud and dissolved metals before calling water safe.
Chemists and chemistry technicians do four main kinds of work. They analyse samples to find out what they contain; they make useful substances such as medicines, fertilisers and cement; they control quality in factories, checking every batch; and they research new materials and better processes. Table 4.1 lists some careers and where they are found in Rwanda.
Table 4.1: Careers that use chemistry
| Career | What the person does | Where in Rwanda |
|---|---|---|
| Analytical chemist | measures what a sample contains and how much | Rwanda Standards Board, university laboratories |
| Pharmacist | prepares and checks medicines, advises patients | hospitals, pharmacies, Rwanda Food and Drugs Authority |
| Laboratory technician | prepares samples, runs tests, looks after equipment | hospitals, schools, factories |
| Water-quality analyst | tests water before and after treatment | water treatment plants, district water offices |
| Forensic scientist | analyses evidence such as drugs, blood and ink | Rwanda Forensic Institute |
| Chemical or process engineer | designs and runs the plant that makes a product | cement works, breweries, methane power plants |
| Food scientist | keeps food safe and improves how it is processed | dairies, tea and coffee factories |
| Soil and fertiliser chemist | tests soils and recommends fertilisers | Rwanda Agriculture and Animal Resources Development Board |
| Environmental officer | checks air, water and soil for pollution | Rwanda Environment Management Authority |
| Mineral analyst | tests ores to find their metal content | mines, Rwanda Mines, Petroleum and Gas Board |
| Chemistry teacher | teaches the next generation | secondary schools, TVET schools, universities |
Worked example
Problem. Match each task to a career from Table 4.1.
Solution.
Every Rwandan student studies chemistry from S1 to S3. To go further, choose an A-Level combination that includes chemistry, or a TVET school that trains laboratory and food-processing technicians (Figure 4.2). Careers in medicine and pharmacy need chemistry and biology; engineering needs chemistry with mathematics and physics.
Figure 4.2: Routes from S1 chemistry to a career. P = Physics, C = Chemistry, M = Mathematics, B = Biology, G = Geography.
Worked example
Problem. Umutoni wants to become a pharmacist. Gatete wants to become a chemical engineer at a methane power plant. Which A-Level combination suits each of them?
Solution.
Important
Skills every chemistry career needs: working safely; measuring accurately; recording results honestly and exactly as observed; working in a team; and explaining results clearly to people who are not chemists. A chemist who changes a result to make it "look right" can put lives at risk.
Warning
Common mistake: thinking that chemistry careers are only for people who want to work in a laboratory. Chemists also work in factories, hospitals, mines, farms, offices and classrooms, and many run their own businesses, such as soap, juice or cosmetics firms.
Tip
Choose your A-Level combination by working backwards: pick the career, find the university course it needs, then check which subjects that course asks for.
Tahatū Career Navigator: A day in the work life of a chemist (3 min). Notice how many different tasks fill one working day.
Practice
Further reading
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
