Introduction to Chemistry

1. What is Chemistry?

Chemistry is the branch of science that studies the composition, structure, properties, and changes of matter.

Everything around us is made of matter, and chemistry helps us understand how different substances interact, combine, and change.

Branches of Chemistry

2. Role of Chemistry in Daily Life

In the Home

• Cleaning: Soaps, detergents, bleaches are chemicals that help clean.
• Cooking: Baking soda (NaHCO3) helps cakes rise. Salt (NaCl) adds flavour.
• Medicine: Paracetamol, aspirin, antacids are chemical compounds.
• Clothing: Synthetic fabrics like nylon, polyester are chemically manufactured.

In Agriculture

• Fertilisers: Urea, ammonium nitrate provide nutrients to plants.
• Pesticides: Protect crops from insects and diseases.

In Industry

• Construction: Cement, bricks, paint are products of chemical processes.
• Batteries: Chemical reactions produce electricity.

In Health

• Disinfectants: Dettol, hydrogen peroxide kill germs.
• Vitamins and minerals: Essential chemicals for body function.

Exam Focus (2 marks): 'State two uses of chemistry in everyday life.'

(1) Soaps and detergents help in cleaning. (2) Medicines cure diseases.

3. Laboratory Safety

General Safety Rules

1. Always wear a lab coat and safety goggles.
2. Never eat or drink in the laboratory.
3. Never taste or touch chemicals with bare hands.
4. Keep your work area clean and tidy.
5. Read the label carefully before using any chemical.
6. Do not run or play in the laboratory.
7. In case of a chemical spill, inform your teacher immediately.

Handling Chemicals

• Use a spatula to handle solid chemicals, never your fingers.
• Smell chemicals by wafting (fanning the air toward your nose), never directly.
• Do not return unused chemicals to their original containers.
• Always add acid to water slowly, never water to acid.

Common Mistake: Pouring water into concentrated acid. This causes a violent reaction. Always add acid to water slowly.

4. Common Laboratory Apparatus

Worked Example: Which apparatus would you use to measure exactly 25 mL of water?

A measuring cylinder. It is graduated to measure precise volumes.

5. Common Safety Symbols

6. Self-Test

1. Define chemistry.
2. List two uses of chemistry in: (a) home (b) agriculture (c) medicine.
3. What should you do if a chemical spills on the lab bench?
4. Name the apparatus used to: (a) measure 10 mL of liquid (b) heat a substance (c) transfer solid chemicals.
5. Why should you never return unused chemicals to the original container?
6. What is the correct way to smell a chemical?
7. List three safety rules to follow in a chemistry laboratory.

7. Answers to Self-Test

1. Chemistry is the branch of science that studies the composition, properties, and changes of matter.
2. (a) Home: soaps for washing, baking soda for cooking. (b) Agriculture: fertilisers for plant growth, pesticides to protect crops. (c) Medicine: paracetamol for fever, antacids for acidity.
3. Inform the teacher immediately. Do not try to clean it yourself unless instructed.
4. (a) Measuring cylinder (b) Bunsen burner (c) Spatula.
5. It may contaminate the original stock.
6. Wafting (fan the air toward your nose with your hand). Never smell directly.
7. (a) Wear a lab coat and safety goggles. (b) Never eat or drink in the lab. (c) Read labels before using any chemical.