Chemistry in Daily Life — Exercise Solutions Guide
Solve each textbook exercise on your own first, then compare your answers below. Focus on understanding the reasoning, not just memorising the answer.
I. Multiple Choice Questions (MCQs)
II. Fill in the Blanks
1. Penicillin was first discovered by Alexander Fleming. 2. World ORS Day is July 29. 3. Combustion is a chemical reaction in which a substance reacts with an oxidizing agent. 4. In the presence of water, the ignition temperature of paper is not reached. 5. Fire produced by oil cannot be controlled by water. 6. The chemical process where a substance reacts with oxygen to produce heat is called Combustion. 7. Substances which vaporize during burning produce flames. 8. Antacid neutralizes stomach acid. 9. Histamine is a chemical messenger involved in complex biological reactions. 10. Medicines are used to treat disease and improve health. 11. Once infection is sensed, the immune system releases a chemical called pyrogen. 12. Sensing pyrogens, the hypothalamus increases body temperature by releasing prostaglandin. 13. Analgesics react like pain-suppressing chemicals released by the body. 14. Antibiotic resistance is the ability of microorganisms to resist effects of an antibiotic. 15. Salts and sugars pull water into the bloodstream and speed up rehydration.
III. True or False
Q1. Antibiotics work for viruses like cold and flu. False. Antibiotics kill bacteria, not viruses. Colds and flu are caused by viruses, so antibiotics are ineffective against them.
Q2. Analgesics lower the temperature during fever. False. Antipyretics lower fever; analgesics reduce pain. They serve different purposes.
Q3. All fuels form flame. False. Only substances that vaporize during burning produce flames. Coal and charcoal do not vaporize, so they glow but do not produce a flame.
Q4. Oxygen is necessary for combustion. True. Combustion requires fuel, oxygen (or another oxidizing agent), and heat reaching the ignition temperature.
Q5. Burning wood and coal causes pollution of air. True. They release carbon dioxide, carbon monoxide, soot, and ash, contributing to air pollution.
Q6. If there is inadequate salt in the intestinal wall, the body cannot absorb water. True. Salts (electrolytes) create the osmotic gradient needed for water absorption through the intestinal wall.
Q7. Acidity arises from excess production of acetic acid. False. Acidity is caused by excess production of hydrochloric acid (HCl), not acetic acid.
Q8. Stomach lining has a pH of 4–6. False. The stomach lining has a pH of 1–3, which is highly acidic to aid digestion and kill microbes.
Q9. Staphylococcus bacteria cause deadly diseases like pneumonia. True. Staphylococcus bacteria can cause serious infections including pneumonia.
Q10. Fleming named the mould Penicillium notatum. True. Alexander Fleming identified the mould as Penicillium notatum, from which he derived the name penicillin.
Q11. Paracetamol interacts with receptors and reduces pain signal intensity. True. Paracetamol blocks pain receptors in the brain, reducing the intensity of pain signals.
Q12. Bacteria and viruses can thrive above a certain temperature. True. Beyond a certain temperature, however, bacteria and viruses are destroyed — which is why fever is a body defence mechanism.
Q13. Adverse effects of antihistamines are mouth dryness and sleepiness. True. Common side effects of antihistamines include dry mouth and drowsiness.
Q14. Complete combustion produces a yellow flame (hottest part). False. Complete combustion produces a blue flame, which is the hottest zone. The yellow flame comes from partial combustion.
IV. Match the Following
Set 1 — Medicines and Combustion
| Column A | Column B |
|---|---|
| Antipyretic | Reduce body temperature |
| Analgesic | Reduce pain |
| Antacid | ORS Solution |
| Phosphorus | Spontaneous combustion |
| Carbon dioxide | Leads to respiratory problem |
Set 2 — Flame Colour and Substance
| Substance | Flame Colour |
|---|---|
| Epsom salt | White |
| Potassium chloride | Indigo |
| Bleaching powder | Blue |
| Table salt | Orange |
Set 3 — Flame Zone and Colour/Substance
| Flame Zone | Colour / Substance |
|---|---|
| Inner zone | Black |
| Outer zone | Blue |
| Middle zone | Yellow |
| Green flame | Borax powder |
V. Analogy
Q1. Inner zone of flame : \_\_\_\_ :: Outer zone of flame : \_\_\_\_ Black, Blue — The inner zone appears black (unburnt vapours), while the outer zone is blue (complete combustion).
Q2. Tincture : \_\_\_\_ :: Histamine : \_\_\_\_ Antiseptic, Chemical messenger — Tincture of iodine is an antiseptic; histamine is a chemical messenger involved in biological reactions.
VI. Very Short Answers
Q1. Name the first viral disease detected in human beings. Yellow fever.
Q2. Name three greenhouse gases. Carbon dioxide (CO₂), Methane (CH₄), and Chlorofluorocarbons (CFCs).
Q3. Name substances used as antiseptic as well as disinfectant. Garlic, Turmeric, and Aloe vera.
Q4. What are the main constituents of Dettol? A mixture of chloroxylenol and terpineol.
Q5. What is the unit for calorific value? kJ/kg (kilojoules per kilogram).
Q6. Name the types of combustion. Rapid combustion, Spontaneous combustion, and Explosion.
Q7. What are the essential requirements for producing fire? Fuel, Heat, and Oxygen.
Q8. What are antipyretics? Chemicals that reduce fever by suppressing prostaglandin release in the hypothalamus.
Q9. What are antiseptics? Substances applied to the exterior of the body that kill or inhibit the growth of microorganisms.
Q10. Name natural antiseptics. Garlic, Turmeric, and Aloe vera.
Q11. Define histamine. A chemical messenger involved in complex biological reactions, particularly allergic and inflammatory responses.
Q12. Complete: CH₄ + 2O₂ → \_\_\_\_ + \_\_\_\_ + Heat CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Q13. Name substances that produce flames on burning. Wax and Kerosene.
Q14. Give an example of spontaneous combustion. Phosphorus.
Q15. Give an example of slow combustion. Respiration.
Q16. Name the classes of fire. Class A, B, C, D, and K.
Q17. Give examples of Class B fire. Petrol, Turpentine, and Paint.
VII. Short Answers
Q1. Why should medicines not be taken without consulting doctors? Taking the wrong medicine may not cure the illness and can produce harmful side effects. A doctor diagnoses the condition, identifies the cause (bacterial vs. viral, for example), and prescribes the correct medicine at the right dosage and duration.
Q2. Differentiate between antiseptics and disinfectants with examples. Antiseptics are applied to living tissue (skin, wounds) to kill or inhibit microbes — e.g., Dettol, iodine tincture. Disinfectants are applied to non-living surfaces (floors, instruments) to destroy microbes — e.g., phenol, chlorine solution. The key difference is the surface of application: living vs. non-living.
Q3. What is ignition temperature? The minimum temperature at which a substance catches fire and starts burning is called its ignition temperature. Substances with low ignition temperatures (like petrol) are called inflammable.
VIII. Detailed Answers
IX. Higher Order Thinking Skills (HOTS)
Q1. Why is a person covered with a blanket when their clothes catch fire? Fire requires oxygen to burn. Covering the person with a thick blanket cuts off the supply of air (oxygen) to the flames. Without oxygen, the fire is extinguished. This is the same principle as smothering — removing one element of the fire triangle.
Q2. Why does a candle flame always point upward? The hot vapour produced by the burning wax is less dense than the surrounding air. As it heats up, it rises due to convection currents. The cooler, denser air moves downward to replace the rising hot gases, sustaining the upward flame direction.
X. Common Mistakes to Avoid
1. Saying antibiotics work for viruses. Antibiotics target bacteria only; they are completely ineffective against viruses like cold and flu. 2. Confusing antipyretics and analgesics. Antipyretics reduce fever (body temperature); analgesics reduce pain. Paracetamol does both, but the categories are distinct. 3. Saying the yellow flame is the hottest. The outer blue zone is hottest (complete combustion). The yellow middle zone is only moderately hot (partial combustion). 4. Confusing antiseptics and disinfectants. Antiseptics are used on living tissue; disinfectants are used on non-living surfaces. 5. Saying all fuels produce flames. Only substances that vapourize during burning produce flames. Coal and charcoal do not vapourize, so they glow without a flame. 6. Thinking water can extinguish oil fires. Water is heavier than oil and sinks below it, causing the oil to spread and the fire to intensify. Use sand or CO₂ extinguishers instead. 7. Confusing slow combustion and rapid combustion. Slow combustion occurs at low temperatures (e.g., respiration); rapid combustion occurs quickly with visible flame (e.g., burning petrol).
XI. Exam Checklist
- [ ] Types of medicines: Antibiotics, Analgesics, Antipyretics, Antacids, Antihistamines — definitions and examples
- [ ] Candle flame zones: Outer (blue/hottest/complete combustion), Middle (yellow/luminous/partial combustion), Inner (black/unburnt vapours)
- [ ] Combustion types: Rapid, Spontaneous, Explosion, Slow — definitions and examples
- [ ] Fire triangle: Fuel, Oxygen, Heat — all three required
- [ ] Ignition temperature definition and examples of inflammable substances
- [ ] Calorific value: definition, unit (kJ/kg), and calculation method
- [ ] ORS: composition, importance on World ORS Day (July 29), and how glucose aids rehydration
- [ ] Antibiotic resistance: definition, causes, and consequences
- [ ] Classes of fire: A, B, C, D, K — examples for each
- [ ] Fire extinguisher types: Water, CO₂, Dry chemical — working principle and suitable fire class
- [ ] Histamine and prostaglandin role in fever mechanism
- [ ] Natural antiseptics: Garlic, Turmeric, Aloe vera
- [ ] Dettol constituents: Chloroxylenol and Terpineol
- [ ] Flame colours for substances: Epsom salt (white), Potassium chloride (indigo), Bleaching powder (blue), Table salt (orange), Borax (green)