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Class 10 Chemistry Chapter 20 Water Test 2 | Board Model Papers 2027
Grade 10 Chemistry Chapter 20 Water Test 2
Prepare for the Punjab Board Class 10 Chemistry Examination 2027 with Chapter 20: Water – Class Test No. 2. This test is part of our Class 10 Chemistry Full Unit Model Papers and Chapter-Wise Test Series, designed to help students revise important concepts and assess their preparation. Based on the new Chemistry syllabus issued by PECTAA Punjab, this practice test supports effective exam preparation, concept revision, and self-assessment for the Punjab Board 2027 Model Papers. Practice chapter-wise Chemistry tests to strengthen your subject knowledge and prepare confidently for the 10th Class annual examinations.
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1. The change in colour from white to blue indicates the presence of:
(Q-4)
A. AirB. HeatC. WaterD. Acid
Answer: C. Water – white anhydrous CuSO4 turns blue on adding water.
2. The freezing point of pure water at STP is:
(Q-6)
A. −10 °CB. 0 °CC. 10 °CD. 100 °C
Answer: B. 0 °C
3. The pH of distilled water is:
(Q-14)
A. 5B. 6C. 7D. 9
Answer: C. 7 – distilled water is neutral.
4. Which of the following is a heavy metal pollutant?
(Q-19)
A. SodiumB. CalciumC. LeadD. Oxygen
Answer: C. Lead (Pb)
5. Main types of impurities that are commonly found in natural water is :
(Q-22)
A. OneB. TwoC. ThreeD. Four
Answer: C. Three – suspended, dissolved and biological (microorganisms).
6. In World Health Organization, polluted water causes diseases in world wide.
(Q-31)
A. 20%B. 40%C. 60%D. 80%
Answer: D. 80% – WHO: about 80% of diseases worldwide are caused by polluted water.
7. Micro-nutrients are generally required in the range of:
(Q-43)
A. 1–5 kg per acreB. 6–200 grams per acreC. 5–200 kg per acreD. Above 500 kg per acre
Answer: B. 6–200 grams per acre
8. Phosphorus helps in plants is:
(Q-54)
A. Leaf colourB. Seed and fruit formationC. Water absorptionD. Photosynthesis only
Answer: B. Seed and fruit formation
786Times • Chemistry Chapter-20
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i. How does anhydrous copper(II) sulphate test for water?
(Q-3)
Ans: Anhydrous CuSO4 is white. When water is added it forms hydrated CuSO4·5H2O, which is blue. White → blue shows water is present.
ii. What is the effect of impurities on the purity of water?
(Q-6)
Ans: Impurities raise the boiling point and lower the freezing point of water. They also change its taste, colour and smell and make it unfit for drinking.
iii. Why is tap water a conductor of electricity? Write its pH range.
(Q-9)
Ans: Tap water contains dissolved salts that form ions, which carry electric current. Its pH range is 6.5–8.5.
iv. What is dissolved oxygen?
(Q-12)
Ans: Oxygen gas dissolved in water. Aquatic animals and plants need it to breathe, so it is an indicator of water quality.
v. Mention harmful effects of heavy metals on human health.
(Q-16)
Ans: Heavy metals such as lead, mercury and arsenic damage the liver, kidneys and nervous system, and can cause cancer and brain damage.
vi. What is eutrophication?
(Q-18)
Ans: Excess nutrients (nitrates and phosphates from fertilizers and sewage) in water cause rapid algae growth. Algae die and decay, using up dissolved oxygen and killing aquatic life.
vii. Write activated carbon method.
(Q-23)
Ans: Water is passed through a bed of activated charcoal. Its large surface area adsorbs dissolved organic impurities, chlorine, bad smell and colour, making the water clean.
viii. What is trachoma?
(Q-27)
Ans: An eye disease caused by bacteria and spread through unclean water and poor hygiene. It can lead to blindness.
ix. What are fertilizers?
(Q-37)
Ans: Natural or synthetic substances added to soil to supply essential nutrients (N, P, K) to plants and increase crop yield.
x. What is the role of nitrogen in plant growth?
(Q-42)
Ans: Nitrogen is needed to make proteins and chlorophyll. It gives leaves a dark green colour and promotes healthy leafy growth.
SECTION-II (4+4)
1. Which measures should be taken to avoid water-borne disease?
(Ex.D.20.2)
Ans:
- Boil or chlorinate water before drinking.
- Use filtered or treated water.
- Keep water tanks and containers clean and covered.
- Do not mix sewage with drinking water; repair leaking pipes.
- Wash hands before eating and after using the toilet.
- Spread awareness about hygiene and sanitation.
2. What are the main functions of nitrogenous, phosphatic and potassium fertilizers?
(Ex.D.20.4)
Ans:
- Nitrogenous (e.g. urea): promote leafy growth, give dark green colour, help make proteins.
- Phosphatic (e.g. superphosphate): strengthen roots, help flowering, seed and fruit formation.
- Potassium (e.g. potassium sulphate): improve disease resistance, fruit quality and water balance in plants.
786Times • Chemistry Chapter-20
