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Class 10 Chemistry Chapter 20 Water Test 7 | Full Unit Test
Grade 10 Chemistry Chapter 20 Water Model Paper 2027
Prepare for the Punjab Board Class 10 Chemistry Examination 2027 with Chapter 20: Water – Class Test No. 7. This full chapter test covers the complete chapter, including textbook exercises, and is designed to help students revise important concepts and assess their exam preparation. These Class 10 Chemistry Model Papers 2027 follow the new syllabus issued by PECTAA Punjab and are part of our comprehensive Full Unit Model Papers and Chapter-Wise Test Series. Practice this Water chapter test to strengthen your Chemistry knowledge, improve problem-solving skills, and prepare confidently for the 10th Class annual board examinations.
PAPER NO.
07
CHAPTER
WISE
WISE
Roll No.(in Figures):
(in Words):
Chapter 20:
Maximum Marks: 12
Water
OBJECTIVE TYPE
Time Allowed : 15 Minutes
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NOTE:Four possible answers A, B, C and D to each question are given. The choice which you think is correct, fill that circle in front of that question with Marker or Pen ink. Cutting or filling two or more circles will result in zero mark in that question.
Q1.12
1.The pH of distilled water is:
(A) 6.5(B) 8.5(C) 7(D) 7.5
Ans: (C) 7
2.If melting point of water sample is below 0°C, it suggests:
(A) Pure water(B) Presence of impurities(C) Alkaline water(D) Acidic water
Ans: (B) Presence of impurities
3.The unpleasant odour in water can be removed by:
(A) adding chlorine(B) treating it with activated charcoal(C) sedimentation(D) filtration
Ans: (B) treating it with activated charcoal
4.The health and diversity of an aquatic ecosystem depends directly on the level of:
(A) Heavy metals(B) Dissolved oxygen(C) Floating microplastics(D) Nitrogen fertilizers
Ans: (B) Dissolved oxygen
5.The source of harmful microbes in natural water:
(A) human and animal wastes(B) fertilizers used for crops(C) industrial waste-water(D) microbes in rocks
Ans: (A) human and animal wastes
6.Chemical substances discharged into water bodies from manufacturing units are called:
(A) Domestic sewage(B) Agricultural run off(C) Industrial effluents(D) Natural minerals
Ans: (C) Industrial effluents
7.Which gases are dissolved in natural water from the atmosphere through diffusion?
(A) O2 and CO2(B) N2 and CO2(C) O2 and N2(D) O2, N2 and CO2
Ans: (D) O2, N2 and CO2
8.Nutrients required in large amount for plant growth are called:
(A) Micro-nutrients(B) Trace elements(C) Macro-nutrients(D) Micro nutrients
Ans: (C) Macro-nutrients
9.The fertilizer harmful to paddy rice is:
(A) Super phosphate(B) Ammonium nitrate(C) Urea(D) Potassium sulphate
Ans: (B) Ammonium nitrate
10.A good fertilizer should NOT:
(A) Provide nutrients to plants(B) Be stable in soil(C) Alter the pH of soil(D) Be soluble in water
Ans: (C) Alter the pH of soil
11.Fertilizers which increase the resistance of plants towards diseases and make plants strong by healthy root development are:
(A) Nitrogenous fertilizers(B) Phosphate fertilizers(C) Potassium fertilizers(D) Magnesium fertilizers
Ans: (B) Phosphate fertilizers
12.Which of the following is the main constituent of nitrogen :
(A) Fats(B) Carbohydrates(C) Proteins(D) Vitamins
Ans: (C) Proteins
Here is Subjective Part of Model Paper. All questions taken from textbook issued by PECTAA PUNJAB.
Roll No.(in Figures):
(in Words):
Chapter 20:
Water
SUBJECTIVE TYPE(PART – I)
Maximum Marks: 48
Time Allowed :1.45 Hours
Q2.Write short answers to any FIVE (5) questions:(5×2=10)
(i)Name two methods to check the purity of water.
Ans: (1) Melting point / freezing point: pure water melts at exactly 0°C. (2) Boiling point: pure water boils at exactly 100°C at 1 atm pressure.
(ii)How does anhydrous CuSO4 help to detect water?
Ans: Anhydrous CuSO4 is a white powder. When water is added it turns blue because hydrated copper sulphate (CuSO4·5H2O) forms. The colour change shows that water is present.
(iii)Write chemical equation of water test with CuSO4?
Ans: CuSO4 (white) + 5H2O → CuSO4·5H2O (blue)
(iv)How do impurities affect the melting point of water?
Ans: Impurities lower the melting point of water, so impure water melts below 0°C (and its boiling point rises above 100°C). Pure water melts at exactly 0°C.
(v)How water is distilled in the laboratory?
Ans: Impure water is heated in a distillation flask until it boils. The steam passes through a condenser (Liebig condenser) cooled by running water, where it turns back into liquid. The pure liquid is collected in a receiver as distilled water.
(vi)What is the main difference between tap water and distilled water?
Ans: Tap water contains dissolved minerals, gases and some microbes, while distilled water is pure H2O free from dissolved salts and impurities.
(vii)Name useful and harmful substances present in water.
Ans: Useful: dissolved oxygen, minerals such as calcium, magnesium, sodium and potassium salts. Harmful: heavy metals (lead, arsenic, mercury), harmful microbes, pesticides and excess nitrates and phosphates.
(viii)Write the applications of distilled water.
Ans: It is used in laboratories for making solutions and experiments, in car batteries, steam irons, preparation of medicines and injections, and in cooling systems.
Q3.Write short answers to any FIVE (5) questions:(5×2=10)
(i)How would you remove harmful bacteria and other microbes present in water?
Ans: By boiling, by adding chlorine (chlorination), by ozone treatment or by ultraviolet (UV) light, all of which kill microorganisms.
(ii)What minerals does tap water contain?
Ans: Tap water contains salts of calcium, magnesium, sodium and potassium, such as bicarbonates, chlorides and sulphates.
(iii)What is the difference between sedimentation and filtration?
Ans: In sedimentation, heavy suspended particles settle down at the bottom under gravity and the clear water is poured off. In filtration, water is passed through a filter (sand, gravel or filter paper) which traps the smaller insoluble particles.
(iv)How are fertilizers classified?
Ans: According to the main nutrient they supply, fertilizers are classified as nitrogenous, phosphatic and potassium fertilizers. Fertilizers containing more than one of these are called mixed or compound (NPK) fertilizers.
(v)Name any three water-borne diseases.
Ans: Cholera, typhoid and dysentery (others: hepatitis A, diarrhoea and trachoma).
(vi)How do heavy metals enter natural water?
Ans: Through industrial effluents, mining waste, old batteries and metal dumps, pesticides, and leaching or erosion of rocks and soil that carries them into rivers and lakes.
(vii)Why fertilizers containing nitrogen element are added into the soil?
Ans: Nitrogen is needed for making proteins and chlorophyll and for leafy growth. Crops remove nitrogen from the soil, so nitrogenous fertilizers are added to replace it and increase yield.
(viii)Why are nitrates and phosphates present in natural water?
Ans: They are washed into water from agricultural fertilizers, sewage, animal waste and detergents.
Q4.Write short answers to any FIVE (5) questions:(5×2=10)
(i)What is trachoma disease?
Ans: Trachoma is a bacterial eye infection (caused by Chlamydia trachomatis) spread through dirty water, poor hygiene and flies. It can lead to blindness if untreated.
(ii)How are tastes and odours removed from water?
Ans: By passing water through activated charcoal, which adsorbs the substances that cause bad taste and smell. Aeration also helps.
(iii)Describe the negative effects of using plastics in every day life.
Ans: Plastics are non-biodegradable. They choke drains, pollute soil and water, harm aquatic animals, break into microplastics that enter the food chain, and release toxic gases when burnt.
(iv)How can negative effects of water pollutants be controlled?
Ans: By treating sewage and industrial waste before discharge, using fertilizers and pesticides carefully, not dumping waste in water bodies, recycling water, enforcing laws and spreading awareness.
(v)Explain one method to remove dissolved impurities present in water.
Ans: Distillation: water is boiled and the steam is condensed. Dissolved salts and other impurities remain behind in the flask, and pure water is collected.
(vi)How can better irrigation techniques help address water scarcity?
Ans: Drip and sprinkler irrigation and lined canals give water directly to the roots and reduce evaporation, seepage and wastage, so more land is irrigated with less water.
(vii)Why urea is regarded as a good nitrogenous fertilizer?
Ans: Urea, CO(NH2)2, contains about 46% nitrogen, the highest of any solid nitrogen fertilizer. It is water soluble, cheap and easy to store and apply.
(viii)What are potassium fertilizers and what is their role?
Ans: They are fertilizers that supply potassium, e.g. potassium chloride (KCl) and potassium sulphate (K2SO4). Potassium activates enzymes, regulates water balance, increases resistance to disease and improves the quality of fruits and grains.
Q5.(a)How domestic water supply can be made fit for drinking?5
Ans: Domestic water is made fit for drinking in these steps:
- Sedimentation: water is stored in tanks so heavy particles settle.
- Coagulation: alum is added so fine particles clump together and settle.
- Filtration: water passes through sand and gravel beds to remove small particles.
- Aeration / charcoal treatment: removes bad taste and odour.
- Disinfection: chlorine (or ozone/UV) kills harmful microbes.
Q5.(b)Which measures should be taken to avoid water-borne disease?4
Ans:
- Drink boiled or chlorinated water.
- Dispose of sewage properly so it does not mix with drinking water.
- Keep water tanks and storage containers clean and covered.
- Wash hands with soap before eating and after using the toilet.
- Spread health awareness and use vaccination where available.
Q6.(a)What are fertilizers? Mention the essential qualities of a good fertilizer.5
Ans: Fertilizers are natural or synthetic substances added to the soil to supply essential nutrients to plants and increase crop yield.
Qualities of a good fertilizer:
Qualities of a good fertilizer:
- It should be soluble in water so roots can absorb it.
- It should contain a high percentage of the needed nutrient.
- It should be stable in soil and not wash away or evaporate quickly.
- It should not be harmful to plants or change the pH of the soil.
- It should be cheap and easily available.
Q6.(b)What two physical constants can be used to determine if a sample of water is pure?4
Ans: Melting point: pure water melts at exactly 0°C; impurities lower it. Boiling point: pure water boils at exactly 100°C at 1 atm; impurities raise it. If the sample shows these exact values it is pure; any change shows impurities.
Q7.(a)How do nitrates and phosphates enter in natural water and affect its quality?5
Ans: Entry: They enter natural water through run-off from fields where fertilizers are used, sewage, animal waste and detergents.
Effects:
Effects:
- They cause rapid growth of algae (eutrophication).
- When the algae die and decay, dissolved oxygen is used up.
- Fish and other aquatic life die, and the water becomes smelly and unfit for use.
- Water high in nitrates is harmful to babies (blue baby syndrome).
Q7.(b)Write a note on water scarcity in Pakistan4
Ans: Pakistan is a semi-arid country with low rainfall, especially in the south (below 200 mm a year), and high evaporation. Water scarcity is increasing because of:
- rapid population growth and rising demand;
- climate change, which affects glaciers and monsoon rains;
- few dams and reservoirs, so flood water is wasted;
- wasteful flood irrigation and seepage from unlined canals;
- water pollution from industry and sewage.
