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NIOS Class 10 Science and Technology Chapter 26 Air and Water
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Air and Water
Chapter: 26
INTEXT QUESTIONS 26.1
1. A chemical substance may occur as an element, mixture or compound. To which category does air belong?
Ans: Mixture.
2. Name the major constituents of air. Which constituents are inevitable for survival of plants and animals?
Ans: Nitrogen and oxygen; oxygen.
3. If you were to compare the relative amounts of nitrogen and oxygen in the atmosphere. Which will be four times the other?
Ans: Nitrogen.
4. Air also contains water vapour. But is its percentage in air the same at all places?
Ans: It varies from place to place.
INTEXT QUESTIONS 26.2
1. Why is oxygen essential for life? What would happen if there is no oxygen in air?
Ans: Needed for respiration by plants and animals; animals would die
2. Carbon dioxide acts as food for plants. Name the process in which it is utilised for making food.
Ans: Photosynthesis.
3. What is dry ice and what is it used for?
Ans: Solid CO2 , used as a refrigerant.
4. If you were to analyse all proteins, you would find a particular element common to all. Which one is it?
Ans: Nitrogen.
INTEXT QUESTIONS 26.3
1. What happens to atmospheric pressure as we climb a mountain?
Ans: It decreases with altitude.
2. At high altitude the people find their nose bleeding. Why?
Ans: It is because the blood pressure in blood vessels of the body is much more than the air pressure at high altitude, so the capillaries burst and bleeding occurs.
3. Which layer of atmosphere is the closest to the earth’s surface and which is the farthest from earth’s surface?
Ans: (i) Troposphere.
(ii) Thermosphere.
4. In which layer of atmosphere is the ozone layer present?
Ans: Stratosphere.
5. Name:
(i) A green house gas.
Ans: Methane.
(ii) Gas responsible for acid rain.
Ans: Sulphur oxide (SOx).
(iii) Chemicals causing ozone hole.
Ans: Chloro fluoro carbons (CFCs).
INTEXT QUESTIONS 26.4
1. It is said that more of earth is water than land. How much of the earth’s surface is covered by water?
Ans: Three fourths.
2. Name any two sources of water.
Ans: Rain and sea (or any other).
3. Is rainwater pure or impure? Give one reason to support your answer.
Ans: Pure/ Distilled.
4. What does chlorination do to water in order to purify it?
Ans: Kill microorganisms.
5. I could not form lather with soap while washing my hands, which type of water was it?
Ans: Hard water.
6. Name the type of hardness caused to water due to presence of bicarbonates of Ca2 + or Mg2 +
Ans: Hard water.
7. Name the type of hardness caused to due to presence-of chloride or sulphate of Ca2 + or Mg2 +
Ans: Permanent hardness.
8. Which type of hardness is removed by the following:
(i) Boiling _____________.
Ans: Temporary.
(ii) Ion exchange method. ______________.
Ans: permanent.
9. Is water a polar or a non polar solvent? Why do you think so?
Ans: Polar—reasons to be given.
10. At what temperature does water take up least space?
Ans: 40 C.
INTEXT QUESTIONS 26.5
1. State any two uses of harvesting rain water?
Ans: Two uses of harvesting rain water are mentioned below:
(i) It conserves valuable ground water.
(ii) It reduces local flooding and drainage problems.
2. How would industries and agriculture suffer in the event of acute scarcity of water?
Ans: Industries: coolant purpose, production of steam, use as solvent for many chemical would be affected Agriculture: irrigation of crops, germination of seeds and growth of plants would be affected.
3. What does rainwater do to groundwater?
Ans: Raises the declined water level.
4. Why does rainwater prove to be suitable for washing with soap?
Ans: Because rain water is in the form of soft water.
| TERMINAL EXERCISES |
1. Multiple choice type questions.
(i) Air is.
(a) compound.
(b) element.
(c) mixture.
(d) none of these.
Ans: (c) mixture.
(ii) Major components of air are
(a) CO2 and H2 O.
(b) N2 and O2.
(c) CO2 and He.
(d) H2O and Xe.
Ans: (b) N2 and O2.
(iii) The instrument used to measure humidity is
(a) Barometer.
(b) Hygrometer.
(c) Lactometer.
(d) Thermometer.
Ans: (b) Hygrometer.
(iv) Water has maximum density at
(a) 0°C.
(b) 10 °C.
(c) 5°C.
(d) 4 °C.
Ans: (d) 4 °C.
2. List the utility of oxygen and nitrogen in our lives.
Ans: The utility of oxygen and nitrogen in our lives are mentioned below:
Oxygen:
(i) Oxygen is used up by living beings in the respiration process.
(ii) It is used for burning fuels.
Nitrogen:
(i) Food industry. Nitrogen gas is also used to provide an unreactive atmosphere.
(ii) Light bulbs industry.
3. What is atmospheric pressure?
Ans: The region of air around earth is called the atmosphere. Atmosphere protects us and all living organisms from harmful radiations of the sun like ultraviolet rays etc. We can divide the atmosphere into different layers according to temperature, pressure variation and composition. The main layers of the atmosphere (figure 26.4) from the surface of earth upward are the troposphere (0-10 km), stratosphere (10-50 km), mesosphere (50-85 km) and thermosphere (85-500 km).
4. How does the atmospheric pressure depend on altitude?
Ans: Atmospheric pressure decreases with increases in altitude. As we know that the density of air becomes heavier near the surface of the earth (due to gravity) and begins to lighten as we go to higher altitudes and eventually leads to empty space, i.e. outside the atmosphere of the earth.
5. Give an activity, which proves that air exerts pressure.
Ans: When we fill air in a balloon, the balloon expands due to air pressure. When it is blown more and more, it eventually bursts due to air pressure.
6. What is relative humidity?
Ans: Relative humidity (RH) (expressed as a percent) also measures water vapour, but RELATIVE to the temperature of the air. In other words, it is a measure of the actual amount of water vapour in the air compared to the total amount of vapour that can exist in the air at its current temperature.
7. What is the different source of water? Mention any two.
Ans: Rainwater is the primary source of water. The water cycle is a series of events that include evaporation, condensation and precipitation with rainfall as the final product. In the water cycle, the source of water is critical.
8. Why is water called a universal solvent?
Ans: Water is called the “universal solvent” because it is capable of dissolving more substances than any other liquid. This is important to every living thing on earth. It means that wherever water goes, either through the air, the ground, or through our bodies, it takes along valuable chemicals, minerals, and nutrients.
9. What are the different ways to purify drinking water? What is the role of chlorination?
Ans: The way of purification of drinking water is by boiling it as when boiled the bacteria present in water are destroyed.
The chlorine is used as disinfectant while mixing in water or by the presence of it in bleaching powder. So, it is a disinfectant substance.
10. What do you mean by hard and soft water? Explain the types of hardness in water.
Ans: The simple definition of water hardness is the amount of dissolved calcium and magnesium in the water. Hard water is high in dissolved minerals, largely calcium and magnesium. You may have felt the effects of hard water, literally, the last time you washed your hands.
11. How are the temporary and permanent hardness removed from water?
Ans: Temporary hardness can be removed by boiling, but permanent hardness can’t. Water softening at home can be done using a resin coated with sodium. Other methods of removing hardness include Clark’s process, Calgon’s process, and ion-exchange resin.
12. Explain the following properties of water.
Ans: It is a colourless, tasteless and odourless liquid.
Water exists in three states: Solid(ice), Liquid (water), and Gas (steam). Water expands on cooling. Water has high melting and boiling point.
13. (i) Surface tension.
Ans: The pressure of water in a particular area is known as the surface tension.
(ii) Density.
Ans: The ratio of the mass to the volume is known as the density of that substance.
14. What is rainwater harvesting? How is it beneficial for everyday life?
Ans: Rainwater Harvesting is one of the most commonly used methods to save water. It refers to storing of rainwater for various uses. The notion behind rainwater harvesting is to not waste the rainwater and prevent it from running off. In other words, it is done to collect rainwater using simple mechanisms.
By harvesting the rain water the level of ground water increased.
15. Why is the presence of carbon dioxide in the atmosphere essential? Give two reasons.
Ans: Carbon dioxide is Earth’s most important greenhouse gas: a gas that absorbs and radiates heat. Unlike oxygen or nitrogen (which make up most of our atmosphere), greenhouse gases absorb heat radiating from the Earth’s surface and re-release it in all directions including back toward Earth’s surface.
(i) It acts as a blanket and keeps the average temperature of the Earth.
(ii) It contains all the gases which are essential for sustaining life on the Earth.
16. Give any two medical uses of oxygen.
Ans: Two medical uses of oxygen:
(i) Oxygen is used up by living beings in the respiration process.
(ii) It is used for burning fuels.
17. What are primary and secondary air pollutants? Give one example of each.
Ans: Water is called the universal solvent because it is capable of dissolving more substances than any other liquid. Water is a polar covalent molecule in which the hydrogen atom has a positive charge, whereas oxygen has a negative charge.
18. What are the sources of the following pollutants:
(i) Chlorofluorocarbons.
Ans: CFCs are man-made chemicals that were widely used in refrigerants, aerosol propellants, and industrial processes. Production of CFCs has been banned due to their negative impact on the ozone layer. However, existing CFCs can still leak into the atmosphere from old appliances and products.
(ii) Nitrogen oxides.
Ans: Nitrogen oxides are a group of gases that form from the combustion of fuels at high temperatures.
Major sources of NOx include:
(i) Transportation: Cars, trucks, buses, ships, and aeroplanes all release NOx when they burn fuel.
(ii) Industrial facilities: Many industries, such as factories and refineries, release NOx into the air.
(iii) Particulate matter.
Ans: Particulate matter (PM) is a mixture of solid and liquid particles suspended in the air. It can come from both natural sources and human activities.
Some of the major sources of PM include:
(i) Combustion processes: The burning of fossil fuels, wood, and other materials releases PM into the air. This includes emissions from vehicles, power plants, and industrial facilities.
(ii) Natural sources: Windblown dust, wildfires, and volcanic eruptions can all release PM into the atmosphere.
19. Why are the following substances considered air pollutants:
(i) Carbon monoxide.
Ans: There is substantial evidence that CO can adversely affect health, participate in atmospheric chemical reactions that result in formation of ozone air pollution, and contribute to climate change.
(ii) Carbon dioxide.
Ans: Carbon dioxide (CO2 ) is produced by complete combustion of fuels in motor vehicles and various industries. It is a colourless, odourless and non-toxic gas. (A person dies in atmosphere of carbon dioxide due to lack of oxygen and not due to its toxic nature).
(iii) Sulphur oxides.
Ans: Sulphur oxides (SOx) (mainly sulphur dioxide, SO2 ) are produced by combustion of coal and petroleum and also produced in volcanoes. It is also produced in various industrial processes. Oxidation of sulphur dioxide (SO2 ) to sulphur trioxide (SO3 ) results in formation of sulphuric acid (H2 SO4 ) which causes acid rain.
(iv) Volatile organic compounds.
Ans: Volatile organic compounds (VOCs) include methane, benzene, toluene and xylene. While methane is a major green house gas, others are suspected to be carcinogens (cancer inducing).
20. What are:
(i) photochemical smog.
Ans: The high levels of nitrogen and ozone when mixed in air create a ozone hole in the atmosphere region which is known as photochemical smog.
(ii) Ground level ozone.
Ans: In automobile industries these types of violating hydrocarbon compounds are present.
21. What are
(i) point source pollution. and
(ii) non-point source pollution?
Give one example of each.
Ans: (i) Point source pollution refers to contaminants that enter a water body from a single identifiable source such as a pipe or a ditch.
(ii) Nonpoint source pollution refers to diffused contamination that does not originate from a single discrete source but is the cumulative effect of contaminants gathered from a large area such as leaching of fertilisers and pesticides from agricultural land.
22. Dive any two of the water for each of the following purposes.
(i) Domestic.
Ans: For cooking food drinking.
(ii) Industrial.
Ans: For cooling plants, smelting.
(iii) Agricultural.
Ans: For the irrigation purpose.
23. What do you mean by conservation of water? How is it useful?
Ans: Water conservation is a process of preventing wastage of water, using water carefully and recharging groundwater. Water conservation can be done by: 1) Repairing leaking pipes and taps. 2) Not wasting water during brushing teeth, shaving, bathing, washing clothes and during other activities.
The conservation of water means the storing of water for different purposes like the uses in agricultural, household works etc.
24. You are incharge of the residents welfare association./ prepare two slogans to make residents aware of the need for conservation of water.
Ans: The slogan which will create an awareness in the resident is SAVE THE WATER FOR OUR FUTURE GENERATIONS.
This type of awareness is also very necessary for our water harvesting.
25. The atmospheric envelope around living beings is the provider of the gases essential for their survival, which are these gases, what is their proportion in air and how are they responsible for survival?
Ans: This gas is carbon dioxide as this gas play an important role in the photosynthesis process. As this gas helps the plant for the making of their food. In this process the oxygen gas also come out.
26. How does rain water pollute water bodies with the air pollutants?
Ans: As the rain water become acidic with the presence of Different toxic gases present in air. So, when this water is falling on the water resources then we see that water is polluted.
27. Recall five properties of water and write a paragraph justifying that water is an indispensable resource.
Ans: Five properties of water and write a paragraph justifying that water is an indispensable resource are:
(i) Lather formation: Water produces lather upon introduction with soap. This is a very useful property of water that makes it a suitable liquid for washing clothes, cleaning dishes, bathing etc. daily household chores. Hence, this property makes the water very useful for us.
(ii) Universal solvent: Water is a universal solvent. It can dissolve so many things. This property makes water a very suitable liquid for the formation of so many solutions and electrolytes. This property makes water a very useful liquid for some domestic and industrial works.
(iii) Surface tension: It is a very important property found in almost all liquids. In water, the surface tension makes water take up the smallest space possible. Surface tension makes water take up the shape of a drop instead of spreading like a thin layer. This property of water assists water to flow through the roots, stems and other parts of the plants.
(iv) Capillarity: A tube with a two-sided opening through a fine hole is called a capillary tube. When one side of this capillary tube is dipped in water, it rises upwards in the capillary. This property of water makes it easy for nutrients to rise upwards to the stems and leaves from soil.
(v) Water is necessary for the effective absorption of nutrients in the body. These nutrients are best absorbed with the help of water. Also, water is an essential part of numerous biological reactions taking place inside the body.
28. How does boiling of hard water convert it such that it can be used for washing clothes?
Ans: As in hard water there present a substance like the calcium or magnesium in its sulphide forms so, by boiling it we can do that. As the water is also known as the universal solvent.
