GSEB Class 9 Science Solutions Chapter 14 Natural Resources

Page 193

 

Question 1. How is our atmosphere different from the atmospheres on Venus and Mars?
Answer: Earth's atmosphere holds a blend of gases such as nitrogen, oxygen, carbon dioxide, and water vapor. This blend helps to sustain life since the amount of carbon dioxide in Earth's air is small compared to other gases. Yet, the air on Venus and Mars is mostly carbon dioxide, which cannot support life on those planets.
In simple words: Earth's air has a mix of gases, with less carbon dioxide, helping life. Venus and Mars have mostly carbon dioxide, which cannot support life.

Exam Tip: Remember to compare the key atmospheric compositions (Earth's N, O2, CO2 vs. Venus/Mars' high CO2) and link these directly to their suitability for sustaining life.

 

Question 2. How does the atmosphere act as a blanket?
Answer: The atmosphere acts as a blanket because:

• It maintains Earth's average temperature quite steady.
• It stops quick temperature rises during the daytime.
• It lessens heat loss into space at night.

In simple words: The atmosphere keeps Earth's temperature steady, prevents rapid warming in the day, and slows heat loss at night, like a blanket.

Exam Tip: When describing the atmosphere as a blanket, focus on its temperature-regulating properties: preventing extremes and maintaining a stable environment.

 

Question 3. What causes winds?
Answer: Because land and water heat up unevenly, land warms more quickly during the day. The air above the land then rises, making a low-pressure area. Consequently, air from over the sea travels towards this low-pressure area on land. This movement of air generates winds.
In simple words: Winds happen because land and water heat differently. Land gets hotter faster, making air rise and creating low pressure. Air from the sea moves to fill this space, causing wind.

Exam Tip: Key terms for wind formation are "unequal heating," "low-pressure area," and "movement of air" from high to low pressure. Illustrating with land/sea breeze helps score.

 

Question 4. How are clouds formed?
Answer: Water turns into vapor from water bodies and from the life processes of living things. This water vapor rises into the air. As the air goes higher, it grows larger and gets colder. This cooling causes the water vapor to gather around small dust specks in the air, creating very small drops. These droplets then come together to form clouds.
In simple words: Water evaporates, becomes vapor, rises, cools, and then turns into tiny drops around dust, forming clouds.

Exam Tip: Explain the cloud formation process in sequence: evaporation, rising air, cooling, condensation (around particles), and droplet formation.

 

Question 5. List any three human activities that you think would lead to air pollution.
Answer: The human activities that would lead to air pollution are:

• Burning coal in power stations to make electricity.
• Using fuels such as petrol and diesel in cars.
• Widespread cutting down of trees.

In simple words: Air pollution comes from burning coal for power, using vehicle fuels, and cutting down many trees.

Exam Tip: When listing activities, choose distinct categories like industrial, transport, and environmental impact to provide a comprehensive answer.

Page - 194

 

Question 1. Why do organisms need water?
Answer: Living organisms need water for:

• Performing the many metabolic and chemical processes happening in their bodies.
• Moving different materials from one body part to another within living things.

In simple words: Living things need water for body processes and to move substances around inside them.

Exam Tip: Focus on water's role as a solvent and a medium for biochemical reactions and transport within organisms.

 

Question 2. What is the major source of freshwater in the city/town/village where you live?
Answer: The primary supply of water is from rivers and reserves of groundwater.
In simple words: Rivers and water found underground are the main sources of fresh water.

Exam Tip: Common major sources include rivers, lakes, groundwater (wells/borewells), and reservoirs; mention the most prominent for your locality.

 

Question 3. Do you know of any activity which may pollute this water source?
Answer: The activity which pollutes the water resource are:

• Too much use of fertilizers and pesticides, which wash into waterways, making them dirty.
• Wastewater that flows straight into rivers.

In simple words: Overusing fertilizers and pesticides that wash into water, and raw sewage flowing into rivers, can make water dirty.

Exam Tip: When discussing water pollution, key examples include agricultural runoff (pesticides/fertilizers) and untreated domestic/industrial sewage discharge.

Page - 196

 

Question 1. How is soil formed?
Answer: Soil develops through many physical, chemical, and biological actions that cause rocks to break down into tiny soil pieces over millions of years. Soil formation happens because of elements and processes like the Sun, water, wind, living creatures, and lichens.

1. Sun: Rocks grow larger when the Sun warms them during the day. At night, the rocks become cooler and shrink. This causes cracks to form in the rocks, as their expansion and shrinking rates differ. The rocks then split apart and break into smaller bits.
2. Water: Water helps break large rocks into tiny pieces in two ways. Water gets into cracks and small gaps in the rocks, is heated unevenly by the Sun, and when it expands as it freezes in winter, it breaks the rocks. Moreover, quickly moving water over the rock surfaces also causes them to wear away, forming soil.
3. Wind: Air movements move small stones and sand from one spot to another. These powerful winds rub against bigger rocks, causing them to wear away.
4. Living Organisms (Lichens): Chemical materials released by living things such as lichens break down rocks and change them into tiny soil bits.

In simple words: Soil forms over millions of years from rocks breaking down due to Sun, water, wind, and living things like lichens. The Sun heats and cools rocks, causing cracks. Water gets into cracks and freezes, breaking rocks, and also wears them down as it flows. Wind rubs sand against rocks, eroding them. Lichens release chemicals that break down rocks into soil.

Exam Tip: Detail the processes of weathering (physical, chemical, biological) and provide specific examples for each, such as thermal expansion/contraction by the sun, frost wedging by water, abrasion by wind, and biotic weathering by lichens.

 

Question 2. What is soil erosion?
Answer: The action where the rich top layer of soil is taken away is known as soil erosion.
In simple words: Soil erosion is when the top, fertile layer of soil gets removed.

Exam Tip: Define soil erosion clearly as the removal of topsoil, which is the most fertile layer, highlighting its negative impact on agriculture and the environment.

 

Question 3. What are the methods of preventing or reducing soil erosion?
Answer: The methods to prevent soil erosion are:

• Cattle grazing too much should be stopped.
• Planting many trees should be done because plant roots stop soil from being washed away.
• Growing more plants on the land lessens the effect of moving water on soil and keeps it from being carried off.
• Farming along the natural curves of the land can be done by making grooves across the slope to catch water as it flows down.
• Terrace farming is used in hilly areas; this slows down water flow and gives it more time to soak into the soil.

In simple words: To stop soil erosion, prevent overgrazing, plant more trees to hold soil, increase plant cover to reduce water impact, use contour farming to trap water, and practice step farming on slopes to slow water flow.

Exam Tip: Focus on methods that stabilize soil (vegetation, afforestation) and those that manage water flow (contour farming, step farming), linking each to how it counters erosion.

Page - 201

 

Question 1. What are the different states in which water is found during the water cycle?
Answer: Water is found in three different states during the water cycle:

• Solid: as ice or snow.
• Liquid: as water.
• Gas: as water vapor.

In simple words: In the water cycle, water exists as a solid (ice/snow), a liquid (water), and a gas (water vapor).

Exam Tip: List the three states of matter (solid, liquid, gas) and provide the common forms of water associated with each state in the water cycle.

 

Question 2. Name two biologically important compounds that contain both oxygen and nitrogen.
Answer: Proteins and the nucleic acids (like DNA and RNA) are crucial biological compounds that hold both oxygen and nitrogen.
In simple words: Proteins and nucleic acids (DNA and RNA) are vital compounds in biology that have both oxygen and nitrogen.

Exam Tip: Remember proteins (for structure and function) and nucleic acids (for genetic information) as primary examples of biomolecules containing both oxygen and nitrogen.

 

Question 3. List any three human activities which would lead to an increase in the carbon dioxide content of the air.
Answer: The human activities which would lead to an increase in the carbon dioxide content of the air are:

• Using coal in power stations to make electricity.
• Using fuels such as petrol and diesel in cars.
• Widespread tree cutting, which causes a reduction in green plants and trees that use carbon dioxide for photosynthesis.

In simple words: Three human actions increasing air carbon dioxide are burning coal for power, using vehicle fuels, and cutting down many trees, which reduces plants that absorb CO2.

Exam Tip: Focus on activities that release CO2 (combustion of fossil fuels) and those that reduce CO2 absorption (deforestation).

 

Question 4. What is the greenhouse effect?
Answer: The event where sunlight can enter Earth's air but warmth sent back from the ground is held by gases like carbon dioxide, water vapor, and methane in the atmosphere is known as the greenhouse effect.
In simple words: The greenhouse effect is when certain gases in the atmosphere trap heat radiated from Earth's surface, keeping the planet warm.

Exam Tip: Define the greenhouse effect by describing how certain atmospheric gases trap reflected heat, preventing it from escaping into space and thus warming the planet.

 

Question 5. What are the two forms of oxygen found in the atmosphere?
Answer: The oxygen is found in the atmosphere in two forms:

• As a diatomic molecule \( O_2 \), which has two oxygen atoms.
• As a triatomic molecule \( O_3 \), which has three oxygen atoms. This is known as ozone.

In simple words: Oxygen in the air comes as \( O_2 \) (two atoms) and \( O_3 \) (three atoms), which is called ozone.

Exam Tip: Clearly distinguish between diatomic oxygen (\( O_2 \)) and triatomic oxygen (ozone, \( O_3 \)), explaining their composition.

In-Text Activities Solved

Textbook Page 190

Measure the temperature of the following: Take -

1. a beaker full of water
2. a beaker full of soil/sand
3. a closed bottle containing a thermometer.

Keep them in bright sunlight for three hours. Now measure the temperature of all 3 vessels. Also, take the temperature reading in shade at the same time.

 

Question 1. Is the temperature reading more inactivity (i) or (ii)?
Answer: The temperature reading shows more inactivity in option (ii).
In simple words: The temperature reading is less active for option (ii).

Exam Tip: Relate 'inactivity' in temperature reading to less change or a more stable reading, which typically occurs with materials that heat/cool slowly.

 

Question 2. Based on the above finding, which would become hot faster - the land or the sea?
Answer: The land will get warm more quickly.
In simple words: Land will heat up quicker than the sea.

Exam Tip: Recall that land has a lower specific heat capacity than water, meaning it absorbs and releases heat more rapidly.

 

Question 3. Is the thermometer reading of the temperature of air (in shade) the same as the temperature of sand or water? What do you think is the reason for this? And why does the temperature have to be measured in the shade?
Answer: The air's temperature (in the shade) is lower than that of sand and water. This occurs because the land and water directly take in the Sun's rays.
In simple words: Shaded air is cooler than sun-heated sand or water because air does not directly absorb sunlight. Measuring in shade stops direct sun from heating the thermometer itself.

Exam Tip: Explain that air's temperature is influenced by conduction from surfaces, while surfaces directly absorb solar radiation. Measuring in shade isolates air temperature from direct solar heating.

 

Question 4. Is the temperature of air in the closed glass vessel/bottle the same as the temperature taken in the open air?
Answer: The temperature of the air within the sealed glass container is higher than the temperature recorded in the open air.

1. This happens because glass lets the Sun's rays come in but stops the heat rays that bounce back from leaving.
2. This occurrence is called the greenhouse effect. It can be readily seen in a car left in the sun with its windows shut. The inner temperature of the car gets hotter than the air outside.

In simple words: The air in the closed bottle is hotter than open air. This is because the glass lets sunlight in but traps the heat inside, similar to how a car gets hot in the sun with its windows closed—this is called the greenhouse effect.

Exam Tip: Explain that glass is transparent to short-wave solar radiation but opaque to long-wave infrared radiation, trapping heat inside, similar to the atmospheric greenhouse effect.

Textbook Page 190

Activity 14.2

Place a candle in a beaker or wide-mouthed bottle and light it. Light an incense stick and take it to the mouth of the above bottle (Figure is shown below).

 

Question 1. Which way does the smoke flow when the incense stick is kept near the edge of the mouth?
Answer: The smoke moves inward towards the fire because the warm air surrounding the flame rises, forming an area of lower pressure. Cooler air from outside, which is at higher pressure, then quickly moves in. Thus, the smoke is drawn towards the flame.
In simple words: Smoke moves into the flame because hot air around the flame rises, creating low pressure. Cooler, higher-pressure air from outside rushes in, pulling the smoke with it.

Exam Tip: Explain the principle of convection: hot air rises, creating a low-pressure area, which then draws in cooler, denser air from surrounding areas.

 

Question 2. Which way does the smoke flow when the incense stick is kept a little above the candle?
Answer: The warm air travels upward, and the smoke ascends with it.
In simple words: The hot air goes up, and the smoke goes up too.

Exam Tip: This illustrates the upward movement of heated air (convection current), carrying the smoke along with it.

 

Question 3. Which way does the smoke flow when the incense stick is kept in other regions?
Answer: The smoke goes up, spreads out, and mixes in the air when the incense stick is placed in other areas.
In simple words: In other areas, the smoke rises, spreads, and mixes with the air.

Exam Tip: If no strong convection current is present, smoke disperses through diffusion and weaker air currents rather than a directed flow.

Textbook Page 191

Activity 14.3

Take an empty bottle of the sort in which bottled water is sold. Pour about 5-10 mL of water into it and close the bottle tightly. Shake it well or leave it out in the Sun for ten minutes. This causes the air in the bottle to be saturated with water vapour. Now, take a lighted incense stick. Open the cap of the bottle and allow some of the smoke from the incense stick to enter the bottle. Quickly close the bottle once more. Make sure that the cap is fitting tightly. Press the bottle hard between your hands and crush it as much as possible. Wait for a few seconds and release the bottle. Again press the bottle as hard as you can.

 

Question 1. When did you observe that the air inside seemed to become 'foggy'?
Answer: When we cease squeezing and compressing the bottle, and the internal pressure is let go, the air inside appears cloudy or 'foggy'.
In simple words: The air in the bottle looked foggy when we stopped pressing it and released the pressure.

Exam Tip: Link the observation of 'fog' to the sudden decrease in pressure, which causes cooling and condensation of water vapor.

 

Question 2. When does this fog disappear?
Answer: The cloudy appearance vanishes when the bottle is compressed once more.
In simple words: The fog goes away when the bottle is pressed again.

Exam Tip: Explain that re-compressing the bottle increases air pressure and temperature, causing the condensed water droplets to evaporate and the fog to disappear.

 

Question 3. When is the pressure inside the bottle higher?
Answer: The internal pressure of the bottle increases when we push or squeeze it.
In simple words: The pressure inside the bottle goes up when we press or crush it.

Exam Tip: Directly state that applying external force (pressing/crushing) to a closed container increases the internal pressure.

 

Question 4. Is the 'fog' observed when the pressure in the bottle is high or when it is low?
Answer: The cloudy mist is seen when the bottle's internal pressure is reduced.
In simple words: The fog appears when the pressure inside the bottle is low.

Exam Tip: Emphasize that a decrease in pressure leads to a drop in temperature, which is essential for condensation and fog formation.

 

Question 5. What is the need for smoke particles inside the bottle for this experiment?
Answer: The tiny smoke bits serve as central points where the water vapor collects, making small liquid drops.
In simple words: Smoke particles are needed because they give the water vapor something to condense around to form tiny droplets.

Exam Tip: Highlight that smoke particles act as condensation nuclei, providing surfaces for water vapor to condense upon and form visible droplets.

 

Question 6. What might happen if you do the experiment without the smoke from the incense stick? Now try it and check if the prediction was correct. What might be happening in the above experiment in the absence of smoke particles?
Answer: The misty haze does not form without the smoke. Small droplets do not appear because there's no central point for the water vapor to gather around.
In simple words: Without smoke, no fog forms. This is because the water vapor has nothing to condense onto to make droplets.

Exam Tip: Emphasize the crucial role of condensation nuclei (smoke particles) for water vapor to condense into visible droplets; without them, condensation is much less likely or requires extreme conditions.

Textbook Page 192

Activity 14.4

Collect information from newspapers or weather reports on television about rainfall patterns across the country. Also, find out how to construct a rain gauge and make one. What precautions are necessary in order to get reliable data from this rain-gauge? Now answer the following questions:

 

Question 1. In which month did your city/town/village get the maximum rainfall?
Answer: Our city, town, or village received the most rain in July and August, thanks to the Southwest monsoon winds.
In simple words: Our area gets the most rain in July and August because of the Southwest monsoon.

Exam Tip: Base your answer on typical monsoon patterns or local climate data, specifying the months that generally receive the heaviest rainfall in India due to the Southwest monsoon.

 

Question 2. In which month did your state/union territory get the maximum rainfall?
Answer: The most rain in our state or union territory also happens in July and August because of the Southwest monsoon.
In simple words: Our state also gets its highest rainfall in July and August, caused by the Southwest monsoon.

Exam Tip: Align your answer with the general monsoon season in your region (typically June to September in India), identifying the peak months for rainfall.

 

Question 3. Is rain always accompanied by thunder and lightning? If not, in which season do you get more of thunder and lightning with the rain?
Answer: No, rain doesn't always come with thunder and lightning. Thunder and lightning happen more frequently during the rainy season's storms.
In simple words: Not all rain has thunder and lightning. They happen more often during heavy rainstorms in the rainy season.

Exam Tip: Differentiate between general rainfall and thunderstorms. Explain that thunderstorms (with lightning and thunder) are more common during specific seasons or conditions, often associated with intense convective activity.

Textbook Page 192

Activity 14.5

 

Question 1. Find out more about monsoons and cyclones from the library. Try and find out the rainfall pattern of any other country. Is the monsoon responsible for rains the world over?
Answer: Monsoons are seasonal wind shifts that cause distinct wet and dry seasons, especially in tropical regions. Cyclones are intense rotating storms that form over warm ocean waters, bringing heavy rain and strong winds. The monsoon systems significantly influence global rainfall patterns, particularly across Asia and parts of Africa, contributing to much of the world's annual precipitation. Different countries experience varied rainfall patterns based on their geography and climate zones, influenced by global atmospheric circulation and local conditions.

• The amount and type of rain are set by the dominant wind directions in that area.
• Indeed, the monsoon system causes rainfall in many parts of the globe.

In simple words: Monsoons are seasonal wind changes causing wet and dry times. Cyclones are strong storms over warm oceans. Monsoons affect global rain, especially in Asia and Africa. Rain patterns vary by country based on climate and winds. Yes, monsoons cause rain in most of the world.

Exam Tip: Provide clear definitions of monsoons and cyclones. Address the global impact of monsoons and acknowledge regional variations in rainfall, indicating that while monsoons are significant, other factors also influence rainfall patterns.

Textbook Page 193

Activity 14.6

 

Question 1. Organisms called lichens are found to be very sensitive to the levels of contaminants like sulphur dioxide in the air. As discussed earlier in section 7.3.3, lichens can be commonly found growing on the barks of trees as a thin greenish-white crust. See if you can find lichen growing on the trees in your locality.
Answer: Lichens can be spotted on tree bark in hilly or clean areas. They are absent from places with polluted air.
In simple words: Lichens are found on trees in clean, hilly areas but not in polluted places because they are very sensitive to air pollution like sulphur dioxide.

Exam Tip: Explain that lichens are bio-indicators, meaning their presence or absence and health directly reflect air quality, especially in relation to sulfur dioxide pollution.

 

Question 2. Compare the lichen on trees near busy roads and trees some distance away.
Answer: The lichens on trees close to busy roads appear darker compared to those on trees situated farther away.
In simple words: Lichens near busy roads are darker than those on trees far away from roads.

Exam Tip: Relate the color difference to the accumulation of pollutants (like soot and dust) from vehicle emissions, which are higher near busy roads, indicating poorer air quality.

 

Question 3. On the trees near roads, compare the incidence of lichen on the side facing the road and on the side away from the road.
Answer: The lichens on the side closest to the road appear darker than those on the side facing away. Additionally, there are more lichens on the side that faces away from the road.
In simple words: On trees near roads, lichens facing the road are darker and fewer than those on the side facing away from the road.

Exam Tip: Explain that the side facing the road receives a higher concentration of pollutants from traffic, leading to darker, less abundant lichens, while the sheltered side shows healthier growth.

Textbook Page 193

Activity 14.7

Many municipal corporations are trying water-harvesting techniques to improve the availability of water.

 

Question 1. Find out what these techniques are and how they would increase the water that is available for use.
Answer: The techniques of rainwater harvesting are:

1. Water is guided into the ground through roadside drains. This subterranean water can then be used by digging wells or setting up tube wells, thus increasing water availability.
2. The method of collecting rainwater from rooftops can be used to gather water into a storage tank or to replenish groundwater levels by letting it soak into the earth through a deep hole. Both approaches boost the overall water supply.

In simple words: Rainwater harvesting techniques, like directing water underground via roadside drains or collecting rooftop water in tanks/recharge pits, help increase available water by refilling groundwater or storing it for later use.

Exam Tip: Detail specific rainwater harvesting methods (e.g., rooftop collection, recharge pits, check dams) and explain how each method directly contributes to increasing the usable water supply.

Textbook Page 193

Activity 14.8

 

Question 1. Select a small area (say, 1 m²) near a water-body, it may be a river, stream, lake or pond. Count the number of different animals and plants in this area. Also, check the number of individuals of each type or species.
Answer: Near a water-body, a wide variety of different animal and plant species would typically be observed, often with a large number of individuals for each species due to the abundant water resources supporting diverse life forms.
In simple words: Close to water, you'd usually find many types of animals and plants, often with lots of each kind, because water helps support lots of different life.

Exam Tip: Emphasize that water bodies create favorable conditions for high biodiversity due to nutrient availability and stable microclimates, leading to more species and individuals.

 

Question 2. Compare this with the number of individuals (both animals and plants) found in an area of the same size in a dry, rocky region.
Answer: In a dry, rocky region of the same size, there would be a noticeably smaller variety of plant and animal species, and fewer individuals overall, as the harsh conditions and lack of water limit the types of life that can thrive there.
In simple words: A dry, rocky area would have much fewer kinds of plants and animals, and fewer total individuals, because the tough conditions and lack of water restrict what can live there.

Exam Tip: Contrast the rich biodiversity near water with the limited diversity in dry, rocky regions, attributing the difference to the availability of essential resources, particularly water.

 

Question 3. Is the variety of plant and animal life the same in both these areas?
Answer: No, the range of plant and animal life is not the same in these two places. The spot near a water source has more different kinds of living things than the dry, rocky place.
In simple words: No, the types of plants and animals are different in these two areas. The wet area has more diversity than the dry area.

Exam Tip: State clearly that biodiversity is significantly higher in areas with readily available water compared to arid, rocky environments.

Textbook Pages 193-194

Activity 14.9

• Select and mark out a small area (about 1 m²) in some unused land in or near your school.
• As in the above activity, count the number of different animals and plants in this area and the number of individuals of each species.
• Remember to do this in the same place twice in a year, once during summer or the dry season and once after it has rained.

 

Question 1. Were the numbers similar both times?
Answer: No, the numbers were not similar both times.
In simple words: No, the counts were different on both occasions.

Exam Tip: Explain that seasonal changes, especially rainfall, significantly impact plant and animal populations, leading to differing counts at different times of the year.

 

Question 2. In which season did you find more variety of plants and animals?
Answer: More types of plants and animals were found in the rainy season.
In simple words: There was a greater variety of plants and animals during the rainy season.

Exam Tip: Relate the increase in biodiversity directly to the availability of water during the rainy season, which supports lush vegetation and, in turn, a wider range of animal life.

 

Question 3. In which season did you find more number of individuals of each variety?
Answer: A higher count of each type of living thing was observed in the rainy season.
In simple words: More individual plants and animals of each kind were seen in the rainy season.

Exam Tip: Explain that increased water and resources during the rainy season lead to better growth and reproduction, resulting in larger populations for many species.

Textbook Page 195

Activity 14.10

Take some soil and put it into a beaker containing water. The water should be at least five times the amount of soil taken. Stir the soil and water vigorously and allow the soil to settle down. Observe after some time.

 

Question 1. Is the soil at the bottom of the beaker homogeneous or have layers formed?
Answer: The soil is not uniform throughout. Instead, it sorts itself into distinct layers.
In simple words: The soil is not all the same; it forms different layers.

Exam Tip: Explain that soil is heterogeneous, consisting of particles of various sizes (sand, silt, clay), which settle at different rates, leading to distinct layers.

 

Question 2. If layers have formed, how is one layer different from another?
Answer: Yes, the layers vary based on the size of their particles, their color, and what they are made of.
In simple words: The layers differ in particle size, color, and what materials they are made from.

Exam Tip: Describe how larger, heavier particles (like sand) settle first, followed by lighter ones (silt, clay), and then organic matter, leading to variations in texture, color, and composition across layers.

 

Question 3. Is there anything floating on the surface of the water?
Answer: Yes, you can see plant pieces that are dead and partly broken down floating on top of the water.
In simple words: Yes, dead and partly decayed plant bits float on the water.

Exam Tip: Identify the floating material as organic matter (e.g., plant debris) that is less dense than water and hasn't yet fully decomposed or settled.

Textbook Page 196

Activity 14.11

• Take two identical trays and fill them with soil. Plant mustard or green gram or paddy in one of the trays and water both the trays regularly for a few days, till the first tray is covered by plant growth. Now, tilt both the trays and fix them in that position. Make sure that both the trays are tilted at the same angle. Pour an equal amount of water gently on both trays such that the water flows out of the trays as shown in the figure below.
• Study the amount of soil that is carried out of the trays. Is the amount the same in both the trays?

 

Question 1. Is the amount the same in both the trays?
Answer: No, the quantity of soil washed away is a little greater from the tray that lacks plants.
In simple words: No, slightly more soil is washed away from the tray without plants.

Exam Tip: Explain that plant roots help bind soil particles, reducing erosion, so the tray with plants will lose less soil than the one without.

• Now pour equal amounts of water on both the trays from a height. Pour three or four times the amount that you poured earlier.
• Study the amount of soil that is carried out of the trays now. Is the amount the same in both the trays?

 

Question 2. Is the amount the same in both the trays?
Answer: No, a much larger quantity of soil is washed away from the tray without plants compared to the tray that has plants.
In simple words: No, far more soil is lost from the tray without plants than from the one with plants.

Exam Tip: Emphasize that increased water volume and velocity significantly amplify erosion, but the protective effect of plant roots remains evident, albeit with more total soil loss from both trays.

• Is the amount of soil that is carried out more or less or equal to the amount washed out earlier?

 

Question 3. Is the amount of soil that is carried out more or less or equal to the amount washed out earlier?
Answer: The amount of soil carried out in this vigorous pouring is more than the amount washed out earlier during the gentle pouring.
In simple words: More soil is washed away with the strong pouring compared to the gentle pouring.

Exam Tip: Conclude that increased water energy (from higher pouring and greater volume) causes greater soil erosion, highlighting the direct relationship between water force and soil loss.

(Textbook Page 199)

Activity 14.12

 

Question 1. Find out what the consequences of global warming would be.
Answer: The consequences of global warming would be:

• The snow of the mountains will melt at a quicker speed, which will raise the quantity of water in the rivers. This will cause great flooding and harm to human life and plants.
• Polar ice caps will melt at a quicker speed, the ocean level will go up, and many seaside regions might get covered by water.
• Many animals that are not able to survive the changes in heat would vanish forever.
• The wildlife would get negatively impacted.

In simple words: Global warming will make mountain snow and polar ice melt faster, leading to floods and rising sea levels. Many animals may also become extinct, and wildlife will be harmed.

Exam Tip: When discussing consequences, consider both immediate and long-term impacts on different parts of the ecosystem, like water bodies, land, and living creatures.

 

Question 2. Also, find out the names of some other greenhouse gases.
Answer: Besides carbon dioxide, the additional greenhouse gases are methane, CFCs, and water vapour.
In simple words: Other gases that cause the greenhouse effect, besides carbon dioxide, include methane, CFCs, and water vapor.

Exam Tip: Remember to name at least three other greenhouse gases beyond carbon dioxide, as they are key contributors to the greenhouse effect.

(Textbook Page 201)

Activity 14.13

 

Question 1. Find out which other molecules are thought to damage the ozone layer.
Answer: The other molecules which harm the ozone layer are:

• Many hydrocarbons
• Bromochloromethane
• Pesticides like methyl bromide

In simple words: Other substances that are believed to harm the ozone layer include many hydrocarbons, bromochloromethane, and pesticides such as methyl bromide.

Exam Tip: When asked about ozone-depleting substances, list specific chemical categories or examples beyond the most common ones like CFCs.

 

Question 2. Newspaper reports often talk about the hole in the ozone layer.
Answer: Newspaper reports frequently discuss the hole in the ozone layer, which was initially found over Antarctica in 1985. The ozone hole means the layer is getting thinner, which has happened because of the too much use of ozone-depleting substances like the CFCs. The ozone layer takes in the dangerous ultraviolet rays of the Sun, which may lead to cataract, cancers, skin issues, and harm to animal and plant life. The Montreal Protocol was agreed upon by countries in 1987 and in 1994; the United Nations announced that 16th September would be observed as 'World Ozone Day'.
In simple words: News reports often discuss the ozone hole, first found in 1985 over Antarctica, caused by chemicals like CFCs. This thinning ozone layer protects us from harmful sun rays that can cause health problems. Countries signed the Montreal Protocol to help, and September 16th is 'World Ozone Day'.

Exam Tip: When explaining the ozone hole, mention its discovery, cause (CFCs), effects (UV radiation harm), and international efforts like the Montreal Protocol, including 'World Ozone Day'.

 

Question 3. Find out whether the size of this hole is changing and in what manner scientists think this would affect life on Earth (figure is given below).
Answer: Reduction in the ozone layer was about 3% during 1981. By 2005, the ozone hole grew to about 24 million sq km, which is roughly the same size as North America.
In simple words: The ozone hole has been growing. In 1981, ozone loss was 3%, but by 2005, the hole reached 24 million square kilometers, similar to the size of North America.

Exam Tip: When discussing changes in the ozone hole, cite specific data points or comparisons to illustrate its growth or reduction over time.

 

Gujarat Board Class 9 Science Natural Resources Textbook Questions and Answers

 

Question 1. Why is the atmosphere essential for life?
Answer: The atmosphere is vital for living things because:
1. It maintains the average temperature of the Earth quite steady.
2. It stops a quick rise in temperature throughout the day.
3. It makes it harder for heat to leave into outer space during the night.
4. The gases like oxygen, carbon dioxide, and nitrogen present in the air assist in supporting existence on Earth.
In simple words: The atmosphere is crucial for life because it keeps Earth's temperature stable, prevents sudden heat increases, slows heat loss at night, and provides necessary gases like oxygen, carbon dioxide, and nitrogen.

Exam Tip: When explaining the atmosphere's importance, focus on its roles in temperature regulation and providing essential gases for life.

 

Question 2. Why is water essential for life?
Answer: Water is crucial for living because it aids in:

• Performing different life-sustaining chemical reactions happening in the body of creatures.
• Moving different materials from one area of the body to another in living organisms.

In simple words: Water is very important for life because it helps living things carry out all the chemical reactions in their bodies and moves substances around from one part to another.

Exam Tip: Highlight the two main functions of water in living organisms: metabolic processes and transport of substances.

 

Question 3. How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?
Answer: Living organisms rely on the soil as soil gives:

• Home for the living organisms.
• Offers sustenance, meals, and essential elements to different creatures.
• Animals that dig tunnels reside in the burrows made in the soil, for example, rabbits, rats.
• The naturally occurring elements and water found in the soil help the development of plants, which give sustenance to animals.

No, the organisms that live in water are not fully separate from soil as a source because the breakdown organisms found in the soil beds inside water help in reusing various essential elements mixed in water, which sustain the existence of these organisms. The nutrients freed from the earth are present in a mixed form in the water used by the water-dwelling creatures.
In simple words: Living things rely on soil for homes, food, and nutrients. Animals like rabbits live in soil burrows, and minerals and water in soil help plants grow, which feed other animals. Water organisms are not completely separate from soil because decomposers in soil help recycle nutrients in the water, supporting aquatic life.

Exam Tip: For this question, ensure you cover both aspects: how terrestrial organisms depend on soil (habitat, nutrients, shelter) and how aquatic organisms are also linked to soil through nutrient cycling.

 

Question 4. You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Answer: The weather can be forecast by examining the wind patterns common in a region, as these wind patterns determine the way of the precipitation in that area. The regions of high pressure and low pressure can be identified by looking at the direction of air movement. The rain in India happens because of the Southwest monsoon and Northeast monsoon. A majority of precipitation falls during the Southwest monsoon as it affects a wide area of the country.
In simple words: We can predict weather by studying wind patterns, which show us where rain will fall. High and low pressure areas, determined by air flow, also help. In India, rain comes from the Southwest and Northeast monsoons, with most rain happening during the Southwest monsoon because it covers a large part of the country.

Exam Tip: Focus on key factors like wind patterns, pressure systems, and specific regional phenomena (like monsoons in India) when explaining weather prediction.

 

Question 5. We know that many human activities lead to increasing levels of pollution of the air, water-bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?
Answer: Yes, if human activities that lead to rising amounts of pollution of the air, water-bodies, and soil are kept to certain, small regions, it would help in lessening pollution.

• Good methods for handling waste can decrease water and land contamination.
• The water discharged from houses and factories can be processed to get rid of damaging contaminants before releasing them into the water bodies.
• The heated water released from the industries damages water creatures. It can be let to become cold before releasing it into water bodies.
• The industries and factories can be moved far from residential areas to lessen the threat of sound and atmospheric contamination.
• The harmful gases released from the vehicles, power plants, and industries can be processed to rid them of toxic fumes and tiny airborne particles before being released.

In simple words: Yes, if polluting human activities are confined to specific areas, it would help reduce overall pollution. This includes better waste management, treating wastewater and gases, cooling hot industrial water, and moving factories away from homes.

Exam Tip: When suggesting solutions for pollution control, mention both isolating pollution sources and implementing specific waste treatment and management techniques.

 

Question 6. Write a note on how forests influence the quality of our air, soil and water resources.
Answer: Forests play a vital part and affect the standard of air, soil, and water supplies because they:
1. Maintain the equilibrium of oxygen and carbon dioxide in nature by absorbing carbon dioxide and giving off oxygen during photosynthesis.
2. The roots of the trees in the forests hold the earth firmly and stop dirt from washing away.
3. The forests assist in keeping up the water cycle in nature.
4. Forests play a vital part in the natural element loops.
5. The roots of the trees and the plants help to catch the flowing water and boost its seeping into the ground.
6. The forests help in keeping the heat steady of the nearby area.
In simple words: Forests are very important for clean air, healthy soil, and good water. They balance oxygen and carbon dioxide through photosynthesis, and their roots hold soil to prevent erosion. Forests also help maintain the water cycle, trap water into the ground, and keep the local temperature stable.

Exam Tip: For a comprehensive answer, categorize the influence of forests into their impact on air quality, soil conservation, and water management, giving at least two points for each.