Maharashtra Board Class 9 Geography Chapter 6 Properties of Sea Water Solutions

Properties Of Sea Water Class 9 Questions And Answers Maharashtra Board

Class 9 Geography Chapter 6 Properties Of Sea Water Questions And Answers Maharashtra Board

Geography Class 9 Chapter 6 Question Answer Maharashtra Board

Question 1. Tick the correct box according to the salinity of the ocean water ✓
(a) Slanting sunrays, melting snow
(b) Cloudy sky, rainfall throughout the year
(c) Clear skies for the most part, perpendicular sunrays
(d) Less supply of freshwater, desert area around
(e) Low temperatures, ample supply of river water
(f) Continental location, desert around, low rainfall
Answer:
(a) Low
(b) Low
(c) High
(d) High
(e) Low
(f) High.
In simple words: This question assesses understanding of factors influencing ocean salinity. Each option describes a condition, and the corresponding answer indicates whether that condition leads to low or high salinity. Factors like freshwater supply, evaporation rates, and solar radiation play key roles.

🎯 Exam Tip: For such questions, remember the core principles: more freshwater input and less evaporation lead to lower salinity, while less freshwater input and high evaporation lead to higher salinity.

 

Question 2.(a) Salinity is low in the land-locked Baltic Sea.
Answer:
• The Baltic Sea lies in the temperate region.
• In temperate regions, the sunrays are slanting and therefore, the temperatures are lower.
• The supply of fresh water is also more, as numerous rivers empty their waters into the Baltic sea.
• Therefore, in spite of being landlocked, due to low rate of evaporation and ample supply of fresh water, the salinity of the Baltic Sea is low.
In simple words: The Baltic Sea has low salinity despite being landlocked because it's in a cooler temperate zone with slanted sunrays, leading to less evaporation, and receives a large amount of fresh water from many rivers.

🎯 Exam Tip: When explaining salinity variations, always link evaporation rates, freshwater influx (rivers, precipitation), and temperature/solar radiation conditions of the specific region.

 

Question 2.(b) There is higher salinity in the northern Red Sea while lower in the southern.
Answer:
• The Red Sea is one of the saltiest bodies of water in the world, owing to high evaporation.
• The salinity is 36‰ in the southern part because of the effect of the Gulf of Aden.
• It reaches 41‰ in the northern part, owing mainly to the Gulf of Suez and the high evaporation as well as very little precipitation.
• Hence, there is more salinity in the northern Red Sea while lesser in the south.
In simple words: The northern Red Sea has higher salinity (up to 41‰) due to high evaporation and low precipitation, especially influenced by the Gulf of Suez, whereas the southern part has slightly lower salinity (36‰) due to the influence of the Gulf of Aden.

🎯 Exam Tip: Geographical factors like enclosed water bodies, proximity to gulfs, and specific climatic conditions (high evaporation, low rainfall) are crucial for explaining regional salinity differences.

 

Question 2.(c) Oceans located at the same latitude do not have same salinity.
Answer:
• The salinity of the oceans depends on factors like rate of evaporation and supply of fresh water.
• In Oceans where rate of evaporation is more than the supply of fresh water, the salinity is higher.
• In Oceans where supply of freshwater exceeds the rate of evaporation, salinity is low.
• Salinity is not affected much in areas where supply of freshwater and the evaporation of water is low.
• Thus, oceans located on the same latitude do not have the same salinity.
In simple words: Oceans at the same latitude can have different salinities because salinity is influenced by local factors like evaporation rates and freshwater supply from rivers or rainfall, which can vary significantly even at similar latitudes.

🎯 Exam Tip: Emphasize that while latitude affects general climatic zones, localized factors (river runoff, landlocked status, ocean currents) are critical determinants of actual salinity values and can override latitudinal uniformity.

 

Question 2.(d) With increasing depth, the temperature of sea water decreases to a certain limit.
Answer: With increasing depth, the temperature of sea water decreases to a certain limit because-
• While most of the sunrays radiate back from the surface of the sea, some of them penetrate to certain depths in the water.
• As a result, the intensity of sunrays decreases with the increasing depth.
• The temperature decreases up to 2000m depth.
• After 2000m, the temperature of the seawater is uniform everywhere.
In simple words: Sea temperature drops with increasing depth because sunlight, which heats the surface, cannot penetrate very far, causing the intensity of solar radiation to diminish rapidly with depth until a uniform temperature is reached below 2000m.

🎯 Exam Tip: Key points for this explanation are the limited penetration of sunlight, the concept of a thermocline (though not explicitly named here), and the depth at which temperature becomes stable.

 

Question 2.(e) There are more salt-pans on the Western coast of India than its eastern coast.
Answer:
• The Arabian Sea lies lying to the west and Bay of Bengal lies to the east of India.
• Many large peninsular rivers drain their waters in the Bay of Bengal and on the contrary, only small seasonal coastal rivers drain in the Arabian Sea.
• Hence, the salinity of the eastern coast is 34‰, while it is 35‰ in the Arabian Sea.
• Thus, there are more salt-pans on the Western coast of India than its Eastern coast.
In simple words: The Western coast of India has more salt-pans because the Arabian Sea (to its west) has higher salinity (35‰) compared to the Bay of Bengal (to its east, 34‰), primarily due to fewer large rivers supplying freshwater and higher evaporation in the Arabian Sea.

🎯 Exam Tip: Connect the presence of salt-pans directly to higher salinity, and then explain the salinity difference by contrasting freshwater input from rivers and evaporation rates between the Arabian Sea and the Bay of Bengal.

 

Question 2.(f) Salinity increases in the mid-latitudinal zones.
Answer:
• Mid-latitudinal zones lies between 25° to 35° north and south of the equator.
• In this zone, the rainfall is less and the supply of fresh water from rivers is also low.
• This region experiences high-temperature conditions which are marked by the presence of hot deserts of the world. These high-temperature conditions lead to a high rate of evaporation.
• Thus, the salinity of the seas is found to be higher in mid-latitudinal zones.
In simple words: Salinity is higher in mid-latitudinal zones (25°-35° N/S) because these regions typically have less rainfall, low freshwater supply from rivers, and high temperatures, leading to increased evaporation.

🎯 Exam Tip: When explaining salinity in mid-latitudes, highlight the interplay of low precipitation, scarce riverine input, and high temperatures (often associated with deserts), all contributing to elevated evaporation and thus higher salinity.

 

Question 3.(a) What are the factors affecting the salinity of the sea water?
Answer:
1. The uneven distribution of temperature on earth and uneven supply of freshwater affects the salinity of seawater.
2. In the tropical zone, temperature is higher. Rate of evaporation is also higher and therefore, the salinity is higher.
3. Around 5° N and S of the equator, in the equatorial calm belt, the sky is cloudy for a long period of time and convectional rainfall occurs every day.
4. Large rivers like Congo and Amazon in the equatorial regions meet the sea. Therefore, supply of freshwater is abundant, too. But because of higher temperatures, rate of evaporation is more and therefore, the seas in these areas are more saline.
5. In mid-latitudinal zones (25° to 35° N and S), rainfall is lesser and the supply of freshwater from rivers is also low. This zone has the hot deserts of the world. Thus, the salinity of the seas is found to be higher here.
6. In temperate regions, the sunrays are slanting and therefore, the temperatures are lower. Because of the melting of the snow, the supply of water is also more, and therefore, in this zone, salinity decreases with increasing latitudes.
7. In the polar areas, temperatures are very low. Evaporation is also very less in polar areas. So, salinity is low.
8. Landlocked seas have higher salinity than open seas as the rate of evaporation is more. There is a lack of supply of fresh water from large rivers. Thus, there is a difference in the salinities of open and closed seas.
In simple words: Sea water salinity is affected by uneven global temperature and freshwater distribution; higher temperatures and less freshwater (like in mid-latitudes and landlocked seas) increase salinity, while lower temperatures and more freshwater (like in temperate and polar regions) decrease it.

🎯 Exam Tip: For factors affecting salinity, categorize them into: (1) Evaporation (influenced by temperature, solar radiation, wind), and (2) Freshwater input (rainfall, river runoff, melting ice). Explain how these vary by latitudinal zones and in landlocked vs. open seas.

 

Question 3.(b) Explain the distribution of salinity around the Tropic of Cancer and tropic of Capricorn.
Answer:
• The uneven distribution of temperature on earth, and uneven supply of freshwater affects the salinity of sea water.
• Region, between the Tropic of Cancer and Tropic of Capricorn is called as the Tropical zone.
• In the tropical zone, temperature is higher.
• Hence, the rate of evaporation is also higher, and therefore, salinity is higher.
In simple words: Around the Tropics of Cancer and Capricorn, which form the tropical zone, temperatures are high, leading to increased evaporation, and consequently, higher sea surface salinity.

🎯 Exam Tip: Focus on the tropical zone's high temperatures and direct sunlight, which are the primary drivers of increased evaporation and thus higher salinity in these regions.

 

Question 3.(c) What are the factors affecting the temperature of the sea water?
Answer:
1. Temperature is a major property of the sea water.
2. Sea water upto the depth of 500m is called as surface water. The surface temperature of the sea water is not uniform everywhere. This is dependent on different factors. .
3. Latitudinally, the surface temperature of the seawater decreases from the equatorial areas towards the poles.
4. The average temperature in equatorial areas is around 25° C, while it is about 2° C near the poles.
5. Besides this, cyclones, rainfall, sea waves, ocean currents, salinity, pollution, convectional currents, and seasons also affect the surface temperature.
6. Regions where cold ocean currents flow, the surface temperature of ocean water is less, while the regions where the warm currents move, the temperature increase.
In simple words: Sea surface temperature is influenced by latitude (decreasing from equator to poles), and also by factors like cyclones, rainfall, sea waves, ocean currents (warm currents increase temperature, cold currents decrease it), salinity, pollution, and seasonal changes.

🎯 Exam Tip: Group factors affecting sea temperature into: (1) Solar radiation/Latitude, (2) Atmospheric conditions (cyclones, rainfall), (3) Water movement (waves, currents, convectional currents), and (4) Other influences (salinity, pollution, seasons).

 

Question 3.(d) Explain the changes occurring in the temperature of sea water according to the depth.
Answer:
• While most of the sunrays radiate back from the surface of the sea, some of them penetrate to certain depths in the water.
• As a result, the intensity of sunrays decreases with the increasing depth.
• The temperature decreases up to 2000m depth.
• After 2000m, the temperature of the seawater is uniform everywhere.
• It is around 4°C everywhere from the equatorial regions to the polar areas.
• Temperature reduces only up to 4° C according to depth, and therefore, the water at greater depths does not freeze.
• The temperature of the seawater changes rapidly with depth at the equatorial areas. The difference in temperature is lesser in polar areas.
• There is also a difference in open seas and landlocked seas. In low latitudes, because the salinity of the landlocked seas is more, the temperature of the landlocked seas is higher than the open seas.
In simple words: Sea water temperature generally decreases with depth up to about 2000m due to diminishing sunlight penetration, after which it stabilizes to a uniform 4°C globally, with the most rapid temperature change occurring in equatorial areas.

🎯 Exam Tip: Focus on the concept of light penetration and its effect on heating, the depth at which temperature becomes constant, and how the rate of change varies by latitude.

 

Question 3.(e) Name the factors affecting salinity.
Answer: Due to the sun's heat, evaporation happens at a faster rate. Evaporated water turns into water vapour and reduces in quantity. But amount of salt remains the same in the remaining water and therefore the salinity of water increases.
• In seas where the rate of evaporation is high than the supply of fresh water, salinity is high.
• In seas where the supply of freshwater exceeds the rate of evaporation, salinity is low.
• Salinity is not affected much in seas where both the supply of freshwater and evaporation of water is low.
In simple words: Salinity is primarily affected by the balance between evaporation and freshwater supply; high evaporation and low freshwater input increase salinity, while the opposite decreases it, and low rates of both result in little change.

🎯 Exam Tip: When listing factors affecting salinity, always include evaporation (driven by heat) and freshwater input (from rivers, rainfall, ice melt) as the two main opposing forces.

 

Question 4.(a) the density of sea water
Answer:
• If temperature reduces, density of water increases.
• Hence, cold water is denser than hot water.
In simple words: When the temperature of seawater decreases, its density increases, meaning cold water is denser than hot water.

🎯 Exam Tip: Remember the inverse relationship: lower temperature leads to higher density. This is a fundamental property of water, except for the anomalous expansion near 4°C for freshwater, which isn't typically the primary factor in ocean density at a large scale.

 

Question 4.(b) the salinity of sea water
Answer:
• If the salinity of water is high, the density of water increases.
In simple words: Higher salinity in water directly results in higher water density.

🎯 Exam Tip: Understand the direct relationship: higher salinity leads to higher density. Salt adds mass to the water, making it heavier per unit volume.

 

Activity:

Complete the table showing the salinity of open and land-locked seas.

Answer:

Evaporation of Water						Supply of freshwater			Average salinity
Region	Latitude	Solar Energy	Rainfall	River water	Snow water
Equatorial	0° C to 15° C	High	Perennial	High	-	34‰
Tropical	15° C to 35° C	Medium	Seasonal	Low	-	37‰
Temperate	35° C to 65° C	Low	Seasonal	Medium	-	33‰
Polar	65° C to 90° C	Low	Seasonal	Low	Ample	31‰
Landlocked sea
	Solar Energy	Rainfall	River water	Snow water	Average salinity
Mediterranean sea	High	Low	Low	-	39‰
Red sea	High	Low	Very Low	-	41‰
Baltic sea	Low	Medium	Medium	-	7‰
Dead sea	High	Very less	Very less	-	332‰
Caspian sea	Medium	Low	Low	-	155‰
Great Salt lake	Medium	Low	Low	-	220‰

In simple words: The table illustrates how factors like solar energy, rainfall, river water, and snowmelt influence the average salinity in different latitudinal zones and landlocked seas, highlighting the balance between water evaporation and freshwater supply.

🎯 Exam Tip: Pay close attention to how each variable (solar energy, rainfall, river water, snow water) directly or indirectly impacts the evaporation and freshwater supply, thereby determining the final salinity values in each region.

 

Class 9 Geography Chapter 6 Properties Of Sea Water Intext Questions And Answers

Observe the following Map and answer the questions:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह मानचित्र विश्व के विभिन्न महासागरों और समुद्रों में लवणता के वितरण को दर्शाता है, जिसे प्रति हज़ार (‰) में समोच्च रेखाओं द्वारा दर्शाया गया है। यह भूमध्यरेखीय क्षेत्रों से ध्रुवों तक और भूमध्य सागर, अटलांटिक, प्रशांत और दक्षिणी महासागरों जैसे विशिष्ट समुद्रों में लवणता में भिन्नताओं को उजागर करता है, जिससे छात्रों को दृश्य रूप से वैश्विक लवणता पैटर्न को समझने में मदद मिलती है।

Question 1. What is the salinity around the tropics?
Answer: The salinity around the tropics is 36‰.
In simple words: The map indicates that the salinity in the tropical regions is typically around 36 parts per thousand.

🎯 Exam Tip: For map-based questions, carefully read the map legend and contour lines to extract specific data points accurately.

 

Question 2. Which region has the least salinity?
Answer: The Bay of Bengal has the least salinity of 32‰.
In simple words: Based on the map, the Bay of Bengal exhibits the lowest salinity, measuring approximately 32 parts per thousand.

🎯 Exam Tip: Identify areas with the lowest numerical values on the salinity contours to determine regions of least salinity. River discharge areas are often good candidates.

 

Question 3. Which ocean has salinity more than 37‰?
Answer: Atlantic ocean has salinity of more than 37‰.
In simple words: The map shows that parts of the Atlantic Ocean have salinity levels exceeding 37 parts per thousand.

🎯 Exam Tip: Look for areas where the salinity contours indicate values higher than the specified threshold. Note that salinity can vary within a single ocean basin.

 

Question 4. What are the reasons of differences in salinity on a global level?
Answer: The uneven distribution of temperature on earth, and uneven supply of freshwater, etc. are the reasons for differences in salinity on a global level.
In simple words: Global salinity variations are caused by the uneven distribution of temperature, which affects evaporation, and the inconsistent supply of freshwater across different regions.

🎯 Exam Tip: Broadly summarize the primary global controls on salinity: temperature (influencing evaporation) and freshwater input (from precipitation and land runoff).

 

Observe the Graph and answer the questions:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख समुद्र जल की गहराई और तापमान के बीच संबंध को दर्शाता है। इसमें दिखाया गया है कि जैसे-जैसे गहराई बढ़ती है, समुद्र जल का तापमान एक निश्चित सीमा तक घटता जाता है, विशेष रूप से 'टॉरिड ज़ोन' और 'मध्य अक्षांश' क्षेत्रों में। यह स्थिर जल तापमान घटने की प्रवृत्ति को भी इंगित करता है।

Question 1. What is the maximum temperature of seawater in equatorial areas? How much is this temperature at a depth of 500 m?
Answer: The maximum temperature of sea water in equatorial areas is 18° C. The temperature at the depth of 500 m is 11° C.
In simple words: The graph shows the highest equatorial sea temperature at the surface is 18°C, which drops to 11°C at a depth of 500 meters.

🎯 Exam Tip: Read both axes of the graph carefully (Depth and Temperature) and identify the specific points requested for surface and depth readings in the relevant zone.

 

Question 2. What is the temperature of seawater at the sea level in the mid-latitudes?
Answer: The temperature of seawater at the sea level in the mid-latitudes is 14° C approximately.
In simple words: At sea level, the mid-latitudes experience a seawater temperature of approximately 14°C, according to the graph.

🎯 Exam Tip: Locate the "Mid latitudes" line on the graph and trace it to the surface (0 depth) on the temperature axis to find the corresponding value.

 

Question 3. How much has this temperature changed at 1500 m depth?
Answer: The temperature is about 5° C at the depth of 1500 m. Thus the temperature of sea water at mid-latitudes has changed from 14°C at the sea level to about 5°C at the depth of 1500 m i.e. temperature has changed (reduced) by 9°C.
In simple words: The temperature at 1500m depth is about 5°C, representing a 9°C reduction from the surface temperature of 14°C in mid-latitudes.

🎯 Exam Tip: Calculate the difference between the surface temperature and the temperature at the specified depth to find the change, paying attention to the specific latitudinal zone if mentioned.

 

Question 4. What does the thermal graph for the high latitude say? What is its temperature at 500, 1000 and 1500 m depths?
Answer: In high latitudes the temperature of sea water at all depths remains constant at 4° C.
In simple words: The thermal graph indicates that in high latitudes, the sea water temperature remains constant at 4°C at all depths, including 500m, 1000m, and 1500m.

🎯 Exam Tip: Observe the high latitude curve on the graph; if it's a vertical line or flat, it signifies constant temperature across depths. Read the corresponding temperature value.

 

Question 5. After what depth does the seawater temperature remain stable everywhere?
Answer: After 2000 m, the temperature of the sea water is uniform everywhere.
In simple words: Beyond a depth of 2000 meters, the temperature of the seawater becomes consistent and stable globally.

🎯 Exam Tip: Identify the depth at which the temperature curves for different latitudes converge or become horizontal, indicating a stable, uniform temperature.

 

Question 6. With increasing depth, what decreases: temperature, salinity or density?
Answer: Temperature and salinity decreases with increasing depth.
In simple words: As you go deeper into the ocean, both temperature and salinity generally decrease.

🎯 Exam Tip: Understand the general trend of ocean properties with depth: temperature and salinity typically decrease, while density usually increases (though the provided OCR graph for density shows a slight increase then stability, not a decrease overall). Ensure your answer aligns with the specific graph if one is provided.

 

Question 7. After what depth does the change in these factor become almost zero?
Answer: After the depth of 1000 m there is no change in all these factors.
In simple words: Beyond 1000 meters depth, the changes in temperature, salinity, and density become negligible, indicating stable conditions.

🎯 Exam Tip: Look for the depth where the lines on all three graphs (temperature, salinity, density) become relatively flat, indicating minimal or no further change.

 

Question 8. Till what depth is the change in these factors higher?
Answer: The higher change can be seen up to a depth of about 500m.
In simple words: The most significant changes in temperature, salinity, and density occur within the first 500 meters of ocean depth.

🎯 Exam Tip: Identify the upper section of the graphs where the slopes of the lines are steepest, signifying the most rapid changes in the factors.

 

Question 9. Explain the correlation between all the three factors.
Answer: If the temperature is less, density is more. If the salinity is less, then density is also less. However temperature affects the density more as compared to the salinity. If the temperature is less, then the density is more despite less salinity.
In simple words: Lower temperature increases water density, while lower salinity decreases it. Temperature, however, has a greater influence on density than salinity; thus, colder water can be denser even if it has slightly lower salinity.

🎯 Exam Tip: Emphasize the primary influence of temperature on density, followed by salinity. Illustrate how these two factors interact to determine the overall density of seawater.

 

Let's Recall.

Question 1. Which is the largest water storage of the world?
Answer: Oceans are the largest water storage of the world.
In simple words: The world's largest reservoir of water is found in the oceans.

🎯 Exam Tip: This is a factual recall question; remember that oceans hold the vast majority of Earth's water.

 

Question 2. Why is the seawater salty?
Answer:
• Salt in the ocean comes from rocks on land.
• Rivers carry dissolved salts to the ocean.
• Water evaporates from the oceans to fall again as rain and to feed the rivers, but the salts remain in the ocean.
In simple words: Seawater is salty because salts erode from land rocks, are carried to the ocean by rivers, and then remain in the ocean as water evaporates and returns to land as precipitation.

🎯 Exam Tip: The key mechanism to explain is the hydrological cycle: rivers dissolve minerals from rocks and transport them to the sea, where water evaporates but salts are left behind, concentrating them over millions of years.

 

Question 3. What are the reasons for high salinity in the oceans?
Answer: High rate of evaporation and low supply of fresh water leads to high salinity in the oceans:
In simple words: High rates of water evaporation combined with a limited influx of freshwater are the main causes of increased ocean salinity.

🎯 Exam Tip: Always link high salinity to two primary factors: high evaporation (which removes pure water) and low freshwater input (which prevents dilution).

 

Question 4. How can we obtain the salts from the ocean water?
Answer:
• Sea water contains a large amount of common salt and the salts of other metals dissolved in it.
• Near the sea-shore, the sea water is collected in shallow pits (salt pans) and allowed to evaporate in the sunshine.
• In a few days, the water evaporates, leaving behind salt.
• The salt so obtained is collected and transported to factories, where it is purified and packed for consumption.
In simple words: Salts are obtained from ocean water by collecting seawater in shallow salt pans near the shore, allowing the water to evaporate under sunlight, and then collecting and purifying the remaining salt crystals.

🎯 Exam Tip: Describe the process of "solar evaporation" in salt pans, emphasizing the role of sunlight in evaporating water and leaving behind the dissolved salts for collection and purification.

 

Question 5. What is the use of the salts in the oceans to us?
Answer:
• The salts is used in the food we eat.
• It is used for making various chemicals and medicines.
• Salt is also used to preserve things for longer periods. It is also used in ice factories.
In simple words: Salts from the ocean are vital for us as they are used in food, chemical and medicine production, for preservation, and in industrial applications like ice factories.

🎯 Exam Tip: List key applications of ocean salts, focusing on common salt (sodium chloride) for food and preservation, and the broader utility of other dissolved minerals in industries like chemicals and medicines.

 

Can You Tell?

Question 1. What is the difference in the temperatures of the land and the sea?
Answer: During the daytime land is hotter than the sea whereas, during the night time land is cooler than the sea.
In simple words: Land heats up faster than the sea during the day, making it hotter, but also cools down faster at night, becoming cooler than the sea.

🎯 Exam Tip: Highlight the differential heating and cooling capacities: land has lower specific heat capacity, leading to faster temperature changes, while water has higher specific heat capacity, resulting in slower, more moderate changes.

 

Question 2. What would be the difference in the temperature of the seawater from the equatorial region to the polar areas?
Answer: Latitudinally, the surface temperature of the seawater decreases from the equatorial areas towards the poles. The average temperature in equatorial areas is around 25° C while it is about 2° C near the poles.
In simple words: Seawater temperature decreases from about 25°C in equatorial regions to approximately 2°C near the poles, due to the latitudinal variation in solar radiation.

🎯 Exam Tip: State the general latitudinal trend clearly: temperatures are highest at the equator and decrease significantly towards the poles. Provide approximate temperature ranges for these extremes if possible.

 

Think about it.

Question 1. If you think about India there is the Arabian sea to the west and the Bay of Bengal to the east. The salinity of the eastern coast is 34‰ while it is 35‰ in the Arabian sea. What could be the reason of higher salinity in the western coastal region?
Answer: Many large peninsular rivers drain their waters in the Bay of Bengal and on the contrary only small seasonal coastal rivers drain in the Arabian sea. Hence the salinity of Arabian sea is more than the Bay of Bengal.
In simple words: The Arabian Sea has higher salinity because fewer large rivers discharge freshwater into it compared to the Bay of Bengal, which receives significant freshwater runoff from major peninsular rivers.

🎯 Exam Tip: The key is riverine input. More major rivers draining into the Bay of Bengal dilute its waters, leading to lower salinity compared to the Arabian Sea, which has less freshwater influx.

 

Try this.

Question 1. In which container has the water increased or decreased?
Answer:
• The water has increased in the container which is in the classroom in which freshwater was added.
• The water has decreased in the container which was kept in the sun outside.
In simple words: Water increased in the classroom container where freshwater was added, and decreased in the outdoor container due to evaporation from sun exposure.

🎯 Exam Tip: Relate water level changes directly to the actions performed: addition of water causes increase, and exposure to sun leads to evaporation and decrease.

 

Question 2. What could be the reasons behind the decrease or increase?
Answer:
• Since freshwater was added to one of the containers in the classroom the water level increased.
• The water has decreased in the container which was kept outside in the sun due to evaporation.
In simple words: The water level increased in the classroom container because freshwater was added, while it decreased in the outdoor container due to evaporation caused by the sun's heat.

🎯 Exam Tip: Clearly state the cause-and-effect: addition of water for increase, and evaporation for decrease. Mentioning "sun" as the source of heat for evaporation is important.

 

Question 3. What could be the reason behind the low and high salinity of the water in the container?
Answer:
• In the container which as kept outside in the sun, due to high rate of evaporation, the salinity is high.
• As we kept on adding fresh water to the container kept in the classroom the salinity is low.
In simple words: The container left outside in the sun experienced high evaporation, concentrating the salts and increasing salinity, while the classroom container with added freshwater had its salts diluted, resulting in low salinity.

🎯 Exam Tip: Connect the observed changes directly to salinity principles: evaporation increases salinity by removing pure water, and adding freshwater decreases salinity by dilution.

 

Class 9 Geography Chapter 6 Properties Of Sea Water Additional Important Questions And Answers

Select the correct option:

Question 1. The average temperature in equatorial areas is
(a) 25° C
(b) 35° C
(c) 15° C
(d) 5° C
Answer: (a) 25°C
In simple words: The equatorial regions typically experience an average temperature of 25°C.

🎯 Exam Tip: This is a direct recall question. Remember the approximate average temperature for equatorial areas.

 

Question 2. The average temperature in mid-latitudes is
(a) 25° C
(b) 10° C
(c) 16° C
(d) 5° C
Answer: (c) 16°C
In simple words: Mid-latitudinal areas generally have an average temperature of 16°C.

🎯 Exam Tip: Know the approximate average temperatures for different latitudinal zones, specifically mid-latitudes, for factual questions.

 

Question 3. The average temperature near poles is about
(a) 10° C
(b) 20° C
(c) 15° C
(d) 2° C
Answer: (d) 2°C
In simple words: The regions near the Earth's poles have an average temperature of approximately 2°C.

🎯 Exam Tip: This is a factual recall. Associate the poles with significantly colder average temperatures, around 2°C.

Question 4. With the increasing depth of sea, the intensity of sunrays
(a) increases
(b) decreases
(c) remains constant
(d) is uneven
Answer: (b) decreases
In simple words: As you go deeper into the sea, less sunlight can penetrate, so the sun's intensity decreases.

🎯 Exam Tip: Understanding the relationship between depth and light penetration is crucial for questions on marine ecosystems and water properties.

Question 5. Seawater upto the depth of 500m is called
(a) ground water
(b) surface water
(c) deep water
(d) saline water
Answer: (b) surface water
In simple words: The uppermost layer of the ocean, extending to about 500 meters, is known as surface water.

🎯 Exam Tip: Distinguish between surface, deep, and ground water definitions in oceanography for accurate responses.

Question 6. ocean is the most saline ocean in the world.
(a) Pacific
(b) Arctic
(c) Indian
(d) Atlantic
Answer: (d) Atlantic
In simple words: The Atlantic Ocean generally has higher salinity due to factors like evaporation and ocean currents.

🎯 Exam Tip: Remember specific geographical facts like the most saline ocean, as these are common knowledge-based questions.

Question 7. The sea lying on the border of Israel and Jordan has a salinity of %0.
(a) 37
(b) 50
(c) 256
(d) 332
Answer: (d) 332
In simple words: The Dead Sea, bordered by Israel and Jordan, is famously known for its exceptionally high salinity.

🎯 Exam Tip: Be aware of unique geographical features like the Dead Sea and their extreme properties, often tested in exams.

Question 8. The buoyancy of the sea water increases because of its
(a) evaporation
(b) salinity
(c) density
(d) high temperature
Answer: (b) salinity
In simple words: Higher salinity means more dissolved salts, which increases the water's density and thus its buoyancy.

🎯 Exam Tip: Connect salinity with density and buoyancy; understanding these relationships is fundamental to oceanography.

Question 9. has an altitude of - 400m.
(a) Baltic Sea
(b) Arabian Sea
(c) Dead Sea
(d) the Mediterranean Sea
Answer: (c) Dead sea
In simple words: The Dead Sea is Earth's lowest elevation on land, significantly below sea level, reaching approximately -400 meters.

🎯 Exam Tip: Recall specific facts about unique geographical features like the Dead Sea, including its elevation, for general knowledge questions.

Question 10. act as temperature controllers at a global level.
(a) Ocean currents
(b) Sea breeze
(c) Land breeze
(d) Trade winds
Answer: (a) Ocean currents
In simple words: Ocean currents distribute heat around the globe, warming polar regions and cooling equatorial areas, thus regulating Earth's climate.

🎯 Exam Tip: Focus on the large-scale impact of ocean currents on global climate and temperature distribution.

Question 11. is a major porperty of the sea water.
(a) Temperature
(b) Uniform salinity
(c) Buoyancy
(d) Equal Density
Answer: (a) Temperature
In simple words: Temperature is a primary characteristic of seawater, influencing its density, currents, and marine life distribution.

🎯 Exam Tip: Identify key physical properties of seawater, such as temperature, as they are fundamental concepts in geography.

Question 12. have higher salinity than open seas.
(a) Equatorial seas
(b) Landlocked seas
(c) Freshwater lakes
(d) Seas in polar regions
Answer: (b) landlocked seas
In simple words: Landlocked seas often have higher salinity due to limited water exchange and increased evaporation rates.

🎯 Exam Tip: Understand the factors affecting salinity, such as limited water exchange and high evaporation, which are characteristic of landlocked water bodies.

Question 13. Temperature decreases upto depth.
(a) 500 m
(b) 1000 m
(c) 1500 m
(d) 2000 m
Answer: (d) 2000m
In simple words: Sea temperature generally decreases with depth, becoming uniform at around 2000 meters in most ocean regions.

🎯 Exam Tip: Recall the general oceanic temperature profile; the 2000m mark is often cited as the depth where temperature stabilizes.

Question 14. In regions where cold currents flow, the surface temperature of ocean water is
(a) high
(b) less
(c) uniform
(d) uneven
Answer: (b) less
In simple words: Cold ocean currents bring cooler water from polar regions, thus lowering the surface temperature in the areas they flow through.

🎯 Exam Tip: Understand the direct impact of ocean currents on local sea surface temperatures; cold currents lead to lower temperatures.

Question 15. Temperature of seawater changes rapidly with depth in areas.
(a) equatorial
(b) mid latitudinal
(c) temperate
(d) polar
Answer: (a) equatorial
In simple words: In equatorial regions, the warm surface water and much colder deep water create a sharp temperature gradient, leading to rapid changes with depth.

🎯 Exam Tip: Identify the thermocline's prominence in equatorial regions due to stronger solar heating and the resulting stratification.

Question 16. In seas where the rate of evaporation is than the supply of fresh water, salinity is high.
(a) less
(b) high
(c) same
(d) low
Answer: (b) high
In simple words: When more water evaporates than is replenished by freshwater, the concentration of salts increases, leading to higher salinity.

🎯 Exam Tip: A key principle of salinity is that high evaporation combined with low freshwater input results in increased salt concentration.

Question 17. The salinity of Bay of Bengal is than that of Arabian sea.
(a) less
(b) more
(c) same
(d) equal
Answer: (a) less
In simple words: The Bay of Bengal receives significant freshwater input from large rivers like the Ganga and Brahmaputra, reducing its salinity compared to the Arabian Sea.

🎯 Exam Tip: Consider the impact of major river discharges on regional ocean salinity; higher river input generally leads to lower salinity.

Question 18. In areas the salinity of sea water is low.
(a) equatorial
(b) mid-latitudinal
(c) temperate
(d) polar
Answer: (d) polar
In simple words: Polar regions have lower salinity due to melting ice and low evaporation rates, despite extremely cold temperatures.

🎯 Exam Tip: Remember the factors that influence salinity in different climatic zones; polar regions exhibit low salinity due to ice melt and reduced evaporation.

Question 19. The salinity of Battic sea is %.
(a) 332
(b) 32
(c) 37
(d) 7
Answer: (d) 7
In simple words: The Baltic Sea has exceptionally low salinity compared to other seas, primarily due to large freshwater input from surrounding rivers and limited connection to the open ocean.

🎯 Exam Tip: Specific salinity values for unique water bodies like the Baltic Sea are important for factual recall questions.

Question. Match the Column:

Column A	Column B
(1) Equatorial areas	(a) Salinity of 332%0
(2) Mid-latitudinal areas	(b) Slanting sunrays, melting of snow
(3) Temperate regions	(c) Cloudy sky and convectional rainfall
	(d) Hot deserts

Answer: (1-c), (2- d), (3 - b)
In simple words: This question tests your knowledge of how different geographical zones correlate with specific oceanographic characteristics like salinity, sun exposure, and rainfall patterns.

🎯 Exam Tip: For match-the-column questions, link each item from Column A to its most appropriate description in Column B by understanding the defining characteristics of each region.

Answer In One Sentence:

Question 1. What is the major property of seawater?
Answer: Temperature is a major property of seawater.
In simple words: Temperature is a primary characteristic that significantly influences all other properties and behaviors of seawater.

🎯 Exam Tip: Understand that fundamental properties like temperature are critical for comprehending oceanographic processes.

Question 2. What is the average surface temperature of seawater in equatorial areas, mid-latitudes & poles?
Answer: The average surface temperature of seawater is equatorial areas is around 25°C in mid-latitude it is around 16°C & 2°C near the poles.
In simple words: Surface seawater temperatures decrease significantly from warm equatorial regions (25°C) to cooler mid-latitudes (16°C) and cold polar regions (2°C).

🎯 Exam Tip: Memorize the approximate surface temperature ranges across different latitudinal zones for accurate comparisons.

Question 3. After what depth is the seawater temperature uniform everywhere?
Answer: After 2000m, the temperature of seawater is uniform everywhere
In simple words: Beyond 2000 meters depth, the ocean temperature becomes consistently stable at around 4°C globally.

🎯 Exam Tip: The 2000m mark is a significant depth in oceanography where thermal stratification largely ceases.

Question 4. Name the instruments used to measure salinity?
Answer: Hydrometer, Refractometer and salinometer are used to measure salinity.
In simple words: Specialized tools like hydrometers, refractometers, and salinometers are employed to accurately determine the salt content of seawater.

🎯 Exam Tip: Familiarize yourself with the names of common scientific instruments and their specific uses, especially in environmental studies.

Question 5. Which is the most saline ocean?
Answer: The Atlantic ocean is the most saline ocean.
In simple words: The Atlantic Ocean holds the distinction of being the most saline ocean globally, influenced by its geographical features and climatic patterns.

🎯 Exam Tip: Remember specific factual information about the oceans, such as which has the highest average salinity.

Give Geographical Reasons:

Question 1. The climate of the earth gets affected by ocean currents.
Answer:
• The ocean currents are generated because of the difference in the properties of seawater.
• They act as temperature controllers at the global level.
• The distribution of temperature gets controlled due to the ocean currents.
• Thus, the climate of the earth gets affected by ocean currents.
In simple words: Ocean currents redistribute heat from the equator to the poles and cold water back, acting as global temperature regulators that profoundly influence regional and global climates.

🎯 Exam Tip: Emphasize the role of ocean currents in heat transfer and temperature regulation when explaining their impact on climate.

Question 2. Dead Sea has a salinity of 332%0.
Answer:
• The sea lying on the border of Israel and Jordan has a salinity of 332%0.
• The average salinity of ocean is 35%0.
• Jordan is the only large river meeting this sea.
• Low rainfall, low supply of freshwater and high evaporation is the reason of high salinity.
In simple words: The Dead Sea's extremely high salinity (332%o) results from minimal freshwater inflow, high evaporation rates in an arid climate, and being a terminal lake with no outlet.

🎯 Exam Tip: When explaining extreme conditions like the Dead Sea's salinity, always refer to the specific geographical and climatic factors that contribute to it.

Question 3. The surface temperature of the sea is not uniform everywhere.
Answer:
• The surface temperature of sea water is not uniform everywhere and it changes with latitudes.
In simple words: Ocean surface temperatures vary due to uneven solar heating across latitudes, influenced by factors like cloud cover, ocean currents, and seasonal changes.

🎯 Exam Tip: The primary reason for non-uniform surface temperature is differential solar insolation across latitudes, a fundamental concept in physical geography.

Question 4. The seas in equatorial calm belt are more saline.
Answer:
• Around 5° N and S of the equator, in the equatorial calm belt, the sky is cloudy for a long period of time and convectional rainfall occurs every day.
• Large rivers like Congo and Amazon in the equatorial regions meet the sea.
• Therefore, supply of freshwater abundant too.
• But because of higher temperatures, rate of evaporation is more and therefore, the seas in these areas are more saline.
In simple words: Despite high rainfall and river discharge in equatorial calm belts, intense solar radiation leads to very high evaporation rates, concentrating salts and resulting in more saline seas.

🎯 Exam Tip: Highlight the interplay between high evaporation due to temperature and significant freshwater input; the net effect often determines salinity.

Explain

Question 1. Factors affecting surface water temperature
Answer:
• Temperature is a major property of the seawater. The surface temperature of the seawater is not uniform everywhere. This is dependent on different factors.
• Latitudinally, the surface temperature of the seawater decreases from the equatorial areas towards the poles.
• Besides this, cyclones, rainfall, sea waves, ocean currents, salinity, pollution, convergence flow and seasons also affect the surface temperature.
• Regions where cold ocean currents flow, the surface temperature of ocean water is less. The regions where the warm currents move, the temperature increase.
In simple words: Surface seawater temperature is influenced by factors like latitude (solar radiation), ocean currents (heat transfer), weather phenomena (cyclones, rainfall), salinity, and seasonal changes.

🎯 Exam Tip: Provide a comprehensive list of factors and briefly explain how each impacts surface water temperature for a complete answer.

Question 2. Density of sea water
Answer:
• Temperature and salinity are the two properties of sea water that control the density of the sea water.
• If temperature reduces, density of water increases.
• Cold water is denser, and so is saline water.
• As compared to salinity, temperature affects the density more. Hence, sometimes, more saline water has lower temperature at the surface.
• Sea water having higher temperature and low salinity, can have lower density.
In simple words: Seawater density is primarily controlled by temperature and salinity; colder and saltier water is denser, with temperature generally having a greater influence than salinity.

🎯 Exam Tip: Clearly state the two main factors (temperature and salinity) influencing seawater density and explain their individual effects, noting which has a stronger impact.

Question 3. Measurement of salinity of sea water.
Answer:
• The weight of all dissolved salts in water in ratio of parts per thousand of water is called the salinity of seawater.
• For example, if the weight of dissolved salts in 1000g (1 kg) of seawater is 40g, then the salinity is 40%o i.e. 40 per thousand parts.
• Hydrometer, refractometer and salinometer are also used to measure salinity.
In simple words: Salinity is measured as the total dissolved salts in grams per kilogram of seawater (parts per thousand, %o), using instruments like hydrometers or salinometers.

🎯 Exam Tip: Define salinity clearly, provide an example of its measurement, and list the instruments used for complete understanding.

Question 4. Factors affecting salinity of sea water.
Answer:

Latitudes	Temperature / Rate of evaporation	Supply of fresh water	Salinity
Tropical Zone 5°N - 5°Sof equator	High	Abundant from (River Congo / Amazon)	High
Midlatitudes (25° - 35° N and S)	High (hot desert are found here)	low	High
Temperate regions	Temperature is lower due to slanting sunrays	The supply of water is more due to melting snow	low
Polar regions	Very low	low	low

In simple words: Seawater salinity is influenced by a balance of evaporation, precipitation, freshwater input from rivers, and ice melt, varying significantly across different latitudinal zones.

🎯 Exam Tip: To explain factors affecting salinity, organize your answer by climatic zones, detailing how temperature, evaporation, and freshwater supply interact in each.