Geography Question Answers Chapter 6 The Properties of Sea Water Class 9 Maharashtra Board

Questions Answers For All Chapters – Geography Class 9th

Exercise

Q1. Tick the correct box according to the salinity of the ocean water

(a) Slanting sunrays, melting snow

• Low salinity: Slanting sunrays mean less heat, and melting snow adds fresh water, reducing salinity.

(b) Cloudy sky, rainfall throughout the year

• Low salinity: Constant rainfall adds lots of fresh water, lowering salinity.

(c) Clear skies for the most part, perpendicular sunrays

• High salinity: Strong sunrays cause more evaporation, increasing salinity.

(d) Less supply of freshwater, desert area around

• High salinity: No fresh water and high evaporation in deserts raise salinity.

(e) Low temperatures, ample supply of river water

• Low salinity: Cold areas with lots of river water add fresh water, reducing salinity.

(f) Continental location, desert around, low rainfall

• High salinity: Landlocked areas with deserts have high evaporation and little fresh water, increasing salinity.

Q2. Give reasons.

(a) Salinity is low in the land-locked Baltic Sea.

• The Baltic Sea gets lots of fresh water from rivers like the Neva.
• It has low evaporation due to cold climate, so salinity stays low (7%).

(b) There is higher salinity in the northern Red Sea while lower in the southern.

• The northern Red Sea has more evaporation and less fresh water input.
• The southern part gets some fresh water from the Gulf of Aden, reducing salinity.

(c) Oceans located at the same latitude do not have same salinity.

• Salinity varies due to differences in rainfall, river water, and evaporation.
• For example, landlocked seas or desert coasts increase salinity compared to open oceans.

(d) With increasing depth, the temperature of sea water decreases to a certain limit.

• Sunrays heat only the surface, and their effect decreases with depth.
• After 2000 meters, the temperature stays steady at about 4°C everywhere.

(e) There are more salt-pans on the Western coast of India than its eastern coast.

• The western coast (Arabian Sea) has higher salinity (35%) due to less river water and more evaporation.
• The eastern coast (Bay of Bengal) has lower salinity (34%) from big rivers like Ganga, so fewer salt-pans.

(f) Salinity increases in the mid-latitudinal zones.

• Mid-latitudes (25° to 35° N and S) have hot deserts, less rainfall, and high evaporation.
• This reduces fresh water supply, making salinity higher (37%).

Q3. Answer the following questions.

(a) What are the factors affecting the salinity of the sea water?

• Evaporation: More evaporation increases salinity.
• Fresh water supply: Rivers, rainfall, and snow reduce salinity.
• Temperature: Higher temperatures increase evaporation, raising salinity.
• Location: Landlocked seas have higher salinity than open seas.

(b) Explain the distribution of salinity around the Tropic of Cancer and Tropic of Capricorn.

• Around the Tropics (23.5° N and S), salinity is high (37%) due to strong sunrays and high evaporation.
• There’s less rainfall and fewer big rivers, so fresh water supply is low, increasing salinity.

(c) What are the factors affecting the temperature of the sea water?

• Latitude: Temperature decreases from equator (25°C) to poles (2°C).
• Ocean currents: Warm currents raise temperature, cold currents lower it.
• Depth: Temperature drops with depth, steady at 4°C after 2000 meters.
• Seasons, cyclones, and rainfall: These also change surface temperature.

(d) Explain the changes occurring in the temperature of sea water according to the depth.

• Surface water is warm (e.g., 25°C at equator) due to sunrays.
• Temperature decreases fast with depth up to 2000 meters.
• After 2000 meters, it stays constant at about 4°C everywhere.

(e) Name the factors affecting salinity.

• Evaporation rate.
• Fresh water from rivers and rainfall.
• Temperature of the water.
• Location (open or landlocked sea).

Q4. Explain how temperature affects the following.

(a) The density of sea water

• When temperature drops, sea water gets colder and denser because cold water sinks.
• Higher temperature makes water less dense, but salinity can still increase density even if water is warm.

(b) The salinity of sea water

• High temperature increases evaporation, leaving more salt and raising salinity.
• Low temperature reduces evaporation, and with fresh water input, salinity decreases.

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

(Filling missing parts based on the chapter’s content.)

Notes:

• Tropical: High solar energy and low river water increase salinity.
• Temperate: More snow and river water lower salinity.
• Polar: Very low evaporation and snowmelt keep salinity low.
• Landlocked seas: High evaporation and low fresh water cause very high salinity (e.g., Dead Sea).