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§ 41. Properties of water of the oceans (textbook)

§ 41. Properties of water of the oceans


1. Give examples of substances which dissolve easily in water.

2. What is the taste of sea water?


Water temperature. Ocean receives from the Sun much heat. But the sunlight heats only surface layer of water. His temperature in different parts of Ocean Divers. Surface water temperature of water depends on climate and decreases from equator to the poles. The highest temperature of 25? 27 0C - in equatorial and tropical latitudes of the hot climate. The lowest (-1.8 0C) - In the polar regions with cold climates.

At negative temperatures, fresh water rivers and lakes freeze. The temperature is freezing salt water is lower and -2 0C. Because the water of the oceans covered with ice only in polar regions. Permanently ice covered only central part of the Arctic Ocean and surrounding Antarctica. In winter ice cover is increasing, decreasing in summer.

Except that the oceans are floating ice from the ice cover vidkolyuyutsya Antarctic islands and polar latitudes. Sea currents and winds move them temperate latitudes, where they gradually fade away.

Temperature water changes with depth: the deeper, the water is colder. Deeper 1000 m temperature is always 2? 3 0C. On the day she hlybokovodyh Depression is 0 0C. The average temperature is the whole mass of oceanic water is only 4 0Warm water S. concentrated in relatively thin surface layer approximately 100 m thickness. Such depth penetrates sunlight, deeper - darkness prevails. Thus, the ocean - cold, salty and dark.

Fig. Floating ice off Antarctica


Salinity of sea water. Water - excellent solvent. So naturally there is no water, which did not contain a specific amounts of dissolved substances. In sea water contains dissolved substances a huge amount. Number grams of substance dissolved in 1 liter of water, called salinity. In 1 liter of seawater dissolved in 35 g of different average substances. Salinity and can be expressed in units called ppm. Ppm (‰) – This millesimal whole, as opposed to percent (%) - one hundredth of a share. In these units average salinity of waters of the oceans is 35 ‰. This means that in 1000 Mr. (1 liter) of seawater contains 35 g of salt.

Fresh is the water salinity is less than 1 ‰. That is too salty river water, but very slightly compared to the sea. However, it was the river flowing down from land, were to blame that for millions of years of water in the Pacific Ocean became more salty.

In dissolved water oceans on Earth all known substances, but in different quantity. It found aluminum, copper, silver and even gold. However, their tiny amount. Most are dissolved in seawater is well known to all salt. She gives it a salty taste. A bitter aftertaste provide the dissolved magnesium salt. Through high content of salts of pcrop such water is impossible. Therefore, sailors on ships that go in swimming, taking with them freshwater.

Salinity waters of the oceans are not all equal. It depends on the evaporation of water from surface ocean and arrival in his fresh water rivers and from atmospheric precipitation. Therefore, salinity changes from the equator to the poles. In tropical latitudes salinity largest - 38 ‰, because there is little rain, and great evaporation. When evaporation of salt water in the sea remains. In equatorial latitudes lower salinity (34 ‰) - there is heavy rainfall. In polar areas of reduced salinity to 32 ‰. Precipitation there falls a little, but slight evaporation. Salinity is reduced and as a result of melting ice.

Most salinity has Red Sea (42 ‰)Situated in the tropical latitudes and is not no river flows. If the Red Sea water has been received Strait of Indian Ocean, it would be dried up. In Black Sea, Due to the influx of river water salinity is 18 ‰. Azov Sea is malosolonym – 12–14 ‰. The least salty water - Baltic Sea (4 ‰).


Questions and Tasks

1. How does the temperature of surface waters of the oceans from the equator to poles?

2. Why is the water temperature decreases with depth?

3. Why is the freezing temperature of sea water below 00C?

4. Decide on a map where the border of floating ice?

5. What is called the salinity of water? What it means: salinity 14 ‰?

6. Which reduces the salinity of the ocean? And that increases salinity?

7. Calculate how many kilograms of various substances can be obtained from 1 t Black Sea water salinity if 18 .