Geography teacher MBOU-SOSH №7 of the city of Mtsensk
Pikurova N.S.
Lesson type : learning new material
The purpose and objectives of the lesson:
to expand existing knowledge about the main properties of sea water: temperature, salinity;
to acquaint students with new concepts;
continue to develop the ability to work with a geographic map;
Also, on the ocean's surface, the polar nature of water allows it to form what can be thought of as a sticky "skin" that is strong enough to support objects like insects. This phenomenon is known as surface tension, and water has the highest surface tension of all common liquids. The colder the water, the higher its surface tension. You might say it can't be important. On this surface of the skin lives a whole marine community called neuston.
Materials on the Internet
Neuston includes organisms such as bacteria, protozoa, fish eggs, copepods, and even floating jellyfish. In addition, many researchers are studying how pollutants affect neuston, as well as the effect of ultraviolet light on plankton. Viscosity is not the same as density. Viscosity describes the degree of internal friction of a fluid. Density is a measure of mass per volume of an object, and in terms of water, hydrogen bond. Density, however, is vital to marine organisms because, while living in water, they do not need extensive supporting structures such as massive bones or strong trunks of land animals and plants.
develop a cognitive interest in the subject.
develop research skills, the ability to analyze observed phenomena, formulate conclusions
Forms and methods: Explanatory and illustrative, partly search; informational and illustrative; demo; independent work with the text of the textbook, conversation, work with the map.
Since most divers learn in their training, water is 800 times denser than air, which provides quite a lot of support if you can find a way to live in it. This is why creatures like whales can survive, even swim gracefully in the sea, but cannot survive on land because they will be crushed by their own weight. It is fully supported by numerous air-filled sacs.
The density of water also depends on temperature: when water cools, it forms more hydrogen bonds due to slower molecular motion. In addition, water molecules move closer together, which increases its density. Pure water actually reaches its maximum density when it cools down to 8? But surprisingly, if it cools further, its density begins to decrease. When the water freezes, the larger hydrogen-bonded molecules take on a lattice structure that pushes the molecules further apart, increasing their volume.
Expected result of the lesson:
creative thinking of schoolchildren,
the ability to acquire knowledge from various sources,
analyze facts,
generalize
express your own judgments.
Equipment:
presentation of the lesson "Properties of the waters of the World Ocean",
textbook “Geography. Initial course "grade 6,
This makes water a very unusual substance because it is actually less dense in its solid form than it is in liquid form. It is also a fortunate occurrence for life on Earth because it means that ice is floating. If water was a more normal substance, the liquid state is less dense than the solid, the ice will sink. This would stall most of the water on Earth in a constant mass of ice, making the ice ages look like no more waste in a cooler at the end of a hot day.
The expansion of water as it freezes also has some important biological consequences. In particular, organisms that inhabit the polar regions must inhibit the formation of ice crystals within their cells and body fluids. If ice formed, it would destroy their internal structures, resulting in death. Again, Mother Nature to the rescue. Many species of fish that live in the polar regions have antifreeze in their blood, which lowers the freezing point of their internal fluids.
atlas grade 6,
physical map of the world;
multimedia projector, screen.
During the classes
I. Organizational moment.
– Good day! Guys, today we are again waiting for a journey through the endless world of the ocean. You will become members of the expedition of Captain Nemo, the hero of Jules Verne's novel 2000 Leagues Under the Sea.
II ... Repetition. Homework check.
Invertebrates deal with the problem in a different, but no less effective way. They increase the salt content of their tissues, thereby lowering the freezing point. The importance of a stable home life. The primary difference between living at sea and land is heat seas. Compared to terrestrial environments, where extreme temperatures can fluctuate by tens of degrees in a single day, sea temperatures are fairly stable. the temperate nature is that water has such a high ability to withstand rapid temperature changes, which is called "heat capacity".
But in order to take a tripCaptain Nemo has prepared a little test for you. The captain's boat will be waiting for you in the Indian Ocean at coordinates 30 Oyush and 80 Ov. Each crew will try to get to this place from different points. We will draw lots. (Moscow, S.-P., Vladivostok) Crews led by captains need to draw up a sailing route for their ship in such a way as to cover the distance from the home port to a given point in the shortest time. Route descriptions are entered in the logbooks. (Time 4 minutes).
The reason for this, again, is the reliable hydrogen bonds between the molecules. Understanding the phenomenon is related to what you may have already learned in an advanced diving course. Heat is nothing more than a measure of molecular motion. Therefore, if the temperature of the water rises, it means that the molecules are moving faster. But in order for these molecules to move faster, energy is required for the first break of hydrogen bonds. Conversely, in order for the water temperature to cool, a large amount of heat must be removed so that hydrogen bonds can re-form, thereby slowing down molecular motion.
So tell us about your routes.
III ... Learning new material.
1 slide ... All of you have successfully passed the test and the captain is pleased to welcome you on board his ship.
2 slide During our trip, you will learn about the properties of the world's oceans, such as salinity and temperature. We will make many observations and record the results in the logbook. So, let's go.
This phenomenon is also where we get the concept of "calorie". A calorie, unlike what you might think, has nothing to do with food or fat. It is just a measure of energy. Specifically, it is the amount of energy required for 1 gram of water that must be changed by 1 degree Celsius.
Interestingly, sea life requires a lot of heat to move ice into liquid water rather than change the temperature of liquid water. This amount of energy required to change water from a solid to a liquid is known as the "latent heat of fusion". For example, converting 1 gram of water at 0? Note that 80 calories are absorbed or excreted in water, but do not change its temperature. The practical consequence of this phenomenon is both ecological and biological significance.
3 slide - Guys, you all know what water is. - What properties of water do you know?
4slide
Transparency
Odorless
Fluidity
can simultaneously be in three states of aggregation
has low thermal conductivity
5slide - And water is also a very good solvent, therefore ocean water Is a solution of various substances. It contains 73 of 110 known chemical elements... Sodium and chlorine, which form table salt, account for more than 85% of all substances dissolved in ocean water. Aluminum, copper, silver, gold are found in the ocean water, but in very small quantities.
As for the sea, because of the latent heat of melting, the oceans gradually cool the winter. Biologically latent heat of fusion reduces the possibility of freezing in the bodies of marine organisms. In essence, the water in the tissues of plants and animals acts as a heat reservoir.
Another question that arises when considering the stability of the world's oceans: with such a large amount of incoming solar radiation why does the ocean temperature keep rising? The reason is that while most of the heat is absorbed, much is also removed by evaporative cooling at the surface. Evaporation releases heat and water vapor into the atmosphere.
Dissolved gases, including oxygen, are also present in ocean water. What is oxygen for?(for the life of marine organisms)
Also essential for life are calcium, silicon and phosphorus, which make up the shells and skeletons of marine animals.
Have you tried sea water? What does it taste like?(Salty)
The amount of heat lost during evaporation is called "latent heat of evaporation" and is much higher than the latent heat of fusion. For example, latent heat of vaporization releases 595 calories per gram of water evaporating from the ocean at 0? Evaporative cooling is also an important process for tidal marine organisms that are occasionally exposed to air. Finally, heat is transported in the ocean mainly by convective currents caused by uneven temperatures and even the influence of gravity.
But that is the subject of a later article on physical oceanography. The term universal solvent applies fairly well to water, and again this is due to the polar nature of the water molecule. A good example, illustrated in Figure 3, is how salt dissolves in water. In this case, crystals of salt or sodium chloride interact with charged water molecules. Water molecules, due to their polar characteristics, act like tiny magnets and push each crystal apart. Charged particles or ions of sodium and chloride become discounted salt crystals.
Correctly say bitter-salty. The bitter taste of ocean water comes from magnesium salts.
6 slide - One of the properties of water is salinity.
Salinity is the amount of minerals in grams dissolved in 1 liter (1 kg) of water. Expressed in ppm (thousandths of a number), denoted by ‰. Write down the definition in your logbooks.
Substances that do not ionize can still dissolve in water, but by other mechanisms beyond the scope of this discussion. The creatures that inhabit the ocean of the world swim in a substance that contains almost every known, natural element, but these elements do not occur in equal or even consistent amounts. The most common materials, called "mineral salts", dissolve in the sea water is shown in the figure. These elements behave in a very interesting and predictable way, they always maintain the same proportion to each other.
7 slide The average salinity of the World Ocean is 35 ‰. Let's try to bring the average salinity of the ocean water into a liter jar (35 g of salt needs to be added).
Tell me, is there salt in the water you drink?
How to prove that there is salt in fresh water?(Salt can be seen by evaporating a few drops of water)
Thus, if someone knows the proportion of one, the others can be easily calculated. This consistency of composition in seawater is sometimes referred to as the "first law of chemical oceanography." While it may or may not interest you, it is nonetheless significant as it affects many different chemical, physical, and biological processes in the ocean. The answer is that the addition of salts is balanced by the removal of salts by various chemical, physical and biological processes.
One way is to dump the river. In this case, rivers flowing into the ocean add salt as well as other minerals that dissolve from the soil when rain seeps through the land into the sea water. Another entrance comes from water circulating through the hydrothermal vents of the mid-ocean ridges. Here, minerals are added to seawater as it flows through volcanically heated rocks near mountain ranges. This may seem like a rather inconsequential source until you realize that all of the ocean's water flows through these hot springs every 8-12 million years.
HeldAN EXPERIENCE. You need to drop a few drops of water on the glass and evaporate it by heating the glass on an alcohol lamp. Salt deposits will remain on the glass.
Also, scale remains on the bottom of pots and kettles - these are various salts.
That water is considered fresh,1 liter of which contains less than 1 g of solutes.
Rivers and hot springs work together to create the salinity of the seawater. Hot springs also chemically change seawater, adding some materials while removing others. Thus, over time, the addition of solutes to the ocean is counterbalanced by the removal of dissolved materials, one of the best balancing actions on Earth.
These elements include phosphates, nitrates, and silicon. The former two are vital to the vital functions of all living things, while the latter is required by some plankton to create their glass skeletons. These elements, however, do not behave in the way discussed earlier.
8 slide. Look at a schematic map of the distribution of salinity in the world's oceans. - Is the salinity of the water the same everywhere? (No)
9 slide distribution of salinity. You can see on the slide that the salinity in the seas is also not the same.
In the Red Sea, salinity is 42 ‰
in the Black Sea salinity - 18 ‰
Nitrates and phosphates differ in concentration due to biological activity. In some marine communities where algae and other plants are active in photosynthesis, nitrates and phosphates may be in short supply. When this happens, the amount of biological activity that can take place is limited. However, some marine ecosystems, especially coral reefs, have evolved with low nutrient levels, and the introduction high levels nutrients can spell disaster.
Since anyone who has ever been to the ocean west coast North America, and then dived in some tropical place, can confirm the sea is not uniformly salty. But how can this be if the main ions in seawater always keep practically the same proportions? The answer, once again, is the water itself. Salinity changes are due to differences in local rates of evaporation and precipitation over the ocean, as well as the volume of fresh water discharged into a particular ocean basin from rivers.
In the Baltic Sea salinity is 6-8 ‰
In the Gulf of Finland Baltic Sea salinity 3-4 ‰
In the Barents Sea, salinity is 35 ‰
Group work.
Now, try to bring the salinity of the ocean water of these seas.
1 crew - Red Sea salinity
2 crew - the salinity of the Black Sea water
3 crew - the salinity of the Baltic Sea water
Explain your actions. How did you get this salinity?
What problem do you think we will solve in the next step? (Why is salinity different everywhere, what reasons affect salinity?)
Guys, how can I change the salinity in my jar of water?
pour the water; 2) evaporate
Let's think about what processes in nature can pour water into the ocean?
( rain, rivers )
And what processes can remove the water and leave the salt? (Evaporation )
And where should you put a jar of water so that the water evaporates faster? (To a warm place ).
And what other process can take water, and leave the salt? (Ice )
10 slide - Let's draw a conclusion, what factors influence the salinity of the World Ocean water. (Salinity is influenced by: precipitation, evaporation, number and fullness of rivers, ice formation ). Write it down in your logs.
11 slide. And now the crews will complete this task.
1 crew - explain why the Red Sea is the saltiest sea on Earth?
2 crew - explain why the salinity in the Black Sea is less than the average salinity of the ocean.
3 crew - explain why the salinity in the Baltic Sea is the smallest?
( An example answer: In the marginal seas, the salinity is close to the average oceanic. V Black Sea many rivers that carry fresh water flow into it: the Dnieper, Don, Danube, etc. The Baltic Sea is far from the equator, so there is little evaporation, many rivers flow into it, desalinating water. V The Gulf of Finland flows into deep river Neva. Not a single river flows into the Red Sea, it is crossed by the tropic, which means little precipitation falls, and evaporation is large, since the sea is close to the equator )
The sailors learned about the approach of the coast by the salinity of the water. How could you find out?(Near the coast, the water is less salty, because rivers flow into the sea from the land, desalinating the water)
Why is the equator less salty than the tropics?(There is a lot of rainfall near the equator, little rainfall in the tropics)
12 slide - Look at the schematic map, which ocean is the saltiest?(Atlantic)
And in which ocean is the lowest salinity? (North-Arctic )
13 slide. Average salinity of the oceans:
Pacific Ocean - 34.6% o
Atlantic Ocean - 37.5% o
Indian Ocean - 34.8% o
Arctic Ocean - 32% o
14slide - If all the salts dissolved in the waters of the World Ocean are evaporated and evenly distributed over the surface of the Earth, then our planet will be covered with a layer of salt 45 meters thick.
15 slide - Consider the following property of the waters of the World Ocean "Temperature".
Dear crew members, a disaster struck on the ship. The captain's cockpit contains all the recorders from all the instruments. The device that records temperature changes at depth and on the surface of the water is out of order. An urgent need to draw graphs of changes in water temperature.
Group work.
1 crew - draw a graph of the change in water temperature at the surface, study the data on the water temperature and draw a conclusion how it changes at the surface.
16 slide Temperature surface waters:
0 c... w .: + 26С
30 p. w .: + 20С
60 p. NS. : + 5С
90 p. w .: - 1.5С
Output : howfarther from the equator, the watercolder .
2 crew - draw a graph of the change in water temperature with depth. Examine the water temperature data and draw a conclusion about the change in water temperature with depth.
0 m: + 20С
200 m: + 10С
1000 m: + 3С
2000 m: + 2С
5000 m: + 2С
Output : temperature with depthgoes down ... The water heats upsolar rays. The rays only penetrateupper layers of water. Below a depth of 1000 m, the temperature remainsequally low ... The sun's rays do not penetratedepth .
17 slide ... So, let's summarize again, what does the water temperature depend on?
18 slide (from climate) Record the output in your logs
3 crew - study the map of temperature distribution over the water surface and tell me which of the oceans is the warmest, coldest and draw a conclusion why? Word 3 to the crew.
19 slide. The highest water temperature at the surface in Pacific(+ 19.4 ° C), Indian (+ 17.3 ° C), Atlantic (+ 16.5 ° C) oceans, the lowest water temperature in the Arctic Ocean (-1 ° C).
20 slide. average temperature waters of the World Ocean - 3.5 ° С
On the ocean surface, the highest temperature recorded in the shallow Persian Gulf Indian Ocean(above + 35С), the coldest water in the Weddell Sea in Antarctica is 1 - 2С.
Ocean water freezes at temperature- 2C
The higher the salinity of the water, the lower its freezing point.
IV ... Lesson summary
What we learned today about the salinity and temperature of the waters of the World Ocean.
21 slides. Complete the sentences "I know that ..."
salinity is measured in ppm
salinity in the seas and oceans is not the same
salinity depends on evaporation, precipitation, rivers flowing into the sea
fresh water has a salinity of 1 ‰
the saltiest sea - Red
surface waters are heated by the sun's rays
the deeper the colder the water
the water temperature drops to a depth of 1000 m, then remains constant
the temperature at the equator is + 26 ... + 27С
at the poles the temperature is -1С
salt water freezes at a temperature of - 2С
22 slide. V. Homework. § 26, back. 3
Slide 23. Lesson summary
The waters of the World Ocean, in addition to the basic properties of water (for example, salinity, the ability to dissolve), have their own unique specific properties.
Properties of the waters of the World Ocean
Scientists rightly call the World Ocean the main heat accumulator on our planet. The average temperature of the world's oceans is +17 degrees.
The water column is warmed up by the sun's rays more slowly than the land surface. However, unlike the continental surface, ocean water is slower to release its heat to the atmosphere.
The heating of the planet at night occurs precisely due to the heat that the ocean waters emit. Ocean waters freeze when low temperatures, however, if for land waters such temperatures should be below 0 ° С, then for oceanic waters - below -4 ° С.
This is because the waters in the oceans have a very high salinity. The density of water in the ocean also depends on temperature.
In northern latitudes, icebergs form on the surface of the oceans, their density is much less than the density of the ocean surface: due to this, they can move short distances.
The movement of the waters of the oceans
The incredibly voluminous masses of water in the World Ocean tend to move, they are often in the process of constant movement. The main indicator of the movement of oceanic and sea waters are the waves.
Sometimes they are very small and form only slight ripples on the surface, sometimes they can reach several meters, flooding into islands and coastal cities.
Three factors affect the movement of waters in the oceans and seas: the influence of the wind, the movement of lithospheric plates, and the attraction of the moon (provoking the ebb and flow).
A strong wind can move large volumes of water over long distances, it is the wind that forms the sea and ocean currents.
Ocean currents
Currents are periodic or constant movements of water in the thickness of the world's oceans. Ocean currents are of different types.
Depending on the temperature of the water, there are cold and warm currents. Based on the frequency, there are periodic, constant and irregular currents.
In addition, there are also underwater and surface currents that are located in the ocean and on its surface, respectively.
The most famous warm current located in Atlantic Ocean is the Gulf Stream. It originates from the coast of North America and reaches the Florida Strait.
Often, in a broad sense, the Gulf Stream means a system of warm currents that are located between the coast of Florida and the shores of Scandinavia.
Features of the waters of their area
The waters of different areas are very different from each other. The study of the waters of their area is a very exciting activity, because all students must know all the properties of the waters of the nearest reservoirs, since without this further study of geography will be very difficult.
