Does ice sink in water in spring. Why doesn't ice sink in water. Experimenting with the power of water expansion

01.08.2020 Tools and fixtures

Young children very often ask interesting questions to adults, and they cannot always answer them right away. In order not to seem stupid to the child, we recommend that you familiarize yourself with a full and detailed, well-founded answer regarding the buoyancy of ice. After all, it floats, not drowns. Why is this happening?

How to explain complex physical processes to a child?

The first thing that comes to mind is density. Yes, in fact, ice floats because it is less dense than. But how to explain to a child what density is? No one is obliged to tell him the school curriculum, but to reduce everything to what is quite real. Indeed, in fact, the same volume of water and ice has different weights. If you study the problem in more detail, then you can voice several more reasons, in addition to density.
not only because its reduced density prevents it from sinking lower. The reason is also that small air bubbles are frozen in the ice. They also decrease the density, and therefore in general it turns out that the weight of the ice plate becomes even less. When the ice expands, it does not capture more air, but all those bubbles that are already inside this layer remain there until the ice begins to melt or sublimate.

Experimenting with the power of water expansion

But how can you prove that the ice is actually expanding? After all, water can also expand, how can one prove this in artificial conditions? An interesting and very simple experience can be made. This will require a plastic or cardboard cup and water. Its amount does not have to be large, you do not need to fill the glass to the brim. Also, ideally, you need a temperature of about -8 degrees or lower. If the temperature is too high, the experience will last an unreasonably long time.
So, water is poured inside, you have to wait for ice to form. Since we have chosen the optimal temperature at which a small volume of liquid turns to ice within two to three hours, you can safely go home and wait. You need to wait until all the water turns into ice. After a while, we look at the result. A deformed or ice-torn cup is guaranteed. At lower temperatures, the consequences look more impressive, and the experiment itself takes less time.

Negative consequences

It turns out a simple experiment confirms that ice blocks really expand with decreasing temperature, and the volume of water easily increases when it freezes. As a rule, this feature carries a lot of problems for forgetful people: a bottle of champagne, left on the balcony for a long time on New Year's Eve, bursts due to the influence of ice. Since the expansion force is very large, it cannot be influenced in any way. Well, as for the buoyancy of ice blocks, there is nothing to prove here. The most curious can easily carry out a similar experiment in spring or autumn on their own, trying to drown pieces of ice in a large puddle.

Municipal educational autonomous institution

secondary school with. Vasilievka

Research work

Why doesn't ice sink in water?

Pupils 3 "b" grade

Belogubova Sophia

Head: Klimenko

Lyudmila Sergeevna,

teacherI qualification

The content of the work.

1. Introduction……………………………………………………………. 3

2.Main part: ………………………………………………… ... 4-6

2.1. Why do objects float? ............................................. .....

2.2. Ancient Greek scientist Archimedes ……………………………………

2.3. Archimedes' law ……………………………………………………….

2.4. Experiments ……………………………………………………… ..

2.5. An important feature of water ………………………………………… ...

3. Conclusion ……………………………………………………… .7

4. References ………………………………………………… 8

5. Appendices ………………………………………………………… 9-10

Introduction.

Doesn't burn in fire

Doesn't sink in water.

Relevance of the topic

Why do some substances sink in water, while others do not? Understanding the laws of buoyancy allows engineers to build ships from metals that float and do not sink.

Nobody doubts that ice floats on water; everyone has seen it hundreds of times, both on the pond and on the river.

But why is this happening?

What other objects can float on the water?

This is what I decided to find out.

Set a goal:

Determine the reasons for the unsinkable ice.

Outlined a number of tasks:

Find out the swimming conditions of bodies;

Find out why the ice does not sink;

Conduct an experiment to study buoyancy.

Made a hypothesis:

Perhaps the ice does not sink, because water is denser than ice.

Research methods:

Theoretical analysis of literature;

Observation method;

Practical method.

Practical material will be useful to me in reading lessons, the surrounding world.

Main part

If you submerge a body in water, it will displace some of the water. The body takes over where the water used to be, and the water level rises.

According to the legend, the ancient Greek scientist Archimedes (287 - 212 BC), while in the bath, guessed that a submerged body displaces an equal volume of water. A medieval engraving depicts Archimedes making his discovery (see Appendix 1)

The force with which water pushes out a body immersed in it is called the pushing force.

Archimedes' law states that the pushing force is equal to the weight of the liquid displaced by a body immersed in it. If the pushing force is less than the weight of the body, then it sinks; if it is equal to the weight of the body, it floats.

Experiment No. 1 (see Appendix 1)

I decided to see how the pushing force works, marked the water level, dipped a plasticine ball with an elastic band into a vessel with water. After the immersion, the water level rose and the length of the rubber band decreased. She marked the new water level with a felt-tip pen.

Conclusion: From the side of the water, a force directed upwards acted on the plasticine ball. Therefore, the length of the elastic band has decreased, i.e. the ball immersed in water became lighter.

Then she made a boat out of the same plasticine and carefully lowered it into the water. As you can see, the water has risen even higher. The boat displaced more water than the ball, which means that the pushing force is greater.

The magic has happened, the sinking material floats on the surface! Ah yes Archimedes!

To prevent the body from sinking, its density must be less than the density of water.

Not sure what density is? This is the mass of a homogeneous substance per unit volume.

Experiment # 2: (see Appendix 2)

She poured water into a glass and put it on the street. When the water froze, the glass burst. I put the formed ice in a container with cold water and saw that it was floating.

In another container, I salted the water well and stirred until it was completely dissolved. I took ice and repeated the experiment. Ice floats, and even better than in fresh water, almost half protruding from the water.

All clear! The ice cube floats because when it freezes, the ice expands and becomes lighter than water. The density of ordinary, liquid water is somewhat greater than the density of frozen water, that is, ice. As the density of the liquid increases, the buoyancy force increases.

Scientific facts:

1Fact Archimedes: a buoyant force acts on any body immersed in a liquid.

2 fact Mikhail Lomonosov:

Ice does not sink because it has a density of 920 kg / m3. And the water is denser - 1000 kg / cubic meter.

Output:

I found 2 reasons why ice is unsinkable:

a buoyant force acts on every body immersed in water;

the density of ice is less than the density of any water.

Let's try to imagine what the world would look like if water had normal properties, and ice, as it should be for any normal substance, is denser than liquid water. In winter, a denser ice freezing from above would sink in the water, continuously sinking to the bottom of the reservoir. In summer, the ice, protected by the cold water column, could not melt.

continuous icy desert, here and there covered with a thin layer of melt water. One of these unique properties of water is its ability to expand when frozen. After all, all substances when they freeze, that is, when they pass from a liquid state to a solid, contract, and water, on the contrary, expands. At the same time, its volume increases by 9%. But when ice forms on the surface of the water, then it, being between cold air and water, prevents further cooling and freezing of water bodies. This unusual property of water, by the way, is also important for the formation of soil in the mountains. Falling into small cracks, which are always found in stones, rainwater expands when it freezes and destroys the stone. So, gradually, the stone surface becomes able to shelter plants, which, with their roots, complete this process of destruction of stones and lead to the formation of soil on the mountain slopes.

Ice is always on the surface of the water and serves as a real heat insulator. That is, the water under it does not cool so much, the ice coat reliably protects it from frost. That is why a rare body of water freezes to the bottom in winter, although this is possible at extreme temperatures.

The sudden increase in volume when water passes into ice is an important feature of water. This feature often has to be reckoned with in practical life. If you leave a barrel of water in the cold, the water will freeze and burst the barrel. For the same reason, you should not leave water in the radiator of a car parked in a cold garage. In severe frosts, you need to beware of the slightest interruption in the supply of warm water through the water heating pipes: the water that has stopped in the outer pipe can quickly freeze, and then the pipe will burst.

Yes, a log, no matter how large, does not sink in water. The secret of this phenomenon is that the density of wood is less than that of water.

Conclusion.

So, after doing a lot of work, I understood. That my hypothesis, about why the ice does not sink, was confirmed.

Reasons for unsinkable ice:

1. Ice consists of water crystals with air between them. Consequently, the density of ice is less than the density of water.

2. A buoyant force acts on the ice from the water side.

If water were normal and not a unique liquid, we would not enjoy skating. We're not rolling on glass, are we? But it is much smoother and more attractive than ice. But glass is a material on which skates won't slide. But on ice, even of not very good quality, it is a pleasure to skate. You will ask why? The fact is that the weight of our body presses on the very thin blade of the skate, which exerts strong pressure on the ice. As a result of this pressure from the ridge, the ice begins to melt with the formation of a thin film of water, on which the ridge glides perfectly.

List of references

Children's encyclopedia "I get to know the world."

Zedlag W. "Amazing on Planet Earth".

Internet resources.

Rakhmanov A. I. "Phenomena of Nature".

Encyclopedia "The World of Nature".

Appendix 1

Appendix 2

Appendix 3

Each of us watched ice plates floating on the river in spring. But why are they do not drown? What keeps them on the water surface?

One gets the impression that despite their weight, something simply does not allow them to go down. I am going to reveal the essence of this mysterious phenomenon.

Why doesn't the ice sink

The thing is that water is very unusual substance... It has amazing properties that we sometimes just don't notice.

As you know, almost all things in the world expand when heated and contract when cooled. This rule also applies to water, but with one interesting note: when cooled from + 4 ° C to 0 ° C, water begins to expand... This explains the low density of the ice masses. Expanded from the phenomenon above, the water becomes lighter than the one in which, and begins to drift on its surface.

Why is such ice dangerous?

The phenomenon described above is often found in nature and everyday life. But if you start to forget about it, then it can become the source of many problems. For example:

in winter, frozen water can burst water pipes;

the same water, freezing in mountain cracks, contributes destruction of rockscausing rock falls;
we must not forget drain water from a car radiatorto avoid the above situations.

But there are also positive aspects. After all, if water did not possess such amazing properties, then there would be no such sport as skating... Under the weight of the human body, the blade of the skate presses on the ice so hard that it simply melts, creating a water film ideal for sliding.

Water in the ocean depths

Another interesting point is that even despite the zero temperature in the oceanic (or sea) depths, the water there does not freezedoes not become an ice block. Why is this happening? It's all about pressure, which is rendered by the upper water layers.

In general, pressure helps to solidify various liquids. It causes a reduction in the volume of the body, greatly facilitating its transition to a solid state. But when water freezes, it does not decrease in volume, but, on the contrary, increases. And so the pressure, preventing water expansion, reduces its freezing point.

That's all I can tell you about this interesting phenomenon. I hope you learned something new for yourself. Good luck with your travels!

Kim Irina, 4th grade student

Research paper "Why Doesn't Ice Sink?"

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Preview:

Municipal State Educational Institution "Krasnoyarsk Secondary School"

Research work

Performed:

Kim Irina,

studying 4 classes.

Leader:

Ivanova Elena Vladimirovna,

primary school teacher.

from. Krasny Yar 2013

1. Introduction.

2.Main part:

Why do objects float?

Ancient Greek scientist Archimedes.

Archimedes' law.

Experiments.

An important feature of water.

3. Conclusion.

4. References.

5. Applications.

Introduction.

Why do some substances sink in water, while others do not? And why are there so few substances that can float in the air (i.e. fly)? Understanding the laws of buoyancy (and immersion) allows engineers to build ships from metals heavier than water and to design airships and balloons that can float in the air. Air is pumped into a life jacket, so it helps a person stay on the water.

Nobody doubts that ice floats on water; everyone has seen it hundreds of times, both on the pond and on the river. But why is this happening? What other objects can float on the water? That's what I decided to find out.

Purpose:

Determination of the reasons for the unsinkable ice.

Tasks:

1.Find out the swimming conditions for bodies.

2. Find out why the ice does not sink.

3. Conduct an experiment to study buoyancy.

Hypothesis:

Perhaps the ice does not sink, because water is denser than ice.

Main part:

Why do objects float?

If you submerge a body in water, it will displace some of the water. The body takes over where the water used to be, and the water level rises.

The force with which water pushes out a body immersed in it is called the pushing force.

Experiment # 1 : (see Appendix 2)

Conclusion: From the side of the water, a force directed upwards acted on the plasticine ball. Therefore, the length of the elastic band has decreased, i.e. a ball immersed in water has become lighter.

The magic has happened, the sinking material floats on the surface! Ah yes Archimedes!

To prevent the body from sinking, its density must be less than the density of water.

Not sure what density is? This is the mass of a homogeneous substance per unit volume.

Experiment 2: "The dependence of the buoyancy force on the density of water" (see Appendix 3)

I took: a glass of clean water (incomplete), a raw egg and salt.

I put an egg in a glass, if the egg is fresh, it will sink to the bottom. Then she began to carefully pour salt into the glass and watched the egg begin to float.

Conclusion: As the density of the liquid increases, the buoyancy force increases.

The egg has an air bag, and as the density of the liquid changes, the egg floats to the surface in the manner of a submarine.

Earlier, before the invention of refrigerators, our ancestors checked whether an egg was fresh or not: fresh eggs drown in clean water, and spoiled ones float, as gas forms inside them.

Experiment No. 3 "Water floating lemon" (see Appendix 4)

She took water into a container and dipped a lemon into it. The lemon floats. And then she peeled it off and put it back in the water. The lemon drowned.

Conclusion: the lemon drowned due to the fact that its density increased. The rind of a lemon is less dense than the inside and contains many air particles that help the lemon stay on the surface of the water.

Experiment # 4 (see Appendix 5)

1. I poured water into a glass and put it on the street. When the water froze, the glass burst. I put the formed ice in a container with cold water and saw that it was floating.

2. In another container, I salted the water well and stirred until it was completely dissolved. I took ice and repeated the experiment. Ice floats, and even better than in fresh water, almost half protruding from the water.

Scientific facts:

1Fact Archimedes: a buoyant force acts on any body immersed in a liquid.

2 fact Mikhail Lomonosov:

Ice does not sink because it has a density of 920 kg / m3. And the water is denser - 1000 kg / cubic meter.

Output:

I found 2 reasons why ice is unsinkable:

Any body immersed in water is subjected to a buoyant force.
The density of ice is less than the density of any water.

Let's try to imagine what the world would look like if water had normal properties and ice, as befits any normal substance, is denser than liquid water.

In winter, a denser ice freezing from above would sink in the water, continuously sinking to the bottom of the reservoir. In summer, the ice, protected by the cold water column, could not melt.

Gradually, all lakes, ponds, rivers, streams would freeze completely, turning into giant ice blocks. Finally, the seas would freeze, and beyond them the oceans. Our beautiful blooming green world would become a solid ice desert, in some places covered with a thin layer of melt water. One of these unique properties of water is its ability to expand when freezing. After all, all substances when they freeze, that is, when they pass from a liquid state to a solid, contract, and water, on the contrary, expands. At the same time, its volume increases by 9%. But when ice forms on the surface of the water, then it, being between cold air and water, prevents further cooling and freezing of water bodies. This unusual property of water, by the way, is also important for the formation of soil in the mountains. Falling into small cracks, which are always found in stones, rainwater expands when it freezes and destroys the stone. So, gradually, the stone surface becomes able to shelter plants, which, with their roots, complete this process of destruction of stones and lead to the formation of soil on the mountain slopes.

Yes, a log, no matter how large, does not sink in water. The secret of this phenomenon is that the density of wood is less than that of water.

By the way...

There are trees that are drowning in water! The reason for this is that their density is greater than the density of water. These trees are called "iron". The "iron trees" include, for example, Persian parrotia, azobe (African tropical iron tree), Amazonian wood, ebony, rosewood, or rosewood, kumaru and others. All these trees have very hard and dense wood, saturated with oils, the bark of these trees is resistant to decay. Therefore, a boat made of such a tree will immediately sink to the bottom, but "iron trees" are an excellent material for making furniture.

In the seas and oceans, sometimes there are huge ice mountains - icebergs. These are glaciers sliding down from the polar mountains and carried away by the current and wind into the open sea. Their height can reach 200 meters, and their volume can be several million cubic meters. Nine-tenths of the total mass of the iceberg are hidden under water. Therefore, meeting with him is very dangerous. If the ship does not notice the moving ice giant in time, it can be seriously damaged in a collision or even die.

Fig. 4. Nine-tenths of the mass of an iceberg are under water.

Even in spite of the fact that the ship is made of iron, very heavy, and even carries people and goods, it does not sink. Why? And the thing is that there is air in the ship besides the crew, passengers, cargo. And air is much lighter than water. The ship is designed so that inside it there is some space filled with air. It is this that supports the ship on the surface of the water and prevents it from sinking.

Submarines

Submarines sink and float, changing their relative density. They have large containers on board - ballast tanks. When air leaves them and water is pumped inside, the density of the boat increases and it sinks. To float to the surface, the crew removes water from the tanks and pumps air there. The density decreases again and the boat floats up. Ballast tanks are placed between the outer shell and the walls of the inner compartment. The crew lives and works in the inner compartment. The submarine is equipped with powerful propellers that allow it to move through the water column. Some boats are equipped with nuclear reactors.

Conclusion.

So, after doing a lot of work, I understood. That my hypothesis, about why the ice does not sink, was confirmed.

Reasons for unsinkabilityice:

1. Ice consists of water crystals with air between them. Consequently, the density of ice is less than the density of water.

2. A buoyant force acts on the ice from the water side.

application

Appendix 1

In the ocean, polar ice blocks and icebergs drift, and even in drinks the ice never sinks to the bottom. It can be concluded that ice does not sink in water. Why? If you think about it, this question may seem a little strange, because ice is hard and - intuitively - must be heavier than liquid. While this is true for most substances, water is the exception to the rule. Water and ice are distinguished by hydrogen bonds, which make ice lighter when it is solid than when it is liquid.

Scientific question: why does not ice sink in water

Imagine that we are in a lesson called "The World Around" in grade 3. “Why doesn't the ice sink in the water?” The teacher asks the children. And kids, not having deep knowledge in physics, begin to reason. "Perhaps this is magic?" Says one of the children.

Indeed, the ice is extremely unusual. There are practically no other natural substances that, in a solid state, could float on the surface of a liquid. This is one of the properties that makes water such an unusual substance and, if you confess, it is it that changes the evolutionary paths of the planets.

There are some planets that contain huge amounts of liquid hydrocarbons such as ammonia - however, when it freezes, this material sinks to the bottom. The reason why ice does not sink in water is that when it freezes, the water expands, and at the same time its density decreases. Interestingly, the expansion of the ice can break stones - the process of water icing is so unusual.

Scientifically speaking, during the freezing process, rapid weathering cycles are established and certain chemicals released on the surface are capable of dissolving minerals. In general, water freezing is associated with processes and opportunities that the physical properties of other fluids do not imply.

Density of ice and water

Thus, the answer to the question of why ice does not sink in water, but floats on the surface, is that it has a lower density than liquid - but this is a first level answer. For a better understanding, you need to know why ice has a low density, why things float in the first place, how density leads to float.

Let us recall the Greek genius Archimedes, who found out that after immersing a certain object in water, the volume of water increases by a number equal to the volume of the immersed object. In other words, if you place a deep dish on the surface of the water and then place a heavy object in it, the volume of water that will pour into the dish will be exactly equal to the volume of the object. It doesn't matter if the object is submerged completely or partially.

Water properties

Water is an amazing substance that basically feeds life on earth, because every living organism needs it. One of the most important properties of water is that it has the highest density at 4 ° C. Thus, hot water or ice is less dense than cold water. Less dense substances float on top of denser substances.

For example, when preparing a salad, you may notice that the oil is on the surface of the vinegar - this can be explained by the fact that it has a lower density. The same law is also valid for explaining why ice does not sink in water, but sinks in gasoline and kerosene. It's just that these two substances have a lower density than ice. So, if you launch an inflatable ball into the pool, it will float on the surface, but if you throw a stone into the water, it will sink to the bottom.

What changes occur to water when it freezes

The reason ice doesn't sink in water is due to hydrogen bonds that change when the water freezes. As you know, water consists of one oxygen atom and two hydrogen atoms. They are attached by covalent bonds that are incredibly strong. However, another type of bond that forms between different molecules, called hydrogen bonds, is weaker. These bonds are formed because positively charged hydrogen atoms are attracted by negatively charged oxygen atoms from neighboring water molecules.

When water is warm, the molecules are very active, move a lot, quickly form and decompose bonds with other water molecules. They have the energy to get close to each other and move quickly. So why doesn't ice sink in water? Chemistry hides the answer.

Physicochemistry of ice

As the temperature of the water drops below 4 ° C, the kinetic energy of the liquid decreases, so the molecules no longer move. They do not have the energy to move and they do not have the same ease as at high temperatures to break and form bonds. Instead, they form more hydrogen bonds with other water molecules to form hexagonal lattice structures.

They form these structures in order to keep the negatively charged oxygen molecules apart from each other. There is a lot of emptiness in the middle of the hexagons formed by the activity of molecules.

Ice sinks in water - reasons

Ice is actually 9% less dense than liquid water. Therefore, ice takes up more space than water. In practice, this makes sense because the ice is expanding. This is why it is not recommended to freeze a glass bottle of water - frozen water can create large cracks even in concrete. If you have a liter bottle of ice and a liter bottle of water, then a bottle of ice water will be lighter. The molecules are farther apart at this point than when the substance is in a liquid state. This is why ice does not sink in water.

When the ice melts, the stable crystal structure breaks down and becomes denser. When the water warms up to 4 ° C, it receives energy and the molecules move faster and further. It is for this reason that hot water takes up more space than cold water and floats on top of cold water - it is less dense. Remember, when you are on the lake, when swimming, the upper layer of water is always pleasant and warm, but when you lower your feet deeper, you feel the coldness of the lower layer.

The importance of the freezing of water in the functioning of the planet

Despite the fact that the question "Why doesn't ice sink in water?" for grade 3, it is very important to understand why this process occurs and what is important for the planet. Thus, the buoyancy of ice has important consequences for life on Earth. Lakes freeze in cold places in winter - this allows fish and other aquatic animals to survive under the ice blanket. If the bottom froze, then there is a high probability that the entire lake could be frozen.

In such conditions, not a single organism would have survived.

If the density of the ice was higher than the density of water, then the ice in the oceans would sink, and the ice caps, which in this case would be at the bottom, would not allow anyone to live there. The ocean floor would be full of ice - and what would it all be? Among other things, polar ice is important because it reflects light and protects planet Earth from overheating.