Three aggregate states of substances are distinguished: liquid, water and gas. All of them differ in their properties. A special place in this list is occupied by liquids. Unlike solids, molecules are not arranged orderly in liquids. A liquid is a special state of a substance that is intermediate between a gas and a solid. Substances in this form can exist only with strict observance of intervals of certain temperatures. Below this interval, the liquid body will turn into a solid, and above - into a gaseous one. In this case, the boundaries of the interval directly depend on the pressure.
Water
One of the main examples of a liquid body is water. Despite belonging to this category, water can take the form of a solid or gas - depending on the ambient temperature. In the process of transition from a liquid to a solid state, molecules of ordinary matter are compressed. But water behaves completely differently. When freezing, its density decreases, and instead of drowning, ice floats to the surface. Water in its usual fluid state has all the properties of a liquid - it always has a specific volume, however, there is no definite form.
Therefore, water always retains heat under the surface of the ice. Even if the ambient temperature is -50 ° C, then under the ice it will still be about zero. However, in elementary school you can not go into details about the properties of water or other substances. In Grade 3, the simplest examples of liquid bodies can be given - and it is desirable to include water in this list. After all, an elementary school student must have general ideas about the properties of the world around him. At this stage, it is enough to know that water in its usual state is a liquid.
Surface tension - a property of water
Water has a greater surface tension than other liquids. Due to this property, raindrops are formed, and, therefore, the water cycle in nature is maintained. Otherwise, water vapor could not so easily turn into drops and spill onto the earth's surface in the form of rain. Water, indeed, is an example of a liquid body, on which the possibility of the existence of living organisms on our planet directly depends.
The surface tension is explained by the fact that the liquid molecules are attracted to each other. Each of the particles seeks to surround itself with others and leave the surface of the liquid body. That is why soap bubbles and bubbles formed during boiling water tend to take a liquid form - in this case, only a ball can have a minimum surface thickness.
Liquid metals
However, not only the substances that are familiar to humans, with which they deal in everyday life, belong to the class of liquid bodies. Among this category are many different elements of the periodic table. An example of a liquid body is also mercury. This substance is widely used in the manufacture of electrical devices, metallurgy, and the chemical industry.
Mercury is a liquid, shiny metal that evaporates even at room temperature. It is able to dissolve silver, gold and zinc, while forming amalgams. Mercury is an example of what kind of liquid bodies are classified as dangerous to human life. Her fumes are toxic, hazardous to health. The damaging effect of mercury is manifested, as a rule, some time after the contact of poisoning.
A metal called cesium also refers to liquids. Already at room temperature it is in semi-liquid form. Cesium in appearance is a substance of a golden white hue. This metal is a bit like gold in color, however, it is lighter than it.
Sulfuric acid
Almost all inorganic acids are also an example of what liquid bodies are. For example, sulfuric acid, which in appearance is a heavy oily liquid. She has neither color nor smell. When heated, it becomes a very strong oxidizing agent. In the cold, it does not interact with metals - for example, iron and aluminum. This substance shows its characteristics only in pure form. Diluted sulfuric acid does not exhibit oxidizing properties.
The properties
What liquid bodies exist besides those listed? These are blood, oil, milk, mineral oil, alcohol. Their properties allow these substances to easily take the form of containers. Like other liquids, these substances do not lose their volume if they are transferred from one vessel to another. What other properties are inherent in each of the substances in this state? Liquid bodies and their properties are well studied by physicists. Consider their main characteristics.
Fluidity
One of the most important characteristics of any body in this category is fluidity. This term refers to the ability of the body to take a different shape, even if it does not have a relatively weak effect from the outside. It is thanks to this property that each liquid can be poured in jets, sprayed on the surrounding surface with drops. If the bodies of this category were not fluid, it would be impossible to pour water from a bottle into a glass.
Moreover, this property is expressed in different substances to varying degrees. For example, honey changes shape very slowly compared to water. This characteristic is called viscosity. This property depends on the internal structure of the liquid body. For example, honey molecules are more like tree branches, and water molecules are more like balls with small bulges. When a liquid moves, honey particles seem to “cling to each other” - it is this process that gives it a higher viscosity than other types of liquids.
Saving Form
It must be remembered that no matter what example of liquid bodies we are talking about, they only change shape, but do not change volume. If you pour water into a beaker, and transfer it to another container, this characteristic will not change, although the body itself will take the form of a new vessel into which it has just been transferred. The property of conservation of volume is explained by the fact that both the forces of mutual attraction and the repulsive forces act between the molecules. It should be noted that liquids are almost impossible to compress through external influences due to the fact that they always take the form of a container.
Liquid and solid bodies differ in that the latter do not obey Pascal's law. Recall that this rule describes the behavior of all liquids and gases, and consists in their ability to transmit pressure exerted on them in all directions. However, it should be noted that those liquids that have a lower viscosity do this faster than more viscous liquid bodies. For example, if you put pressure on water or alcohol, then it will spread quite quickly.
Unlike these substances, the pressure on the honey or liquid oil will spread more slowly, however, also uniformly. In Grade 3, examples of liquid bodies can be given without indicating their properties. Pupils will need more detailed knowledge in high school. However, if the student prepares additional material, this may contribute to a higher grade in the lesson.