懂你英语Level3unit2精编版..docVIP

???????????????????????必威体育精装版 料推荐??????????????????? Level 3 unit 1 part1 Listening Matter is made of atoms and molecules. Water, for example, is the H2O molecule. This means that a molecule of water has 3 atoms. A water molecule has 2 hydrogen atoms and one oxygen atom. Substances like sugar have many atoms in their molecules. A molecule of sugar has many atoms, including carbine, hydrogen and oxygen. -What is H2O? The water molecule. -What is matter made of? - Atoms and molecules Matter is made of molecules such as the H2O which is the water molecule. Matter can be in one of 3 states, solid, liquid or gas. Water and ice are the same substance, but they are in different states. These states depend on the temperature of the molecules. When we heat a substance, the molecules move faster and try to take up more space. When we cool a substance, the molecules move more slowly. When we cool a substance to its freezing point, it becomes a solid. -How many states of matter are there? - Three. - -What happens when we heat a substance? the molecules move faster and try to take up more space. -What happens if we cool a liquid to its freezing point? It becomes a solid. 1 ???????????????????????必威体育精装版 料推荐??????????????????? In a solid, the molecules move very little. Their positions are almost fixed. To be fixed means that their positions dont change. If we heat the molecules, they move faster and away from each other. The solid begins to melt, like ice cream on a hot day. -How can we change a solid into a liquid? heat it up. -How can we change a liquid into a solid? cool it down. - At a certain temperature, a solid begins to change into a liquid. The temperature at which a solid changes into a liquid depends on the substances. For water, the solid begins to change into a liquid when its temperature rises to above 0 degrees Celsius. For some substances, such as steel, the temperature at which it becomes a liquid is much higher. Steel often melts at around 1370 degrees Celsius. -At what