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 carbon, hydrogen and oxygen.
物质由原子和分子组成。
水，例如H2O分子。
这意味着水分子有3个原子。
水分子有两个氢原子和一个氧原子。
像糖这样的物质分子中有许多原子。
糖分子有许多原子，包括碳、氢和氧。
Matter is made of molecules, such as H2O, which is the water molecule.
Matter can be in one of three 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.
物质是由分子组成的，比如水分子H2O。
物质有三种状态:固态、液态或气态。
水和冰是同一种物质，但它们处于不同的状态。
这些状态取决于分子的温度。
当我们加热一种物质时，分子运动得更快，并试图占据更多的空间。
当我们冷却一种物质时，分子运动得更慢。
当我们把一种物质冷却到它的冰点时，它就变成了固体。
In a solid, the molecules move very little.
Their positions are almost fixed.
To be fixed means that their positions don't 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.
在固体中，分子很少运动。
他们的位置几乎是固定的。
固定意味着他们的位置不变。
如果我们加热分子，它们就会运动得更快，远离彼此。
固体开始融化，就像在炎热的日子里吃冰淇淋一样。
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 substance.
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.
在一定的温度下，固体开始变成液体。
固体变成液体的温度取决于这种物质。
对于水，当它的温度上升到0摄氏度以上时，固体开始变成液体。
对于某些物质，如钢，它变成液体的温度要高得多。
钢通常在1370摄氏度左右熔化。
If we continue to heat a liquid, the molecules move even faster.
At a certain temperature, the liquid begins to change into a gas.
For water, the liquid begins to change into a gas at 100 degrees Celsius.
That is the boiling point of water.
如果我们继续加热液体，分子运动得更快。
在一定的温度下，液体开始变成气体。
对于水，液体在100摄氏度时开始变成气体。
这是水的沸点.
Inside a star, such as our Sun, the temperature is very high.
Everything inside the Sun is a gas.
According to scientists, there are over 65 elements inside the Sun.
These include oxygen and iron.
Over 90 percent of the Sun is hydrogen gas.
在恒星内部，比如我们的太阳，温度非常高。
太阳内部的一切都是气体。
据科学家说，太阳内部有超过65种元素。
其中包括氧气和铁。
太阳的90%以上是氢气。
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