L3-U2-P1-3 Listening : States of Matter

States of Matter

Matter is made of atoms and molecules.

Water, for example, is the H2O molecule.

This means that a molecule of water have 3 atoms.

A water molecule has two 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.

What is H2O? - It's the water molecule.
Matter is made of atoms and molecules.

Matter is made of molecules, such as H2O, which is the water molecule.

Matter can be 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.

How many states of matter are there? -There are three states of matter.

What happens if we cool a substance to its freezing point? -When we cool a substance to its freezing point, it becomes a solid.

Water and ice are the same substance,but they are in different states.

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.

In which state are the molecules almost fixed? - In a solid, the molecules move very little.
The solid begins to melt, like ice cream on a hot day.
Matter is made of atoms and molecules.
Their positions are almost fixed.
To change a soild into a liquid, add heat.
A molecule of sugar has many atoms, including carbon, hydrogen and oxygen.
Water and ice are the same substance, but they are in different states.

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 about 0 degree 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.

What does the melting temperature depend on? -The temperature at which a solid changes into a liquid depends on the substance.
At a certain temperature, a solid begins to change into a liquid.

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.

What happens if we continue to heat a liquid? - If we continue to heat a liquid, the molecules move even faster.
If we continue to heat a liquid, the molecules move even faster.

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.

What is the temperature inside a star? - Inside a star, such as our Sun, the temperature is very high.
According to scientists, there are over 65 elements inside the Sun.
That is the boiling point of water.
Over 90 percent of the Sun is hydrogen gas.
For some substances, such as steel, the temperature at which it becomes a liquid is much higher.
For water, the liquid begins to change into a gas at 100 degrees Celsius.

substance和matter表示“物质”时的区别在于，matter是不可数名词，指构版成物体的材料的总称，而substance是可数名词，指具体的某种混合物或纯净物，权包括单质和化合物。