Matter is made of atoms and molecules.
Water, for example, is the H2O molecule.
This means that the molecule of water has 3 atoms.
A water molecule has 2 Hydrogen atoms and 1 oxygen atom.
Substances like sugar have many atoms in their molecules.
A molecule of sugar has many atoms including carbon, hydrogen and oxygen.
Matter is made of molecules such as H20, 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.
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.
To change a solid into a liquid, add heat.
At a certain temperature, a solid begins to change into a liquid.
The temperature at which a solid change into a liquid depends on the substance.
For water, the solid begins to change into a liquid when its temperature rises to above 0 degree Celsius.
For some substances, such as steel, the temperature which it becomes a liquid is much higher.
Steel often melts at around 1370℃.
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.
Inside a start, 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% of the Sun is hydrogen gas.
