Lesson 3 Part 1
All substances are made up of tiny particles called atoms. For example, water is made up of oxygen atoms and hydrogen atoms. When one oxygen atom and two hydrogen atoms are bonded, they form a water molecule (H2O).
Molecules of water are always moving. When water is heated, its molecules move faster. When the water is hot enough to boil, the water molecules separate from each other and go into the air to become a gas called water vapor.
On the other hand, when water is cooled to near zero degrees Celsius, water molecules can hardly move. Then it freezes and becomes ice.
Molecules of water are always moving. When water is heated, its molecules move faster. When the water is hot enough to boil, the water molecules separate from each other and go into the air to become a gas called water vapor.
On the other hand, when water is cooled to near zero degrees Celsius, water molecules can hardly move. Then it freezes and becomes ice.
Lesson 3 Part 1-1
All substances are made up of tiny particles called atoms.
Lesson 3 Part 1-2
For example, water is made up of oxygen atoms and hydrogen atoms.
Lesson 3 Part 1-3
When one oxygen atom and two hydrogen atoms are bonded, they form a water molecule (H2O).
Lesson 3 Part 1-4
Molecules of water are always moving.
Lesson 3 Part 1-5
When water is heated, its molecules move faster.
Lesson 3 Part 1-6
When the water is hot enough to boil, the water molecules separate from each other and go into the air to become a gas called water vapor.
Lesson 3 Part 1-7
On the other hand, when water is cooled to near zero degrees Celsius, water molecules can hardly move.
Lesson 3 Part 1-8
Then it freezes and becomes ice.
Lesson 3 Part 2
When a solid substance changes into liquid at a certain temperature, the temperature is called the melting point of the substance. In the same way, the temperature at which a liquid substance changes into a gas is called the boiling point.
We have a lot of examples in our daily life.
If the boiling point of a substance is lower than room temperature, you will see the substance as a gas. If a substance you see is a solid, its melting point must be higher than room temperature.
Therefore, when you compare the boiling points and melting points of a solid, a liquid and a gas that exist at room temperature, the solid has the highest boiling point and the gas has the lowest melting point.
We have a lot of examples in our daily life.
If the boiling point of a substance is lower than room temperature, you will see the substance as a gas. If a substance you see is a solid, its melting point must be higher than room temperature.
Therefore, when you compare the boiling points and melting points of a solid, a liquid and a gas that exist at room temperature, the solid has the highest boiling point and the gas has the lowest melting point.
Lesson 3 Part 2-1
When a solid substance changes into liquid at a certain temperature.
Lesson 3 Part 2-2
The temperature is called the melting point of the substance.
Lesson 3 Part 2-3
In the same way, the temperature at which a liquid substance changes into a gas is called the boiling point.
Lesson 3 Part 2-4
We have a lot of examples in our daily life.
Lesson 3 Part 2-5
If the boiling point of a substance is lower than room temperature.
Lesson 3 Part 2-6
You will see the substance as a gas.
Lesson 3 Part 2-7
If a substance you see is a solid.
Lesson 3 Part 2-8
Its melting point must be higher than room temperature.
Lesson 3 Part 2-9
Therefore, when you compare the boiling points and melting points of a solid, a liquid and a gas that exist at room temperature.
Lesson 3 Part 2-10
The solid has the highest boiling point and the gas has the lowest melting point.
Lesson 3 Part 3
When a liquid substance changes into a gas, its volume increases. The mass, however, will not change. For example, when you leave 1 gram of dry ice (solid carbon dioxide) at room temperature, it changes into 0.5 liters of gaseous carbon dioxide. It is about 800 times the volume of the dry ice, but the whole mass of the carbon dioxide is still 1 gram.
The mass of a substance is constant regardless of its state because the number of particles in it will not change. But the volume of a substance changes according to the temperature because it depends on how fast the particles move. The faster the particles move, the larger the volume of the substance is.
The mass of a substance is constant regardless of its state because the number of particles in it will not change. But the volume of a substance changes according to the temperature because it depends on how fast the particles move. The faster the particles move, the larger the volume of the substance is.
Lesson 3 Part 3-1
When a liquid substance changes into a gas, its volume increases.
Lesson 3 Part 3-2
The mass, however, will not change.
Lesson 3 Part 3-3
For example, when you leave 1 gram of dry ice (solid carbon dioxide) at room temperature.
Lesson 3 Part 3-4
It changes into 0.5 liters of gaseous carbon dioxide.
Lesson 3 Part 3-5
It is about 800 times the volume of the dry ice.
Lesson 3 Part 3-6
But the whole mass of the carbon dioxide is still 1 gram.
Lesson 3 Part 3-7
The mass of a substance is constant regardless of its state.
Lesson 3 Part 3-8
Because the number of particles in it will not change.
Lesson 3 Part 3-9
But the volume of a substance changes according to the temperature.
Lesson 3 Part 3-10
Because it depends on how fast the particles move.
Lesson 3 Part 3-11
The faster the particles move, the larger the volume of the substance is.