States of Matter
Matter is made of atoms([物] 原子) and molecules([化学] 分子).
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.
Exercise:
1. — What is H2O?
— It's the water molecule.
2. 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.
Exercise:
1. — How many states of matter are there?
— There are three states of matter.
2.— What happens if we cool a substance to its freezing point?
— When we cool a substance to its freezing point, it becomes a solid.
3. 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.
Exercise:
1.— In which state are the molecules almost fixed?
— In a solid, the molecules move very little.
2. The solid begins to melt, like ice cream on a hot day.
Repeat & Read Sentences:
1. Matter is made of atoms and molecules.
2. Their positions are almost fixed.
3. To change a soild into a liquid, add heat.
4. A molecule of sugar has many atoms, including carbon, hydrogen and oxygen.
5. 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.
Exercise:
1.— What does the melting temperature depend on?
— The temperature at which a solid changes into a liquid depends on the substance.
2. 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.
Exercise:
1.— What happens if we continue to heat a liquid?
— If we continue to heat a liquid, the molecules move even faster.
2. 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.
Exercise:
1. — What is the temperature inside a star?
— Inside a star, such as our Sun, the temperature is very high.
2. According to scientists, there are over 65 elements inside the Sun.
Repeat & Read Sentences:
1. That is the boiling point of water.
2. Over 90 percent of the Sun is hydrogen gas.
3. For some substances, such as steel, the temperature at which it becomes a liquid is much higher.
4. For water, the liquid begins to change into a gas at 100 degrees Celsius.
Test Results
Yesterday there was an important science test.
Lisa, Tom and 20 other classmates took the test.
The test was about the states of matter and how they are different.
There were 25 questions on the test, and they had 45 minutes to take it.
Exercise:
1.— What happened yesterday?
— There was an important science test.
2.— How long did they have to take the test?
— They had 45 minutes to take the test.
3. The test was about the states of matter and how they are different.
Here are some of the test results.
Two students got perfect scores.
The lowest score was 68 out of a hundred.
The average score was 86.3.
Eleven students scored higher than average.
Eleven students had below average scores.
Exercise:
1.— What was the average score?
— The average score was 86.3.
2. — How many students got perfect scores?
— Two students got perfect scores.
3. Eleven students scored higher than average.
Repeat & Read Sentences:
1. Two students got perfect scores.
2. The lowest score was 68 out of a hundred.
3. The test was about the states of matter.
4. There were 25 questions on the test, and they had 45 minutes to take it.
5. The test was about the states of matter and how they are different.
Tom missed two questions on the test, so his score was 92.
His score was the eighth highest in the class.
Lisa missed two and a half questions, so her score was 90.
Her score was the tenth highest score.
Her score was 4 points higher than the average score.
Exercise:
1. — How many questions did Tom miss?
— Tom missed two questionson the test, so his score was 92.
2. — How many students scored higher than Tom?
— Seven students scored higher than Tom did.
Lisa was disappointed with her test results.
She studied hard for the test, but she still didn’t do well.
As a result, she plans to study harder for the next test.
The next test will be in about two weeks.
Exercise:
1. — When is the next test going to be?
— The next test will be in about two weeks.
2. — How did Lisa feel about her test results?
— Lisa was disappointed with her test results.
3. She studied hard for the test, but she still didn’t do well.
Tom was surprised and happy with his test results.
He didn’t study hard, so his result was better than he expected.
He was also happy that he did better than Lisa did.
Exercise:
1. Tom was surprised and happy with his test results.
Repeat & Read Sentences:
1. Lisa was disappointed with her test results.
2. The next test will be in about two weeks.
3. Her score was 4 points higher than the average score.
4. Lisa missed two and a half questions, so her score was 90.
5. She studied hard for the test, but she still didn’t do well.
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