Emma and Jack are two high school students who are curious about the states of matter. They decide to do some experiments with different substances and temperatures to learn more about this topic.
They start by collecting some samples of common substances, such as ice, water, steam, butter, oil, wax, and iron. They use a thermometer to measure the temperature of each substance in degrees Celsius, and a scale to measure the mass in grams. They also observe the shape and volume of each substance and record their results in a table:
| Substance | State | Temperature (°C) | Mass (g) | Shape | Volume |
|-----------|-------|-------------------|----------|-------|--------|
| Ice | Solid | 0 | 100 | Fixed | Fixed |
| Water | Liquid | 20 | 100 | Variable | Fixed |
| Steam | Gas | 100 | 100 | Variable | Variable |
| Butter | Solid | 10 | 50 | Fixed | Fixed |
| Oil | Liquid | 20 | 50 | Variable | Fixed |
| Wax | Solid | 25 | 20 | Fixed | Fixed |
| Iron | Solid | 25 | 20 | Fixed | Fixed |
They notice that solids have a fixed shape and volume, liquids have a variable shape but a fixed volume, and gases have a variable shape and volume. They also notice that the mass of each substance does not change, regardless of its state. They wonder what would happen if they changed the temperature of each substance. They use a stove and a freezer to heat and cool each substance and observe what happens.
They see that some substances change their state when they reach a certain temperature. For example, ice melts into water at 0°C, water boils into steam at 100°C, butter melts into oil at 35°C, and wax melts into liquid at 60°C. They also see that some substances do not change their state easily, such as iron, which remains solid even at high temperatures. They measure the temperature and mass of each substance after the change and record their results in another table:
| Substance | State | Temperature (°C) | Mass (g) |
|-----------|-------|-------------------|----------|
| Ice | Liquid | 0 | 100 |
| Water | Gas | 100 | 100 |
| Steam | Liquid | 100 | 100 |
| Butter | Liquid | 35 | 50 |
| Oil | Solid | -10 | 50 |
| Wax | Liquid | 60 | 20 |
| Iron | Solid | 200 | 20 |
They compare the two tables and realize that the mass of each substance is conserved, even when the state changes. They also notice that the temperature of each substance remains constant during the change, until the change is complete. They learn that the temperature at which a solid changes into a liquid is called the melting point, and the temperature at which a liquid changes into a gas is called the boiling point. They also learn that the reverse processes are called freezing and condensation, respectively.
Emma and Jack are satisfied with their experiments and feel that they have learned a lot about the states of matter. They decide to write some questions and answers based on their observations to test their knowledge. Here are some examples:
Q: What are the three common states of matter?
A: Solid, liquid, and gas.
Q: What are the characteristics of each state of matter?
A: Solids have a fixed shape and volume, liquids have a variable shape but a fixed volume, and gases have a variable shape and volume.
Q: What is the term for the amount of matter in an object or substance?
A: Mass.
Q: What happens to the mass of a substance when it changes its state?
A: The mass of a substance does not change when it changes its state.
Q: What is the term for the degree of hotness or coldness of an object or substance?
A: Temperature.
Q: What happens to the temperature of a substance when it changes its state?
A: The temperature of a substance remains constant when it changes its state, until the change is complete.
Q: What is the term for the change of state from solid to liquid?
A: Melting.
Q: What is the term for the change of state from liquid to gas?
A: Boiling.
Q: What is the term for the change of state from gas to liquid?
A: Condensation.
Q: What is the term for the change of state from liquid to solid?
A: Freezing.
Q: What is the term for the temperature at which a solid changes into a liquid?
A: Melting point.
Q: What is the term for the temperature at which a liquid changes into a gas?
A: Boiling point.