Physical Properties of Water Boiling Point, Melting Point and Freezing Point

TEKS 5.7D

5.5 The student knows that matter has physical properties and those properties determine how matter is classified, changed, and used. The students is expected to:

5.5B identify the boiling and freezing/melting points of water on the Celsius scale.

Physical Properties of Water

Boiling Point, Melting Point and Freezing Point

Boiling point is the temperature at which something becomes a gas.

Water has a boiling point of 100° C.This means that at 100° C, water changes from a liquid to a gas.

Melting point is the temperature at which something becomes a liquid.

Water has a melting point of 0° C.This means that at 0° C, water changes from a solid to a liquid.

Melting Point or Freezing Point?The melting point of ice and the freezing point of water are at exactly the same temperature.

The melting point is when solid is changing to liquid. (ice to water)

The freezing point is when liquid is changing to solid. (water to ice)

Which of the following is the temperature at which ice melts?

A. 0o Kelvin

B. 0o Fahrenheit

C. 0o Celsius

D. 0o Gram

Which of the following is the temperature at which ice melts?C. 0o CelsiusCorrect - The Celsius scale uses 0o as the

melting point.

D. 0 Gram Incorrect Gram (g) is the measurement unit used to represent mass – not temperature.

B. 0o Fahrenheit Incorrect Fahrenheit is the measurement unit that is traditional in the U. S. The temperature would have to be 32o F for ice to melt.

A. 0 Kelvin IncorrectKelvin is the measurement unit that includes absolute zero. The temperature would have to be 274 K for ice to melt.

If you are camping at sea level and want to boil water so it will be safe to drink, what temperature will it need to reach?

A. 15 K

B. 100o C

C. 100o FD. 150 g

If you are camping at sea level and want to boil water so it will be safe to drink, what temperature will it need to reach?

A. 15 K IncorrectKelvin is the measurement unit that includes absolute zero. The temperature would have to be 373o K for water to boil.

C. 100o F IncorrectFahrenheit is the measurement unit that is traditional in the U. S. The temperature would have to be 212o F for water to boil.D. 150 g IncorrectA gram is the measurement unit for mass – not temperature.

B. 100o C CorrectThe Celsius scale uses 100o as the boiling point for water.

Four students were working together in a lab group. They had to predict the temperature at which water would boil. They recorded their predictions in the table below.

Student Prediction o C

1 752 903 1004 125

Which student’s prediction was the

closest to the boiling point of water?

A. Student 1B. Student 2C. Student 3D. Student 4

Student Prediction o C

1 75

2 90

3 100

4 125

Which student’s prediction was the closest to the boiling point of water?

C. Student 3 Correct

100o C is the boiling point of water.

Student Prediction o C

1 75

2 90

3 100

4 125

A. Student 1 IncorrectB. Student 2 IncorrectD. Student 4 Incorrect

None of these are the boiling point of water on the Celsius scale.

Students were doing a lab to find the melting point of ice. Which thermometer would show the temperature in o Celsius at which ice would begin to melt?

A. Thermometer 1 C.

Thermometer 3

B. Thermometer 2 D.

Thermometer 4

1 2 3 4

Students were doing a lab to find the melting point of ice. Which thermometer would show the temperature in o Celsius at which ice would begin to melt?

C correct - because ice melts above 0o C and the question asks at what temperature ice would begin to melt.

1 2 3 4

100° 50 ° 0 ° -5 °

Three students were discussing what they understood about boiling, freezing and melting point of water.

- Sarah thought that the boiling, freezing, and melting point depended on how much water was in the container.

- Bill thought that the boiling, freezing, and melting point of water were all the same - 100°C.

- Carol thought that the freezing and melting point of water were both the same but the boiling point of water was 100°C.

Who do you agree with and why?

Three students were discussing what they understood about boiling, freezing and melting point of water. Carol is correct. The freezing and melting point of

water are both the same and 0°, but the boiling point of water was 100°C.

Sarah and Bill are incorrect.Sarah - Because boiling, freezing, and melting points are physical properties, they do not change just because there is more or less water.

Bill - the boiling point is 100°C, but freezing and melting are much lower at 0°.

A student drew this illustration in their journal. Discuss all of the information about the boiling point, freezing and melting point of water that is shown in this drawing.

• Boiling point is 100°

• Freezing and melting point is 0°

• Freezing and melting point is the same.

• Water goes from melting/freezing to liquid and then solid when heat is added.

• Water goes from gas to liquid and then solid when heat is removed (cooling happens)

• Boiling point changes liquid water to a gas

• Melting point changes solid water to a liquid

• Freezing point changes liquid water to a solid