Melting, Freezing and Boiling Points of Liquids

Grade Level: 8th; Type: Physical Science

Objective:

This project compares different liquids and determines differences in freezing, melting and boiling points.

Research Questions:

• Which liquids freeze at the highest and lowest temperatures?
• Which liquids don’t freeze in a conventional household freezer?
• Which liquids melt at the lowest and highest temperatures?
• Which liquids boil at the lowest and highest temperatures?
• Are the liquids that freeze, melt and boil at the lowest and highest temperatures the same?
• What properties affect these differing temperatures?

We are surrounded by all types of liquids: water, oils, vinegar, soda, juice. All of these liquids look, smell and feel different. How do these liquids differ in terms of boiling, freezing and melting points? What is it about them that does this?

Materials:

• As many different liquids as you can find. Suggestions: water, juice, soda, different types of oil (canola, corn, coconut, olive), wax, vinegar, chocolate, etc.
• A cooking or candy thermometer
• A small pot to use on the stove
• A freezer
• An adult to supervise
• Notebook and pencil to record observations

Experimental Procedure:

1. Note observations of each item at room temperature. Is it liquid or solid?
2. Determine the freezing point if it is a liquid by placing it in the freezer with a thermometer inside. Check it every 10 minutes to see if it has solidified, and note the temperature when it has.
3. Measure the melting temperature for each of the frozen items. For those that are solid at room temperature, slowly heat in a double-boiler (a bowl inside of a pot with water at the bottom will work: be sure to have the thermometer ready to measure the temperature when it becomes a liquid). Determine the melting point of each item.
4. Heat each liquid in the pot until it just starts boiling. Measure the temperature with the thermometer.
5. Record all results and make a chart comparing each liquid. Note which liquids have the highest and lowest points overall for freezing, melting and boiling.
6. Note whether the lowest and highest points are the same items for freezing, melting and boiling.

Terms/Concepts: physical state, room temperature, melting point, boiling point, freezing point, liquid, solid