The italicized font represents information to be shared orally or physically completed with the students at this time.

The non-italicized font represents additional information included supporting the teacher’s understanding of the content being introduced within the CELL.

ASK WHY

Remind students that heat, thermal energy, and temperature greatly influence the way we live. We monitor our body temperature, dress for the hot and cold, build homes, schools, and cars with heating and cooling systems, and passionately search for alternative fuels as the threat of global warming takes hold. To live safely and productively, it is important to understand the thermal behaviors that govern our bodies and the world. 

BRANCH OUT

Remind students that environmental engineers design the structure and irrigation for rooftop gardens, helping reduce building heating and cooling costs. They also help refineries reduce their toxic gas emissions, which contribute to acid rain and global warming.

GET FOCUSED

Inform students that the Investigation is designed to help them to answer the following Focus Questions:

• How do changes in thermal energy relate to the freezing and boiling point of water? The boiling point of water represents the transfer of enough thermal energy to increase the kinetic energy of molecules and break the bonds of molecules so that water changes from a liquid to a gas. The freezing point of water represents the transfer of thermal energy such that the kinetic energy of molecules and the formation of bonds between molecules results in the change of liquid water to solid ice.

• How does the addition of a solute change the freezing and boiling point of water? Adding a solute to water decreases the freezing point of water and increasing its boiling point.

Note: These questions are located in students’ SDRs at the beginning and end of the Investigation.

Note: These are succinct responses to the Focus Questions and are placed here for your reference at this time. Fully developed responses to the Focus Questions can be found on the PostLab page.

GO DEEPER

As a class, read the Background(s) in the Investigation. Have students read the information aloud or silently to themselves. When students have finished, discuss the following concepts as a class:

• Heat is transferred from areas of higher kinetic energy (higher temperature) to areas of lower kinetic energy (lower temperature).
• A thermometer works off the premise of heat transfer between the liquid in the thermometer and the surrounding substance.
• Increases in the kinetic energy of the liquid molecules in a thermometer cause the liquid to expand and move up the glass column of the thermometer.
• The boiling point of water (at sea level) is 100^oC.
• As a liquid gains kinetic energy, the bonds between molecules weaken, and the liquid turns to a gas (vaporization).
• Boiling point elevation is the term used to describe the increase in the boiling point when solutes are added to a liquid, such as water.
• Decreases in the kinetic energy of the liquid molecules in a thermometer cause the liquid to contract and move down the glass column of the thermometer.
• The freezing point of water is 0^oC.
• As a liquid loses kinetic energy, the bonds between molecules strengthen, and the liquid turns into a solid (freezing).
• Freezing point depression is the term used to describe the lowering of the freezing point when solutes are added to a liquid, such as water.

Note: These concepts are integrated into the Background(s) and are used to deepen students’ comprehension of the big ideas.

LEARN THE LabLearner LINGO

The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

• freezing point depression
• boiling point elevation
• rate

Note: Definitions to these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.

SET FOR SUCCESS

• Assess the background knowledge of the students by asking them to complete the prediction questions in their SDRs.

Note: Students will formulate answers to these questions after they have completed the Investigation.

• Review the Celsius scale on the thermometer.
  • Focus students’ attention on the 0^oC mark.
  • Direct students’ attention to the graduations BELOW the 0^oC mark.
  • Explain that these graduations represent temperature below 0^oC.
  • Numerically these temperatures are represented with a negative sign (-) in front of them. For example, the line corresponding to the number 5 below 0^oC is read as “-5^oC “ or “negative five degrees Celsius. Another way of referring to this temperature is 5 degrees Celsius below 0.

Note: Students will need the knowledge of reading negative temperatures for Trial 1.

• Play the video below. Stop to ask students questions or answer students’ questions when necessary. Remind students to follow along with their SDRs and make any notes that they think might be helpful.
• After the video, direct students to divide into their lab groups to discuss their strategy for the lab. For example, they may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow students to anticipate the laboratory experience they will soon encounter. Students should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.

HOMEWORK

Tell students that they should review the Investigation in preparation for the Lab.