Introductory Activity :

Duration: 45 minutes

Description: Students conduct an experiment to investigate how temperature affects the evaporation rate of water.

Goals:

1. Students will understand the processes that shape the Earth, which include the water cycle and the role of evaporation in this process.
2. Students will understand that the weight of an object is equal to the sum of the weights of its parts.
3. Students will utilize appropriate tools and materials to collect data accurately.

Body :

(Depending on availability of materials, students may work individually or in small groups.)

Prior to the lesson, cut four 10 square cm pieces of paper towel for each student (or group). For the activity, each student will need four pieces of paper towel, two Petri dishes, two plastic bags, a graduated cylinder, access to a balance scale, and graph paper.

Students should begin by folding each piece of paper towel in half, twice. Then, one piece of paper towel will be placed in each Petri dish and plastic bag. Next, students pour 10 ml of water into each paper towel. The plastic bags should now be sealed. Students will measure the mass of each wet paper towel with the container it is in and record on their data sheet (see Materials ). Next, students place one bag and one Petri dish under a heat lamp (or outside in sunny area). The remaining bag and Petri dish should be placed on a table away from the heat lamp or sun. After 15 minutes have passed, the mass of each item should be measured again and recorded on the data sheet.

(During the waiting period, students can begin construction of their bar graphs. Students will construct a double bar graph for their data--one bar for "before evaporation" and the other for the "after evaporation" data for each of the bags and Petri dishes.) After the post-evaporation data has been collected, students may complete their bar graphs.

Discuss the following:

1. Which paper towels evaporated the fastest? How do you know?
2. What effect does heat or sun energy have on evaporation?
3. What happened to the paper towel inside the bags? What, if any, changes did you see in the plastic bags?

Conclusion Activity :

Special Comments: It is important to remind students to measure accurately. Experience with volumetric measurement and the use of balance scales is recommended for students prior to conducting this lesson.

Vocabulary Words :

• Conservation of Matter - A law of science which states matter is neither created nor destroyed, but changes into something else.
  
• Evaporation - The process of water turning from a liquid into a vapor or gas.
  
• Hydrologic Cycle - Also known as the water cycle. The process by which water is cycled through the environment. This includes evaporation, condensation, transpiration, and precipitation.
  
• Mass - The measure of the amount of matter in a body.
  

Evaluation Activity :

Collect students' data sheets and bar graphs to check for accuracy and completeness.

Internet Resources Referenced in this Lesson :

Southwest Florida Water Management District
The Watercourse and the Council for Environmental Education, Project WET Curriculum and Activity Guide
Data Sheets (note that there are 5 data sheets on the page)