Grade level(s):Elementary School (K-5), Grade 4, Grade 5
Subjects(s):FOSS-Related, Physical Science, Science Skills
Topic:Differential Heating of the Earth
Water is a heat sink, specifically, it heats up more slowly than soil, but conversely cools down more slowly.
Before: procedure, thermometer, syringe, data table, increase, decrease, dependent variable, independent variable
During and After: earth material, solar energy, energy transfer, heat sink, uneven
What you need:
For pair of students: see materials list on page 159 of FOSS: Water Planet
1 piece of cardboard
2 containers 1/4 liter
2 lids for containers with slits for thermometers
2 numbered thermometers
1 post it
For the class:
1 Bag of potting soil
4 containers 1 liter
2 syringes 50 ml
2 100ml beakers
2 rolls transparent tape
clock or stopwatch
if doing it inside you will need 8-16 clip on light set ups with 100 watt incandescent bulbs, you'll also need enough power strips and extension cords to plug all of them in to an outlet.
It is best to have students in pairs for maximum engagement, but it can work in groups of 3 or 4.
The graphing exercise can be done as a whole group with the teacher modeling on the overhead projector.
It can take place entirely in the classroom, or partly in the classroom and partly on the school yard.
One session for set up
One session for data collection, either indoors or outdoors
One session for graphing and discussion
Students develop an experimental plan to investigate the question how solar energy heats different earth materials (water and land). A container half filled with water and half with soil is exposed to full sun (if doing it outside) or placed under incandescent lights (inside). Students take temperature readings of both materials for 15 minutes and then either bring setups to a shady spot or turn off the lights. Again students record change in temperature in intervals during the next 15 minutes and then graph results. Lesson introduces the concepts energy transfer, solar energy, and heat sink.
- how to enter data into a table and how to plot coordinates on a line graph.
- experience interpreting line graphs so they can make appropriate conclusions based on the graph.
- how to use a syringe and read a thermometer accurately.
- know about the water cycle, and the role of the sun in the water cycle
- know that 2/3 to 3/4 of the Earth is covered in water
As a foundation for understanding that uneven heating of the Earth causes convection currents (ES4a), students will understand that one of the properties of water is that it is a heat sink, and as a result, it heats up and cools down at a different rate than soil (land).
- When an object absorbs light, the object becomes warmer. In the process, light energy transforms into heat energy. This energy transfer changes the temperature of the material.
- When two objects or materials of different temperatures come into contact, heat energy will transfer from the warmer object to the cooler object. Transfer will continue from warm to cool until the objects are the same temperature. That's the way hear energy flows, and there are no exceptions.
- Air in contact with the Earth's surface engages in energy transfer. If the surface is warmer than the air, the air will get warmer and the surface will get cooler. And the opposite is true: Warm air will transfer heat to a cool surface. The air will cool down and the surface will heat up.
If you are doing the experiment inside because of inclement weather uncertainty, you will need to get the clip on lights (SEP resource center) and plan for how you will set them up in your classroom.
If doing it outside, you will need to choose a sunny site large enough for your class that has a shady spot nearby, and plan to do it as close to noon as possible to get the most dramatic results.
Either way, you will have to have some idea of what the students will do during the time in between temperature readings.
The soil must be dry, so if it is damp you will need to lay out the soil on newspaper for a day or two to dry.
Plan a place for the setups to be stored overnight in your classroom while they equilibrate.
Set up earth materials stations for students to gather materials for their setups.
Be sure that students are familiar with and good at reading Celsius thermometers.
Prepare overhead transparencies of experiment write up that you will use to model recording as well as transparencies for modeling graphing of data.
Lesson Implementation / Outline
- Review the water cycle and the fact that the energy that fuels the water cycle comes from the sun.
- Review what the students know about how much of the Earth is made up of land and how much is covered by water, or plan to do a lesson on it.
- Ask, how might that combination of water and land affect us?
- Review and ask introductory questions
- Introduce the term earth material: non-living substances that make up or come from the Earth. Ask for examples (water, rocks, minerals, sand, gravel, air)
- Propose setting up an experiment to find out how solar energy heats the two earth materials land and water. Hold up equipment you have for students to use (container, syringe, 100ml beaker)
- Ask students to talk in their groups about the design of an experiment. Give them 5 minutes do discuss a rough plan.
- Decide as a class the best way to set up the experiment to answer the question we have. Model how you want them to enter the question, materials, and procedure in their science notebook or on page 264 of FOSS Water Planet using an overhead transparency.
- Students get materials and set up containers.
- Introduce Cardboard surface- we don't want heat from the ground to affect our results so we will use these to keep heat from entering from the ground.
- Store the setups
- Optional: collect student notebooks or page 264 to check for understanding of question and procedure
- Review question and experimental procedures
- Take beginning temperature reading before leaving the classroom, or before placing set ups under lights. Place the setups in the 'sunny' spot. Have students take readings every 3 minutes.
- After the 15 minute interval, have students place set ups in 'shady' spot (turn off the lights if using clip lights) and record data for the next 15 minutes.
- While walking around, ask students about their results: Did they both behave in the same manner? What happened?
- As whole class activity, model graphing the data on the overhead, reviewing terms like dependent variable and independent variable.
- Discuss what conclusions we can draw from the graph.
- Discuss energy transfer: Sunshine is solar energy. Solar energy comes to Earth in the form of light. Solar energy travels through space and through Earth's air, hits the earth materials in the containers, and heats them up. This process is called energy transfer. In this activity, light energy from the sun is absorbed by the water and soil in the containers. When solar energy transfers to soil and water, the water and soil get heated.
- Introduce the concept of Heat Sink: Any material that can absorb heat is called a heat sink. Water is a very good heat sink because it can hold a lot of heat. Soil is not a good heat sink, as it heats up and cools down quickly.
Have students write conclusions in their science journal: What they learned and what questions they still have, or have them write a formal summary of the experiment and results along with their conclusions.
I-Check Investigation 4 from FOSS Water Planet, page 445 has a Earth materials graph and questions about it that the students need to answer. This can be given to the students after the convection lesson and discussed prior to making the connection between liquid convection and convection of local air currents caused by differential heating.
Review our conclusions and ask students how they think this phenomena might affect weather.
Extensions and Reflections
FOSS Water Planet, page 317 has a math extension that gives students practice identifying dependent and independent variables in controlled experiments.