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Grade Level(s): 6-8
Introduction: There has probably been a small increase in global precipitation over land during the twentieth century. When speaking of precipitation, cloud droplets are dew which forms on tiny dust and salt crystals which are blown by the winds. These condensation particles are so minute that they can only be observed under the electron microscope with a magnification of several thousand times. The most efficient particles result from the evaporation of water from tiny droplets in the spray from the ocean. Precipitation has increased over land in high latitudes of the northern hemisphere in conjunction with temperature increases. Precipitation has decreased after the 1960’s between the equator and about 35 degrees latitude, from Africa to Indonesia, as temperatures increased.
Learner Objectives:
- Students will be able to demonstrate the formation of clouds.
- Students will be able to differentiate between precipitation, evaporation and condensation.
- Students will be able to understand the phenomenon of global precipitation.
Florida Sunshine State Standards: Science: SC.H.1.3.5. SC.A.1.3.5. Math: MA.B.3.3.1. MA.B.4.3.1.
Competency-Based Curriculum: Science : Sci.M/J1 I-3-A Math: M/J1 III-3-A
M/J3 II-13-C
Materials:
1 liter of water
Kettle
Glass bowl with ice
Pie tin
Water colors
A few sheets of shiny paper
Activity Procedures:
- Boil 1 liter of water in a pot ( to be used in the second section ).
- Pass out two sheets of shiny paper, a cup of water and a set of water colors to each student.
- Have the students dip their brushes into the yellow paint.
- Have the students make many large yellow drops over one sheet of the shiny paper.
- Rinse the brushes off and dip the brushes into the blue paint.
- Make many blue drops between the yellow drops. Be sure that the students do not mix the colors.
- With a second sheet of shiny paper covering the desk, have the students lift their paper so that it is perpendicular to the desk and the drops start to run down the paper.
- The drops should slide down the paper and mix with each other dripping off the bottom of the paper as large green drops.
- Ask students a series of questions such as:
- What happened to the blue and yellow drops when you lifted your paper?
- What happened to the paper flat on your desk?
- Is there a new color on your paper?
- If there is a new color what is that color?
- How did the new color get there?
- Were the drops which fell off the bottom of your paper the same size as the blue and yellow drops?
- The class should gather around a common work place where they can view the hot pot of boiling water and the bowl of ice.
- The teacher should hold the bowl of ice water over the pot of boiling water.
- Ask : What do you think will happen-to the bowl of ice? To the steam? To the bottom of the bowl?
- Once the water is boiling, hold the bowl of ice over the steam.
- Place a pie tin so that the water which drips from the bottom of the bowl will collect in the tin.
- The class should observe and share what they observe happening. Some questions which should help are:
- What do you see happening on the bottom of the bowl?
- What do you see happening on the bottom of the pie tin?
- How does the water get on the bowl?
- Are the water drops on the side of the bowl the same size? Why?
- Which drops are falling from the bowl? Why?
- Which drops look like rain?
- Which drops look like a cloud?
- How are the big drops formed?
- Explain that the small misty drops which have condensed onto the side of the bowl of ice represents a cloud. The winds in a cloud blow the small drops around so that they collide with one another. During these collisions, some drops will combine with others making larger and larger drops. When the drops become so large that the winds cannot keep them in the sky, the drops fall as precipitation. This is similar to the large drops falling from the bottom of the bowl.
Vocabulary: global precipitation, condensation, evaporation
Student Assessment:
Allow the student to answer critical thinking skills questions assigned by the teacher:
- Identify ten common types of clouds and list which of these produce precipitation
- Stimulate student thought by asking the following questions:
1. What is rain?
2. How is rain made?
3. What are clouds made of?
Activity Extensions:
Allow students to construct a Venn Diagram which compares and contrasts five different types of precipitation. (Language Arts)
Home Learning Activity:
Have students calculate the amount of rainfall in Miami for the hurricane season in inches and convert them into metrics (cm.).
References/Related Links:
http://www.ncdc.noaa.gov/ol/climate/globalwarming.html
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/home.rxml
ftp://www.gsfc.nasa.gov/pub/PAO/Releases/2001/01-05.htm
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