Grade Levels: 7th, 8th, and 9th

Subjects:  Science, Social Studies, and Math

Learner Outcomes:

Students should be able to:

• Describe changes in states of matter, and the energy changes involved.
• Compare and contrast three methods of heat transfer (conduction, radiation, and convection).
• Describe the major elements of weather, including temperature, relative humidity, dew point, barometric pressure, wind, and precipitation..
• Name the instruments used to measure each of the elements of weather.
• Describe and use various instruments to take measurements of weather parameters.

Materials:

• a classroom weather station which includes instruments to measure temperature, relative humidity, barometric pressure, and rainfall amounts.  If a weather station is not available, thermometers, a barometer, and a rainfall gauge can be used independently to collect data.
• Thermometers which measure in Fahrenheit.
• Clean, empty soup or coffee cans
• Ice and water
• cotton balls or cotton shoe strings
• rubber bands or string

• weather station or instruments to measure air temperature, barometric pressure, relative humidity, and rainfall amounts.

• If a weather station is not available, teachers can use thermometers and a barometer to take measurements of their own.  The activity on Day 2 describes how to make a psychrometer to find the relative humidity, and tables can be used to calculate the dew point temperature.
• Before doing the activity on Day 2, be sure you have permission to let the students go to the designated areas to take temperature readings.  Depending on your school situation, you may want to keep the entire class together and go to a few locations for the readings.
• A sample data table for the students can be found at weatherdata.xls.  Teachers may edit this table to include only those items they wish the students to keep records of before printing out copies for their students.
• While scientific data should always be measured in SI units (i.e. ^oC, meters), I use ^oF, inches of mercury, and inches of rainfall when teaching about weather since these are the standards used in weather forecasting in this country.  This allows students to compare the data they collect with historical data or data collected by other local weather stations.
• Before conducting the activities, explain to students the importance of using care with thermometers, especially if they contain mercury.

• Day 1
• You may wish to introduce the topic of weather by asking students how weather affects their lives, and why weather prediction is so important to us.  (We actually have TV and radio stations devoted entirely to 24 hour a day weather information.)  Discuss various occupations that are especially impacted by weather conditions (farming, sports events, city and road maintenance, etc.) and also talk about the effects of severe weather on various parts of the US and the world.  What major weather events have impacted their own lives or cities?
• Show students the weather station, and explain to them that they will be taking readings from the weather station every day for the next month or so.  At the end of that time, they will learn how to use Excel to prepare a table and several graphs of their data.  Then they will compare their readings to historical data, or to other recent data taken in their area.
• Give them each a printed copy of the weather data worksheet that they will use to record their data.  Explain why it is important for them to take readings at approximately the same time each day.
• Proceed to take and record that day's readings, showing students how to properly use the weather station.  Focus on explaining how to take each reading, rather than on what the individual readings mean.  Tell them the units that they will be using, and explain why they will not use SI units in their measurements.
• You may wish to assign individual students to take the readings at the designated time each day and record them on the board, or somewhere convenient for all students to see.  Each student should put  the day's readings on their own worksheets.  Every student should have the opportunity to take the readings at some point during the recording period.
• Day 2
• After recording the day's readings, the teacher will use a lecture / discussion / activity format to begin teaching students about phase changes and methods of energy transfer.  Explain that both concepts are important in understanding weather phenomena.
• Hand out the worksheet on phase changes, or use the board or overhead to present the information.  Explain to the students that as they study weather they will need to understand how energy (heat) affects the changes in state of matter (of water, especially), as well as the density and volume of water as it changes states.  Point out that the evaporation and condensation points are at the same temperature, as are the melting and freezing points.
• Next, use the handout on Heat Transfer.  Explain the three ways that thermal energy can be transferred.  Have students do the brief exercise at the bottom of the page to be sure that they understand the concepts.  These can be done in class or as a homework activity.

• Day 3
• Discuss the following elements of weather:
• Temperature:
• instrument - thermometer
• units of measurement - ^oF
• should be placed 2 meters above the ground in a location protected from rain, snow, or   direct sunlight.
• Relative Humidity:
• instrument - psychrometer
• units of measurement - %
• relative humidity = (amount of moisture in the air / amount of moisture the air can hold at that temperature) x 100%.  Explain that warmer air can hold more moisture (water vapor) than cooler air, because the cooler the air, the more condensation will take place, removing water vapor from the air.  Warmer air holds more moisture because the water vapor will evaporate into the air.
• Activity - Measuring Relative Humidity:

Divide students into teams of 2 to 4 students each.  Each team will need two thermometers, a cotton ball and rubber band or piece of string, or a cotton shoestring, and a small square of cardboard (approximately 4 inches square).  The cotton ball or shoestring should be moistened with room temperature water, and attached to the ball of one of the thermometers.  This is the wet bulb thermometer.  Each team should select a different location in the school (such as the gym, locker room, classroom, computer lab, office, hallways, rest rooms, outdoors, etc.).  They will go to that location, and take and record two readings.  First they will measure the temperature with the dry bulb thermometer.  Then they will fan the dampened cotton ball with the cardboard until the temperature on the wet bulb thermometer stops dropping (about 2 minutes).  They will record this second temperature, then return to their classroom with the data they collected.  Remind students that evaporation requires an increase in energy.  Therefore, as the moisture evaporates from the moistened cotton ball or shoestring, it takes energy away from the bulb of the thermometer, cause its temperature to drop.  Upon returning, they will use the relative humidity tables to determine the relative humidity of the location they tested.  If these tables are not available in their texts, students can use the weather calculator on the NOAA website.   They should then record their data on the board for other students to see.  Follow up with a brief discussion of why the humidity might be different in different locations, and whether the results were as expected.

• Day 4
• Begin by reminding students to record their readings from the weather station.  Review results of previous day's activity if there was not time to finish.  Continue lecture / discussion / activity as shown below.
• Dew Point:
• instrument - none; this is a calculated value using temperature and relative humidity
• units of measurement - ^oF
• the temperature at which dew (or frost) will form; the temperature at which the relative humidity reaches 100%, and water vapor condenses out of the air.  The dew point depends upon the air temperature, since air at different temperatures can hold different amounts of moisture before becoming saturated.  Also, if the dew point is below 32^oF, then frost will form instead of dew if the dew point is reached.
• Activity - Finding the Dew Point

This can be done in groups, or as a demonstration by the teacher.  Fill an aluminum can with room temperature water, and observe the temperature. Then slowly add ice to the water, stirring gently. Observe the temperature on the thermometer as it drops.  When condensation appears on the outside of the can, note the temperature of the water.  This is the dew point.  The air around the can was warmer than the water in the can.  This caused the air around the can to cool until it reached its dew point, resulting in condensation.
 
• Barometric Pressure
• Instrument - barometer
• Units - mm Hg (mercury), inches Hg, or millibars.  We will use inches of Hg.
• The pressure (weight per unit area) of a column of air above the ground.
• High Pressure (H for Happy) means fair weather.

Low Pressure (L for Lousy) means clouds and / or precipitation.
• Explain that changes in barometric pressure are more significant than the current pressure readings.  Rising pressure means fair weather is on the way.  Falling pressures predict bad weather coming.
Here's why.  (The students should understand these concepts!)
Happy Highs:
High pressure means the air must be more dense or heavier than surrounding air, so it tends to sink.  Sinking air warms as it gets nearer to the Earth's surface.  As it warms, it can hold more moisture.  Therefore, moisture in the air evaporates, so no clouds or precipitation forms.

Lousy Lows:
Low pressure means the air must be less dense, or lighter, than surrounding air, so it tends to rise.  As it rises, it cools.  But cool air cannot hold as much moisture, so the water vapor in the air begins to condense, forming clouds and possibly precipitation.
 

• Wind (direction and speed)
• results from the differences in barometric pressures across a region.  Air tends to flow from regions of high pressure to regions of low pressure.
• direction - measured using a wind vane; wind direction always refers to the direction the wind is blowing FROM.
• speed - measured using an anemometer; units are in miles per hour or in knots.
 
• Day 5
• Look at the data that students have been collecting from the weather station to see that they collecting all the data they need.  Remind them to continue taking readings for the next several weeks.  They will use the data to prepare tables and graphs using Excel when they are done.  Direct them to look at the barometric pressure readings.  Have they been changing throughout the week?  Do higher readings correspond to sunny days and lower readings to cloudy or rainy days?
• Review the information on phase changes, heat transfer, and the elements of weather (temperature, relative humidity, dew point, barometric pressure, and wind).  Tell them that they will be taking a short quiz to show that they understand the concepts that have been presented so far.  Have them work on the review sheet individually before going over it together.  Alternatively, it may be assigned for homework.

• In the activity on day 2, some students may be unable to move easily about the school to take readings.  Have these students take humidity readings in the classroom you are working in.
• If the weather station is not in an easily accessible location, make sure that students unable to take readings on their own get the data from classmates, and understand what the measurements represent.

• While the students are taking their daily readings from the weather station, you might have them use the internet to keep a similar table that contains readings from their local news stations or weather channels.  These values could be graphed at the end and compared to the readings taken by the students.
• Alternatively, the students could use the internet to retrieve historical data or averages for each day in their recording period.  These average values could be graphed alongside their actual data for comparison at the end of this unit.
• Using the internet, have students try to find sites that show them the various cloud types.  Have them list the suffixes and prefixes for cloud names and tell what they mean (i.e. nimbus, cumulus, stratus, etc.)  Ask them to write a brief summary of the cloud types they can identify.

• Quiz on the elements of weather, heat transfer and phase changes.

National Standards:
Science:  Understands atmospheric processes and the water cycle.
Geography:  Understands the characteristics and uses of maps, globes, and other geographic tools and technologies.
Math:  Understands and applies basic and advanced concepts of statistics and data analysis.

Job / Career Clusters:
Science and Technology

References:
www.srh.weather.gov/elp/wxcalc/wetbulb.shtml
www.weatherbase.com
http://wvde.state.wv.us
www.mcrel.org
www.bom.gov/au/climate/glossary
www.weatherbase.com

Author:
Debbie Messenger, Clare McCarty, Susan Popp
cmccarty@stjosephhs.org
St. Joseph Central Catholic High School
 

Lesson Overview

Lesson 1

Lesson 2

Lesson 3

Lesson 4

Lesson 5