ALCA Members PLC Domains Data Standards Map Plan Curriculum Assessment Strategies

To Dew or Not to Dew, That is the Question Copy

Dew is hiding all around us each and every day! This activity will aid in detecting dew, making it visible, and its significance in the weather that affects our everyday lives. Comparisons with dew points in other areas could provide information for the student to plot dew points on a map and see different air masses, their boundaries and weather associated with each.

Engaging Questions

  • Could there be a relationship between the dew point and the weather outside? If so give some possibilities.

  • Where did the moisture on the outside of the can come from?

  • Why did it collect on the metal can?

Teacher Goals

  • Data Collection - The student will obtain experience in data collection, evaluation, and making conclusions.

Learner Goals

  • Students will be able to see the connection between temperature and the point water vapor condenses forming liquid water.

Required Resources

  • Equipment

    • Metal container
    • Thermometer
    • Ice
    • Water
    • Wet/Dry Bulb HydrometerEquipment

Optional Resources

  • Wet/Dry bulb hydrometer is optional if one wants to explore the effect of evaporation and the level of water vapor in the air.

Steps

  1. Taking Experimental Data

    Follow these directions to determine dew point (temperature water begins to condense).

    1. Fill your metal can about half full of room temperature water.
    2. Check the outside of the metal can for the presence of liquid.
    3. Put the thermometer into the metal can, holding it so that it doesn't touch the bottom.
    4. Record the beginning temperature of the water.
    5. Add a small amount of ice water, stir with the thermometer, checking the temperature and looking for liquid on the outside of the can.
    6. Continue adding small amounts of ice water until you see liquid (dew) on the outside of the metal can.
    7. Record the temperature (dew point).

Teacher Notes

  • If one has a temperature probe it would make the determination of dew point easier.

  • Everyone has noticed water on the outside of their soft drink can or cup.  Many have never really considered where that moisture comes from.  

    Dew point is really quite easy to find and requires no expensive equipment or tedious procedures.  Some type of small metal food can with the label removed will work very well. 

    Thermometers should be easy to read and the student should be instructed on safety because of the possibility of breakage.  Dew points should be taken approximately the same time each day to reduce experimental variables somewhat.

    Some days the air may be too dry for you to get a dew point reading.  Have a class discussion about this when it happens.Use external resources such as The Weather Channel, local TV stations, etc. to get dew points not only for your area but surrounding areas. 

    These can be plotted on a line map with points of fairly equal dew points connected.  This will help delineate different air masses and students can associate different weather with these masses and their boundaries.

Learner Notes

  • Do NOT rush NOR add too much ice at one time.  Gradually add ice over time.

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