Dew Formation

Dew forms when moist air near the ground cools and the water vapor in the air changes into water droplets. In this activity, you will model the formation of dew but the water droplets appear as fog on the outside of the glass.

Question: Can cold air hold more or less water vapor than warm air?

Hypothesis: ______

Materials:

2 Beakers, Water (room temperature), Ice, Thermometer, Timer

Procedure:

1.Fill two beakers, each about two-thirds full of water WITHOUT GETTING THE OUTSIDE OF THE BEAKER WET. If you get it wet, just wipe it dry with paper towels. Record the temperature of the room and the water.

2.Add ice cubes gently until the beaker is almost full. DO NOT LET IT OVERFLOW. The outside of the beaker should be dry. Record the temperature of the water at 10-seconds intervals.

3.Observe the outside of the beaker. Note the time and temperature at which the outside of the beaker becomes foggy (dew formation). Circle that time and temperature on the data table below.

Data Table:

Temp of Room in oC
Temp of Water before ice in oC
Time in Second / Temp of water after ice in °C
10
20
30
40
50
60
70
80
90

What was the DEW POINT (the temperature at which condensation begins) in your experiment?______Was it above freezing or below freezing?______

Observations:

1)Where did the dew on the glass come from? Did the fine water droplets come from inside or outside of the beaker? Explain why (hint: read p.303).

2) Make a line graph of the temperature of the water. Plot time on the horizontal axis, and temperature on the vertical axis.

3) Write a conclusion paragraph about what you have learned from this experiment.

  • What was your hypothesis?
  • How did you test the hypothesis?
  • What was you result? What evidence do you have?
  • Did your result agree with your earlier hypothesis?
  • Explain your observation or relate your finding to your daily experience.

Dew Formation

Write Up Instructions

  1. Cover Sheet must state lab title, your name, period
  1. Introduction: Include an explanation of how dew forms and how this activity shows that process.
  1. Methods/Materials: A list of equipment required and the steps you followed.
  1. Data: The actual numbers from the activity and the graphs from the computer.
  1. Conclusion: Answer questions 1, 2 and 4 from the bottom of the lab in this section. Also, talk about possible errors and explain any anomalies in your data.
  • Be sure to keep your write-up in this order.
  • Remember to skip a space before and after section headings.
  • Remember to underline section headings.
  • Always use good spelling and grammar.
  • The report must be typed.
  • Use 1 or 1.25 inch margins, 12 point font and double space
  • This write-up is worth 25 points.