Up to 32 students
45-60 minutes Introduction:
Weather is the changes in humidity (amount of water in the atmosphere), air pressure, temperature and such on a short term basis, daily, seasonally or yearly. This is not to be confused with climate which is defined as long term weather patterns such as those found in the tropics (hot and moist) versus the desert (dry) or polar regions (dry and cold).
We receive most of our energy from the sun. The sun heats the surface of the Earth, the rock surfaces and the oceans. In turn things heat up and as we saw with the convection demo in our plate tectonics activities hot things rise due to density changes. When the oceans heat up and absorb energy it will evaporate and turn into its gaseous form, water vapor. Because the upper parts of the troposphere are significantly cooler water vapor will cool, condense and fall out of the atmosphere as precipitation (snow, rain, hail).
Just as heat is rising from the tropics and moving toward the lower pressures in the high latitudes it allows for cooler and denser air from the high latitudes to move toward the equator. These are called Hadley Cells; they are simply gaseous convection cells.
Water is an amazing molecule and does not follow conventional density laws due to its dipolar nature. Water is densest a couple of degrees before freezing, upon freezing its density is less than that of water. This is why ice floats. Learning Objectives:
- Weather is atmospheric changes on a short term basis. Climate is weather over the long term.
- Become familiar with the terms evaporation, condensation, precipitation and their meanings.
What is weather? What is climate? How does rain happen? Materials
Large Marker per group of up to 8 students
2-3 500ml Beakers
Hot Plates or a Microwave
Room temperature water
Plastic baggies filled with ice
Tongs and/or oven mitts Activity 1: L.I.N.K. on Weather (Assessment opportunity for an introductory activity to a new unit)
Have each group of students write down ideas about weather and climate for approximately 3 minutes. Topics can be posted together or separately. “What do you know about weather? How does the weather change? Why does the weather change from location to location on the globe? What is climate and is it different from weather?”
Following the 3-minute activity ask students to look around at other group’s concept maps and inquire about vocabulary or concepts they may be unfamiliar. Maps may either be taken down and students prompted to write down what they may have just learned about the topic discussed or maps may be left up for duration of unit to be built upon at a later time in substitution for a word wall. Review with the class the ideas of density and convection in the mantle and apply it to the atmosphere. Activity 2: Rain Maker Prep note: water takes a long time to heat up so have the beakers heating up a minimum of 15 minutes before this activity
Students should make observations of the boiling water; what do you see rising from the beaker, without using a thermometer what temperature do you think the boiling water is, what phase of matter is water, what phase of matter is the steam?
Direct the student to remove the beaker from the hot plates and carefully cover the top of the beaker with plastic wrap. Have the students take note of what is happening to the plastic wrap (it should form a dome by the rising hot air that is now trapped).
Students should then gently place the bag of ice on top of the plastic wrap dome and take notes on what is happening on the inside of the beaker (water should be condensing on the plastic wrap and will soon after fall off in little droplets – rain!). Activity 3: Think, Pair, Share
Have the class break into small groups to discuss their observations and answer the following questions:
Why did the plastic wrap bubble up? Why did water form on the plastic wrap when the ice was placed on top? When and where did you see density changes in the water and water vapor? What are the steps in phase changes you saw? Conclusion and Wrap Up
Have a volunteer from each group offer up their findings to the class, point out the ideas of evaporation, condensation and precipitation. Emphasize the density concepts and the transfer of energy as this will help in ocean concepts to follow.
Have students add new concepts to their LINK.
Vocabulary to note:
Phases of Matter New York State Scope and Sequence: Intermediate and High School Science Standards
1.2g, 2.2a - 2.2d, 3.1