What s Up with Weather Part 1

Transcription

1 What s Up with Weather Part 1 Author: Sara Kobilka Institute for Chemical Education and Nanoscale Science and Engineering Center University of Wisconsin-Madison Purpose: To learn about the ingredients of weather and how they interact. Learning Objectives: 1. Warm fluids rise and cold fluids sink (both water and air are fluids). 2. The water cycle involves the warming and cooling of water as it travels through the earth s crust, surface and atmosphere 3. Clouds need small particles (called Cloud Condensation Nuclei, CCN) for the water to condense Next Generation Science Standards: ESS2.A: Earth s Materials and Systems (partial) ESS2.C: The Role of Water in Earth s Surface Processes (partial) ESS2.D: Weather and Climate (partial) Suggested Previous Activity: Weather 101 Grade Level: 3-8 Time: 45 minutes Materials: Transparent tub (fish tanks work as well) with room-temp water Blue ice cubes Hot water (heated using an electric kettle or microwave), 100 ml per group Thermometer Funnel Tongs or spoon Blue, red and purple writing utensils (for drawing on worksheet) Multiple colors of cord or string (cut into 9 strands) Plastic beads in small containers separated by color: dark blue, light blue, green, yellow, white, clear (or color-changing solar beads) Scissors and tape Wide-mouth, clear jar, at least 15cm (6 ) tall with a lid Water Medium to large rubber balloons

2 Strong rubber band Small piece of a paper towel, about 8cm x 8cm (3 x 3 ) Matches Black sheet of paper (larger than the size of the jar) Flashlight Optional: Blue construction paper and white paper (same size, 1 for each student), ruler and glue sticks IF Cloud Coverage Challenge was not completed during Weather 101. If it was completed, have student cloudy sky sheets and the chart for estimating coverage (see worksheet) Safety: Students should not be allowed to handle the lit match or burning paper towel. Be aware that the burnt paper towels will create some smoke. You may want to leave a window open or have students take turns making the clouds in a bottle so you don t accidentally set off the fire alarm. Pre-Activity Preps: Freeze blue water in an ice cube tray (the darker the color, the better so use plenty of food coloring). Heat water and add red food coloring (again darker is better). Fill the tub ¾ full of water as soon as possible so that it can be close to room temp when you begin the experiment. Cut off the neck of the balloons as shown below. Test to make sure this can be stretched to fit over mouth of the jar. Introduction: The primary ingredients for weather are the sun and water. Sunlight puts energy into the system, warming the solid earth/air close to the surface and causing water to evaporate. The air temperature generally cools as you climb up in the lowest part of the atmosphere (hence the reason mountains are snowcapped). The first activity students will be doing shows them that warm water rises and cold water sinks, just like warm air and cold air. The second activity focuses on how water moves through the water cycle. The third activity involves making a cloud and the extra ingredient (cloud condensation nuclei) for clouds to form. Procedures: 1. Convection Demonstration a. Place the tub in a location where students can closely observe it but where it is less likely to be bumped or jostled. b. Have students measure the temperature of the water in the transparent tub, the hot water and the ice cubes. c. Gently place 1 blue ice cube into the water on one side of the tub. Have students closely observe what is happening (the blue color

3 will sink and they may see it swirling while it sinks). Have them draw their observations on the worksheet d. On the other side of the tub, gently dip the base of the funnel 5-7cm (2-3 ) below the surface of the water. Slowly pour the hot water in and have students closely observe what is happening. It is VERY important to pour this in slowly and to not add too much water. Draw observations on the worksheet. e. Continue to check on the tub and its contents as the ice cube melts. Ask students what pattern they see and have them draw again on their worksheet. What way does the cold water go? (down) What way does the warm water go? (up) Do they want to mix together on their own or do they stay separated? (stay separated) Can then think of other things that stay separated? (i.e. water and oil) The reason why the cold water sinks and hot water rises is because the cold water is more dense. The same thing is true in the atmosphere. Cold air sinks and warm air rises. In water and in the air, we call this up and down movement convection. The sun shines on the ground warming it up, the air closest to the ground is heated up and starts to rise. Sometimes that rising air brings moisture with it and that will be discussed in the next activity. 2. Water Cycle Bracelet a. Have each student pick what color cord/string they would like for their bracelet and tie a large knot on one end. Looking at the water cycle on the worksheet, have the students decide which color represents the different elements of the water cycle. Have them add beads to their bracelet in the order they could travel through the cycle. Note, students can repeat the exact same pattern each time or can go back and forth between stages as long as they are true to the cycle s flow. For example, rain can fall into a lake/river twice in a row. As they put the beads on, have them explain out loud what is happening in the water cycle. One example is the sun (yellow) shines on the land (green) causing the water to evaporate (clear or color changing bead). These invisible drops of water vapor cool and condense into clouds (white) and when there are enough big drops, they fall as rain (light blue) which falls into a lake (dark blue). Water at the bottom of the lake soaks into the land (green) but when the sun (yellow) shines, the water evaporates (clear color changing bead) 3. Cloud in a Jar (Fun with Chemistry, Vol. 2, Institute for Chemical Education, UW-Madison) a. Pour a small amount of water into a jar. Put the lid on and shake the jar. Pour out the water.

4 b. Roll up the piece of paper towel (that will be burned) and fold it so it fits in the bottom of the jar. c. The adult ONLY should light a match and drop it onto the towel (optionally, the towel can be lit and then immediately dropped into the jar). d. Wait for the approximately half of the towel to burn and then the adult should place the lid on the jar without screwing it on. Once the flame has gone out, quickly remove the lid and replace it with the piece of rubber from a balloon. Tightly fasten the balloon around the mouth of the jar with a rubber band. e. Note: It is easier to see the cloud if there is a black background and a flashlight is shining into the container. If the smoke is not visible in the container, a second piece of burning towel may need to be added. f. Quickly and firmly pull up on the balloon; the cloud will form in the jar. Release the balloon and the cloud will disappear. You may want to have one person hold the jar. Pull the balloon up hard, being careful not to tear it or poke a hole in it. 4. Cloud Cover Challenge (Skip to d if cloudy sky sheets have already been make) a. Have students decide what percentage of cloud cover they want to represent (between 10 and 90% and the number must be a multiple of 10). b. Have each child take a white sheet of construction paper. The long edge of the paper is 10 inches so you can help the students easily cut off the percentage they ve chosen. For example, if they ve chosen 30%, measure 3 inches along the 10 inch edge and make a mark. Draw a straight line from top to bottom and cut along that line. The remaining white paper should be discarded. c. After cutting off their chosen percentage of white paper, have them cut it or rip it into pieces. Each ripped piece of paper represents a cloud and should be attached to the blue sheet of construction paper. None of the clouds should overlap or hang off the edge but students have complete freedom beyond that as to how they want to distribute them (all in 1 corner, spread out evenly, spread out in uneven clumps etc). When they are finished, they should write the percentage of cloud cover on the back of the blue sheet and their name on the front. d. Using the Cloud Cover worksheet, have students view each other s sheets and estimate what percentage of cloud cover they are seeing. Once everyone has done this, compile results (possibly on the white board or on a poster) and have the students look for patterns. Do they tend to overestimate or underestimate? What distribution patterns are most difficult for estimating? Try heading outside to see how easy or difficult it is to estimate real cloud cover.

5 5. (Optional) Become a Weather Observer a. Gather (or build) the following equipment: thermometer, barometer, anemometer, windy vane, rain gauge, sling psychrometer b. Use the above equipment to take weather readings over a period of time (ideally more than a month) and mark them in a weather log along with cloud cover and current precipitation type (rain, snow etc). Ideally, try to do your readings at the same time of day each day in the same location. If you don t have a long time period for this activity, take 4-5 measurements over the course of a day and repeat for as many days as you can. The rain gauge is the only object that needs to stay outside for the entire time period. Take wind readings in an area that is as open as possible (away from buildings). Discussion: Part 1 of What s Up with Weather focuses on the forces involved with air movement up and down (heating causing convection) and the role water plays in the weather. Part 2 will move on to the force that causes air to move side to side, (air pressure). Evaluation: Walk me through the water cycle using the beads on your bracelet. Why does the air move? What do you need to have in order for clouds to form? This lesson is the product of the Institute for Chemical Education and the Nanoscale Science and Engineering Center at the University of Wisconsin-Madison. This Material is based upon work supported by the National Science Foundation under grant number DMR SCIENCountErs Lessons are licensed under a Creative Commons Attribution- NonCommercial 4.0 International License. Permissions beyond the scope of this license may be available by ing ice@chem.wisc.edu.