Science 10 Weather Unit Tracey Webb It would be difficult for me to pick any one topic that is my favourite to teach, but I’d certainly agree that weather is one of the most intriguing subjects! Students already have a good background of firsthand experience in this area and are usually eager to learn more. I will outline my approach for two sections, starting with the Weather portfolio work, even though I start teaching with the heat section first. Section 1 – Weather Portfolio I feel that the weather unit lends itself particularly well to a portfolio for several reasons – the students are generally keen about the topics, there are many opportunities for creative expression, independent research and presentations, and they are likely to keep their work once finished. I explain the entire portfolio requirements to the students at the beginning of the heat section, as they need 2 – 3 weeks to complete the weather journal. This portfolio is in addition to the regular class work according to the text. Part A: Weather Journal The students record specific weather data over a given period of time (I assign between 7 to 15 days depending on time available). The days need not be consecutive, although that would be preferred. I suggest that the students record their data at the same time every day for consistency. The students develop a chart to record the following: barometric pressure, high and low temperatures of the day (projected or actual, but stick with one or the other), probability of precipitation, UV index, wind speed and direction. For each day, they are also responsible for an anecdotal entry – one full paragraph minimum. At the completion of their data collection, they graph at least three of the above values and pass in with their journal. Part B: Student Lab (partner work) I give my students a choice of select labs (done in the Heat section) to submit for this requirement. Part C: Clouds This section has three parts – A chart involving the ten major types of clouds – which includes a description of their location in the atmosphere, type of commonly associated weather and a description of their appearance. (One good general site is www.i5ive.com/article.cfm/boating/16716) A 50 word or more poem (the student’s own) about some aspect of clouds/weather OR a complete explanation about 5 folklore myths – why they are or are not accurate! At least three of them must be ones that do work. A handmade collage illustrating the ten cloud types – students can draw or use a variety of materials to do this. Part D: Quirky Weather Quest Depending on time, this may be done as partner work or individually assigned; presented to the class in two-minute segments or simply collected. I find that the students enjoy presenting their research about intriguing weather phenomena. The student or partner pair is given (chooses) a topic from a master list (to avoid duplication) and researches the scientific explanation for the phenomena – when, where, how, what etc. If presenting to the class, they are encouraged to show pictures or use a power point format. The outcome is that they teach their classmates and answer relevant questions about their topic. A sample of the topics I use: doldrums, hypercane, Chinook, diamond dust, “Bear’s Cage”, sun pillar, mirage, “Brocken Bow” or glory, “Green Flash”, “Blue jets”, “sprites and elves”, sun dogs, “St. Elmo’s Fire”, crespuscular rays, ball lightning, fulgerite; winds – Haboob, Santa Ana, Nor’easter, anabatic, katabatic, Bora, buran and mistral winds, hoarfrost, downbursts, microbursts, etc… Part E: Weather Map Interpretation I have the students interpret weather maps after we’ve learned about frontal systems, the many symbols on maps for pressure, wind speed, direction, automatic stations, precipitation, temperatures etc. I have working maps from CFB Greenwood to study from, and gave out class sets of these at the last AST conference. You can download daily maps from Environment Canada though, and they work just as well (http://gfx.weatheroffice.ec.gc.ca/analysis/data/). The students are responsible for passing in a “Forecast” based on their weather map, with a detailed explanation. Note: I have a wonderful Powerpoint presentation prepared by Bob Howell (former manager of CFB Greenwood Weather Services) for an inservice he did for the Grade 10 Science teachers in AVRSB. It covers many aspects of weather maps, and also career aspects of meteorologists. He kindly gave his permission to share it, so if you are interested simply send me an email, and I will send it along. (email@example.com) Section 2: Heat Initially I work through the concepts of heat exchange, calculations of specific heat capacities, the heat of fusion and vaporization, dew point and relative humidity. The students learn to relate these mechanisms to the driving forces of the sun’s solar energy and various aspects of weather systems. One activity the students anticipate is my lab dealing with temperature and why the oceans do not freeze over at 0 °C…we make ice cream and monitor the temperature to observe the lowered freezing point of water due to the salt. Granted, it is more to prepare and clean up than doing, for example, “Lab #3 – Freezing and Melting Points”. It is also more expensive, as I spend $20.00 or so total on ingredients for five classes (~ 155 students), not including the ice. However, when I consider that the learning outcomes are the same, and wonder which activity they would probably remember in five years time, the ice cream wins every time! ☺ The following directions result in tasty, “foolproof” ice cream easily accomplished in a one-hour class. It usually takes about 20 – 25 minutes for the stirring and freezing process. Ice Cream Lab Introduction: The process of making ice cream involves lowering the freezing point - the temperature at which a liquid solidifies. The early settlers treated themselves to ice cream by using salt to lower the freezing point of water, making a “slurry” of slushy ice water, thereby allowing the milk mixture to freeze inside its container. Time needed: 10 – 15 minutes to prepare the milk mixture 2 hours minimum to chill the mixture. I find that leaving the mixture to set overnight in the fridge produces a smoother, richer tasting ice cream. Materials: Thermometer (or temperature probe), 400 mL beaker, 5 oz. paper cup – like Dixie drinking cups, popsicle sticks (one for stirring and one for a “spoon”), crushed ice, large basin to hold crushed ice, supply of ice cold water to top up ice in beaker, rock salt – or table salt or pickling salt. Note: I found that I needed ~1 ½ bags of ice and ~1 kg of pickling salt per class. After spending $10.00 on ice I realized that our cafeteria had an ice-making machine – explore that option if possible! Preparing the Ice Cream (Teacher): The following ingredients listed on the left will make enough ice cream for 50 students, filling the 5 oz. cups ½ to ¾ full. I made a triple batch for 5 classes, which is the list on the right: 50 students: For ~150 – 160 students: 1 quart (litre) half-and-half 3 litres half-and-half 7 cups of milk (I used 2%) * 5 litres of milk 2 ½ cups white sugar * 2 kg of sugar 4 large eggs 1 dozen large eggs 1 tsp. salt 1 Tbsp. salt 3 Tbsp. Vanilla * 1 (235 mL) bottle vanilla For the list on the right, the asterisk (*) indicates the amount you need to buy and measure from – I didn’t use quite all of the 5 litres of milk, 2 kg of sugar or vanilla. I mix each batch separately anyway, according to the list on the left, using a very large bread- making bowl. Blend all of the above ingredients and then beat until smooth for one or two minutes. Store the mixture in a gallon container (the 4 L plastic ones used for spring water are ideal) in the fridge – keep chilled until ready to use! I am the official “Pourer of the Ice Cream Mixture” – otherwise some students will take more than required and you could run out. Having said that, I discovered that after carefully pouring for five classes, I actually had just enough for my grade 12 Geology class. Since we were starting Glaciation at the time, I did a little creative introduction, and they had no problem exploring the freezing aspects! ☺ Making the Ice Cream (Students): Read all instructions carefully BEFORE starting the process! Layer some crushed ice, salt and ice water in the 400 mL beaker, leaving room to put 5 oz. cup in beaker as well. The ice mixture (slurry) should appear to be slushy, and be no higher than 2 cm below the rim of the beaker. If it is higher, there is the risk of sloshing salty ice water into the ice cream mixture. Fill the paper cup ½ to ¾ full of the ice cream mixture. Record the temperature of the slurry mixture initially and then every 3 minutes throughout the process. While carefully holding the paper cup to one side of the beaker, stir the slurry at regular intervals with a popsicle stick to keep the salt and ice mixture moving, adding more ice and a bit of salt as necessary. At the same time, use another popsicle stick to stir the ice cream gently, scraping along the sides of the cup as it begins to freeze. It must be stirred often. Continue until the ice cream has reached the desired consistency. Enjoy! (One could always splurge on chocolate syrup topping…) Analysis: (some sample questions) If the temperature is less than 0 °C, how can water be a liquid? What are other factors that can alter the temperature at which a substance freezes or boils? (i.e. altitude, pressure) Why must both mixtures be stirred regularly? Explain. Why did the ice cream mixture freeze while surrounded by a liquid? Consider the implications on the global environment and weather if our oceans were not salt water. Describe and explain at least three repercussions that would occur, and any long-lasting effects. Note – there are many interesting variations of ice cream recipes on the Internet, as well as activities that could be explored to extend or enhance the lesson. The Feb. 2000 issue of Scientific American has an article “Melting Below Zero”, which offers an interesting counterpoint.