BSCS Science Tracks: Connecting Science & Literacy

Transcription

1 BSCS Science Tracks: Connecting Science & Literacy Second edition, 2006 by BSCS Investigating Weather Systems Unit Overview 5415 Mark Dabling Blvd. Colorado Springs, CO

2 Module Overview Introduction to Investigating Weather Systems Weather is a subject of interest to most people, including children, because weather affects almost everything we do. Many people plan their day based on the weather forecast, including what they wear, how early they leave for work or school, and what they do with leisure time. Everyone notices the weather; they experience changes in the weather, both over the course of a day and over the course of the seasons. Many people wonder what causes the different weather conditions they experience, especially when weather is particularly severe. This module presents many factors, such as the angle of the Sun s light rays and the tilt of Earth s axis. It also presents how one s proximity to water, winds, and elevation determines what the weather is generally like in a particular location. The investigations help students understand how complex weather systems are and why local meteorologists cannot always predict the weather accurately. Module Overview Module Overview 21

3 At the heart of all weather is the Sun. Young children associate the Sun only with sunny weather; however, in this module students make connections between the Sun and other weather phenomena such as clouds, winds, changing air pressure, and seasonal variations. When students understand that the Sun s energy heats Earth unevenly, they can begin to build a model of the many observable differences in weather from place to place and from season to season. Vacation experiences at the beach or high in the mountains provide firsthand evidence that supports the students developing concepts of the causes of weather. This module uses students knowledge of different weather in different places, whether it was gained vicariously or in person, to engage them in thinking about the causes of the variations in weather conditions. Why are there warm places to visit even when it is snowing at home, or why are there mountains with snow on which to ski even when it is summer at home? As students progress through the lessons in the module, they add conceptual depth to their early ideas by actively working to answer the question, What is it about a place that makes its temperature different from that of another place? They analyze temperature data, make models of the Earth-Sun system, determine the difference in heating between land and water, and recognize elevation as a factor in the temperature of a particular location. 22 Investigating Weather Systems

4 Once students recognize that the Sun heats places on Earth unevenly, they are ready to explore how this unequal heating affects conditions other than temperature. They observe the evaporation and condensation of water and recognize the role heat plays in the water cycle and, by extension, in the formation of clouds. Students build a smoke box to observe how temperature differences cause air movement known as winds. They investigate the properties of air and relate them to air in a smoke box, thereby recognizing the interconnectedness of temperature, air pressure, and winds. As students apply their growing understanding of the Sun s influence on all weather, they see the relationship among many phenomena, or how the many pieces work together to create weather systems. In understanding students conceptual development in regard to weather phenomena, it might be important to understand students conceptions of the abstract notions of air, gases, evaporation, condensation, and air pressure. As reported by Driver and her colleagues, most students of this age level understand that air takes up space, especially in a closed container, but not all understand that air has weight or mass. Leboutet-Barrell suggests that this is because children s most common related experience is that gases tend to rise or float. This view is supported by studies which show that children aged 9 13 tend to predict Module Overview 23

5 that gases have the property of negative weight and hence that the more gas that is added to a container, the lighter the container becomes (Driver et al., 1994, p. 80). Additional studies suggest that, to a certain number of children, air is not the same everywhere, either in a container or in a room. From these observations, we can conclude that children aged experience various difficulties in understanding that a quantity of air and its mass are preserved when it undergoes transformations. They seem to be able to understand that the quantity of air is conserved when it undergoes transformations at constant temperatures; however, they have difficulties in conceptualizing what happens when its temperature changes (Driver et al., 1985, p. 113). For example, students of this age level sometimes have difficulty explaining what happens to air when it is heated in either a closed or an open container. They often believe that heating a quantity of air actually creates more air, not that the mass is conserved and that the given quantity of air takes up more space because the molecules move farther apart. These conceptual difficulties might come into play when students are trying to make sense of the movement of air in the smoke box in lesson 6 and of the air investigations in lesson 7. Take time to ask questions of students to determine what they understand about why air moves from one place to another and how they explain changes in air pressure. These are complex concepts and will take time to develop. 24 Investigating Weather Systems

6 Regarding the concept of evaporation, older students realize that water doesn t simply disappear; they usually suggest that bits of water go into the air, although some believe that water separates into hydrogen and oxygen when it evaporates rather than forming gaseous water vapor. Students of this age do not necessarily understand that mass or weight is conserved during the process of evaporation and instead believe that the evaporated water (water vapor) is lighter than the same amount of liquid (Driver et al., 1994, p. 81). Their ideas about condensation are somewhat similar. When asked what happens when water condenses on a container of ice, less than 20 percent of students aged chose the response, the water condensed from water vapor in the air. Forty percent indicated that the coldness changed into water, and another 40 percent believed that cold caused hydrogen and oxygen to change into water. As a result of comparing these with other responses by the same students, the researchers conclude that although pupils know that vapor can be changed to water, applying that knowledge appeared to cause some difficulty (Driver et al., 1994, pp ). These findings suggest that students might not understand completely concepts such as cloud formation, the causes of winds, or the processes within the water cycle. The purpose of the module is not to provide a complete understanding of all the related concepts Module Overview 25

7 regarding air pressure, the properties of air, heat exchange, evaporation, and condensation, but rather to acquaint students with these phenomena and help them connect important processes on the surface of Earth that explain the basics of weather phenomena. The causes of weather are complex, but the understanding of certain basic fundamentals is important. Experience with these basic fundamentals is what this module provides. In addition to enabling students to construct their understanding of designing structures, the lessons in this module provide these things: Hands-on, minds-on learning experiences Critical-thinking and inquiry skills Conceptually developmental and sequenced experiences Literacy strategies in reading, writing, listening, and speaking Opportunities to learn collaboratively with other students Integrated activities that encourage curiosity and imagination See the Module at a Glance for a summary of the lessons and the development of the concepts associated with weather systems. 26 Investigating Weather Systems