Sea Ice Investigation

Transcription

1 Sea Ice Investigation Lesson Focus: Sea Ice & Climate Change Learning Goals: Assess the influence of ice on the heating rates of water Compare heating rates of fresh and salt water Infer to connection between changes in the amount of sea ice to global temperatures Anticipate the impact changing amounts of sea ice might have on global climate Enduring Understandings for the Lesson: The presence of sea ice has a moderating influence on global temperatures. The presence of sea ice can be an indicator of global climate change. Georgia Performance Standards Addressed: SO3. Students will analyze how weather and climate are influenced by the oceans. a. Identify general global patterns of atmospheric and oceanic circulation including variations such as El Nino and monsoons. b. Explain the influence of the Coriolis Effect on winds, ocean currents, and on weather and climate. c. Describe the effects of tilt of the earth, solar energy inputs, and heat capacity of land and oceans on the resulting patterns of weather and climate. d. Explain relationships between climate change, the greenhouse effect, and the consequences of global warming on the ocean. SCSh2. Students will use standard safety practices for all classroom laboratory and field investigations. a. Follow correct procedures for use of scientific apparatus. b. Demonstrate appropriate technique in all laboratory situations. c. Follow correct protocol for identifying and reporting safety problems and violations. SCSh3. Students will identify and investigate problems scientifically. a. Suggest reasonable hypotheses for identified problems. b. Develop procedures for solving scientific problems. c. Collect, organize and record appropriate data. d. Graphically compare and analyze data points and/or summary statistics. e. Develop reasonable conclusions based on data collected. f. Evaluate whether conclusions are reasonable by reviewing the process and checking against other available information.

2 Grade Level: th Materials: (materials for one group) 600 ml beakers Hot plate Stirring rod Celsius thermometer Timing device (stopwatch preferred) Time period: two-three 90-minute periods Background: Water has many unique properties. One special property is its high specific heat. Specific heat refers to the amount of energy need to raise the temperature of a unit mass of a substance by one degree Celsius. Substances that have a high specific heat require more energy to change the temperature. Likewise, if two materials receive the same amount of incoming energy, the temperature of the substance with the higher specific heat will change more slowly. Substances like soil and dirt have a lower specific heat than water. Since our planet is approximately 70% water at the surface, the energy from the sun is received equally by land and water surfaces but the change in temperature is not equal. The presence of such large amount of water helps to moderate how much the temperature changes. Another aspect of water that adds to this moderating effect is the presence of water in the form of ice. Ice has a high albedo (which means it is highly reflective). Therefore, a good deal of the energy that encounters ice at the surface is not absorbed. Even though some energy is being absorbed by the ice, it does not change the temperature of the ice but rather melts the ice. Large quantities of energy can be added to ice but very little temperature occurs since the energy is melting the ice and not raising the temperature. So, not only is the ice reflecting incoming solar energy, the energy that is absorbed does change the overall temperature of the ice. Pure water has special properties. When substances like salt are added to water, some its properties change. These new properties are called colligative properties. Adding salt to water (such as what naturally exists in our oceans) reduces the specific heat of water. It takes less energy to raise the temperature of sea water when compared to an equal amount of fresh water. So, when conversations about global climate change occur in the classroom and in political and scientific venues, it is important that those involved understand how the properties of water help to shape the climate of our planet. But understanding these properties is not enough. Scientists can measure and then infer how the presence of ice in the oceans might influence the rate at which ocean temperatures change. Globally, surface temperatures have changed approximately C over the last 100 years. This rate of temperature change is considered to be rapid when compared to a change of C during the most recent 50,000 years. What would be truly valuable information would be to know if there is a relationship between amount of sea ice and the rate at which temperature changes. If scientists could

3 establish a quantifiable connection, then knowing the amount of sea ice that is present on our planet can help scientists predict the rate at which global temperatures would change. Learning Procedure: Day One: Day Two: Begin class with a discussion that introduces the students to the following properties of water: specific heat, heat capacity, colligative properties and phase changes of water. To demonstrate these concepts, students will observe sea and land surface temperatures of various locations (latitudes) at different times of the day and different times of the year. I will use websites and handouts to show these observations. The goal will be for students to recognize the difference between heating on land v. water to illustrate the concept of heat capacity/specific heat. To address the concept of colligative properties, we will discuss the use of salt as a way to prevent roads from freezing in the winter and why salt is added during the process of making ice cream with an ice cream maker. In addition to properties of water, we will discuss the distribution of water on the planet (salt v. fresh, land v. water). I will use a demonstration that shows the percentage breakdown for each part for the fresh water (i.e. 2.5 % ice, etc.). Once students recognize the distribution of water and land, I will ask them to infer how water s heat capacity and the distribution of water on our planet might influence the climate for an area. Students will take notes using a power point on the variables that influence the climate for a location (such as elevation, latitude, ocean currents, etc.). Students will be asked to examine how changes in the surface features (urbanization, water to ice, etc) of the Earth might influence the climate in an area. Day Three: 1. Students will participate in the Sea Ice lab. First, introduce the goals for lab participation. Students will be placed into one of eight lab groups and assign them a specific ecosystem (Great Lakes, North Atlantic, Artic Ocean and Arctic Lake). We will revisit our previous lessons on variables that influence climate. 2. Next, give an overview of the procedure for the activity and describe all safety practices that must be followed when working with heated materials. Students will create their ice/water mixture, note times and temperatures and begin the heating process. Students should gently stir will heating (always using caution around heating devices and hot liquids). 3. Students will observe the time it takes for the ice to melt during the heating process. They will record time for and temperature at which the melting occurs. 4. Students will continue heating beyond the melting point for the same length of time it took to melt the ice (i.e. three minutes to melt the ice means three more minutes of additional

4 heating). At the conclusion of that time period, the heating device is turned off and the temperature of the liquid is recorded. Students should NOT attempt to move the hot beaker of water. They will continue observing the temperature to record the highest temperature the liquid attained. 5. Finally, students will look at the volume mark that was made at the beginning of the experiment and observe for any changes in volume. 6. Students will record data for their team on their data sheet. Then, they will compile their data with class data regarding the four different ecosystems by recording the data from other groups on their data tables. 7. Students will use the data to complete the calculations and answer the questions provided in the lab report. 8. Conclude the sea ice activity by discussing student results (rates of melting for fresh and salt and rates of temperature change with and without ice). Ask students infer how the results of this investigation might have implications to our global climate. In other words, how does the presence of sea ice possibly influence changes in ocean temperatures? Evaluation: 1. Formally assess students by observing laboratory techniques. 2. Summatively assess the activity by evaluating answers to questions from the activity and by placing lab-related questions on subsequent quizzes and the unit test. Extensions: 1. Have students examine data regarding current trends in global ice cover. 2. Have students create feedback systems (positive and negative) to hypothesize the results of changes in the quantity of sea ice. 3. Have students research marine and/or land organisms that regularly rely upon the presence of sea ice as an integral part of their habitat. Have students anticipate changes in the food web when these organisms are impacted by changes in their environment. 4. Have students investigate changes in past levels of sea ice and how these changes have influenced past coastlines. Resources: 1. Life on an Ocean Planet Chapter 6 pp Chapter 7 pp. 3-14(2006) Current Publishing Corporation. 2. Earth Science Chapter 31 pp , and Climate Exercise p. 596 (1989) D.C. Heath and Company. 3. NOAA data for current sea temperatures ( and current land temperatures ( 4. Earth s water distributions:

5 a. (salt versus freshwater distribution) b. Earth Science: Geology, the Environment, and the Universe Chapter 15 pp (2008) The McGraw-Hill Companies, Inc. (Northern and Southern Hemisphere distributions) c. Essentials of Meteorology: An Invitation to the Atmosphere Chapter 3 pp (2001) Thomson Learning, Inc. This lesson developed by: Scott Schomer, Harrison High School