Dissolved Oxygen and Temperature Lab Lesson Plan

Transcription

1 Dissolved Oxygen and Temperature Lab Lesson Plan Purpose: 1) To observe the relationship between dissolved oxygen and temperature of water and the impact it has on aquatic organisms 2) To observe the relationship between two variables in a real world setting 3) To evaluate examples of human activities that have negative and positive impacts on Virginia s ecosystems Science SOLs: BIO.1 The student will demonstrate an understanding of scientific reasoning, logic, and the nature of science by planning and conducting investigations in which d) graphing and arithmetic calculations are used as tools in data analysis; f) sources of error inherent in experimental design are identified and discussed; h) chemicals and equipment are used in a safe manner; i) appropriate technology including computers, graphing calculators, and probeware, is used for gathering and analyzing data, communicating results, modeling concepts, and simulating experimental conditions; BIO.2 The student will investigate and understand the chemical and biochemical principles essential for life. Key concepts include a) water chemistry and its impact on life processes; BIO.8 The student will investigate and understand dynamic equilibria within populations, communities, and ecosystems. Key concepts include d) the effects of natural events and human activities on ecosystems; and e) analysis of the flora, fauna, and microorganisms of Virginia ecosystems. Math SOLs: A.6 The student will graph linear equations and linear inequalities in two variables, including a) determining the slope of a line when given an equation of the line, the graph of the line, or two points on the line. Slope will be described as rate of change and will be positive, negative, zero, or undefined; and b) writing the equation of a line when given the graph of the line, two points on the line, or the slope and a point on the line. A.8 The student, given a situation in a real-world context, will analyze a relation to determine whether a

2 direct or inverse variation exists, and represent a direct variation algebraically and graphically and an inverse variation algebraically. Materials: Distilled water, hot plate, temperature probe, distilled O2 probe, Vernier LabQuest, LoggerLite program Safety: Safety goggles should be worn when experimenting with chemical reactions. Safety tongs to avoid burning hands. Procedure: Engage 10 min 1. Ask students to turn to their neighbor and brainstorm why certain organisms live in varying temperatures and depths in the same aquatic environments. Ask them to defend their reasoning. 2. Have the class come back for a discussion in order to share their responses. The teacher will be using informal assessment through the use of class discussion. Explore 40 min 3. Students will get into pairs and will answer the pre-lab questions before they begin the lab. 4. Students will then perform the lab and collect data. Explain 20 min 5. Students will answer the post lab questions and perform calculations based on the data. Here the teacher will be using formal assessment of learning through the use of an activity sheet in order to see if the students understood the material. Elaborate 20 min 6. Students will use the last part of class to begin research examples of human activity that change the levels of dissolved oxygen and the effects that it has on the wildlife in a Virginia ecosystem. The teacher will be using this and the paper to look for application of the material learned through the lab. Evaluate Homework 7. For homework the students will write a page paper on what they researched in class. The teacher will use a rubric to grade the assignment based on understanding of the topic and on effort.

3 Name Class Dissolved Oxygen Lab Dissolved oxygen (DO) is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. Oxygen from the air dissolves when it comes into direct contact with water. Running water, because of its churning, dissolves more oxygen than still water, such as that in a reservoir behind a dam. Respiration by aquatic animals, decomposition, and various chemical reactions consume oxygen. If more oxygen is consumed than is produced, dissolved oxygen levels decline. Pre-Lab Questions: 1. Do you think there is a relationship between DO and water temperature? If there is a relationship, what type of relationship exists? 2. What is the independent variable in this experiment? What is the dependent variable? 3. Give your best explanation for how oxygen dissolves in water. Draw a representation of your understanding. Materials: 250mL beaker hotplate distilled water temperature probe distilled O2 probe LoggerLite program Vernier LabQuest Directions:

4 1. Turn on the Vernier LabQuest and plug it into the computer. If this does not open the LoggerLite program then do so by clicking on the icon on the desktop or going to programs and finding it. 2. Plug the temperature probe into the LabQuest. It will begin reading temperature as soon as it is plugged in. Calibrate the temperature probe by using the directions found in the temperature probe manual. 3. Plug the dissolved oxygen probe into the LabQuest. The probe will need to be calibrated upon use. The directions are found in the dissolved oxygen manual. Notes on the probe: Before collecting data the probe will need to warm up first. Leave the probe plugged into the LabQuest and running for approximately 10 minutes in order to warm up the probe. When collecting data the probe will need a constant stream of water running over the membrane so you will need to stir the water for the whole ten minutes using the probe. Be careful about dragging it on the bottom of the beaker and in hitting the temperature probe while stirring. 4. Measure out and pour 100mL of distilled water into the 250mL beaker. 5. Place the temperature and dissolved oxygen probes into the beaker and place the beaker onto the hot plate. 6. Before collecting data make sure that the probes are both receiving readings from the water. Format the time of sample readings by going to Data Collection at the top of the screen and setting number of samples per minute to 12/min and setting total time of collection to 10 min. 7. Turn on the hot plate to high and hit Collect in order to begin collecting data. Constantly stir the water with the dissolved oxygen probe. 8. When data collection is complete turn of the hot plate and remove the probes from the water. CAUTION: The hot plate will be very hot. Leave it to the side out of the way until it cools down. Dump out the water and put away all glass and probeware. Post Lab Questions: 1. Using the provided graph paper, create a graph representing dissolved oxygen versus temperature. Draw a line of best fit. 2. Based on the graph, what is the apparent relationship between temperature and DO in water? Is it positive or negative? Direct or inverse? Explain your answer.

5 3. Calculate the slope for the graph. Write an equation for the line. 4. How would you describe the slopes of these lines? Are they positive, negative, zero or undefined? Explain. 5. Would there be more DO towards the surface of a lake or towards the bottom? Explain your reasoning. 6. Would you expect the DO in water taken from a stream entering a lake to be higher or lower than the DO taken from the lake itself? Explain. 7. In what season would there be the most dissolved oxygen in water? Why? 8. What do you think would happen if the levels of DO in a lake decrease significantly?

6 Exceeds 5 pts. Meets 3 pts. Approaches 2 pts. Does Not Meet 1 pts. Did Not Complete Assignment pts. 0 Focus How well did you research and stay on topic? Content Does the assignment contain relevant information? Human impact addressed? Is a specific Va Ecosystem addressed? Organization Are ideas formatted in a meaningful, logical manner? Style & Mechanics How nice is it? Spelling and grammer? Is it well executed? Length of Paper 20 = 100% 15 = 85% 10 = 70% 5 = 55%

7 Exit Slip 1. What did you learn about dissolved oxygen and temperature from this lab? 2. How do you feel about your final product? 3. If you could do this assignment all over again, what would you do differently/the same? 4. Did you enjoy this assignment? Why or why not? 5. What would you improve for your final product for next time?