Students use bean seedlings to observe the effect of hot air on ten day old seedlings.
thermometer; hand held hair dryer; ten bean seedlings (with two or more leaves); graph paper; paper cup; soil;
Background For Teachers:
While the lesson plan calls for ten day old bean seedlings, you could use full grown plants. If you use the bean seedlings, you will want to plant the beans in individual cups and wait until the seedling has at least two leaves. After the seedlings wilt from the hot air, a fresh water mist may revive them.
Intended Learning Outcomes:
Students will make observations, measurements, and predictions. Students will identify variables and describe relationships between them and will collect and record data. Students will analyze data and draw warranted inferences. Students will understand science concepts and principles. Students will construct graphs.
Show the seedlings to the students and ask, 'What has helped the beans sprout these leaves?' Students should discuss the influence of water, sun, soil, and air on the sprouting of the bean. Ask the students, 'What do you predict will happen to our bean seedlings if we change the temperature of ONLY the air?' Let students make a prediction before doing the experiment. 1. Assign the students into groups of three. Each group should be assigned one bean seedling for their observation/experiment. If the groups are growing their own seedlings, have each group plant two bean seeds in a cup of soil. Instruct the groups to make a small hole in the bottom of the cup and to water the bean seeds daily. Begin the experiment when the bean seedlings have two leaves. When you have bean seedlings with two leaves, spend ten days collecting the following data: 1) Daily measure the air temperature under the leaves (if you are using an outdoor pond, take this temperature in the shade provided by grown trees or bushes rather than the bean seedling leaves), 2) Daily measure the air temperature in direct sunlight. These observations can be noted in a table accompanying this step.
You will probably have to teach the students how to read a thermometer. Assign the students to graph the two sets of data (temperature under the leaves and temperature in sunshine). Discuss any differences noted. Watch for the opportunity to point out the importance of shade trees on humans and wildlife as well as plants. After observing the bean seedlings and taking temperature measurements for ten days, ask students to PREDICT what would happen to plants if a hot wind were to blow on them? Use the hand held hair dryer to simulate a hot wind. Blow hot air onto the seedlings for several minutes. Have the students measure the temperature of the air surrounding the seedling while the blow dryer is turned on. Have the students note observations about the seedlings. Ask students what happened when the hot air was blown on the plant. Why did it happen? What would happen if air that was much colder than normal were blown in the plant? What is the importance of air to plants? How do some plants protect themselves from air that is too hot or too cold? (Cactus have thick, waxy leaves that protect them from drying out in hot air. Deciduous trees lose their leaves. This helps protect them from the cold.) How do farmers protect their crops from cold air? (Cover them with plastic, burn smudge pots around fruit trees.)
After the seedling wilt under the hot air, reviving them with a mist of cool water helps students understand the Dew-Plant Interaction. Standard 3010-02 (Students will describe the characteristics and use of water) and Objective 3010-0202 (Demonstrate the effects of water on plants, animals, and people) correlate well to such an extension.
Check the graphs for accuracy. Make sure students have made their predictions. Ask students to predict what would happen to a garden in their backyard if a very hot wind were to blow all day long one spring day. Ask students to explain the importance of air to plants.
Created Date :
Mar 19 1999 13:38 PM