 |
 |
 |
|
|
What Crushed the Can?Submitted by: Jane Boyd OVERVIEW: In this elementary science activity, students will have an opportunity to solve a "mystery" and discover why a can collapses during a demonstration due to the effects of changes in temperature and atmospheric pressure on a soda can. Students will gain further insight in the process of scientific inquiry as they suggest questions that need to be answered in order to solve what appears at first to be a mystery. LEVEL: Fourth Grade GENERAL OBJECTIVES:- To help the students gain an understanding of the effects of air pressure on objects in their environment.- To help students develop their observational and inquiry skills.- To promote an understanding of inquiry and research processes--raising questions, developing and testing hypotheses. TIME: 45 Minutes BEHAVIORAL OBJECTIVE: After observing a demonstration of the effects of air pressure and temperature on a soda can, students will write an entry in their science journals that accurately explains what caused a soda can to collapse. PROCEDURE: 1.Instruct students to put everything away except their science journals and a pencil. 3.Ask: "What do you see?" (Students should name the items before them.) 4.At this point in the lesson, conduct a discussion relating to recycling while at the
same time casually completing several steps--outlined below--with the materials. Ask: "What do you do with your tin cans and bottles at home when you no longer have any use for them?" (Students will probably say that they put them in a recycling bin or container that their mother will later take to a store or that they take them to the store themselves to get the deposit refund.)- Ask: "When you or your parents take them to the store to get the refund, where do you put the cans?" (Students will say they have to put them in a machine.)- Ask: "What does the machine do to the cans and plastic bottles?" (Students will say that the machine crushes the cans and that it shreds plastic bottles.) Steps to Complete With the Materials During the Discussion: -Measure 1/4 cup of water. -Pour the water into one of the empty soda cans.- Heat the can on the electric hot plate until the water boils and steam is visible.-
6.Observe the students' reactions, and write the reactions observed on the board. (It is anticipated that many students will show surprise or be startled by what they see.) 7. Repeat the demonstration (as in step five above). 8.After the demonstration has been repeated, ask the students: "What questions can you think of that may help you to learn more about what you saw?" (Students will probably respond by asking what happened, how it happened, what was in the can, what was in the water, if there was some trick, if the heat and cold water crushed the can, and if they can try it themselves.) 9.Write the questions students raise on the board. Try to elicit any additional questions that students think will help to solve the "mystery." Give the students time to respond, and record any additions. 10.Call attention to the list of questions with, " Let's look at your questions. Which ones do you think we will need answered in order to find the solution and help you to understand what happened to the cans?" Guide the students through the process of selecting several "key" questions. 11.Ask students to think through what they observed in the demonstration. Say, "Tell me what you know about what I did." On the board, list all the observations and facts the students offer. (Anticipated responses will include the following observations: - You put water in the can. - It cooled fast. 12.At this point, ask students to write what they think caused the can to collapse in their journals. Explain that the journals will not be collected at this time, that students will refer back to what they write a little later. (Some students will probably write that the temperature changed, that it was the change in temperature that made the can collapse, and that the air in the can was sucked out. Using their previous knowledge about the three states of water, students will have realized that by reducing the temperature inside the can, the steam will have condensed into water thereby causing a reduction of air pressure inside the can causing it to collapse.) 13.Invite the students to watch as the demonstration is performed again. Once again, ask students to recall what they observed, and review the their observations. Also ask if they feel they need to know anything more at this point in order to be sure they have solved the problem and that they understand the cause of the collapsing cans. (It is anticipated that if they were not sure about the cause before, some students may raise additional questions at this time because they were aware of the need to concentrate more on exactly what occurred.) 14.Provide the following information to help students determine if their journal responses are scientifically accurate:- Explain that what the students were watching resulted from a change in air pressure. - Ask students what they feel in their ears when going up a long hill or mountain, flying in an airplane, riding through a tunnel, or underwater. (Students will probably respond that their ears become plugged, that they hurt, or that their ears bother them in some ways.)-
Explain that when they are rising or falling rapidly, such as in an airplane, the pressure inside their heads is different than the pressure outside and that the feeling they experience in their ears is a result of that difference in pressure. The difference in pressure is corrected by the steps they have tried.- Discuss how the differences in pressure may be applied to what they observed happening to the cans. Ask the following questions: -- How did I change the pressure inside the can? (Students may suggest it was the heat or a change in the amount of heat.)-- When I heated the can with water, steam was created. We know that steam takes up more space and dry air. When I put placed the hot can in the cold water, what happened to the steam? (Students should say that it condensed or became water again.)-- Ask students: "If the steam condensed into water, what happened to the air pressure inside the can? Will it be greater or less than it was before the steam condensed? (Students who did not think about this before should now reason that it will be less.)-- Ask: "Why then did the cans collapse? (Students should now agree that because the air pressure on the inside of the cans became less than the pressure outside, it was the difference in pressure that caused the cans to collapse.)--
15.At this point, take the students back to the beginning of the activity to discuss the process they have experienced. Review the sequence of the lesson, asking "What happened first in this lesson?" Write the steps students recall on the board. 16. Using the list of steps on the board, order the steps as follows: - Something got our attention. 17.Explain to the students that they had a problem to solve, a scientific "mystery." As they investigated ways to solve the problem, they were doing the work of scientists, using the scientific method to find an answer to the problem. 18.Finally, ask students to record the process they followed--from the list on the board--in their journals for future reference in solving other similar scientific problems. MATERIALS:- Six empty soda cans -A pair of tongs- |
Copyright© Teacher's Desk. Any reproduction of this site in any manner is strictly prohibited. Revised: 19 Mar 2002 11:34:00 -0600. |