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Specific Heat Capacity Lesson Plan Prepared By: Koh Chia Ho, Jared 054554L23 S7904178E Lecturer: Dr Yap Submission Date: 17 Oct 2005 Specific Heat Capacity Topic: Thermal Properties of Matter Subtopics: Specific Heat Capacity Duration: 2 periods (70 minutes) Level: Secondary 3 Express (Pure Physics) Venue: Physics Laboratory Lesson Prerequisites: Students have learnt: a) A rise in average kinetic energy of molecules in a substance corresponds to a rise in its temperature. b) Thermal energy is transferred from a region of higher temperature to a region of lower temperature. c) The motions of particles of substances in the three phases in terms of Brownian motion. d) The Principle of Conservation of energy in the case of heating where the amount of heat energy supplied to a substance is equal to the amount of heat energy gained by it. Specific Instructional Objectives for the Lesson: At the end of the lesson, students should be able to: a) Define the terms heat capacity and specific heat capacity. b) Recall the relationship thermal energy = mass specific heat capacity change in temperature c) Apply the relationship between thermal energy, mass, specific heat capacity and change in temperature to new situations or to solve related problems d) Apply their knowledge of the high heat capacity of water to everyday applications. Learning Aids & Resources: Non IT: i) 1 metal spoon ii) 1 plastic spoon iii) 1 candle iv) 1 balloon filled with air v) 1 balloon half filled with water, half filled with air vi) 1 beaker containing 400ml of water vii) 1 beaker containing 400ml of cooking oil 1 Specific Heat Capacity viii) 2 immersion heaters ix) Data logger with 2 temperature sensors IT: i) PowerPoint Slides ii) Java applet on colorimetry Worksheet: Worksheet 1 New Concepts/Terms: Heat capacity, specific heat capacity. Concept Map: Increases or decreases Heat absorbed or Internal energy of matter released, Q Which in turn increases or decreases Potential energy Heat C Specific Heat (due to Kinetic energy Capacity, C c Capacity, c m intermolecular (due to motion) Q C where m = mass Q mc force) Change in kinetic energy causes Temperature change in matter, Set Induction and Use of Trigger Activity: Demonstrate that despite students’ intuition, a heated water balloon does not burst due to the high heat capacity of water. Students will be rooting for the water balloon to burst and wetting the teacher in the process. When this does not happen, it throws students into a cognitive disequilibrium. They would be very interested to learn why, and as a result, be more attentive during the lesson. Lesson Development: 1) Everyday applications Stimulate students’ minds by recalling their past knowledge of heat insulators and conductors and how it will be tied to heat capacity. 2) Use of IT - Interactive applet demonstration 2 Specific Heat Capacity Stimulate heating different amounts of water. As the science laboratory may not have computers for students to use, this is done via teacher demonstration. An applet is used because this activity is an intuitive concept that students may encounter in their daily lives. The applet is able to produce precise readings that students need to perform calculations on later in the lesson. Demonstration is done with guided questions to engage the students to think about the topic. This also serves as a simple introduction to the concept of having different heat capacities for different amounts of the same substance and sets the pace for the whole lesson. Later on, students can revisit this applet to find the specific heat capacity of water. 3) Experimentation Experimentation to investigate the different rates of heating between oil and water. This allows students to observe first hand that for the same amount of heat supplied, different substances show a different rise in temperature. They are then introduced to the definition of heat capacity. Students can also appreciate the use of cooking oil in cooking because it has a low heat capacity, so we are able to cook food faster. If dataloggers are not available for all students they will have to use thermometers to record the temperature. This also promotes data recording skills in the students. 4) Student participation in learning the definition and calculation of experimental results. Through the use of scaffolding questions, students come up with the definition of heat capacity and specific heat capacity themselves. This helps them to retain this new information better. They then practice what they have learnt in doing some calculations based on their experimental results. This helps give meaning to why they were asked to perform the experiment. Lesson Closure: Ask students to provide an answer to the induction activity performed at the beginning of class based on what they had just learnt. This shows whether students understood the lesson. Use of a concept map to see how what they had learnt fits into the whole picture. This is followed by a quick summary, and students are asked to do some homework questions before the next lesson. Reference: 1) GCE ‘O’ Levels Physics Syllabus (5052) 2) C. Chew, Leong S.C., Chow S.F. (2000) Physics A Course for ‘O’ Level (2nd ed). Singapore: Times Media Private Limited 3) Calorimetry Applet http://www.chm.davidson.edu/java/calorimetry/calorimetry.html 4) Physics Lesson Plan for Thermal Properties of Matter Set E http://teachersportal.nie.edu.sg/kcyap/Physics2002/O%20Level/Thermal%20Properties%20of% 20Matter/Set%20E%20- %20Specific%20Heat%20Capacity/Specific%20Heat%20Capacity%20- %20Lesson%20Plan%20(Set%20E).doc 5) UW Physics Lecture Demonstrations – Heat capacity of a water balloon http://www.phys.washington.edu/facilities/lectdemo/thermo.html#cap 3 Specific Heat Capacity Lesson Plan Stages Activities/Procedures Resources Rationale Set Induction- Show a balloon filled with air, and a balloon half- 1 balloon filled Generate interest in Demo filled with water to the students. with air the topic by Ask students what they would expect if the balloon 1 balloon half- showing a 5 min filled with air is heated by the lighted candle. filled with water, demonstration. Expect students to say the balloon will burst. half-filled with air Students will be Demonstrate that the balloon will burst by bringing 1 lighted candle hoping the water it near the lighter from the top. balloon bursts thus Next, show students the balloon half-filled with PowerPoint wetting the teacher, water and ask them the same question. Slides but that will not Expect a mixture of answers: some say it will burst, happen. some will say it will not. Bring the balloon towards the lighter from the top Only give the slowly making sure the flame does not touch the answer at the end sides of the balloon, just the bottom. Show that the so that they will be balloon does not burst. attentive during the Ask students to think about the reasons why the lesson. balloon does not burst. Feeling the Tell the students that at the end of the lesson, they difference will be able to answer the question. themselves creates a lasting Recall previous knowledge impression. Show the plastic spoon and metal spoon to the class. Let students recall Ask students whether the spoons are at the same their previous temperature. Plastic spoon knowledge of heat Lead students to respond that both spoons are at Metal spoon conductors. Link room temperature. the idea of heat Touch the spoons one after another on most of the PowerPoint conductors and students’ hands. Ask them whether they feel a Slides insulators to the difference between the two materials. property of heat Lead students to recall a concept they had capacity. previously learnt – heat conductors and heat insulators. Lead students to explain the phenomenon they had just experienced based on heat conductance – good heat conductors conduct heat away from our skin faster, making us feel cold. Ask students what kind of material makes up the frying pan’s handle and the actual pan itself. Highlight that this is an application of heat conductors and insulators. Ask students why is it when the same amount of *Note: heat is supplied to a conductor and an insulator, Microteaching one becomes hotter than the other. Tell them that Segment this is also another property that they are going to learn. 4 Specific Heat Capacity Stages Activities/Procedures Resources Rationale Introductory investigation Lesson Show applet on calorimetry to students. Calorimetry An applet is used Development 1- On the applet, heat up 20 ml of water, power applet. in this case because Demo and 100W, for 10 sec and ask students what is the it stimulates the introduction of temperature rise (7.28 degrees Celsius). heating process concept of heat Ask students what they would expect if we double Worksheet faster than actually capacity the amount of water to be heated, all else remain performing the the same. Lead students to intuitively guess that PowerPoint experiment. 10 min they expect a lower temperature rise. Show that Slides Moreover this their guess is correct via the applet (4.52 degrees property is intuitive Celsius raise). so there is no need Remind students to fill in the readings in the applet to perform the into the worksheet actual experiment. Explain to students that when we supply the same amount of heat to different amounts of water, the Start with learning temperature rise is different. This is because a about different heat larger volume of water can absorb more heat before capacities between raising its temperature – it has a larger heat different capacity. substances first. Explain the literal meaning of heat capacity so that This is followed by students can remember easier. learning about Ask students whether for same amounts of different heat different substances, they have the same capacities between temperature rise for the same heat supplied? Make different amounts a guess. of the same substance. *Note: Microteaching Segment Lesson Group students to work in pairs, each student will 1 beaker Reinforce the Development 2- record the temperature of his own beaker of water containing 400 ml concept of heat Reinforcement or oil. of water capacity by heating of heat capacity Students are to heat 1 beaker of water (400ml) and 1 beaker different kinds of and derive its 1 beaker of cooking oil (400ml) using an containing 400 ml liquids. definition. immersion heater. of cooking oil Using temperature sensors connected to datalogger, 2 100 W Show the 20 min students are to observe the difference in heating immersion properties of heat curves. If data loggers are not available, replace heaters capacity first with thermometers. Students are to record down the 2 temperature before introducing temperature every 30 seconds. sensors connected the definition and Remind students to write down the readings in their to datalogger* formula. worksheet with the correct units. Show students that for the same amount of heat Worksheet Deriving the supplied, the rise in temperature is different. definition based on Tell the students they have just observed some PowerPoint their observations properties of heat capacity of matter. Slides help them to recall Derive the definition of heat capacity together with easier. the students and show the formula. Fill in the definition inside the worksheet: the amount of energy needed to raise the temperature of a *normal mercury- substance by 1 K. in-glass Together with students, derive the unit for heat thermometers capacity from the definition. may be used if Highlight that the process of heat absorption is there are reversible – the amount of heat lost during cooling insufficient data is the same as the amount of heat gained for the loggers for same change in temperature. students. 5 Specific Heat Capacity Stages Activities/Procedures Resources Rationale Lesson Ask students to practice doing some questions on Worksheet Applying the Development 3- the worksheet. formula to values Application of Explain to students that the calorimeter in the PowerPoint they recorded formula applet, and the beaker in the demo also absorbs Slides themselves gives heat. Give them the heat capacity of the calorimeter students a greater 10 min as 53.64J/K. White Board sense of closeness Ask students to apply the formula to calculate the to the lesson. heat capacity of water in the applet. Teacher to walk around helping students who encountered difficulties with their calculations. Lesson Explain that since the heat capacity of a substance Worksheet Lead students to Development 3- is dependent on the amount of substance, it is more realize by Extension of convenient to consider the heat capacity per unit PowerPoint themselves that the formula to mass. Slides specific heat specific heat Ask students to divide the heat capacities of water capacity is a capacity obtained from the applet and from the demo by its White Board constant for the respective masses. Remind students that the density same substance. 15 min of water is 1 g/cm3, so its mass in grams Deriving the correspond to its volume in cm3. specific heat Ask them what they observe between the two capacity formula values. They should get roughly the same values; from heat capacity any variance could be due to experimental errors. helps students to From their calculations, explain to students that the link concepts heat capacity of 1 g of the same substance (in this together. case water) is always the same. This is called its specific heat capacity and they have just calculated the specific heat capacity of water. Define specific heat capacity by extending the heat capacity formula; divide heat capacity by its mass. Remind students that because the specific heat capacity of a substance is a constant, it is more meaningful and it is more commonly used than heat capacity. Ask students to practice some questions on the worksheet. Teacher to go through the thinking process with students, providing guidance and scaffolding. Highlight the differences between heat capacity and specific heat capacity in terms of definition and SI unit. Remind students of the naming conventions: C for heat capacity, c for specific heat capacity. Lesson Ask students what applications they can think of Worksheet Let students Development 4 based on the high specific heat capacity of water. PowerPoint understand the Applications Teacher to lead students where necessary. Slides usefulness of heat Some applications: capacity. 5 min 1. Hot water bottle to keep warm on cold nights. White Board 2. Water used as cooling liquid in car engines 3. Land and Sea breezes. Closure Remind students of the demonstration done at the PowerPoint Provide a summary beginning of the lesson, and ask students to explain Slides for the lesson and 5 min why the balloon does not burst based on what they check whether the had learnt on heat capacity: (1) balloon is stretched White Board students are able to very thin there is good thermal contact between understand the 6 Specific Heat Capacity Stages Activities/Procedures Resources Rationale water and flame. (2) due to the high heat capacity concept. of water, heat is quickly absorbed and the rubber does not get heated enough to melt. Remind students to realize that water has a high specific heat capacity. Remind students that heat insulators have very high specific heat capacity so they do not get hot easily. Check for understanding by asking students that they have learnt in the lesson. Recap using a concept map. Answer any queries students may have on the topic. Ask students to do some exercises on heat capacity at the end of the worksheet. 7

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