Tarlac State University College of Education Villa Lucinda Campus Academic Year 2017 – 2018 Lesson Plan in Physics 2: Thermodynamics Expansion of Solids Submitted by: Andrhea P. Soriano BSEd Sciences 2B Submitted to: Professor I. Objectives At the end of the lesson, the students are able to: • Enumerate the factors that affect the expansion of solid materials through heating. • Define thermal expansion in solids more precise. • Compare expansion of solids to expansion of liquids and gases. • Calculate the expansion of an object given its initial length and change in temperature II. Preparation / Preliminaries 1. Title: Thermal Expansion: Expansion of Solids 2. Materials/Instructional Materials: • Experimental video showing how change of temperature affects solid objects. • Pictures and GIFs showing expansion of solids when heated and cooled. 3. References a. Printed: • Physics Alive by Peter Warren b. Online: • http://www.scienceclarified.com/El-Ex/Expansion-Thermal.html • http://ramadan.50megs.com/IGC_Expansion.htm • https://www.youtube.com/watch?v=ZPXr3fL4la8 • https://study.com/academy/lesson/the-kinetic-theory-of-matterdefinition-the-four-states-of-matter.html • https://physics.gurumuda.net/linear-expansion-problems-andsolutions.htm • https://byjus.com/thermal-expansion-formula/ • http://physics.bu.edu/~duffy/py105/Temperature.html#targetText=The %20length%20of%20an%20object,an%20object%20is%20made%20f rom. • https://physics.gurumuda.net/area-expansion-problems-andsolutions.htm 4. Methods or Strategy • Discussion Method - collaborative exchange of ideas among a teacher and students or among students for the purpose of furthering students thinking. • Demonstration Method - is a teaching method used to communicate an idea with the aid of visuals such as flip charts, posters, power point, etc. • Computer Assisted Instruction - uses multimedia to aid the teacher learning process. III. Review / Unlocking of Difficulties The reporter will familiarize the students with the kinetic theory of matter, phases of matter and expansion. • Expansion - the action of becoming larger or more extensive. • Kinetic Theory of Matter - states that matter is composed of a large number of small particles (individual atoms or molecules) that are in constant motion. • Phases of Matter o A solid is matter in which the molecules are very close together and cannot move around. o A liquid is matter in which the molecules are close together and move around slowly. o A gas is matter in which the molecules are widely separated, move around freely, and move at high speeds. IV. Introduction and Motivation Jigsaw Puzzle (Images of solid, liquid, gas, and expansion) The game has 4 rounds and 4 groups playing the game. There is no time limit; the fastest group to solve the puzzle wins the game. Based on the images that were solved, the teacher will review the students about the phases of matter and Kinetic Theory of Matter to further understand thermal expansion. V. Body and Discussion Thermal expansion is the tendency of matter to change its shape, area, and volume in response to a change in temperature. It is the difference between the original size of an object and its size when it’s cooled or heated. Solid, liquid, and gases all undergo thermal expansion. Expansion of Solids • What happen to solids when they are heated and expand? ✓ When a solid is heated its particles vibrate more rapidly. As a result they collide and push each other further apart. ✓ When a solid is heated, its molecules gain kinetic energy and vibrate more vigorously. As the vibration become larger, the molecules are pushed further apart and the solid expands slightly in all directions. ✓ The kinetic energy which is dependent on the temperature is also increasing and these particles of solids are vigorously vibrating and moving. • What happen when solids are cooled? ✓ When a solid is cooled, its molecules lose kinetic energy and have less vibration. As the vibration become lower, the molecules are pulled closer and the solid contracts slightly in all directions. • What are the factors that affect the expansion of solids? ✓ Original length – the original length of an object is one of the more obvious things that depend on temperature. ✓ Temperature change – the dependence of thermal expansion is on the change of temperature. ✓ Material type – some solids expands more easily than others. If you heat wires of aluminum, iron, and tungsten metals—all the wires being the same size and heated to the same temperature—each wire will expand by a different amount. The ease with which a substance expands is given by its coefficient of expansion. • 3 Kinds of Thermal Expansion which solids undergo: ✓ Linear – expansion of solids in length ✓ Superficial or Surface - expansion of solids in surface ✓ Cubical or volume - expansion of solids in volume • Calculating the expansion of solid objects 1. A 1-m long aluminum rod is heated from 30 °C to 50 °C. By how much it will expand? What will its final length be? Given: l = 1 m To = 30oC T = 50oC Find: a. change in length ∆l b. final length l Solution: a. ∆𝑙 = 1 m × 24×10−6 ℃ × 20℃ = 0.00048 m b. Lf = lo + ∆l = 1 m + 0.00048 m = 1.0048 m VI. Summary and Generalization Thermal Expansion Thermal expansion solely depends on the change of temperature. It is the increase or decrease of the size of an object, in length area or volume depending on the type of material used. Without the change of temperature, solids cannot expand. Expansion of Solids • What happen to solids when they are heated and expand? When solid objects absorbs or loses heat energy, the movement of the particles are affected, which causes solid objects to expand. • What happen when solids are cooled? When solid objects are cooled, they lose kinetic energy gained from the increase of temperature. As they lose kinetic energy, the vibration of the particles become less vigorous, causing the solid object to contract. • What are the factors that affect the expansion of solids? The amount on which solids expands depends on its original length, the temperature change and the properties of the material used. • 3 Kinds of Thermal Expansion which solids undergo: These are linear expansion, where solids expand in one direction, surface expansion, where solids expand in two dimension, and volume expansion, where solids expand in three dimensions. • Calculating the expansion of solid objects When calculating linear expansion of solids, the coefficient of linear expansion, since it only expands at one direction, is not multiplied. While in surface expansion of solids, the coefficient given is multiplied by two, because surface expansion expands in two directions. In volume expansion, coefficient is multiplied by three because it expands in three directions. VII. Evaluation 1. Thermal expansion depends on? a. Change of temperature b. Change of position c. Change of material used d. Change of size 2. Solids expand when heated because ____________. a. They are easy to break b. Some solids diffuse in liquids and not in gases c. They absorbs heat energy and vibrate vigorously d. Some solids are cold and some are hot 3. What are the factors that affect expansion of solids? a. Length, weight and material type b. Weight, properties of the object, and change of temperature c. Texture, length and material type d. Length, change of temperature and material type 4. How much taller does the Eiffel Tower become at the end of a day when the temperature has increased by 15 oC? Its original height is 321 m and you can assume it is made of steel. 5. Steel is 40 cm long at 20 oC. The coefficient of linear expansion for steel is 12 x 10-6 oC. What is the change in length and the final length when it is at 70 oC? VIII. Assignment Solve the following problems. 1. The height of the Washington Monument is measured to be at 170 m on a day when the temperature is at 35 oC. What will its height be on a day when the temperature falls to -10 oC? Although the monument is made of limestone, assume that its thermal coefficient is the same as marbles. 2. How large an expansion gap should be left between steel railroad rails if they may reach a maximum temperature 50.0 oC greater than when they were laid? Their original length is 10.0 m. 3. At 20 oC, the length of a sheet of steel is 50 cm and the width is 30 cm. If the coefficient of linear expansion for steel is 10-5 oC-1, determine the change in area and the final area at 60 oC.
