Chapter 4: Heat Capacity and Heat Transfer Chapter 4: Heat Capacity and Heat Transfer
Chapter 4: Heat Capacity and Heat Transfer 4.1 Material Structure 4.2 Temperature and Material Properties 4.3 Heating and Internal Energy 4.4 Heat Capacity and Latent Heat 4.5 Heat Transfer
4.1 Material Structure Atom The smallest unit of element. Molecule Ex. Molecule of water (H 2 O) consists of 2 hydrogen atom and 1 oxygen atom The smallest unit of compound consist of many atoms
4.1 Material Structure The Phase of Matter: Solid Solid Molecules constructs together with strong bond. Therefore, solid has definite volume and shape.
4.1 Material Structure The Phase of Matter: Liquid Liquid Molecules can freely move, but it cannot move so far because of its bond. Therefore, liquid has a definite volume but no definite shape. So, it can change its shape according to it container.
4.1 Material Structure The Phase of Matter: Gas Gas Molecules can freely move with long distance because it has weak bond. Therefore, gas has neither a definite volume nor shape. So, it can change its shape according to it container like liquid.
4.1 Material Structure Moving Ability of Molecules Solid < Liquid < Gas Kinetic Energy of Molecules Solid < Liquid < Gas Internal Energy of Molecules Solid < Liquid < Gas
4.2 Temperature and Material Properties Temperature A measure of the warmth or coldness of an object which depends on internal energy (kinetic energy) of material. High internal energy High temperature Low internal energy Low temperature
4.2 Temperature and Material Properties Temperature Scale
4.2 Temperature and Material Properties Temperature scale in Kelvin, T(K) depends on internal energy (kinetic energy) When T(K) is low, the molecules will move slowly until it stop at 0 K called absolute zero
4.2 Temperature and Material Properties Mercury thermometer Temperature measurement device called Thermometer Advantage: Mercury thermometer can hold the value although it doesn t contact patient. (User needs to flick before measure) Disadvantage: Mercury is toxic. Digital thermometer Now, mercury thermometer is replaced by Digital thermometer.
4.2 Temperature and Material Properties Material will extend when its temperature increase. Material will shrink when its temperature decrease. Because of kinetic energy, when kinetic energy of molecule increases, molecule velocity increase too. It causes the distance between molecules higher. The relation between temperature change and material extending is linear
4.2 Temperature and Material Properties High temperature Low temperature Heat Length difference Referent length Temperature difference Coefficient of linear expansion
4.2 Temperature and Material Properties Example of coefficient of linear expansion
4.2 Temperature and Material Properties Ex. Lead has 3 cm of its length. If temperature increases from 37 ºC to 40 ºC, find the length after heating.
4.2 Temperature and Material Properties Mercury thermometer has bulb to contain liquid mercury at the terminal. Mercury will extend and flow to glass tube when temperature around its bulb increases.
4.2 Temperature and Material Properties To construct railway, we need to abstain around joint for extending of metal to protect the derailing.
4.3 Heating and Internal Energy The energy occurs from the difference of temperature called Heat.
4.3 Heating and Internal Energy In natural, heat transfers from high temperature to low temperature till equilibrium called Thermal Equilibrium. Material that receives heat will increase temperature. Material that losses heat will decrease temperature.
4.3 Heating and Internal Energy Material temperature is not only changed by heating, but it is also changed by mechanical energy and etc. thermometer James Joule s experiment water insulator
4.3 Heating and Internal Energy Heat can change material phase. Exothermic Exothermic Endothermic Endothermic
4.3 Heating and Internal Energy
4.3 Heating and Internal Energy V.S. If we chill watermelon and sandwich, which one can hold longer temperature?
4.3 Heating and Internal Energy Heat Energy (Q) Two materials has the same mass (m), but difference heat capacity (s). If we want to increase temperature, material that has more heat capacity (s) will need more energy (Q) If we give the same energy (Q) to two materials, material that has more heat capacity (s) will change its temperature slowly.
4.3 Heating and Internal Energy Ex. (A) Find heat energy that increases 200g water temperature for 5 degree Celsius. (S water = 1 cal/g.c) Ex. (B) Find heat energy that increases 200g lead temperature for 5 degree Celsius. (S lead = 0.03 cal/g.c)
4.3 Heating and Internal Energy Phase Change Give 1 cal/s of heat energy to 1 g of ice. Water + Vapor Ice Water time Water + Ice
4.3 Heating and Internal Energy Water + Vapor Ice Water time Water + Ice
4.3 Heating and Internal Energy No temperature change Water + Vapor Ice Water time Water + Ice
4.4 Heat Capacity and Latent Heat Heat is used to change phase called Latent Heat. gas Exothermic condensation vaporization Endothermic liquid Exothermic freezing solid fusion Endothermic
4.4 Heat Capacity and Latent Heat We can calculate energy that uses to change phase using the following equation. Q v = Energy of vaporization L v = Latent heat of vaporization Q f = Energy of fusion L f = Latent heat of fusion
4.4 Heat Capacity and Latent Heat
4.4 Heat Capacity and Latent Heat Ex. Aluminum glass contains 800 g of water
4.4 Heat Capacity and Latent Heat Ex. Aluminum glass contains 800 g of water
4.5 Heat Transfer Heat Convection Heat conduction Conduction Heat transfer of material from contact Radiation Convection Heat transfer of material using mass movement Ex. Water in boiler boils thoroughly. Radiation Heat transfer of light, ray, electromagnetic wave, or etc. It can be exothermic and endothermic.
4.5 Heat Transfer Heat transfer occurs from collision of molecules at the contact point Feel Cool K.E. of foot molecule is higher than floor. K.E. will transfer to floor Temperature reduces
4.5 Heat Transfer Heat transfer occurs from collision of molecules at the contact point Feel Hot K.E. of foot molecule is lower than floor. K.E. will transfer to foot Temperature increases
4.5 Heat Transfer
4.5 Heat Transfer Heat Convection In natural, heat convection occurs when object receives heat. Although gas and liquid are not good at heat conduction, it is good at heat convection. Molecules of gas and liquid can flow for long distance, and they will bring heat energy together. It occurs together with movement of medium.
4.5 Heat Transfer Radiation Object releases electromagnetic energy called radiation Electromagnetic wave can travel without medium. Ex. Light from the sun can travel passing space to the earth.
4.5 Heat Transfer In still air, heat from flame transfers with radiation process. In flow air, heat from flame transfers with convection process.
4.5 Heat Transfer Heat and Human body If human has high body temperature or low body temperature, it can cause very dangerous disease such as heat stroke and hypothermia. How to make body temperature lower.
END OF CHAPTER 2 END OF CHAPTER 4 Heat Capacity and Heat Transfer