Temperature Concept of Temperature To feel the Hotness or coldness of an object Different temperature scales and definitions of lower fixed point and upper fixed point Definition of the temperature of the body : a measure of the average kinetic energy of each particle in that body Next Slide Absolute zero (  273  C or 0 K) Explanation Temperature 1

Temperature Concept of Temperature At absolute zero, the average kinetic energy of each particle is minimum. Thermometers : graduated tool used for temperature measurement. 1. Liquid-in-glass thermometer (3 kinds) (a) Mercury-in-glass thermometer Next Slide (b) Alcohol-in-glass thermometer (c) Clinical thermometer Photo Temperature 2

Temperature Concept of Temperature 2. Rotary thermometer Next Slide 3. Resistance thermometer 4. Thermistor thermometer 5. Thermocouple thermometer Diagram Temperature 3

Temperature Concept of Internal Energy Unit of energy : Joule (J) All objects are composed of small particles and every particle has both kinetic energy and potential energy. Definition of Internal Energy : Next Slide the sum of the kinetic and potential energy of all particles in the body Diagram Rise in temperature means increase in internal energy. Heat and Internal Energy 1

Temperature Concept of Heat Different methods to increase the temperature of the object : 1. The object is hammered violently Next Slide 2. The object is put in contact with a hotter object Diagram Heat and Internal Energy 2 3. Energy released in chemical reactions

Temperature Heating Process Next Slide If a hot object is in contact with a cold object, internal energy is transferred from the hot object to the cold object. It is called the heating process. Heat and Internal Energy 3

Temperature Heating Capacity Specific Heat Capacity Next Slide Devices to measure the energy transferred to the heater Experimental set-up to find the relationship between the amount of energy supplied and the rise in temperature Photo Diagram Heat and Internal Energy 4

Temperature Heating Capacity Next Slide Heat Capacity : The energy supplied by heating process to increase the temperature of a body by 1 K (or  C) Energy needed (released) = Heat Capacity  the temperature raised (lowered) in °C Heat and Internal Energy 5

Temperature Specific Heat Capacity Next Slide Specific Heat Capacity : The energy supplied by heating process to increase the temperature of an object with a mass of 1 kg by 1 K (or  C) Energy needed (released) = Mass  Specific Heat Capacity  the temperature raised (lowered) in °C Heat and Internal Energy 6

Temperature Specific heat capacities of common materials Next Slide SubstanceSpecific heat capacity (J kg -1 °C -1 ) Water4200 Methylated spirit2400 Ice2100 Aluminium900 Glass670 Iron460 Lead130 Heat and Internal Energy 7

Temperature Worked Examples Next Slide Example 1 Example 2 Calculation Applications Explanation Heat and Internal Energy 8

END of Temperature

Temperature Next Slide Temperature scale : we choose two temperatures called the fixed points. We define the scale of temperature according to these two fixed points. Celsius scale : lower fixed point (ice point) and upper fixed point (steam point) Lower fixed point : temperature of melting point under normal atmospheric pressure is taken as 0  C Upper fixed point : temperature of steam over boiling water at normal atmospheric pressure is taken as 100  C Temperature 1

Temperature Next Slide melting ice 0C0C lower fixed point boiling water 100  C upper fixed point Two marks are made on the thermometer to indicate the positions of lower fixed point (0  C) and upper fixed point (100  C). Temperature 1

Temperature Click Back to Back to 0C0C10  C20  C30  C40  C50  C60  C70  C80  C90  C100  C Kelvin temperature scale : e.g. 0  C = 273 K, 100  C = 373 K,  273  C = 0 K 0C0C10  C20  C30  C40  C50  C60  C70  C80  C90  C100  C 273K283K293K303K313K323K333K343K353K363K373K Kelvin temperature = Celsius temperature Celsius temperature scale: Temperature 1

Temperature Click Back to Mercury-in-glass thermometer : It is a narrow glass tube. One end of the tube is made into a bulb which contains mercury and the other end is sealed. Normal temperature range measured :  10  C  C Maximum temperature range measured :  39  C  C Back to Temperature 2

Temperature Click Back to Alcohol-in-glass thermometer: It is a narrow glass tube. One end of the tube is made into a bulb which contains alcohol while the other end is sealed. Normal temperature range measured :  30  C - 60  C Maximum temperature range measured :  115  C - 78  C Back to Temperature 2

Temperature Click Back to Clinical thermometer is shown below : It is a special mercury-in-glass thermometer with a narrow bend in the tube. The scale used contains only a few degrees above and below the normal body temperature of 37  C. It is used to measure the body temperature. Back to Temperature 2

Temperature Click Back to Rotary thermometer: When the bimetallic strip with the pointer is heated, it bends because the metal on one side expands more than the metal on the other side. Back to Temperature 3

Temperature Click Back to Structure of a solid: Back to particles vibrate and have K.E. P.E. depends on the relative position of the particles Heat and Internal Energy 1

Temperature Click Back to A solid is hammered as shown below : Back to The particles are then forced to vibrate more vigorously, hence they possess more K.E. Temperature, which is a measure of the average K.E. of the particles, rises. Heat and Internal Energy 2

Temperature Click Back to A solid is in contact with another solid with a higher temperature Back to The particles in the solid with a lower temperature are forced to vibrate more vigorously (temperature rises). On the other hand, the particles in the solid with a higher temperature vibrate less vigorously (temperature drops). Heat and Internal Energy 2

Temperature Next Slide Kilowatt-hour meter: Heat and Internal Energy 4

Temperature Click Back to Joulemeter : Back to Heat and Internal Energy 4

Temperature Next Slide The following set-up is used to investigate the relation between the energy supplied and the rise in temperature. to power supply polystyrene cup stirrer water thermometer immersion heater Joulemeter or kilowatt-hour meter Heat and Internal Energy 4

Temperature Next Slide Results obtained : Energy transfer E (J) Temperature T (  C) Temperature rise  T (  C) 0 Energy transfer E temperature rise  T (  C) graph of E vs.  T Heat and Internal Energy 4

Temperature Next Slide We obtain a straight line which passes through the origin. This means that for a constant mass, the energy transfer is directly proportional to the temperature rise, that is, E   T for constant m. Then we investigate how the energy transfer is related to the mass of water. The time taken to heat different masses of water through the same temperature rise, say 10  C. Results obtained : Energy transfer E (J) Mass of water m (kg) Heat and Internal Energy 4

Temperature Next Slide 0 Energy transfer E mass of water m (kg) graph of E vs. m Again, we obtain a straight line which passes through the origin. This means that for a given temperature change, the energy transfer is directly proportional to the mass of water, that is, E  m for constant  T. Heat and Internal Energy 4

Temperature Click Back to The polystyrene cup is used to hold the water. It is a bad conductor and so the energy lost to the surroundings is reduced. Moreover, it takes up little energy. Back to The stirrer is used to stir the water to maintain a homogeneous temperature in the water. The Joulemeter (or kilowatt-hour meter) can measure the energy supplied to the immersion heater. The unit of the heater is kWh (kilowatt-hour). 1 kWh = J Heat and Internal Energy 4

Temperature Next Slide 2.25 kg of oil is put into the following set-up. polystyrene cup stirrer oil thermometer immersion heater Initial reading of Joulemeter : J Final reading of Joulemeter : J Initial temperature : 30  C Initial temperature : 70  C Heat and Internal Energy 8

Temperature Click Back to Energy supplied by the Joulemeter = (82500  42500) J = J Back to Rise in temperature = (70  30)  C = 40  C Heat capacity of the oil = Specific heat capacity of the oil = Heat and Internal Energy 8

Temperature Next Slide 2 kg of hot water at 80  C is mixed with 4 kg of cold water at 20  C. Suppose no energy is lost to the surroundings, what is the final temperature of the water? (Specific heat capacity of water : 4200 J kg -1  C -1. Heat and Internal Energy 8

Temperature Click Back to Let T°C be the final temperature Back to Energy lost by the 2 kg water : Energy gained by the 4 kg water : By the principle of conservation of energy, the amount of energy lost by the hot body = the amount of energy gained by the cold body Heat and Internal Energy 8

Temperature Click Back to Since water has a relatively high specific heat capacity, it needs a large amount of energy to raise the temperature of water. Back to Coolant of the engine of motor cars Regulate the temperature of living organisms Regulate the temperature of the land near the sea Heat and Internal Energy 8