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Heat and temperature
This document discusses heat and temperature. It begins by explaining early theories of heat, including the caloric fluid theory which was later disproven. It then discusses sources of heat, both natural like the sun and artificial like chemical reactions. Key terms are defined, like conduction, convection and radiation as methods of heat transfer. Common temperature scales are explained including Celsius, Fahrenheit and Kelvin. Effects of heat like expansion and phase changes are covered. The document concludes with a short quiz to test the reader's understanding.
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Heat and temperature
- 1. Heat and Temperature Prepared by: Victor R. Oribe
- 2. What is heat? Upto the middle of 19th century, it was thought that heat was an invisible, weightless substance called Caloric Fluid. When wood, for instance is burned, it is hot because it produces large quantities of caloric fluid which is transferred to other substance close by. The burned wood, having lost its caloric fluid, is said to have cooled off.
- 3. The theory ofCaloric Fluid was disproved around 1800 by Count Benjamin Thompson Rumford, an American-born physicist. Count Benjamin Thompson Rumford concluded that heat was produced from friction alone.
- 4. It was onlyabout 40 years later that an English physicist, James Prescott Joule proved that a measurable amount of mechanical energy could always be transformed into definite amounts of heat. He concluded that heat must be just another form of energy.
- 5. Sources of Heat Natural Sources 1. The Sun When the sun’s energy reaches the earth, 30% of its is immediately reflected back out into space. Only 70% remains to interact with the earth, and warm it up. Of the 70%, 20% is energy to heat both the surface of the earth, as well as the ocean.
- 6. It is thesun’s heat energy that makes plants and animals to provide themselves with energy. These plants provide food for animals. Human eat plants and animals to provide themselves with energy. Much of the heat on earth may be traced back to the sun.
- 7. 2. The interiorof the Earth A great amount of heat also comes from buried hot rocks and lava flow from craters and crevices of erupting volcanoes. The hot spring in Tiwi, Albay, Los Banos, Laguna and in Tayabas Quezon are proofs that the earth’s interior is much hotter than its surface.
- 8. Artificial Sources 1. ChemicalAction When fuels like coal, kerosene, wood, and gasoline are burned, they are used as artificial sources of heat. The oxygen we breathe in burns the food we eat, producing enough body heat to keep our body temperature close to 370 C.
- 9. 2. Mechanical Action Heat energy produced by a friction.
- 10. 3. Electrical Energy Electricity is a very common source of heat at home. Oven toaster and electric iron are heated by the resistance of the heating coils to the electricity passing through them.
- 11. 4. Nuclear Energy The tremendous amount of energy from nuclear reactions can be used to change water into steam, which is then used to operate a turbine to generate electricity.
- 12. How much haveyou learned? 1. Heat is one of the topics in Thermodynamics. What is thermodynamics? 2. Use kinetic molecular theory as a basis to explain how heat is produced. 3. Solar energy is used by plants to manufacture their own food. Give two other examples how solar energy is used. 4. Make a short description of the following kinds of thermometer: A. liquid-in-glass thermometer B. Platinum-resistance thermometer C. Thermocouple D. Optical E. thermograph
- 13. Temperature Scale The mostcommon thermometer used in the laboratory is the Mercury Thermometer.
- 14. Colored alcohol isanother liquid commonly used in thermometer.
- 15. Celsius Scale Commonly knownas Centigrade Scale This scale was devised in 1741 by a Swedish astronomer, Anders Celsius, based on the properties of water.
- 16. On the Celsiusscale, the freezing point of water is fixed at 0 degree Celsius (00 C) The boiling point of pure water under normal atmospheric pressure, 760 mm Hg (at sea level), is 100 degrees Celsius (1000 C). The normal temperature of the human body is 370 C
- 17. Fahrenheit Scale The Fahrenheitscale was devised by Daniel Gabriel Fahrenheit, A German physicist. Unites States of America and England use the Fahrenheit scale for weather observation and other purposes.
- 18. On Fahrenheit scale,320 F is the freezing point of water and 2120 F is the boiling point.
- 19. Kelvin Scale orAbsolute Zero Named after Sir William Thompson (Lord Kelvin) who devised it.
- 20. This temperature scaleis often used when gases are involved. Its zero point (0 K) corresponds to -2730 C and is referred to as Absolute Zero or the temperature at which the molecular energy of matter is minimal. On the Kelvin scale, the freezing point of water is 273 K and the boiling point of water is 373 K.
- 22. To convert temperaturereadings from one scale to another, the equation below are used:
- 23. Converting Units ofTemperature oC to oF oF = (9/5)( oC) + 32 38.7 oC oF oF = (1.8)(OC) + 32 = (1.8) (38.7) + 32 = 69.66 + 32 = 101.7
- 24. oF to oC oC = 5/9 ( oF – 32) 101.7 oF o C oC = 5/9 ( oF – 32) = .555 (101.7 – 32) = (.555) (69.7) = 38.7
- 25. oC to K K = 273 + oC 38.7 oC K K = 273 + oC = 273 + 38.7 = 311.7
- 26. Convert the following 1)37o C to oF 1) 98.6oF 2) 350oF to oC 2) 176.7oC 3) 100oC to K 3) 373 K 4) 95o C to oF 4) 203 oF 5) 130oF to K 5) 327.4 K 6) 39oC to oF 6) 102 oF 7) -160oF to oC 7) -107oC 8) 80.0oF to oC 8) 27 o C 9) 27oC to K 9) 300 K 10) 120oC to oF 10) 248 oF
- 27. How Heat isMeasured? Thermometer only gives us an idea of the total potential energy and kinetic energy of the molecules in an object. It does not tell us how much heat a particular object absorbs or gives off. In fact there is no instrument that directly measures the amount of heat energy that a body gives off or absorbs If you want to calculate the amount of heat given off by a piece of charcoal or a certain kind of gas, then you have to determine the change in temperature it produces on a definite volume of water.
- 28. Units of Heat Commonunits used for measuring heat energy: a. Calorie (cal) b. kilocalorie (kcal) c. joule (J) The SI unit for heat, as for any other form of energy is the Joule (1 N.m = 1 joule) Today, the calorie is defined in terms of the joule: that is 1 cal = 4.184 J. This is the mechanical equivalent of heat 1 Kcal = 1000 calories
- 29. Effects of Heat 1.Generally when a substance absorbs heat, its temperature rises. 2. Solid usually melt or change to the liquid state when heated.
- 30. 3. Liquid mayabsorb enough energy when heated to change to vapor state.
- 31. 4. Almost allobjects expand when heated.
- 32. 5. A changein the heat content of a substance can cause chemical changes.
- 33. 6. Heat causesmany changes in bodily functions of living organisms Enzymes are protein-like substances formed in human cells that act as catalysts in initiating or speeding up specific chemical reactions. Each has a characteristics shape that allows it to hold two or more molecules close enough together so they can react chemically. If the temperature is increased, then the speed of moving molecules is also increased. Bombardment by high speed molecules in the cell can cause the enzymes to lose its shape. It can no longer perform its vital function.
- 35. Two glasses stacktogether. If we twist them apart, one or both of them may break. What is the safest way to separate the two glasses that stick together? One way is to pour some cold water into the inner glass and dip the outer glass in hot water. Within a short while, the two glasses can easily be pulled apart. Why? Generally most substances expands when heated and contract when cooled.
- 36. A change intemperature produces a change in length in almost all solid. Experimental results have shown that change in length is directly proportional to change in temperature and to the original length of the object. Different solids of the same length differ in their expansion for the same change in temperature.
- 37. In liquids theeffect of heat is an increase in their volume while the effect of cooling is a decrease in their volume.
- 38. Expansion of Gases Why do gases expand at a greater rate than solids and liquids?
- 39. Change of Phase Wheneverthe temperature of a substance changes, there is an accompanying change in its molecular structure. If the change in molecular structure is such that it becomes noticeable, then we say that the substance is undergoing a Change of Phase.
- 42. Heat Transfer Heat maybe transferred in three ways: a. Conduction b. Convection c. Radiation
- 43. a. Conduction Transmission of heat from particle to particle Conduction of heat in an object will take place only when one part of the object has a higher temperature than another part. The part with a higher temperature will transfer its heat energy to that part with a lower temperature.
- 45. Solid are thebest conductors of heat. Among solids, metal conduct heat the best. But metals differ in their conductivity. Silver is very good conductor of heat than iron and lead. Why?
- 46. b. Convection The heat energy is distributed by the liquid or gaseous molecules in circling currents.
- 47. c. Radiation Transfer of heat through electromagnetic waves.
- 48. 2 1 3 4
- 49.
- 50. 1. The absolutezero temperature is _____ a. -273 0 C b. -320 C c. 00 C d. 273 K
- 51. 2. The spacebetween the walls of the double-walled thermos bottle is evacuated to ______ a. increase volume b. reduce convection c. reduce heat transfer by conduction d. both b and c
- 52. 3. Dry icehas a temperature of - 110.2 0 F. What would its temperature be on the Celsius scale? a. -7110 C b. -198.3 0 C c. -142.2 0C d. -79 0C
- 53. 4. Room temperatureis often 0 identified as 68 F. What temperature is this on the Kelvin scale? a. 20 K b. 100 K c. 293 K d. 341 K
- 54. 5. The transferof energy from a source to an object by direct contact between them is _____ a. conduction b. convection c. insulation d. radiation
- 55. 6. As moreheat is added to a sample of water boiling in a stove, its temperature ______ a. decreases b. increases c. increases then decreases d. remains the same
- 56. 7. When waterreaches 4 0 C, ____. a. it will expand only if heated. b. its volume will remain constant. c. it will expand whether it is cooled or heated. d. it will contract until it freezes into ice, and then expand.
- 57. 8. When doesvaporization happen? It _____________. a. will occur only at night. b. takes place at very great pressures. c. occurs at the boiling point temperature d. takes only at a definite temperature may occur at a definite temperature or at any temperature.
- 58. 9. Which ofthe following statements is true about boiling? It ____________. a. is lower than evaporation. b. takes place at a definite temperature. c. is the same for all liquids at the same temperature. d. takes place when bubbles begin to appear in the liquid.
- 59. 10. The rateof evaporation may be increase by _______ a. raising the temperature of the liquid. b. increasing the surface area of the liquid. c. decreasing the air pressure on the surface of the liquid. d. any of the above.
- 60. 11. What iscondensation? It ____ a. is an exothermic process. b. is the opposite process of melting. c. is due to the increase in the kinetic energy of the particle of the liquid. d. refers to the change from solid state to gaseous state form of matter.
- 61. Two cars ofthe same model, the same brand, and the same size, are both locked and parked under the sun in an open parking lot. The two cars are parked from 9:00 A.M. to 5:00 P.M. One of the cars is ivory white in color and the other is dark blue. 12. Under the same condition, at 12:00 noon, _____ a. the dark-colored will be hotter inside. b. the ivory-colored car will be hotter inside. c. since both are locked, the sun will not affect either car. d. since both are under the same sun, they will both be equally hot.
- 62. Match Column Awith Column B Column A Column A _____13. William Thompson a. Centigrade tempt. Scale _____14. Anders Celsius b. Absolute Tempt. Scale _____15. D. Gabriel Fahrenheit c. Fahrenheit Tempt. Scale _____16. B.T. Rumford _____17. J. Prescott Joule d. Heat is produced by friction e. Concluded that heat is a form of energy.
- 63. 18-21. Enumerate the different artificial sources of heat. 18. 19. 20. 21.
- 64. 22-24. Enumerate the different methods of heat transfer. 22. 23. 24.
- 65. 25. True orFalse Land breeze and sea breeze occurs because of conviction current.
- 66.
- 67. 1. The absolutezero temperature is _____ a. -273 0 C b. -320 C c. 00 C d. 273 K
- 68. 2. The spacebetween the walls of the double-walled thermos bottle is evacuated to ______ a. increase volume b. reduce convection c. reduce heat transfer by conduction d. both b and c
- 69. 3. Dry icehas a temperature of -110.2 0 F. What would its temperature be on the Celsius scale? a. -7110 C b. -198.3 0 C c. -142.20 C d. -79 0C
- 70. 4. Room temperatureis often 0 identified as 68 F. What temperature is this on the Kelvin scale? a. 20 K b. 100 K c. 293 K d. 341 K
- 71. 5. The transferof energy from a source to an object by direct contact between them is _____ a. conduction b. convection c. insulation d. radiation
- 72. 6. As moreheat is added to a sample of water boiling in a stove, its temperature ______ a. decreases b. increases c. increases then decreases d. remains the same
- 73. 7. When waterreaches 4 0 C, ____. a. it will expand only if heated. b. its volume will remain constant. c. it will expand whether it is cooled or heated. d. it will contract until it freezes into ice, and then expand.
- 74. 8. When doesvaporization happen? It _____________. a. will occur only at night. b. takes place at very great pressures. c. occurs at the boiling point temperature d. takes only at a definite temperature may occur at a definite temperature or at any temperature.