Objectives• After learning: You are excepted to be able to explain the definition of temperature• Measure the temperature of substance by using thermometers• Distinguish various thermometers
Particles are always moving.When you heat water, the water molecules move faster.When molecules move faster, the substance gets hotter.When a substance gets hotter, its temperature goes up.
Learning CheckSuppose you place water in a freezer.A. The water particles move 1) faster 2) slower 3) the sameB. The water will get 1) hotter 2) colder 3) stay the sameC. The temperature of the water will
SolutionSuppose you place water in a freezer.A. The water particles move 2) slowerB. The water will get 2) colderC. The temperature of the water will be 2) lower
Thermometer Measures the hotness or coldness of an object Determined by using a thermometer that contains a liquid that expands with heat and contracts with cooling.
A CTIVITY 2.1. M EASURING T EMPERATURE Procedures A B C Cold water Tap water Warm water
Thermometer Scale Put glass on the flat surface Hold on the tip of thermometer (do not hold bulb of thermometer) bulb Your eyes must be perpendicular with the scale9
Thermometer • Touching sense is unreliable for measuring exact temperature of an object • To measuring exact temperature of an object, we can use Thermometer • The principle used in a thermometer is the volume change of liquid or EXPANSION principle. • For almost all substance will: – expand (volume is increased) when they are heated – contract (volume is decreased)when they are cooled10
Thermometer Scale 1. What are liquids commonly used to filled thermometer? 2. Find the advantages and weakness of alcohol as thermometric liquid. 3. Find the advantages and weakness of mercury as thermometric liquid. 4. Can water used as thermometric liquid? Give reasons for your answer. 5. Make a diagram comparison of Upper fixed point and lower fixed point of Celcius, Reamur, Fahrenheit and Kelvin scale. 6. What is absolute zero?11
Thermometer 1. Column of vacuum space 2. Measured temperature 3. Capillary tube 4. Thermometer scale Bulb filled with mercury Or alcohol12
Thermometer Scale Absolute zero is the lowest possible temperature where nothing could be colder, and no heat energy remains in a substance. Absolute zero is the point at which molecules do not move It is a theoretical limit and cannot be achieved with the current technology available. Absolute Zero = 0 K 0 K = - 459.67 F = - 273.15 C13
Thermometer Determine the Boiling point of pureupper fixed point water at 1 atm (Ta) Divided between Ta and Tb Every part = temperature per unitDetermine the lower Melting point of fixed point (Tb) ice at 1 atm14
Thermometer Scale CELCIUS REAMUR FAHRENHEIT KELVINUpper 100 C 80 R 212 F 373 KpointLower 0 R 32 F 273 K 0 Cpoint 0 F O K = -273 C C : R : F : K AbsolutCOMPARISON 100 : 80 : 180 : 100 SCALE e zero 5 : 4 : 9 : 515
Learning CheckA. Temperature of freezing water 1) 0 F 2) 0 C 3) 0 KB. Temperature of boiling water 1) 100 F 2) 32 F 3) 373KC. Number of Celsius units between the boiling and freezing points of water 1) 100 2) 180 3) 273
SolutionA. Temperature of freezing water 2) 0 CB. Temperature of boiling water 3) 373KC. Number of Celsius units between the boiling and freezing points of water 1) 100
Conversion Unit Tx = temperature of thermometer X Xb = Lower point of thermometer X Xa = Upper point of thermometer X Ty= temperature of thermometer Y Yb = Lower point of thermometer Y Ya = Upper point of thermometer Y18
E XAMPLE 1. What does 45 C equal if it is measured in a Fahrenheit thermometer? Given: TC = 45 C Question: TF = ? TF Fb TC Cb Solution: Fa Fb Ca Cb TF 32 45 0 212 32 100 0 TF 32 45 180 100 45 TF 32 180 100 9 9 45 TF ( 180) 32 81 32 113 F 519 100
2. Arman made his own thermometer called thermometer X and given scale like in the figure below. If thermometer X shows 25, what is the temperature according to celcius scale? CelciTc Cb Tx Xa X us 100 C 40 XCa Cb Xa Xb Tc 0 25 ( 10 )100 0 40 ( 10 ) E XAMPLE 25 X Tc =? Tc 25 10 100 40 10 -10 X 0 C Tc 35 100 50 35 2 70 C Tc 100 35 220 50
Temperature unit conversion Celcius to Reamur scale Celcius to Fahrenheit scale Celcius to Kelvin scale21
Learning Check Do Conversion unit of temperature below.1. 40 R = …………… C2. 10 C = ……………. F3. -40 C = ……………. F4. 27 C = ……………… K5. 283K = ……..………. F6. Thermometer A and B are used to measure temperature of an object. 320 B What is Y when thermometer A shows 100 A? 50 A 20 B
Conversion Unit • Liquid-in-glass thermometer • Gas thermometer • Bimetal thermometer • Pyrometer • Platinum thermometer • Thermocouple thermometer24
Liquid thermometer glass tube filled with liquid (often mercury or alcohol) that expands/contracts Alcohol and mercury have their own advantages and weakness. Advantages WeaknessIt has a regular thermal expansion It wets the tube wallIt has a large coefficient of thermal It has a low boiling point (80 C) It isexpansion unsuitable to measuring high temperatureIt has low freezing point (-115 C), it is It has a high specific heat capacity, sosuitable for measuring low www.tyas- it needs a high energy to raise physics.blogspot.comtemperature temperature25
Liquid thermometer Advantages Weakness It is easy to see, have a shining It is very expensive color It is not wets tube wall It is a poisonous substance It adapts the ambient temperature Unsuitable for measuring a very low easily temperature because it has high freezing point It has regular thermal expansion It has a high boiling point (357C), suitable to measure high temperature It has width scale range (-39 C - 357 C)26
Kinds of thermometer A gas thermometer measures temperature by the variation in volume or pressure of a gas It has width range (2500C - 15000C) This thermometer makes use of a bimetallic strip that consists of two strips of different metal joined together. As temperature increases, the coiled bimetallic strip bends more to rotate a pointer around on a scale.27
Kinds of thermometer Wires made of two different metals are joined together to form two junctions. It is very sensitive and can measure a wide range of temperatures. It is commonly used in industry to measure the temperatures of ovens and furnaces28
Kinds of thermometer Thermometer that measures temperature by changes in the resistance of a spiral of platinum wire An instrument for measuring high temperatures (over 60000C) It used to measure thermal radiation29
• Clinical Thermometer • Wall Thermometer • Maximum and Minimum Six-Bellani Thermometer • Laboratory Thermometer30
Kinds of thermometer Used to accurately determine the temperature of the human body; the most common type is a mercury-in-glass thermometer It has scale range (35 C- 42 C) Used to measure the air temperature of a room31
Kinds of thermometer Also called by Six-Bellani Thermometer Can measure the maximum and minimum temperature during a given time. It is common in use wherever a simple way is needed to measure the extremes of temperature at a location, for instance in meteorology and horticulture. Used for laboratory purpose32
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