9Absolute Zero Point at which all molecular motion has stopped. We have never reached it, but are very close.Scale is used in engineering.
10Rankine Temperature Scale Temperature scale having an absolute zero, below which temperatures do not exist, and using a degree of the same size as that used by the Fahrenheit temperature scale.Absolute Zero corresponds to a temperature of −459.67°F;
11Temperature Difference (DT) Is the primemover or force-like quantity in a thermal system.DT – “Delta T”
12Ex: 110 oF inside and 40 oF outside. What is the DT? DT = 110 – 40 = 70 Fo
13Thermometer Instrument used to measure temperature. Based upon liquid expansion in the tube with respect to temperature.
33calorieThe amount of heat energy required to raise the temperature of 1 gram of water 1 oC.
341 kilocalorie (1000 calories) is used in rating food. Written as Calorie (capital C)
35Both are units of energy. 1 calorie = JBTU – British Thermal Unit (English Unit)
36Fuels are rated by how much heat is given off when a certain amount is burnt.
37Heat Transfer Specific Heat (Cp) amount of energy required to raise the temp. of 1 kg of material by 1 degree Kelvinunits: J/(kg·K) or J/(g·°C)
38Heat Transfer 50 g Al 50 g Cu Al - It has a higher specific heat. Which sample will take longer to heat to 100°C?50 g Al50 g CuAl - It has a higher specific heat.Al will also take longer to cool down.
39Q = m T Cp Heat Transfer Q: heat (J) m: mass (kg) T: change in temperature (K or °C)Cp: specific heat (J/kg·K or J/g.oC)– Q = heat loss+ Q = heat gainT = Tf - Ti
40Heat Transfer heat gained = heat lost Calorimeter Coffee cup CalorimeterCalorimeterdevice used to measure changes in thermal energyin an insulated system,heat gained = heat lost
41Specific Heat (c)Is the quantity of heat required to raise the temperature of a unit mass of that substance by 1oC.
42Joules per kilogram-Celsius degree Units of Specific HeatJoules per kilogram-Celsius degreeJ/kg-Co
43Specific heat of water is 4190 J/kg-Co On Pg. 220 is a table of Specific heat for different substances.
56Water has a very high specific heat capacity: 4190 J/kg-Co Very useful in cooling agent.
57A very small amount of water absorbs a great deal of heat. Ex: radiator.
58Water also takes longer to cool. This resistance to change temp. improves weather conditions/climates in many places.
59Specific Heat Applications Water has a high specific heat capacity, and therefore has several important applications.
601. Car RadiatorsWater is used as a coolant in car radiators. Water can absorb a large amount of heat before it boils because water has a high specific heat capacity. An engine produces a lot of heat when running, so the heat must be removed. Water is circulated throughout the engine where it absorbs the heat. This water is then pumped to a radiator where the heat is released to the metal core of the radiator, which then releases the heat to the surrounding air.
612. Ocean BreezeWater has a much higher specific heat capacity than sand, therefore it takes more energy to heat the water than the sand. The air above the sand heats up faster and rises while cool air above the ocean comes in to take its place. Thus a breeze coming from the ocean toward the sand beach occurs on a hot day. What direction do you think the breeze is at night when the ocean water is warmer than the cool sand?
62Because of high specific heat capacity (ability to accept heat without a large temperature increase) water during the day is cooler than land. Rising air above warm land is replaced by cooler air pushed in from the lake. The reverse happens at night, when the land's temperature has fallen below that of the lake; the lake's temperature drops, too, at night, but not as much as the land's.
74Loosening a tight nut.A nut is very tight on a screw. How shall it be loosened? By heating, or by cooling?The nut expands, the screw expands, and the space expands. Shrink-fit iron rims on wooden wheels.
75Pyrex glass – designed not to expand with increase of temperature. Gasoline
76Expansion of Water 0 – 4 oC Water actually contracts. > 4 oC Water expands.Water is densest at 4 oC
77Remember ice floats on water, so it is less dense. This has to do with the structure of the ice crystals.They form a hexagonal structure.
78Remember ice floats on water, so it is less dense. This has to do with the structure of the ice crystals.They form a hexagonal structure.
80Water's Physical Properties Water is unique in that it is the only natural substance that is found in all three states -- liquid, solid (ice), and gas (steam) -- at the temperatures normally found on Earth. Earth's water is constantly interacting, changing, and in movement.
81Water has a high specific heat index Water has a high specific heat index. This means that water can absorb a lot of heat before it begins to get hot. This is why water is valuable to industries and in your car's radiator as a coolant. The high specific heat index of water also helps regulate the rate at which air changes temperature, which is why the temperature change between seasons is gradual rather than sudden, especially near the oceans.
82Water has a very high surface tension Water has a very high surface tension. In other words, water is sticky and elastic, and tends to clump together in drops rather than spread out in a thin film. Surface tension is responsible for capillary action, which allows water (and its dissolved substances) to move through the roots of plants and through the tiny blood vessels in our bodies.