Ch21: Temperature, Heat, and Expansion & Ch22: Heat Transfer
14 December 2020
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Temperature
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The quantity that tells how hot or cold something is compared with a standard.
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Celsius Scale
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A scale where the gap between freezing and boiling is divided into 100 equal parts, called degrees. The number 0 designates the temperature at which water freezes, and the number 100 designates the temperature at which water boils.
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Fahrenheit Scale
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A scale where the number 32 designates he temperature at which water freezes, and the number 212 designates the temperature at which water boils.
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Kelvin Scale
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The scale used in scientific research where its degrees are the same size as the Celsius degree and are called \”kelvins\”. The number 0 is assigned to the lowest possible temperature — absolute zero.
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Absolute Zero
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At absolute zero, a substance has no kinetic energy to give up. This corresponds to -273 degrees Celsius.
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Heat
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The energy that transfers from one object to another because of a temperature difference between them.
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Thermal Contact
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When heat flows from one object or substance to another it is in contact with, the objects or substances are said to be in thermal contact.
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Thermal Equilibrium
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The state where objects in thermal contact with each other reach the same temperature, no heat flows between them.
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Internal Energy
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The grand total of all energies inside a substance.
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Calorie
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The amount of heat required to raise the temperature of 1 gram of water by 1 degrees Celsius.
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Kilocalorie
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1000 Calories (the heat required to raise the temperature of 1 kilogram of water by 1 degrees Celsius).
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Specific Heat Capacity
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The quantity of heat required to raise the temperature of a unit mass of the substance by 1 degree.
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Bimetallic Strip
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Two strips of different metals welded or riveted together.
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Thermostat
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A practical application of a bimetallic strip.
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Conduction
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Takes place within materials and between different materials that are in direct contact.
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Conductors
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Materials that conduct heat well are known as heat conductors.
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Insulators
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Poor heat conductors; they delay the transfer of heat.
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Convection
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Convection is where heating occurs by currents in a fluid.
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How is temperature commonly measured?
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With a thermometer.
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How many degrees are between the melting point of ice and the boiling point of water on the Celsius scale? Fahrenheit scale?
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Celsius scale: 100 degrees. Fahrenheit scale: 180 degrees.
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Why is it incorrect to say that matter contains heat?
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Because matter contains internal energy, heat is energy flow due to the change in temperature.
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In terms of differences in temperature between objects in thermal contact, in what direction does heat flow?
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From high to low temperatures.
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What is meant by saying that a thermometer measures its own temperature?
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Its temperature equalizes with temperature of surroundings.
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What is thermal equilibrium?
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State where temperatures equalizes.
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What is internal energy?
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Grand total of all energies inside a substance.
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What is the difference between a calorie and a Calorie?
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1000 calories = 1 Calorie calorie = 1 calorie Calorie = 1 kilocalorie
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What does it mean to say that a material has a high or low specific heat capacity?
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High or low capacity to store internal energy.
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Do substances that heat up quickly normally have high or low specific heat capacities?
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Low.
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How does the specific heat capacity of water compare with that of other common substances?
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High.
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Why is the North American west coast warmer in winter months and cooler in summer months than the east coast?
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Because of water’s high heat capacity, ocean temperature does not vary much from summer to winter.
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Why does a bimetallic strip curve when it is heated (or cooled)?
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Because different materials expand and contract at different rates.
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Which expands most for increases in temperature: solids, liquids, or gases?
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Gases.
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At what temperature is the density of water greatest?
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At 4 degrees Celsius.
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Ice is less dense than water because of its open crystalline structure. But why is water at 0 degrees Celsius less dense than water at 4 degrees Celsius?
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Because a given amount of water has its smallest volume (and greatest density) at 4 degrees Celsius. Because of presence of \”microscopic slush\”.
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Why do lakes and ponds freeze from the top down rather than from the bottom up?
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Ice water and ice float at surface. Because water cannot possibly be cooled to 0 degrees Celsius without first being cooled to 4 degrees Celsius. When the water reaches 4 degrees Celsius, it cools, becomes denser and sink before it cools even further and the surface water would continue be cooled to 0 degrees Celsius.
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Why do shallow lakes freeze quickly in winter, and deep lakes not at all?
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All water must first be cooled to 4 degrees Celsius — winter is not long enough for all the water to be cooled to 4 degrees Celsius.
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What is the role of \”loose\” electrons in heat conductors?
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Transfer energy through conducting material.
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Why does a piece of room-temperature metal feel cooler to the touch than paper, wood, or cloth?
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Feels cooler because it is an effecting conductor.
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What is the difference between a conductor and an insulator?
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Conductor moves heat quickly, insulator moves heat slowly.
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Why are materials such as wood, fur, feathers, and even snow good insulators?
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Have many air spaces, air is a good insulator.
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What is meant by saying that cold is not a tangible thing?
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Cold is the absence of heat.
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How does Archimedes’ principle relate to convection?
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Warm air is less dense and is buoyed upward.
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Why does the direction of coastal winds change from day to night?
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Because land temperature is higher during the day, air rises; at night, ocean temperature is higher. (opposite)
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How does the temperature of a gas change when it is compressed? expands?
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Increases when compressed and decreases when decreases when it expands.
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A row of dominoes is placed upright, one next to the other. When one is tipped over, it knocks against its neighbor, which does the same in cascade fashion until the whole row collapses. Which of the three types of heat transfer is this most similar to?
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Conduction
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What is radiant energy?
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The energy in electromagnetic waves.
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How do the wavelengths of radiant energy vary with the temperature of the radiating source?
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Waves are shorter from high temperature sources.
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Why does a good absorber of radiant energy appear black?
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Because it absorbs rather than reflects light.
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Why do eye pupils apear black?
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Because light entering the pupil is absorbed.
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Is a good absorber of radiation a good emitter or a poor emitter?
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Good emitter, otherwise no thermal equilibrium.
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Which will normally cool faster, a black pot of hot tea or a silvered pot of hot tea?
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Black pot will cool faster.
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Which will undergo the greater rate of cooling, a red-hot poker in a warm oven or a red-hot poker in a cold room (or do both cool at the same rate)?
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Red-hot poker in cool room, greater change in temperature.
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Does Newton’s law of cooling apply to warming as well as to cooling?
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Yes.
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What is terrestrial radiation?
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Radiant energy emitted by the earth.
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Solar radiant energy is composed of short waves, yet terrestrial radiation is composed of relatively longer waves. Why?
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Because lower temperature of earth, longer waves.
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What does it mean to say that the greenhouse effect is like a one-way valve?
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Only short waves passes through. It means that this has the ability to prevent convection currents from mixing the cooler outside air with the warmer air inside so it plays a big role in global warming.
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Is the greenhouse effect more pronounced for florists’ greenhouses or for the earth’s surface?
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Earth’s surface.