Reading Quiz - Temperature

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Reading Quiz - Temperature

• 1. All matter is made of
• ___ 1. Atoms.
• ___ 2. Combinations of earth, wind, fire and
  water.
• ___ 3. Identical particles.
• ___ 4. Cells.

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• 2. Which of the following is a temperature scale?
• ___ 1. Celsius.
• ___ 2. Fahrenheit
• ___ 3. Kelvin.
• ___ 4. All of the above.

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• 3. Most materials will
• ___ 1. not be affected
• ___ 2. expand
• ___ 3. contract
• when heated.

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Thermometers Temperature

• Temperature a measure of how hot or cold an
  object is.
• Thermometers Instruments that change some
  physical characteristic which can be used to
  measure temperature.
• Examples a liquid/gas that expands
  increase in pressure of a gas a bimetallic
  strip that bends colored bulbs that
  float/sink changes in color - pyrometer

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• Temperature scales Celsius/Centigrade,
  Fahrenheit, Kelvin
• Thermal equilibrium When two objects starting
  out at different temperatures exchange energy
  until they both reach the same final temperature.
• Zeroth Law of Thermodynamics.

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Conceptual Questions

• 1) What is the problem with 0C 32F 273.15K?
• ____ a) this is mathematically incorrect
• ____ b) this is mathematically correct
• ____ c) mixes units
• ____ d) there is no problem

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• 2) Three different types of thermometers are used
  to read the temperature of a warm glass milk. The
  readings are
• ____ a) the same for all three thermometers
• ____ b) the three read slightly different
• ____ c) the three read very different
  temperatures

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Quantitative Questions

• 1) At what temperature is the Celsius scale the
  same as the Fahrenheit scale?
• 2) The body temperature of a healthy human is
  98.6F. Express this in degrees Celsius.

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Thermal Expansion

• Most substances expand (contract) when heated
  (cooled). Experimentally, the change in length,
  ?L, of almost all solids is directly proportional
  to the change in temperature ?T
• ? is the coefficient of thermal linear expansion.
• Note ? (and therefore ?L) does vary slightly
  with temperature.
• Volume expansion
• ? is the coefficient of volume expansion (? 3?)

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• Anomalous Behavior of Water expands when cooled
  from 4C to 0C! This implies it is densest at
  4C.

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• Great importance to the survival of aquatic life
  during cold winters!
• It expands even more as it freezes evidence -
  ice floats in water and pipes break when water in
  them freezes.

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Conceptual Questions

• 1) The height of a column of mercury in a
  thermometer when placed in hot water
• ____ a) rises immediately
• ____ b) descends slightly and then rises
• ____ c) rises and then descends slightly
• ____ d) descends immediately

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• 2) Rubber has a negative coefficient of linear
  expansion. What happens to the size of a piece of
  rubber as it is warmed?
• ____ a) it expands
• ____ b) it remains the same
• ____ c) it contracts
• ____ d) it expands non-uniformly
• ____ e) it contracts non-uniformly

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• 3) A bimetallic strip, consisting of metal G on
  the top and metal H on the bottom, is rigidly
  attached to a wall at the left. The coefficient
  of linear thermal expansion for metal G is
  greater than that of metal H. If the strip is
  uniformly heated, it will
• ____ a) curve upward.
• ____ b) curve downward.
• ____ c) remain horizontal, but get longer.
• ____ d) bend in the middle.

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• 4) Consider a flat steel plate with a hole
  through its center. When the plates temperature
  is increased, the hole
• ____ a) expand only if it takes up more than
  half the plates surface area.
• ____ b) contract if it takes up less than half
  the plates surface area.
• ____ c) always contract.
• ____ d) always expand.

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• 5) The surface water temperature on a large,
  deep lake is 3C. A sensitive temperature probe
  is lowered several meters into the lake. What
  temperature will the probe read?
• ____ a) A temperature warmer than 3C.
• ____ b) A temperature less than 3C.
• ____ c) A temperature equal to 3C.
• ____ d) There is not enough information to
  determine the answer.

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Quantitative Problems

• 1) The steel bed of a suspension bridge is 200 m
  long at 20C. If the extremes of temperature to
  which it might be exposed are -30C to 40C, how
  much will it contract and expand?
• 2) Vodka that is 100 proof is a mixture of half
  ethyl alcohol and half water (by volume). How
  much profit per liter will a merchant make if he
  buys vodka at 10 per liter at 0C and sells it
  at 10 per liter at 25C?

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Atomic Theory and Ideal Gas

• All matter is ultimately made up of tiny
  indivisible particles called atoms.
• Evidence - chemical reactions with definite
  proportions giving relative weights of the
  different elements Brownian motion.
• Approximate size of atoms? - oil drop experiment.
• Gas laws and absolute zero of temperature Boyle
  s Law - constant T Charless Law -
  constant P Gay-Lussacs Law - constant V

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• Ideal Gas Equation PV nRT where n number
  of moles R gas constant 8.315 J/(mol?K)
• One mole is the amount of substance that contains
  as many atoms or molecules as there are in 12.00
  grams of carbon 12. We call this number
  Avogadros number - NA.
• Hence n N/NA where N is the total number of
  molecules/atoms.
• NA 6.02 x 1023
• Ideal Gas Equation PV NkT where k is the
  Boltzmann constant. k R/NA1.38 x 10-23 J/K

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Kinetic Theory

• Refers to the concept that matter is made up of
  atoms which are in continual random motion.
• By considering the collisions between the atoms
  that make up an ideal gas, and the walls of the
  container, we can show that the pressure exerted
  by the gas molecules is given by

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• Comparing to the ideal gas equation, we see that
• Important conclusion the average translational
  kinetic energy of molecules in a gas is directly
  proportional to the absolute temperature of the
  gas.

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• In the previous equations refers to the
  average of the square of the velocities of the
  molecules in the gas. The molecules in an actual
  gas have a distribution of speeds with a known
  probability

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• The graphs below depict the speed distributions
  at two different temperatures

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• The distribution curves above are called Maxwell
  distributions and have been verified by
  experiment.
• Activation energy minimum kinetic energy two
  molecules must have before they react chemically.
• Rate of chemical reaction is proportional to the
  number of molecules with energy greater than the
  activation energy. Hence we see why reaction
  rates increase rapidly with increased
  temperature.

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Conceptual Question

• 1) According to the ideal gas Law, PV
  constant for a given temperature. As a result, an
  increase in volume corresponds to a decrease in
  pressure. This happens because the molecules
• ____ a) collide with each other more frequently.
• ____ b) move slower on the average.
• ____ c) strike the container wall less often.
• ____ d) transfer less energy to the walls of the
  container each time they strike it.

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• 2) Which of the following is not correct?
• ____ a) Matter is composed of tiny particles
  called molecules.
• ____ b) The molecules are in constant motion.
• ____ c) All molecules have the same size and
  mass.
• ____ d) The differences between the solid,
  liquid, and gaseous states can be
  attributed to the relative freedom of
  motion of their respective molecules.

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• 3) The kinetic theory of gases predicts that, at
  a given temperature,
• ____ a) all of the molecules in a gas have the
  same average speed.
• ____ b) all of the molecules in a gas have the
  same average energy.
• ____ c) light gas molecules have lower average
  energies than heavy gas molecules.
• ____ d) light gas molecules have higher average
  energies than heavy gas molecules.

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• 4) The volume of a gas is held constant while its
  temperature is raised. The pressure the gas
  exerts on the walls of its container increases
  because
• ____ a) the masses of the molecules increase.
• ____ b) each molecule loses more kinetic
  energy when it strikes the wall.
• ____ c) the molecules are in contact with the
  wall for a shorter time.
• ____ d) the molecules have higher average
  speeds and strike the wall more often.

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• 5) The temperature of a gas is held constant
  while its volume is reduced. The pressure the gas
  exerts on the walls of its container increases
  because its molecules
• ____ a) strike the container walls more often.
• ____ b) strike the container walls with higher
  speeds.
• ____ c) strike the container walls with greater
  force.
• ____ d) have more energy.

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Quantitative Problems

• 1) What is the average translational kinetic
  energy of molecules in a gas at 37C?
• 2) Since refers to the average of the square
  of the velocity, the square-root of this quantity
  is called the root-mean-square speed or .
  If a gas is at 0C, to what temperature must it
  be raised to double the rms speed of its
  molecules?
• 3) Why does the moon have no atmosphere?