Holt Physics, Chapter 10

Defining Temperature Feeling hot or coldFeeling hot or cold Need a more precise definition for Need a more precise definition for

how “hot” or “cold” something is.how “hot” or “cold” something is.

Adding or removing energy usually Adding or removing energy usually changes the temperature of an changes the temperature of an object.object.

Temperature is proportional to the Temperature is proportional to the average KE of the atoms or average KE of the atoms or moleculesmolecules

Internal energyInternal energy – energy of a substance – energy of a substance due to the random motion of its due to the random motion of its component particles.component particles. Equals to the total energy of those particles.Equals to the total energy of those particles. Symbol for internal energy: Symbol for internal energy: UU

Temperature is meaningful only when Temperature is meaningful only when it is stableit is stable Warm fruit juice, cold beaker of waterWarm fruit juice, cold beaker of water Thermal equilibriumThermal equilibrium – state in which two – state in which two

bodies in contact with each other have bodies in contact with each other have identical temperatures.identical temperatures.

It’s how a thermometer works!It’s how a thermometer works!

Matter expands as its temperature Matter expands as its temperature increases.increases. Called Called thermal expansionthermal expansion Coefficient of thermal expansionCoefficient of thermal expansion Peculiarity of waterPeculiarity of water The expansion of liquids can be used to The expansion of liquids can be used to

measure temperature.measure temperature.

Measuring Temperature

Make use of a physical change that corresponds to a change in temperature. Volume of a gas or liquids Pressure of a gas at a fixed volume Most common thermometers

Mercury, colored alcohol, or mineral spirits

Calibrating a thermometer requires Calibrating a thermometer requires fixed temperatures.fixed temperatures. Ice point: Ice point: 0 0 ooCC Steam point: Steam point: 100 100 ooCC

Temperature units depend on the Temperature units depend on the scale used.scale used. Most widely used today are the Most widely used today are the

Fahrenheit, Celsius, and Kelvin (or Fahrenheit, Celsius, and Kelvin (or absolute) scales.absolute) scales. Celsius and Fahrenheit: differ in ice point Celsius and Fahrenheit: differ in ice point

and degree sizeand degree size Celsius and Kelvin: differ in ice point only, Celsius and Kelvin: differ in ice point only,

degree size samedegree size same Celsius and Fahrenheit can be positive, Celsius and Fahrenheit can be positive,

negative, and zero valuesnegative, and zero values