Temperature and thermal equilibrium Hot Cold

Temperature is proportional to the kinetic energy of atoms and molecules: T~KE

Thermometer

Celsius, Fahrenheit, Kelvin Andres Celsius ( ). Celsius’ scale relates to the freezing temperature of water 0 ° C and the boiling temperature of water 100°C

Daniel Fahrenheit Daniel Gabriel Fahrenheit ( ) invented the alcohol thermometer mercury thermometer he introduced the temperature scale that bears his name - Fahrenheit Scale. Fahrenheit’s scale places the freezing point of water at 32ºF and the boiling at 212ºF. Exactly 180ºF apart.

T F =9/5 In Russia schools are closed when temperatures reaches -35ºC What is the temperature in Fahrenheit's?

Lord Kelvin Kelvin’s scale related to the absolute zero – the point where nothing else can be colder. T (°C) P(Pa)

Conversion of T scales:

Thermal expansion

As temperature increases, the volume of the object increases as well. The extent of thermal expansion is characterized by the coefficient of volume expansion CVE gases >>> CVE liquids >> CVE solids ?? Why do train wheels rhythmically clink on the rails? ?? Why putting a jar under hot water makes it easier to open it? ?? When do you get more gas for your money: on a cold or a hot day?

Thermal equilibrium T1T1 T2T2 T 1 <T 3 <T 2 the state in which two bodies in contact with each other have identical temperatures

HEAT The process by which energy is exchanged between objects because of a difference in their temperatures. SI: [J] – joules » James Joule

Conduction the process whereby energy is transferred directly through a material without any bulk motion of its particles. Conduction is mostly common in solids. Depending on whether materials conduct heat easily, they are divided into conductors and insulators.

Convection process in which energy is transferred through a material with any bulk motion of its particles. Convection is common in fluids

Radiation the process in which energy is transferred by means of electromagnetic waves.

Internal energy: the energy of a substance due to the random motions of its component particles (atoms and molecules) and equal to the total energy of those particles. U – internal energy 1 2 1) T 1 =T 2 Compare U 1 and U 2 2) U 1 = U 2, Compare T 1 and T 2

Heat / Energy / Work units

Conservation of energy KE + PE + Work = const Work – way to change U of the system For an isolated system (no energy is lost ) If a total mass of 11.5 kg falls through 1.3 m and all of the ME is converted into U of water, by how much will U of water change? What will you observe in the apparatus?

Specific Heat Capacity C p shows how much heat is needed to change the temperature of 1 kg of substance by 1ºC

Examples: How much heat does it take to heat a 580 g aluminum pot (c p =0.92 J/gK) from 20ºC to 180º C? A lead bullet (c p =0.13 J/gK) going 460 m/s strikes a tree. If all the heat generated remains in the bullet, how much does its temperature rise?

3 States of

Phase Change The physical change of substance from one state (solid, liquid, or gas) to another at constant temperature and pressure

Heat Q(J) T(°C) 0ºC

Q(J) 0ºC T(°C)

Q(J) 0ºC T(°C)

At what point will the temperature stop rising? Q(J) 0ºC T(°C) 100ºC

Q(J) 0ºC T(°C) 100ºC

Heat of fusion – the energy per unit mass transferred in order to change a substance from solid to liquid or from liquid to solid at constant temperature and pressure

Heat of vaporization – the energy per unit mass transferred in order to change a substance from liquid to vapor or from vapor to liquid at constant temperature and pressure