Heat and thermodynamics

Question 1

Temperature

Answer 1

Quantity that indicates how warm or cold an object is with respect to some standard

• related to the random motion of atoms and molecules in a substance
• proportional to the average translational kinetic energy of molecular motion

Question 2

Celsius

Answer 2

Centigrade thermometer
0 = freezing
100 = water boiling
Space between is divided into 100 equal parts (degrees)

Question 3

Fahrenheit

Answer 3

32 = freezing
212 = water boils

Question 4

Heat

Answer 4

The energy transferred from one object to another because of a temperature difference between the objects

• matter contains molecular energy and possible potential energy, but it does not contain heat
• HEAT IS ENERGY IN TRANSIT

Question 5

Internal energy

Answer 5

The grand total of all energies inside a substance

• translational kinetic energy
• rotational kinetic energy
• kinetic energy due to internal movements of atoms within molecules
• potential energy due to force between molecules

Question 6

Heat cont

Answer 6

Heat flow is always hot to cold

- how much heat flows depends not only on the temp difference between substances but on the amount of material as well

Question 7

Measuring heat

Answer 7

• heat is the flow of energy from one thing to another due to a temperature difference
• since heat is in form of energy, measured in joules
• in USA more common in calories

Question 8

Calorie

Answer 8

The amount of heat required the change the temperature of 1 gram of water by 1 Celsius degree

Question 9

Kilocal

Answer 9

1000 calories
- heat unit to label foods
- capital Calorie
1 calorie = 4.184 joules

Question 10

Conduction

Answer 10

• how well a solid object conducts heat depends on the bonding within its atomic or molecular structure
• objects with loose outer electrons conduct heat well
• metals have “loosest” outer electrons
• silver, copper, alum, iron

Question 11

Insulators

Answer 11

Poor conductors of heat

• most liquids and gases are poor conductors of heat
• air, snow

Question 12

Convection

Answer 12

Heat transfer due to the actual motion of the fluid/gas

• involves the motion of blobs of matter (overall motion of a fluid)
• as fluid is heated from below, the molecules at the bottom begin moving faster, spreading apart more, becoming less dense and are buoyed upward
• denser, cooler fluid moves down to the bottom, warmer fluid moves away form the heat source
• warm air will expand and rise until the density matches that of the surrounding air

Question 13

Radiation

Answer 13

Transfer of energy by means of electromagnetic waves (a form of radiant energy)

• electromagnetic waves
• wavelength of radiation is related to the frequency of radiation
• frequency is the rate of vibration of the wate

Question 14

High frequency

Answer 14

Short waves

Question 15

Low frequency

Answer 15

Long waves

Question 16

Emission of radiant energy

Answer 16

• radiation emitted by earth is in the form of infrared waves (low frequency) which are below our threshold of sight
• radiation emitted by the sun is in the form of higher frequency radiant energy, much in the visible portion of the electromagnetic spectrum

Question 17

Infrared radiation

Answer 17

• infrared waves absorbed by our kin produce the sensation of heat
• therefore, infrared radiation is often called heat radiation
• when an object is hot enough, some of the radiant energy emitted is in the range of visible light

Question 18

Absorption of radiant energy

Answer 18

• good emitters of radiant energy are good absorbers

- poor emitters of radiant energy are poor absorbers

Question 19

Reflection of radiant energy

Answer 19

• a surface that reflects very little or no radiant energy looks dark
• good reflectors are poor absorbers