Thermal Properties Of Matter

Question 1

Temperature

Answer 1

Is the measure of the average kinetic energy individual particles have in a system (Si unit is Kelvin(K) - not ^C

Question 2

Internal entertainment of a body

Answer 2

Is the total energy (kinetic and potential) of all the particles in the body (Si unit joules(J)

Question 3

How heat moves

Answer 3

Either transferred from one body to another as a result of temp difference
From a region with higher temp to a region with a lower temp so as to reach thermal equilibrium

Question 4

Liquid in glass thermometer

Answer 4

Rely on expansion of a liquid (mercury or alcohol) with temperature

• liquid is contained in a sealed glass bulb and it expands into the fine bore in the thermometer stem
• temperature read using a scale on the thermometer
• the relationship between the temp and the columns height is linear over the small temperature range for which the thermometer is used

Question 5

Disadvantages of the liquid-in-glass thermometer

Answer 5

1) the glass itself expands and contracts and leads to under or over reading of temp
2) parallax error means readings are only 0.1*C accurate
3) the diameter of the bore is not constant
4) their large thermal capacity means they do not react quickly(sensitivity) and they may affect the temp that they are tying to measure
5) due to the freezing and boiling points of the liquids in the thermometer, those thermometer often have a limited temp range

Question 6

Compare :alcohol and mercury

Answer 6

Alcohol - transparent must be used with a dye, poor heat conductor. -sticks to glass, concave meniscus temp range = 180C to -144.9C

-Mercury - is opaque is a metal and therefore a good conductor of heat and does not stick to the glass - convex meniscus temp range = 356C to -39C

Question 7

Constant volume gas thermometer

Answer 7

An example is galileos thermometer - works on the principle of the gas expanding with an increase in temp

Question 8

Thermocouple thermometer

Answer 8

Consists of two wires of different metals joined together at the ends to form two junctions

1) when two dissimilar metals are in contact, on the EMF is produced that is proportional to the temperature at that junction
2) this is called the seed back or the thermocouple effect
3) A thermocouple thermometer uses the EMF producer to desire the temperature at the junction

Question 9

Advantages and disadvantages of thermocouple

Answer 9

Advantages:

• display is easy to read
• durable
• rapid response
• large temp range

Disadvantages:

• ancillary equipment is expensive
• hard to calibrate
• measure on a temp difference

Question 10

Thermistor

Answer 10

Resister when resistance changes with a change in temp. Used in mode electronic thermometers

• temp variation is non-linear
• narrow temp range

Question 11

Linear

Answer 11

Proportional (change) / constant

Question 12

Non-linear

Answer 12

Isn’t straight, non constant

Question 13

Other types of thermometers

Answer 13

• platinum resistance
• vapor pressure
• strain
• bimetallic strip
• liquid strip
• optical pyrometer
• transistor

Question 14

Thermometer design (Liquid in a glass)

Answer 14

Diameter of the bore affects it’s sensitivity ( meaning how long it takes to resister the reading
-d the volume of liquid in the bulb is greater, the less sensitive tube it becomes a o register a reading

Question 15

Thermal expansion

Answer 15

Matter (Solid, liquid and gas) expands when heated, and contracts when cooled

Question 16

Application of thermal expansion

Answer 16

• cold and hot fittings
• expansion gaps on rail tracks
• bimetallic strips

Question 17

Linear expansion

Answer 17

Delta Lenght = A x Lo x delta T

Question 18

Thermal capacity

Answer 18

Basically refers to the energy to heat something up and increases Its temp
-once heated, substances with hugh thermal capacity take time to release that once heat

Question 19

Specific heat capacity

Answer 19

Is the heat energy required to cause a temp change of 1 kelvin of 1kg of a substance
Q=Mc.deltaT

Question 20

Specific latent heat of fusion (Lf )

Answer 20

Of a substance is the quantity of heat needed to change a unit of mass from solid to liquid with light a change in temp
Q=M.Lf

Question 21

Soecific latent heat vaporization (Lv)

Answer 21

Of a substance is the quantity of heat needed to change a unit mass from liquid to gas without change in temp

Q =M.Lv

Question 22

Evaporation

Answer 22

An endothermic process involving phase change from liquid to gas that occurs at all temps

Question 23

Boiling

Answer 23

At a pure substance is an endothermic process that involves phase change from liquid to gas that occurs at a specific temp

Question 24

Factors affecting evaporation

Answer 24

1. happens at a higher rate at higher temps
2. surface area of a liquid is large
3. wind or fraught moving over the surface of the liquid