Thermal Effects | 5 Flashcards
(26 cards)
Kelvin (Formula)
Celsius + 273
Total Internal Energy (Formula)
PE + KE (Potential Energy + Kinetic energy)
When does anomoulas expansion of water occur
When the water reaches 4°C and till it reaches 0C
Specific Heat Capacity (Formula)
E = mcΔT (J/kg/K) (J/Kg/C)
(E = heat energy given to substance)
Energy (Formula)
Power x Time
Latent Heat (Formula)
E = mL (J/Kg)
m = change in mass
L = latent heat
E = heat energy
Absolute 0
At 0k / -273°C
Particles contain the lowest possible energy and cannot lose energy anymore
Particles stop vibrating and freeze in motion
causing them to be unable to exert a force
Temperature
Degree of hotness of coldness of a substance
measuring the IE in a substance
Liquid in glass thermometer
Glass case with thin capillary tube
Bulb contains mercury or alcohol
How do you decide if mercury or alcohol should be used inside the thermometer
Mercury is better when doing experiments with hotter temps
Boils at = 360°C
Freezes at = -39°C
Alcohol is better when doing experiments with colder temps
Boils at = 78°C
Freezes at = -112°C
Explain Thermistors
They are Digital Thermometers
Their resistance changes as temp changes
High temp–> Less resistance–> high current
Low temp–> High resistance–> low current
The current is sent to a circuit which displays the level of current received to a corresponding temperature
Thermal Expansion
When a particle’s temperature increases ,
it gains more energy to push outwards , increasing its volume and effectively expanding
Explain Bimetallic Strips
2 metals are combined into a strip , each having different rates of expansion
EX: Brass and invar
(invar on top , brass on bottom)
As brass has a higher rate of expansion , when exposed to thermal energy , it expands faster and curves up
(opposite of its position , if it is at the bottom , curves up and if it is at the top , curves down)
Bimetallic strips are used in fire alarms and thermostats to do temperature related functions
Explain Anomoulas expansion of water
When water reaches 4°C
Hexagonal structures form with the water to prepare it becoming ice making water expand as it becomes more cold causing it’s density to decrease
This is why ice floats in water
Boyles law
P1 V1 = P2 V2
Pressure and volume is inversely proportional as long as temperature is constant
Gay lussac law
P ∝ T
Pressure and temperatures is inversely proportional as long as volume is constant
Charles Law
V ∝ T
Volume and temperatures is inversely proportional as long as pressure is constant
Specific heat capacity
Amount of heat energy needed to increase temp of a substance of 1KG by 1°C
Is and if so why is water good at cooling
Water can absorb alot of heat energy before it starts boiling as it has a high specific heat capacity , so it is used as a coolant
Latent heat
When a substance changes states , energy supplied through heat is being used to overcome intermolecular forces
As energy is used for that purpose , temp of substance does not change
This is called “Latent heat of vaporization (Liquid to gas) / fusion (Solid to liquid) “
(Only in fusion and vaporization as others are cooling not heating)
Specific latent heat
Amount of heat energy needed to change the state of 1Kg of substance
Conduction
Takes place in conductors
Factors:
area
length
Temp of heat source
Use insulation to minimalize heat loss by conduction
Convection
Takes place in liquids and gases
hot goes up and cold goes down (weight based)
Ac’s are placed high and heaters low for this reason
Close Containers to minimalize heat loss by convection
Radiation
Heat transfer in all mediums (vacuum inc)
White and shiny is good reflector
Black and and matte is a good absorber / emmiter
Use a reflective inside covering and a black outside covering to minimalize heat loss by radiation
