Week 2 Thermal Expansion and Specific Heat Capacity

linear thermal expansion

by applying heat to a solid changes its temperature and can cause the solid to expand (ΔL ∝ L₀ [change in length is proportional to the original length])

what is the equation to find the change in length in linear thermal expansion?

ΔL = α L₀ ΔT, where ΔL=change in length, α=coefficient of linear expansion (inverted K or C), L₀=original length, and ΔT=change in temperature (K or C)

volume thermal expansion

the volume of an object changes when its temperature changes

what is the equation to find the change in volume in volume thermal expansion?

ΔV = β V₀ ΔT, where ΔV=change in volume, β=coefficient of volume expansion (inverted K or C), V₀=original volume, and ΔT=change in temperature (K or C)

how does the coefficient of linear and volume expansion relate to each other?

β = 3 α

specific heat capacity

the amount of heat energy required to raise the temperautre of 1kg of the substance by 1 K (or C)

what is the equation to find the amount of heat supplied/removed to change the temperature of a substance?

𝑄 = 𝑚𝑐∆𝑇, where Q=heat supplied/removed (J), m=mass of the substance (kg), c=specific heat capacity (J/kg*K), and ΔT=change in temperature (K or C)

does the temperature of a mixture change during phase change?

no (provided the system is in thermal equilibrium [could be at the melting/freezing point or boiling point])

latent heat

the energy supplied or removed to change the phase of a substance per kilogram at a constant temperature

what is the equation used to find the amount of heat supplied/removed to change the phase of a specific substance?

Q=mL, where Q=the heat supplied/removed (J), m=mass (kg), and L=latent heat (J/kg)

sublimation

solid to gas

vaporization

liquid to gas

fusion

solid to liquid

deposition

gas to solid

condensation

gas to liquid

solidification/freezing

liquid to solid

practical applications of thermal expansion

overhead electric transmissions, lengths of railway lines, bimetallic strip as thermometers or thermostats

what are 3 heat units other than Joule

kcal (c=1kcal/kg*C)

cal (c=1cal/(g*C)

Btu (British thermal unit) (c=1Btu/lb*F)

what does the value of specific heat capacity depend on

whether the pressure or volume is held constant when heat energy is added or removed from a substance (distinction between pressure and volume is usually insignificant in solids and liquids, but greater value for specific heat capacity for gas is obtained at constant pressure than constant volume)

can a substance exist at equilibrium in more than one phase at a time?

yes, in equilibrium vapor pressure, pressure exerted by a vapor is in equilibrium with its liquid or solid phase

higher temperature = _____ pressure

higher