# Thermal physics

Could you please explain why A is the correct answer? Also, how is density related to temperature change?

https://imgur.com/a/EmAbuNp

Thank you so much!
(edited 3 months ago)
If any material is denser there's more mass for the same volume and that will affect the amount of energy needed to change the temperature. Specific heat capacity is the energy needed to raise the temperature of 1kg of the material by 1 degree C.

Solving the question:

Q = VIt
Q = mcΔθ
Therefore
VIt = mcΔθ
p = m/v so m = pv
Therefore
VIt = pvcΔθ
Bring all constants over to one side and all variables over to the other
VI/vΔθ = pc/t
The voltage of the heating element, the current in the heating element, the volume of the liquid and the change in temperature (10 degrees) are the same for water and oil.
The only things that change are p (density), c(specific heat capacity) and t (time to heat)
Therefore
pwcw/t = poco/to
(w means water, o means oil)
cw = 2.5co
pw2.5co/t = poco/to
pw = 1.1po
1.1po2.5co/t = poco/to
Cancel po and co
1.1*2.5/t = 1/to
1.1*2.5 = 2.75
2.75/t = 1/to
2.75to = t
2.75to = t
We want to (time for oil)
to = t * 1/2.75
1/2.75 ~ 0.36
to = 0.36t
Original post by Jakson123
If any material is denser there's more mass for the same volume and that will affect the amount of energy needed to change the temperature. Specific heat capacity is the energy needed to raise the temperature of 1kg of the material by 1 degree C.

Solving the question:

Q = VIt
Q = mcΔθ
Therefore
VIt = mcΔθ
p = m/v so m = pv
Therefore
VIt = pvcΔθ
Bring all constants over to one side and all variables over to the other
VI/vΔθ = pc/t
The voltage of the heating element, the current in the heating element, the volume of the liquid and the change in temperature (10 degrees) are the same for water and oil.
The only things that change are p (density), c(specific heat capacity) and t (time to heat)
Therefore
pwcw/t = poco/to
(w means water, o means oil)
cw = 2.5co
pw2.5co/t = poco/to
pw = 1.1po
1.1po2.5co/t = poco/to
Cancel po and co
1.1*2.5/t = 1/to
1.1*2.5 = 2.75
2.75/t = 1/to
2.75to = t
2.75to = t
We want to (time for oil)
to = t * 1/2.75
1/2.75 ~ 0.36
to = 0.36t