(a)(i)
For the correct answer:
79kg
To find the mass, first calculate the room’s volume using V=length×width×height=4.5×6.1×2.4=65.88m 3 . Using the density formula ρ= V m , rearrange it to m=ρ×V. Substituting the values, m=1.2kg/m 3 ×65.88m 3 =79.056kg, which rounds to 79kg as required.
(a)(ii)
For the correct answer:
290s
First, calculate the thermal energy required using ΔE=mcΔθ=79×1000×(20.0−16.0)=316,000J. Since power is the rate of energy transfer, use the equation P= t ΔE rearranged to t= P ΔE . The time taken is t= 1100W 316,000J ≈287.3s, which rounds to 290s to two significant figures.
(a)(iii)
For the correct answer:
thermal energy is lost from the room (to the surroundings)
The calculation assumes all energy from the heater goes into the air, but in reality, thermal energy is lost through walls and windows via conduction and convection. Additionally, some energy is used to heat the objects and furniture within the room rather than just the air itself. Consequently, the actual time taken would be longer than this theoretical minimum.
(b)
For the correct answer:
conduction AND convection
Double glazing uses a trapped layer of air or a vacuum between two glass panes to reduce heat loss. Air is a very poor thermal conductor, which significantly limits heat transfer by conduction. Furthermore, because the gap is narrow and sealed, air cannot circulate freely to form large convection currents, thereby minimizing thermal energy transfer by convection to the outside.
