Can someone explain the equation
q = m c delta t
or q = mcδt
!

Q = heat energy , m=mass , c=specific heat , delta T= change in temperature

as you know heat is a form of energy which is usually measured in Joules according to the SI. and also we usually use kilograms for mass.

so you need to know the mass, specific heat, and change in temperature in order to find out the heat energy :)

Q is the quantity of heat energy used to change the temperature of specific mass of certain matter
M is the mass of matter u wanna to change its temperature
C is the specific heat, each substance has its own "C" as specific heat is the quantity of heat to change mass of 1 kg by 1 kalvin deg.
ΔT is the the difference in temp. from and to how much u wanna to change the temp. of your matter 
so if u wanna to change 1L water (for example) which = to 1kg
u wanna to increase its temp. by 2 degrees 
and the "c" is ≈ 4200 then 
the quantity of energy u need to do that is = MCΔT = 1*4200*2 = 8400

Attach the free body diagram and i will you answer the question.! : d

The density of the block of iron is lees than the density of mercury but the density of the block of iron is greater than the density of water