An aluminum rod of mass 1 kg at temperature of 800C is placed into 1l of water of temperature 100C . there is no heat exchange with surroundings. Which material experiences greater change in temperature while system is reaching the thermal equilibrium? (19.2

When two substances with different temperatures are put in contact, they'll intend to reach thermal equilibrium, a state when both of them will have the same temperature. For that, the substances may change heat between them.

For the energy balance, the total amount of heat changed must be equal to 0. Because aluminum is hotter, it will lose heat, and the water will absorb it. The heat can be calculated by Q = m*c*ΔT, where m is the mass, c is the specific heat of each material, and ΔT the change in temperature (final - initial). So, let's call the final temperature as T.

c aluminium = 0.91 kJ/kg.°C

c water = 4.186 kJ/kg.°C

The density of water is 1 kg/L, so m water = 1 kg

Q aluminium + Q water = 0

1*0.91*(T - 800) + 1*4.186*(T - 100) = 0

0.91T - 728 + 4.186T - 418.6 = 0

5.096T = 1146.6

T = 225°C

Thus, ΔT aluminium = 225 - 800 = -575°C

ΔT water = 225 - 100 = 125°C

So, aluminum experiences a greater change in temperature.