Thermodynamics

Thermodynamics States About Energy Conversion Thermodynamics is the branch of science that embodies the principles of energy transformation in macroscopic systems. The general restrictions which experience has shown to apply to all such transformations are known as the laws of thermodynamics. These laws are primitive; they cannot be derived from anything more basic. The first law of thermodynamics states that energy is conserved; that, although it can be altered in form and transferred from one place to another, the total quantity remains constant. Thus, the first law of thermodynamics depends on the concept of energy; but, conversely, energy is an essential thermodynamic function because it allows the first law to be formulated. This coupling is characteristic of the primitive concepts of thermodynamics. The words system and surroundings are similarly coupled. A system is taken to be any object, any quantity of matter, any region, and so on, selected for study and set apart (men

Calorimetry Examination

A vessel with heat capacity can be ignored contain of 500 gram water at temperature 20oC. An ice bar with weight of 200 g at temperature  0oC is dipped on that water. The melting heat of ice 80 cal/g.

Calculate:
a. The end of mixture temperature
b. The total weight of ice melted

Solution:
Energy release = Energy accepted
(m x c x Δt) water = (m x c x Δt) ice + (m x L) ice
c = specific heat of water = 1
L = melting heat

The initial condition contain water and ice on their state but at the end contain water and ice mixture.

1. First assumption all ice melted
The ice need energy for melted all ice = 200 x 80 = 16,000 calory
Water should release their energy at least same with those ice need to melt.

Q = 500 x 1 x 20 = 1000 calory so this impossible to make all ice melted. We assume just m gram of ice melted. So the final mixture will be 0oC, so the end of mixture is 0oC.

(m x c x Δt) water = (m x L) ice

500 x 1 x 20 = m x 80

m = 1000/80 = 12.5 gram so the weight of ice melted is 12.5 grams.