Energy and Enthalpy

•Energy is the ability to do work or produce heat. It exists in two basic forms potential

energy and kinetic energy.

Potential energy is energy due to the composition or position of an object

Ex: A downhill skier poised at the starting gate for a race.

Kinetic Energy is energy in the motion of objects and all people around you.

States that in any chemical reaction or physical process, energy can be converted from one form to another but it isn’t created nor destroyed, this is also known as the First Law of Thermodynamics.

Kinetic and Potential

Websites

http://www.internet4classrooms.com/eoc_chemistry.htm

http://classroom.jc-schools.net/sci-units/energy.htm

http://www.tipton-county.com/mms/practice%20sites%20for%20TCAP.htm

Enthalpy

Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.

Example Problem

Given: The heat of fusion of ice is 333 J/g (meaning 333 J is absorbed when 1 gram of ice melts). The heat of vaporization of liquid water at 100°C is 2257 J/g.

Part a: Calculate the change in enthalpy, ΔH, for these two processes.

H2O(s) → H2O(l); ΔH = ?H2O(l) → H2O(g); ΔH = ?

Part b: Using the values you just calculated, determine the number of grams of ice that can be melted by 0.800 kJ of heat.

Answer

a.)H2O(s) → H2O(l); ΔH = +6.00 kJH2O(l) → H2O(g); ΔH = +40.7 kJ

b.) 2.40 g ice melted