Thermochemistry

Thermochemistry - Chapter 5: Thermochemistry...

Info iconThis preview shows pages 1–18. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 5: Thermochemistry
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Thermochemistry Thermodynamics is the study of energy and heat transfer. Thermochemistry is the study of heat that is absorbed (taken in) or emitted (given off) from the system during a chemical reaction.
Background image of page 2
Energy The ability to do work or transfer heat. Work: Energy used to cause an object that has mass to move. Heat: Energy used to cause the temperature of an object to rise.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Potential Energy (PE) Energy an object possesses by virtue of position or chemical composition (energy of position). PE = mgh = mass x (acceleration due to gravity) x height Units = kg x m/s 2 x m = kg∙m 2 /s 2 Potential Energy
Background image of page 4
Kinetic Energy (KE) Energy an object possesses by virtue of its motion (the energy of motion). Units = kg x (m/s) 2 = kg∙m 2 /s 2 Potential Energy Kinetic Energy KE = ½ mv 2 = ½ mass x (velocity) 2
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Other Types of Energy Electrostatic Potential Energy —the interaction between two charged particles: k is a proportionality constant, Q 1 is the charge of particle #1 ( C ), Q 2 is the charge of particle #2 ( C ), and d is distance in m . Radiant Energy (electromagnetic radiation) Chemical Energy (potential energy stored in bonds between atoms) d Q kQ E 2 1 El =
Background image of page 6
Units of Energy The SI unit of energy is the joule (J). An older, non-SI unit is still in widespread use: The calorie (cal). 1 cal = 4.184 J (exactly, by definition) 1 J = 1 
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
System and Surroundings The system includes the molecules we want to study (here, the hydrogen and oxygen molecules). The surroundings are everything else (here, the cylinder and piston). The universe is the system + surroundings
Background image of page 8
Work Energy used to move an object over some distance. w = F d , where w is work, F is the force, and d is the distance over which the force is exerted.
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Heat Energy can also be transferred as heat. Heat flows from warmer objects to cooler objects.
Background image of page 10
Transfer of Energy a) The potential energy of this ball of clay is increased when it is moved from the ground to the top of the wall.
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Transfer of Energy a) As the ball falls, its potential energy is converted to kinetic energy.
Background image of page 12
Transfer of Energy converted to kinetic energy. a) When it hits the ground, its kinetic energy falls to zero (since it is no longer moving); some of the energy does work on the ball, the rest is dissipated as heat.
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
First Law of Thermodynamics Energy is neither created nor destroyed. In other words, the total energy of the universe is a constant; if the system loses energy, it must be gained by the surroundings, and vice versa. Use Fig. 5.5
Background image of page 14
Internal Energy ( E ) The internal energy of a system is the sum of all kinetic and potential energies of all components of the system; we call it E. Use Fig. 5.5
Background image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Internal Energy By definition, the change in internal energy, E , is the final energy of the system minus the initial energy of the system: E = E final E initial Use Fig. 5.5
Background image of page 16
Changes in Internal Energy ( E) If E > 0, E final > E initial Therefore, the system has absorbed energy from the surroundings.
Background image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 18
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 63

Thermochemistry - Chapter 5: Thermochemistry...

This preview shows document pages 1 - 18. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online