Living By Chemistry SECOND EDITION Unit 5: FIRE Energy, Thermodynamics, and Oxidation-Reduction

Lesson 107: Make It Work Work

ChemCatalyst Describe how you might use a chemical reaction to move something.

Key Question How can a chemical reaction be used to do work?

You will be able to: define work explain how chemical reactions are utilized to do work

Prepare for the Classwork Work individually.

Discussion Notes (cont.) In order to move the ping-pong ball, it is necessary to expend some energy. Work: The transfer of energy that causes an object to move. When a force acts to move an object, work is done on that object. If no motion happens, then work is not done.

Discussion Notes (cont.) Mechanical work is defined as force times distance: W = F • d. Machines can be used to help convert energy to work. There are two main ways to convert chemical energy into work. The energy that is transferred when gases change volume is called PV work. W = P∆V

Wrap Up How can a chemical reaction be used to do work? Energy can be used to do work. When a force acts on and moves an object in the direction of the force, it is doing work on that object. Work is equal to force times distance, W = F • d, and can be expressed in Newton-meters or joules. The two sources of work that can come from chemical reactions are heat transfer and the expansion or contraction of matter (usually expanding gases).

Wrap Up (cont.) PV work is done when matter expands or contracts. Work is equal to pressure times the change in volume, W = P∆V, and is expressed in L • atm, which can be converted to joules. The combustion of fuels in an engine is one way to convert chemical energy into work.

Check-In What is the source of energy in a natural gas power plant?