## Lecture 16: Thermal Energy and Solids

October 24, 2017

• Study: Box on p. 120; Figs 6.1, 6.3, 6.5; Eq 6.21; Ex 2; box on p. 131; box on p. 133; Eqs 6.28, 6.29; Exs 3, 4.

### Objectives

• (Continuing objective) Be able to relate concepts of thermodynamics and statistical mechanics to “everyday” situations and to discuss various applications of the concepts to practical problems in various fields of science, medicine and engineering.
• For a molecular system, be able to explain what thermal energy is.
• Given the molecular weight, density, and Young's modulus of a solid, derive the appropriate mass, equilibrium length, and spring constant of the ball-spring model. Use the ball-spring model to describe properties of a solid, including its molar specific head and speed of sound.
• Given two substances, know that thermal energy flows from hot (larger temperature) to cold (smaller temperature) objects. Be able to quantitatively relate the heat flow to a temperature change.
• Use the First Law of Thermodynamics to relate work done on or by a substance, heat flow into or out of the substance, and change in the thermal energy of that substance.

### Homework

• Wednesday's Assigned Problems: Supp CH 6: 1, 2, 3, 4, 5, 7, 9, 15, 17, 19
• Monday's Hand-In Problems: A48; Supp CH 6: 12, 13, 14, 16, 18; Supp CH 7: 8, 9, 10, 14

### Videos of example problems

First, some videos made using the tablet:
To see the following videos, click on the link below. To play the video example, click on the underlined words "Video Demonstration" near the top of the page with the problem statement.
• Video Example #1: Determing the ball-spring parameters and the speed of sound for gold.
• Video Example #2: Determining the final temperature and the thermal energy transferred between a hot object and a cold object.

### Pre-Class Entertainment

• My Brain is Like a Sieve, by Thomas Dolby
• Mat' Ya Odinok, by Kukuruza
• My Mind's Got a Mind of Its Own, by Jimmie Dale Gilmore
• Major Tom (Coming HOme), by Peter Schilling
• My Shot, by Original Cast of Hamilton
• My Type, by Saint Motel