thermodynamics

Question 1

Define heat.

Answer 1

Heat is energy transferred from one body to another because of a difference in temperature. This energy transfer is always from a hotter to a colder body.

Note that the word “body” is not used in a literal sense. A body in this context can be, for example, all the matter which constitutes a chemical reaction.

Question 2

Define work.

Answer 2

Work is the energy transfered from one body to the next because of a force applied over a distance. In a chemistry context, this manifests as a pressure applied over a change in volume.

If the system (chemical reaction) experiences an increase in volume (greater amount of gaseous product verses gaseous reactant) then we say the system applies a pressure and expands against the surroundings. That is, it does work against the surroundings and energy is lost by the system.

Question 3

Define system.

Answer 3

In thermodynamics context, the system is the “thing” under investigation. For chemistry, this “thing” is usually a chemical reaction.

Question 4

Define surroundings.

Answer 4

Surroundings is everything that is not the system. But more practically, the surroundings is what is in immediate contact with and is affected by the system.

In chem 122, most of our examples will involve chemical reactions in water (as the system) and therefore the most important surroundings will be water.