36 7.2 Thermochemistry essentials

Figures

Figure 7.2.5: The electromagnetic spectrum

A diagram of the electromagnetic spectrum, labeled ‘VISIBLE SPECTRUM’ in the center. The spectrum has a color gradient from violet at 400 nanometres and labelled high energy, to red at 700 nanometres, labelled low energy. Below, the spectrum ranges are indicated: gamma rays from 0.0001 to 0.01 nanometers, X-rays from 0.01 to 10 nanometers, ultraviolet light from 10 nanometers to 400 nanometers. The visible spectrum spans from 400 to 700 nanometers, followed by infrared from 700 nanometers to 1 millimeter, and radio waves extending from 1 millimeter to 100 meters, subdivided into radar, TV, FM, and AM frequencies.

Figure 7.2.9: Types of systems within thermochemistry

Three types of thermodynamic systems using flask illustrations.

The first flask is open and shows an upward arrow marked mass and two horizontal arrows marked heat, indicating both mass and energy can be exchanged with the surroundings.

The second flask, closed, is sealed with a stopper and has ‘mass’ arrows mass inside the bottle pushing outwards and two heat arrows pushing inwards, signifying that only energy can be exchanged, not mass.

The third flask is an isolated system and has internal mass and heat arrows pushing outwards on the flask walls, illustrating that neither mass nor energy is exchanged with the surroundings.

Practice questions

True/false question

1. In chemistry, temperature can be thought of as the kinetic energy of molecules.

Short-answer question

1. Absolute Zero is the temperature at which molecules stop moving. Its value is _______ K.
2. A ___________ system doesn’t allow matter and energy to be exchanged with the environment. A ___________ system allows for energy, but not matter to be exchanged with the environment. A ___________ system allows for both energy and matter to be exchanged with the environment.

Multiple choice questions

1. In fan-forced ovens, what form of heat transfer is primarily occurring?
   1. Conduction
   2. Convection
   3. Radiation
   4. Transmittance
2. What forms of heat transfer can occur over a vacuum?
   1. Conduction
   2. Convection
   3. Radiation
   4. Transmittance

Solutions

True/false question

1. True

Short-answer questions

1. 0 K
2. isolated, closed, open

Multiple choice questions

1. b
2. c