Chapter 4 Flashcards
Describe the steam engine of Hero of Alexandria.
A toy that used steam to spin a hollow ball on stilts. It was one of the first creations to use the power of steam to complete a task.
Describe Thomas Savery’s steam engine.
Water is boiled and steam is allowed to fill a container. Once the steam in the container condenses, a partial vacuum is created, allowing for water in a mine to be pushed out.
Describe Thomas Newcomen’s engine.
Atmospheric engine. A boiler was used to produce steam to move a piston upward within a cylinder. Cold water condensed the steam so that the piston would move back down.
Describe the engine of James Watt.
This version operated on the principle of a pressure difference created by a vacuum to operate the piston. However, it contained two cylinders- a boiler and a condenser- to avoid constant heating and cooling.
Describe Charles Parsons’ steam turbine.
Steam passes through curved blades that are connected to a central axle that turns. As the steam cools and expands, energy is given off.
How did the steam engine influence society?
- Steam became an energy source for machines and vehicles
- The engine facilitated the mass production of commodities
- People moved from countryside to city as the land was united and production boomed
What is the elemental theory of heat?
Matter is made of four basic elements (earth, water, air, fire). Substances that burned contained fire.
What is the phlogiston theory of heat?
Flammable substances contained massless fluid called phlogiston. Phlogiston flowed out when a substance was burned.
What is the caloric theory of heat?
Heat consists of a fluid called caloric that is everywhere. Caloric supposedly flows from warmer to cooler substances.
Why is the elemental theory wrong?
There are more basic elements than earth, air, fire, and water.
Why is the phlogiston theory wrong?
If objects release phlogiston when burned, why are some ashes heavier than their original substance? How could phlogiston flow out but leave more mass behind?
Why is the caloric theory wrong?
Caloric supposedly flows from warmer to cooler objects. Why do cold objects become hot once work is done? (ex. rubbing your hands together, cold metal becoming hot in a factory)
Heat is equivalent to _______
energy.
What is the kinetic-molecular theory of heat?
States that molecules in a fluid increase their speed as their temperature increases. (hot water = fast molecules, cold water = slow molecules)
Define energy.
The ability to do work.
Define work.
The transfer of mechanical energy from one object to another.
Define heat.
The transfer of thermal energy from one object to another.
What is the relation between heat and work?
They are both mechanisms by which energy can be transferred.
What is the difference between heat/thermal energy and temperature?
Heat/thermal energy: a form of energy measured in joules (J).
Temperature: degree of hotness/coldness of a body measured in kelvin (K)—> measure of the average kinetic energy of atoms or molecules.
What is heat capacity?
Amount of energy required to increase the temperature of 1g of a given substance by 1 degree Celsius.
What is the first law of thermodynamics?
Energy cannot be created or destroyed; only transferred or transformed (the total energy of the universe is constant).
What is the second law of thermodynamics?
No process is 100% efficient. Some energy will always remain thermal and thus become “wasted heat”. (ex: a pendulum swinging converts Eg to Ek. If it were 100% efficient, it would swing forever, but with each conversion, some energy becomes waste heat and thus slows it).
