(Note: Material in this section on thermodynamics should be treated descriptively. A rigorous mathematical treatment of the topic is not intended.)
A transfer of heat energy occurs when substances having different temperatures are allowed to mix.
In any transformation of energy, the total amount of energy remains constant. This is called the Law of Conservation of Energy.
Whenever two substances at different temperatures are allowed to mix, heat travels from the hotter substance to the colder one. The quantity of heat given off by the hotter substance is equal to the quantity of heat energy gained by the cooler object, provided that heat energy does not escape to the surroundings. The transfer of energy will continue in this way until both substances reach the same temperature. The is called the Principle of Heat Exchange.
heat energy lost = heat energy gained
EH (lost) = E H (gained)
To investigate heat exchange, an experiment must be designed under controlled conditions, to prevent heat from escaping into the surroundings.
A calorimeter is an insulated container used to make precise measurements of heat exchange.
Carefully controlling variables and experimental conditions, precision in measurement, and quantitative analysis of data are some important experimental techniques used in physics.
Qualitative and quantitative analysis of experimental data both have important roles in scientific investigations.
Two systems, in thermal equilibrium with a third, are in thermal equilibrium with each other. (Zeroth Law of Thermodynamics)
The quantity of heat transferred to a system is equal to the work done by the system plus the change in the internal energy of the system. (First
Law of Thermodynamics, or Law of Conservation of Energy)
A heat engine, such as a steam turbine, is a device which converts heat energy into mechanical work.
The natural direction of heat flow is from a hot object to a colder one. (Second Law of Thermodynamics)
When energy is converted from one form to another the ability to do work can only be lost, and never gained. That is, no device transfers its heat energy completely into work. For that reason, it is impossible to build a perfect heat engine. (A heat pump requires an application of work to transfer heat energy from a low temperature to a higher temperature. Thus, the Second Law of Thermodynamics sets limits on how efficiently heat energy can be converted into work.
The entropy of a pure, perfectly crystalline substance is zero at absolute zero temperature. (Third Law of Thermodynamics)
Both on theoretical and experimental considerations, absolute zero can never be reached. (Some physics texts give this as the Third Law of Thermodynamics)
As one attempts to reach absolute zero, it becomes progressively more difficult to get any closer to it, such that it becomes impossible to ever attain it.
By definition, absolute zero is the temperature at which all molecular motion ceases. But quantum mechanics (Heisenburg Uncertainty) states that even at absolute zero some energy must be present. If there is still some energy present, it is not, by definition, at absolute zero. The condition of zero energy cannot ever be met, so absolute zero cannot ever be reached.
Students will increase their abilities to:
Place ice on the bottom of the flask. As soon as the ice is added, the water begins to boil again. Temperature readings on the thermometer will confirm that the water is no longer at its normal boiling point.
(Caution: Using an ordinary Florence flask for this demonstration may be dangerous. There may be stressed areas on the flask which will break and cause an implosion. Use the special thick-glass Franklin flasks that are available from science supply distributors. Safety glasses and an explosion shield are recommended for this activity.)