14.3 Flashcards
What desire was there following the Industrial Revolution?
Following the Industrial Revolution there was a desire to make steam engines do as much work possible for fuel burnt.
What did James Joule investigate?
James Joule compared worked done by an electric battery consuming zinc and a steam engine consuming a pound of coal. Heat was measured by the temperature increase it produced in water.
What does one calorie of heat achieve?
One calorie of heat will raise temperature of 1kg of water by 1 degree celsius.
What was caloric theory? What did Joule show?
According to caloric theory heat was conserved but Joule showed that work alone can raise water’s temperature significantly.
What is the first law of thermodynamics?
Heat and work produce the same effect. For complex systems, internal energy U can’t be found but change in U can and so heat received/energy transferred thermally, Q= W (work done) + change in U (both can be negative if its energy transferred from the system)
What is the formula for energy transferred?
Change in temperature for a given energy transfer relies on the substance mass and the type of substance.
ENERGY TRANSFERRED = mass of substance * constant for substance * temperature increase
Change in internal energy=mc * change in temperature, where c is a constant (specific thermal capacity) and change in 0 is in degrees.
When can ^U=mcT not be used?
The equation using specific thermal capacity can’t be used when water is boiled as work is done to break bonds.
How can specific thermal capacity of water be found?
An immersion heater is connected to an electric circuit and placed in water. For a metal, sample cylinders with a hole the same dimensions as the heater and another for the thermometer may be used. Make appropriate measurements of the water to find the specific thermal capacity. Q must be minimised so U=W.
