QUANTITY OF HEAT
Heat is a form of Energy
A system possesses energy if it has the ability to do work.
Energy comes in two basic forms: the kinetic energy of motion and the potential energy of position.
Energy is conserved, it cannot be created or destroyed.
When one form of energy decreases another form must increase.
The archetypal example of this is the rock or water in a river at the top of a hill. Due to its height above the bottom of the hill it possesses gravitational potential energy. Give it a push and it will start to roll. If we assume the ideal situation of a closed system where no energy is lost on the way down, then the rock's initial potential energy will equal its final kinetic energy.
Now take the archetypal example one step further. Assume the rock crashes into a wall. Neither the rock nor the wall are made of rubber, so the rock comes to a halt. Now it appears as if we have violated the law of conservation of energy. The kinetic energy is lost and nothing has come along to replace it. Where has the energy gone?
The answer to this question is inside the rock (and inside the wall). The energy has been transformed from the external energy visible as the motion of the rock as a whole to the internal energy of the motion of the invisible parts that make up the rock (and the wall). The two energies are identical in size, but different in appearance.
External energy is visible because it is organized. The translational kinetic energy of a rock is due to coordinated motion. All the parts move forward together. The rotational energy is also coordinated. The parts all rotate together around the center of mass. In contrast, the internal kinetic energy of a rock is invisible since the pieces are so small and numerous and their motion is completely uncoordinated.
Their motions are statistically random with a mean value of zero making the energy invisible to macroscopic beings like us. Potential energy can also exist in external and internal forms. I won't provide you with an example here but I will say that external potential energy is relatively obvious. Internal potential energy is somewhat obscure.
Do all substances change their temperature at the same rate??
Is Temperature the same as Heat?
Hotplate, beakers, 3 different types of liquid.
Keep the Hotplate at a low setting
Alcohols are extremely flammable
Monitor the temperature of the liquids very often,
Turn off the heater if the temperatures get near 60oC
Do not lift / touch the hot liquids.
- fill 3 beakers with the same volume of the 3 liquids, allow them all time to get to the room temperature.
- place the 3 beakers on the hot plate
- carefully measure the temperature of each of the liquids
- start the clock
- turn on the hot plate to a medium setting
- every minute measure the temperature of the liquids TURN OFF THE HOT PLATE WHEN ANY TEMPERATURE IS >50oC
- continue to record the temperatures every minute.
Results / Observations
All the liquids recieved the same amount of heat, but the temperature of the liquids changed by different amounts. This shows us that Heat is different to temperature.
Heat is an energy & Temperature is a measure of 'hotness'