Energy+Transfer

= = __ENERGY TRANSFER__ If a cup of tea (80'c)is made and then left in a room(20'c), it WILL go cold. The tea is hotter than the room. From this everyday occurrence, we can conclude, that hot things will cool down when they are put with colder things. HEAT TRANSFER FROM HOT TO COLD

Past developments in Physics, have provided us with the equation for energy transfer (in regards to heat): E=m c ΔT ENERGY = MASS X SPECIFIC HEAT CAPACTITY X CHANGE IN TEMPERATURE If we apply this formula to the tea in the room situation, we can see that the difference in temperature(represented by deltaΔ T) would be 60’c (80’c-20’c)

We have not met (c) – specific heat capactity before. Scientifically, it is the constant of proportionality that depends on which substance you are heating. Rearranged, c = energy / mΔT

The units of specific heat capacity are j/kgK = jkg-1K-1

Looking at this idea in terms of particles, we know that when you raise the termperature of an object, the kinetic energy of the particles inside that object increases also. This is known as the internal energy. We must supply energy for the object to gain it. The energy needed to raise the tempereature of an object is proportional to increase in temperature and the mass. so. E = mass and temperature.

If things are not DIRECTLY proportional (as this is not) then they must be proportional by a specific constant. In this case the CONSTANT is given by the SPECIFIC HEAT CAPACTITY.


 * __SOURCES OF EXPERIMENTAL ERROR:__**

There are many significant sources of experimental error in both experiments to measure specific heat capacity. MEASURING TEMPERATURE- it is hard to get an even temperature measurement of metal, as the parts nearer the heater will be hotter than the parts further away. (unlike water, in which you can keep stirring to make an average) ENERGY LOST FROM POWER SUPPLIER DURING HEATING - some energy is lost to rise the temp of the heater itself, the thermometer and some energy leaks away through the insulation rather than heating up the actual material

-insulate apparatus well -use thermomters and heater with a small mass in comparison to material's mass. -after supplying a known amount of energy, turn off power suply but keep measuring temperature. This allows energy from heater to pass to material when it's switched off. materials with MASSIVE molecules have LOW specific heat capacity
 * __MINIMISING ERROR:__**
 * __THE MASS OF MOLECULES__**