1st law of thermodynamics

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1st law of thermodynamics

        The first law of thermodynamics is shared with most of science; it is one of the fundamental principals that have shaped our understanding of the working world.

        TOTAL ENERGY OF THE SYSTEM AND IT’S SURROUNDINGS IS CONSTANT or ENERGY IS CONSERVED, Brings back that long established idea that nothing can be created or destroyed. How do we know this? This is an empirical law, which means that we know that energy is conserved because of many repeated experiments by scientists. It's been observed that you can't get any more energy out of a system than you put into it.

Latent heat

        Latent Heat is defined as the  which flows to or from a material without a change to temperature. The heat will only change the structure or phase of the material. E.g. melting or boiling of pure materials.

        One very good illustration of latent heat in action is observed when we reduce ice to water. If we imagine a bucket of ice on the floor in an average temperature room (about 30 degrees Celsius) .The ice doesn’t instantly liquidize, nor does the room instantly freeze. Instead the temperature of the ice rises until it reaches zero degrees Celsius whereupon it begins to melt. During the entire melting process the contents of the bucket remain at zero degrees, however the room temperature would drop indicating that it was putting heat energy into the melting process. This heat energy is described as latent heat.

Specific heat

        The specific heat capacity of a solid or liquid is defined as the heat required to raise unit mass of substance by one degree of temperature.

        Some substances have more resistance to temperature change than others so more energy is required to alter the temperature. This can be very useful particularly in cooling systems.

        Imagine trying to fry an egg in a frying pan with a steel handle, the handle would conduct the heat very nicely to your hand. However the high carbon plastic sheath on most modern pans is very resistant to temperature change and protects your hands.

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        The following equation describes SPECIFIC HEAT CAPACITY.


Where,
Q= Heat supplied to substance, 
m= Mass of the substance,
c= Specific heat capacity, 
T= Temperature rise.

Enthalpy


         Enthalpy is a measure of heat and energy in the system. Scientists figure out the mass of a substance when it is under a constant pressure. Once they figure out the mass, they measure the internal energy of the system. All together, that energy is the enthalpy. They use the formula "H = U + PV." H is the enthalpy value, U is the amount of ...

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