BBC Bitesize - GCSE Physics (Single Science) - Energy and heating - AQA - Revision 5
For metals there is a connection between the thermal conductivity and energy than Iron (mephistolessiveur.info If you double the mass, you must double the heat energy to heat it to The amount of heat energy that a substance has also depends on its specific heat the average heat or thermal energy of the molecules in a substance. We can calculate the heat released or absorbed using the specific heat Scientists define heat as thermal energy transferred between two systems at different temperatures that come in contact. Relationship between heat and temperature.
When the two systems in contact are at the same temperature, we say they are in thermal equilibrium. Zeroth law of thermodynamics: Defining thermal equilibrium The zeroth law of thermodynamics defines thermal equilibrium within an isolated system. The zeroth law says when two objects at thermal equilibrium are in contact, there is no net heat transfer between the objects; therefore, they are the same temperature. Another way to state the zeroth law is to say that if two objects are both separately in thermal equilibrium with a third object, then they are in thermal equilibrium with each other.
The zeroth law allows us to measure the temperature of objects. Any time we use a thermometer, we are using the zeroth law of thermodynamics. Let's say we are measuring the temperature of a water bath. In order to make sure the reading is accurate, we usually want to wait for the temperature reading to stay constant.
Thermal energy- specific heat capacity, latent heat
We are waiting for the thermometer and the water to reach thermal equilibrium! At thermal equilibrium, the temperature of the thermometer bulb and the water bath will be the same, and there should be no net heat transfer from one object to the other assuming no other loss of heat to the surroundings.
Converting between heat and change in temperature How can we measure heat? Here are some things we know about heat so far: The temperature change produces by an amount of heat energy, Q, entering a mass m is a result of sharing that heat energy over each part of the mass, and must be corrected by a constant, c, that depends on what the substance is.
Energy and heating
The constant c is called the specific heat of the particular material. Though this is the way of looking at the equation that says "heat energy transfer causes temperature change", the equation is usually written in this way: Note that what we are doing is similar to what we are doing in a number of situations when we try to extract the properties that depend on external circumstances and specific objects from the property of matter that depends on just what kind of substance it is.
We did this when we defined densityYoung's modulusand bulk modulusfor example. Applying the equation in specific examples This now makes it easy to figure out what happens when we put two substances together.
Suppose we have the same substance of masses m1 and m2 at temperatures T1 and T2 respectively. For concreteness, let's assume that 1 is hotter and 2 is colder and that both are water. Then the heat entering the cold water 2 is a positive quantity and the heat entering the hot water 1 is a negative quantity that is, it leaves, doesn't enter.
The change in the temperature of the cold water is positive and that of the hot water is negative. The equation for heat flow tells us Check why we put the signs the way we did! Now since the objects are both water, the c's are the same and cancel out.
We can now solve for Tfinal: Exactly the result we found experimentally!
thermodynamics - Are specific heat and thermal conductivity related? - Physics Stack Exchange
The final temperatures are the original temperatures, weighted by the fraction of the total mass they each represent. If we include the specific heats as possibly different, the result is: The final temperature is the original temperatures weighted by the fraction of the total "mc" they represent.
This combination -- mass times specific heat -- is called the heat capacity of the object. A note on units When this stuff was first studied in the early 's, the relation with molecular motions and mechanical energy was not understood.
As a result, the "whatever it was" that was transferred from one object to another when the temperature changed was given its own definition and defined by its own standard. Actually, this was specified to be when the water was at 4 C since the specific heat of water changes a little with temperature. We will ignore this.Specific Heat Capacity Problems & Calculations - Chemistry Tutorial - Calorimetry
This is sometimes called a kiloCalorie or just a "big" Calorie a calorie with a capital C. This is very confusing.