Specific heat is the amount of energy required to raise one degree Celsius of one gram of a pure substance. The specific heat of a substance depends on its molecular structure and phase. The discovery of specific heat revived the study of thermodynamics, the study of energy changes through heat and the work of a system. Specific heat and thermodynamics are widely used in chemistry, nuclear engineering, and aerodynamics, as well as in everyday life in automobile radiators and cooling systems. If you want to know how to calculate specific heat, just follow these steps.
Step
Method 1 of 2: Learning the Basics
Step 1. Understand the terms used to calculate specific heats
It's important to understand the terms used to calculate specific heats before you learn the formula for specific heats. You must know how to distinguish the symbols of each term and understand their meaning. Here are some terms that are often used in equations to calculate the specific heat of a substance:
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Delta, or the symbol, represents a change in a variable.
For example, if your initial temperature (T1) is 150ºC, and your second temperature (T2) is 20ºC, then T, or change in temperature, represents 150ºC - 20ºC, or 130ºC
- The mass of the material is denoted by m.
- The amount of heat is denoted by Q. The amount of heat is denoted by units of J or Joule.
- T is the temperature of the substance.
- Specific heat is denoted by Cp.
Step 2. Study the equations for specific heats
If you are familiar with the terms used to calculate the specific heat, you should study the equation to find the specific heat of a substance. The formula is: Cp = Q/mΔT.
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You can change this formula if you want to find the change in heat instead of specific heat. The formula will look like this:
Q = mCpT
Method 2 of 2: Calculating Specific Heat
Step 1. Study the equation
First, you have to look at the equation to find out what you need to do to find the specific heat. Take a look at this problem: Find the specific heat of 350 g of an unknown material if it is given a heat of 34,700 Joules, and its temperature rises from 22ºC to 173ºC without a phase change.
Step 2. Write down the known and unknown factors
If you already understand the problem, you can write down the known and unknown variables to know better what you are doing. Here's how to do it:
- m = 350 g
- Q = 34,700 Joule
- T = 173ºC - 22ºC = 151ºC
- Cp = unknown
Step 3. Plug the known factors into the equation
You already know the value of all variables except Cp, so you have to plug the other values into the original equation and find Cp Here's how you do it:
- Initial equation: Cp = Q/mΔT
- c = 34,700 J/(350 g x 151ºC)
Step 4. Solve the equation
Since you've already factored the known factors into the equation, just use simple arithmetic to solve it. The specific heat, or the final product, is 0.65657521286 J/(g x C).
- Cp = 34,700 J/(350 g x 151ºC)
- Cp = 34,700 J/(52850 g x C)
- Cp = 0, 65657521286 J/(g x C)
Tips
- The SI (International System) unit for specific heat is Joule per degree Celsius per gram.
- Metal heats up faster than water because of its low specific heat.
- Calorimeters are sometimes used for heat transfer when a physical or chemical change occurs.
- When looking for specific heats, cross out the units that can be crossed out.
- Specific heats for many objects can be searched online to check your work.
- The change in temperature for materials with low specific heats is greater than for other materials if all other things are equal.
- Learn the formula for finding the specific heat of a food. Cp = 4,180 x w + 1,711 x p + 1,928 x f + 1,547 x c + 0, 908 x a is the equation used to find the specific heat of food where w is the percentage of water in the food, p is the percentage of protein in the food, f is the percentage of fat in the food, c is the percentage of carbohydrates in the food, and a is the percentage of minerals in the food. This equation considers the mass ratio (x) of all the ingredients in the food. Calculation of specific heat is written in units of kJ/(kg-K).
