Themochemistry Notes
Chemistry 101
Chapter 6
THERMOCHEMISTRY
· Thermochemistry is the study of the quantity of heat energy released or absorbed in a chemical reaction. Example: the burning of fuel: is a heatevolving reaction · Heat : · Energy: is a form of energy the potential to do work (to move matter) exists in many different forms: Electrical energy Kinetic Energy (energy of motion) Light energy Heat energy Chemical energy (energy of substances)
· Different forms of energy can be interconverted Examples: Light bulb: electrical energy is converted to light energy and heat energy Car engine: chemical energy (from gasoline) heat energy kinetic energy
KINETIC ENERGY (Ek) · Definition: is the energy associated with a moving object · Formula:
2 Ek = ½ mv , where
m = mass of the moving object v = speed of the moving object
(in kg) (in m/s)
NOTE:
Two objects moving at different speeds may have the same kinetic energy Example: slow moving truck and fast moving sports’ car
2 2 SI unit of energy = from formula of energy = kg . m /s = joule (J) The joule (J) is a very a very small unit
NonSI unit of heat energy : The calorie (cal) amount of energy required to raise the temperature of one gram of water by one degree Celsius 1 cal = 4.184 J
1
Chemistry 101
Chapter 6
POTENTIAL ENERGY (Ep) · Definition: the energy of an object has because of its position in a field of force is stored energy · Example: Any object above ground level possesses Potential Energy since it is attracted by the gravitational force. As such, it has the potential to fall, and therefore to move. (Potential Energy changes into Kinetic Energy) Ep = mgh, where m = mass of the object g = constant acceleration of gravity h = height (level) of the object aboveground level
· Formula:
NOTE: differences of level are usually more important As an object falls toward ground level: Ø its Ep
Chapter 6
THERMOCHEMISTRY
· Thermochemistry is the study of the quantity of heat energy released or absorbed in a chemical reaction. Example: the burning of fuel: is a heatevolving reaction · Heat : · Energy: is a form of energy the potential to do work (to move matter) exists in many different forms: Electrical energy Kinetic Energy (energy of motion) Light energy Heat energy Chemical energy (energy of substances)
· Different forms of energy can be interconverted Examples: Light bulb: electrical energy is converted to light energy and heat energy Car engine: chemical energy (from gasoline) heat energy kinetic energy
KINETIC ENERGY (Ek) · Definition: is the energy associated with a moving object · Formula:
2 Ek = ½ mv , where
m = mass of the moving object v = speed of the moving object
(in kg) (in m/s)
NOTE:
Two objects moving at different speeds may have the same kinetic energy Example: slow moving truck and fast moving sports’ car
2 2 SI unit of energy = from formula of energy = kg . m /s = joule (J) The joule (J) is a very a very small unit
NonSI unit of heat energy : The calorie (cal) amount of energy required to raise the temperature of one gram of water by one degree Celsius 1 cal = 4.184 J
1
Chemistry 101
Chapter 6
POTENTIAL ENERGY (Ep) · Definition: the energy of an object has because of its position in a field of force is stored energy · Example: Any object above ground level possesses Potential Energy since it is attracted by the gravitational force. As such, it has the potential to fall, and therefore to move. (Potential Energy changes into Kinetic Energy) Ep = mgh, where m = mass of the object g = constant acceleration of gravity h = height (level) of the object aboveground level
· Formula:
NOTE: differences of level are usually more important As an object falls toward ground level: Ø its Ep