Energetics Flashcards
Define energy
measure of the ability to do work
Name some forms that energy comes in
heat, light, sound, electricity, and chemical energy
Distinguish between a system and a surrounding.
System- the area interest.
Surrounding- everything in the universe
Name the two systems
Open- which can exchange energy and matter with surroundings
Closed - can exchange energy but not matter
Define enthalpy
The heat content of a substance
What is an exothermic reaction and give two examples.
When heat energy is transferred from the system to the surroundings. The products have less energy than the reactants.
The enthalpy change is NEGATIVE
Ex. Combustion and neutralization
What is an endothermic reaction and give two examples.
Energy transfer from the surroundings to the system. The products will have more heat content than the reactants.
The enthalpy change is POSITIVE.
Example: photosynthesis.
What are the conditions for standard enthalpy change?
- Tempe of 298k
- 100kPa
- concentration of 1 mol dm^-3
- all substances in their standard sites
Define temperature.
The measure of the average kinetic energy of the particles.
Conditions that influence temperature
- mass
- heat added
- nature of substance
What is the formula of heat change/ change of enthalpy
mass x specific heat capacity x temperature change
Assume you’re using a calorimeter. What happens to the temperature of the water during an exothermic reaction? during an endothermic?
Exo = temperature of water will increase because heat is released
Endo = temperature of the water will decrease because heat is absorbed into the system.
Using a calorimeter, what is the equation to find the heat lost to water?
What is the equation to find the molar heat change of reaction (the change of heat of the substance/limiting reagent?)
- mass x specific heat capacity x temperature change
- mass x specific heat capacity x (temperature change/ moles of limiting reagent)
What is the equation if given volume (in cm) and concentration of the limiting reagent?
What is the equation if given volume (in dm) and concentration of the limiting reagent?
-mass x specific heat capacity x (temperature change/
(v x concentration/ 1000))
-mass x specific heat capacity x (temperature change/
(v x concentration))
What is Hess’s law?
H1 + H2 = H3
