Unit 3: Heat, Energy, and Reactions Flashcards
Heat
(q) energy that transfers from one object to another because of a temperature difference between the objects
Temperature
a measure of the average kinetic energy of particles in matter; temperature determines the direction of heat transfer
Endothermic
a process that absorbs heat from the surroundings
Exothermic
a process that releases heat to its surroundings
Specific heat
the amount of heat needed to increase the temperature of 1 g of a substance 1*C; also called specific heat capacity
Enthalpy
(H) the heat content of a system at constant pressure
Heat of formation
(ΔHf^0) the change in enthalpy that accompanies the formation of 1 mole of a compound from its elements with all substances in their standard states at 25*C
Le Chatelier’s Principle
when a stress is applied to a system in dynamic equilibrium, the system changes is a way that relieves the stress
Transition state
a term sometimes used to refer to the activated complex
Activation energy
the minimum energy colliding particles must have in order to react
catalyst
a substance that increases the rate of reaction by lowering the activation-energy barrier; the catalyst is not used up in the reaction
Entropy
(S) a measure of the disorder of a system; systems tend to go from a state of order (low entropy) to a state of maximum disorder (high entropy)
Spontaneous Reaction
a reaction that favors the formation of products at the specified conditions; spontaneity depends on enthalpy and entropy changes
Non-spontaneous reaction
a reaction that does not favor the formation of products at the specified conditions
1 Calorie
= 1 kilocalorie = 1000 calories
Specific heat formula (C)
C = q/(m * ΔT) q= heat in J or cal m= mass in grams ΔT= change in temp, in *C
Convert calorie to joules
1 cal = 4.184 J
Gibbs free-energy change
ΔG = ΔH – TΔS
q = m * ΔH Vaporization
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rate = k[A]a[B]b
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q = m * ΔH fusion
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Equilibrium constant
K(eq) = ([C]^c * [D]^d) / ([A]^a * [B]^b)
What does the heat capacity of an object partially depend upon?
Mass and chemical composition
Which of the following phases of H2O is arranged in an increasing order of entropy?
Ice, liquid water, and steam
Describe how a container that has an endothermic reaction occurring would feel compared to a container with an exothermic reaction occurring.
An ENDOthermic reaction feels cold
An EXOthermic reaction feels hot
List three factors that will increase the reaction rate in a chemical reaction.
- use of a catalyst
- decrease particle size
- increase concentration of reactants
What is meant when a reaction is referred to as being reversible? Compare the reactant amounts to the product amounts in a reversible reaction.
The conversion of reactants to products and products to reactants occur at the same rate, the concentration of products and reactants are equivalent
What is the difference between temperature and heat?
Temp measures the amount of energy stored in a substance, while heat is a measure of the energy transferred from one substance to another
Calculate the energy needed to produce 10 moles of Cl2O7 using the following balanced equation. 2Cl2(g) + 7O2(g) + 100 kCal 2Cl2O7(g)
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What causes a reaction to be spontaneous? Provide one example.
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