Forms of Energy
Chemical Energy
Ice melting is an example of an [endothermic / exothermic] reaction.
Endothermic
If a system releases 100 joules of energy, will the enthalpy be negative or positive?
NEGATIVE - exothermic reactions will always have a negative enthalpy
*DOUBLE POINTS*
A calorimetry experiment is conducted and the temperature change of the water has shown a 500 kJ absorption of heat. How much energy was released by the reaction?
-500 kJ
Energy is [released / absorbed] when bonds are broken.
Absorbed
The law of conservation of energy states that energy cannot be created or destroyed, only ___________ or ____________.
Transferred or Transformed
*DOUBLE POINTS*
Provide an example of an exothermic reaction and an endothermic reaction.
*answers will vary*
50 grams of water is heated 5'C. Calculate the energy required to do this. The specific heat of water is 4.184 J/g'C.
q = 1046 J
Name three parts of a bomb calorimeter.
Calorimeter, bomb, thermometer, propeller or fan, ignition wires, water, sample
Name three compounds that have a heat of formation of 0 kJ/mol.
All singular elements, and diatomic elements will have a heat of formation of 0 kJ/mol.
What type of energy is directly related to the temperature of a substance?
Kinetic Energy
Thermal equilibrium explains that when two substances with different temperatures come together, heat will move from _________ to _________ until there is no longer heat transfer.
Hotter to Colder
10 grams an unknown metal cools from 88'C to 75'C releasing 87.1 J. What is the specific heat of this unknown metal?
c = 0.67 J/g'C
A 20 g sample of selenium is subjected to a temperature change of +15'C while absorbing 96.3 joules of heat. What is the specific heat capacity of selenium?
0.321 J/g'C
The following combustion or methane releases 500 J of energy. If this reaction were to be written out, would 500 J be a reactant or a product?
Product - Combustion is an exothermic process so the energy will be a product.
What type of energy is due to an objects position in relationship to the planet?
Gravitational Energy
Which state of matter is unable to experience heat transfer through convection?
Solid
How much energy is required to fully vaporize 50 grams of liquid water into water vapor? (all constants are on page 4 of your study guide)
112.99 kJ
Some nickel at 357.75'C is dropped in a container with 539.8 g of water at 30.55'C. The specific heat capacity of water is 4.184 J/g'C, and the specific heat of nickel is 0.44 J/g'C. The system comes to thermal equilibrium at 38.65'C. What is the mass of the sample of nickel?
130.30 g
In the decomposition of hydrochloric acid (HCl) into diatomic hydrogen and diatomic chlorine, what is the heat or reaction? Provide your answer in kJ. Use the heat of formations in your study guide.
184.6 kJ
What type of energy is associated with a rubberband?
Elastic Energy
Provide an example where conduction, convection, and radiation are all present.
*answers will vary*
*DOUBLE POINTS*
A block of 100 grams of ice is heated from -10'C to 50'C. Calculate the energy needed to do this. All of the constants you need are on page 4 of your study guide. HINT: remember to calculate the energy of the phase change. HINT #2: think about how many steps this problem will be.
56.37 kJ
100 grams of boiling water (100'C) is poured into 50 grams of cool water (25'C). What is the temperature of the water once thermal equilibrium is reached?
Tf = 75'C
Calculate the heat of reaction for the combustion of sucrose. Provide your answer and identify if the reaction is endothermic or exothermic.
C12H22O11 + 12 O2 --> 12 CO2 + 11 H2O
-5156.02 kJ, exothermic