WorksheetsHonors Unit 6 Thermochemistry
Total questions: 98
Worksheet time: 49mins
Name
Class
Date
1.
What does the Law of Conservation of Energy state?
a)
Energy can be destroyed
b)
Energy transforms into matter
c)
Energy can be created
d)
Energy cannot be created or destroyed
e)
Energy only flows in one direction
2.
In thermochemistry, what is the 'system'?
a)
Everything in the universe
b)
Air around the lab
c)
Chemicals being studied
d)
Thermometer reading
e)
Only the surroundings
3.
Which direction does heat flow in an exothermic process?
a)
From surroundings to system
b)
From system to surroundings
c)
No flow occurs
d)
Into the core
e)
Only upward
4.
Classify the following: Ice melting.
a)
Exothermic
b)
Endothermic
c)
Neutral
d)
Combustion
e)
Decomposition
5.
Which of the following is an exothermic process?
a)
Boiling water
b)
Melting ice
c)
Candle burning
d)
Evaporation
e)
Baking bread
6.
Choose all processes that are endothermic.
a)
Freezing
b)
Melting
c)
Boiling
d)
Condensation
e)
Sublimation
7.
What is the energy change for the surroundings if a system gains energy?
a)
Surroundings gain energy
b)
No change
c)
Surroundings also gain energy
d)
Surroundings lose energy
e)
Energy is destroyed
8.
Fill in the blank: In an exothermic reaction, energy flows from the ______ to the ______.
(a)
9.
What is the sign of ΔH for an endothermic reaction?
a)
Negative
b)
Positive
c)
Zero
d)
Undefined
e)
Depends on mass
10.
Which of the following real-life processes is endothermic?
a)
Condensation of steam
b)
Lighting a match
c)
Baking bread
d)
Freezing water
e)
Combustion of gasoline
11.
If ΔE_universe = ΔE_system + ΔE_surroundings, what is its value in any physical change?
a)
Positive
b)
Negative
c)
Zero
d)
Equal to heat added
e)
Undefined
12.
Which correctly pairs energy flow with process type?
a)
Endothermic – heat released
b)
Exothermic – heat absorbed
c)
Endothermic – heat absorbed
d)
Exothermic – energy gained
e)
Endothermic – products have lower energy
13.
What must be true of energy exchange between system and surroundings?
a)
They must both increase
b)
Only the system can change
c)
Their total remains constant
d)
Only exothermic reactions exchange energy
e)
Heat always flows to the system
14.
Dissolving ammonium nitrate in water drops the temperature. What kind of process is this?
a)
Isothermal
b)
Exothermic
c)
Endothermic
d)
Combustion
e)
Radiative
15.
What does temperature measure?
a)
Total energy in a system
b)
Average kinetic energy of particles
c)
Potential energy of atoms
d)
Heat flow
e)
Mass of substance
16.
Which is the correct unit for heat energy?
a)
Kelvin
b)
Celsius
c)
Joules
d)
Grams
e)
Moles
17.
What is the formula for heat energy?
a)
q = m + c + T
b)
q = m · c · ΔT
c)
q = T – m · c
d)
q = ΔT / c
e)
q = mc²
18.
What is 'q' in the heat equation?
a)
Mass
b)
Specific heat
c)
Energy transferred
d)
Temperature change
e)
Heat capacity
19.
If 100 g of water (c = 4.18 J/g°C) is heated from 20°C to 30°C, how much energy is absorbed?
a)
418 J
b)
1000 J
c)
4180 J
d)
20.9 J
e)
4.18 J
20.
What happens to heat flow when two objects at different temperatures contact?
a)
No heat transfer
b)
Heat flows from cooler to warmer
c)
Heat flows until both reach same temperature
d)
Heat transfers to smaller object
e)
Only the system gains energy
21.
Choose all valid units for q = mcΔT variables.
a)
q – Joules
b)
m – grams
c)
c – J/g°C
d)
T – Celsius
e)
T – Kelvin
22.
What type of heat transfer occurs in a metal spoon heating in hot tea?
a)
Convection
b)
Radiation
c)
Conduction
d)
Evaporation
e)
Absorption
23.
Which process involves heat transfer via fluid motion?
a)
Conduction
b)
Radiation
c)
Convection
d)
Sublimation
e)
Ionization
24.
Which process involves electromagnetic waves?
a)
Conduction
b)
Convection
c)
Radiation
d)
Sublimation
e)
Absorption
25.
Fill in the blank: Zero Kelvin represents (a) .
26.
What is the temperature in Kelvin for 25 °C?
a)
248.2 K
b)
298.2 K
c)
263.0 K
d)
273.0 K
e)
100.0 K
27.
Which of the following is true about temperature vs heat?
a)
Temperature = total energy
b)
Heat = average energy
c)
Heat depends on mass and ΔT
d)
Temperature is measured in Joules
e)
Heat measures kinetic energy
28.
Heat always flows from ______ to ______.
a)
colder to warmer
b)
smaller to larger
c)
lower mass to higher mass
d)
hotter to colder
e)
system to surroundings
29.
What does specific heat capacity represent?
a)
Total energy of a sample
b)
Average speed of particles
c)
Energy needed to raise 1 g by 1 °C
d)
Total temperature change
e)
Amount of substance
30.
Which substance has the highest specific heat?
a)
Iron
b)
Copper
c)
Water
d)
Aluminum
e)
Ethanol
31.
What is the unit of specific heat?
a)
J/g
b)
J/mol
c)
J/g·°C
d)
J/°C
e)
kJ/mol
32.
How much energy is needed to heat 25 g of iron (c = 0.450 J/g·°C) by 20 °C?
a)
225 J
b)
150 J
c)
281.25 J
d)
450 J
e)
22.5 J
33.
In calorimetry, what is the principle used to equate heat gained and lost?
a)
Law of Entropy
b)
Hess’s Law
c)
Conservation of Mass
d)
Law of Conservation of Energy
e)
Kinetic Theory
34.
What is the equation used in calorimetry to solve for specific heat of a metal?
a)
q = mΔH
b)
q = mcΔT
c)
c = q / (m·ΔT)
d)
ΔT = q / mc
e)
m = q / cΔT
35.
Which of the following explains why water buffers temperature better than metals?
a)
Lower density
b)
Smaller molecular mass
c)
Lower specific heat
d)
Higher specific heat
e)
Better conductor
36.
Choose all that are required for calorimetry calculations.
a)
Mass of water
b)
Specific heat of water
c)
ΔT of both metal and water
d)
Heat of fusion
e)
Mass of metal
37.
Fill in the blank: In calorimetry, q_metal = (a) .
38.
What would indicate your calorimeter lost heat?
a)
Final temp too high
b)
Final temp lower than expected
c)
Initial temp too low
d)
Temp stayed constant
e)
Heat was gained by metal
39.
Why must a calorimeter be insulated?
a)
To heat the metal faster
b)
To cool the water
c)
To prevent energy input
d)
To prevent heat loss to surroundings
e)
To melt the sample
40.
Which of the following is a correct specific heat value?
a)
Water – 0.385 J/g°C
b)
Copper – 4.18 J/g°C
c)
Iron – 0.450 J/g°C
d)
Ethanol – 0.897 J/g°C
e)
Aluminum – 2.44 J/g°C
41.
A 50 g metal heats from 25°C to 75°C with 1000 J of energy. What is its specific heat?
a)
0.2 J/g°C
b)
0.4 J/g°C
c)
0.5 J/g°C
d)
0.8 J/g°C
e)
1.0 J/g°C
42.
What tool is most commonly used to measure temperature change in calorimetry?
a)
Thermocouple
b)
Pressure gauge
c)
Graduated cylinder
d)
Thermometer
e)
Caliper
43.
What type of process is melting?
a)
Exothermic
b)
Endothermic
c)
Neutral
d)
Radioactive
e)
Ionic
44.
During which phase change is heat released?
a)
Melting
b)
Boiling
c)
Sublimation
d)
Freezing
e)
Vaporization
45.
What happens to temperature during a phase change?
a)
It increases rapidly
b)
It decreases rapidly
c)
It remains constant
d)
It fluctuates randomly
e)
It becomes negative
46.
Which equation is used to calculate heat during melting?
a)
q = mcΔT
b)
q = mΔH_vap
c)
q = mΔH_fus
d)
q = ΔT / c
e)
q = m / ΔH
47.
How much energy is needed to melt 100 g of ice? (ΔH_fus = 334 J/g)
a)
334 J
b)
1670 J
c)
3340 J
d)
6680 J
e)
33400 J
48.
Choose all endothermic phase changes.
a)
Melting
b)
Condensation
c)
Boiling
d)
Sublimation
e)
Freezing
49.
Which phase change occurs from solid directly to gas?
a)
Condensation
b)
Melting
c)
Sublimation
d)
Deposition
e)
Freezing
50.
If 50 g of water vapor condenses (ΔH_vap = 2260 J/g), how much energy is released?
a)
1130 J
b)
2260 J
c)
45200 J
d)
113000 J
e)
9050 J
51.
Which of these best describes deposition?
a)
Solid → Gas
b)
Gas → Liquid
c)
Gas → Solid
d)
Liquid → Gas
e)
Solid → Liquid
52.
Why does boiling require more energy than melting?
a)
Vapor has more mass
b)
Gas particles require more kinetic energy
c)
It happens at higher temperature
d)
Melting breaks more bonds
e)
Vaporization doesn't use heat
53.
Fill in the blank: Energy during phase changes is used to (a) .
54.
What does a flat section on a heating curve indicate?
a)
Constant pressure
b)
Phase change
c)
Increasing temperature
d)
Reaction complete
e)
Chemical bond forming
55.
Which of these is an exothermic phase change?
a)
Melting
b)
Sublimation
c)
Condensation
d)
Boiling
e)
Ionization
56.
Which phase changes are used in the 'ice-to-steam' lab?
a)
Melting
b)
Boiling
c)
Freezing
d)
Condensation
e)
Sublimation
57.
What does a heating curve show?
a)
Rate of evaporation
b)
Mass of a substance
c)
Change in temperature and phase over time
d)
Chemical energy output
e)
Bond energies
58.
What does a flat segment of a heating curve represent?
a)
Temperature increase
b)
No energy input
c)
Phase change
d)
Cooling
e)
Kinetic energy drop
59.
During which part of the heating curve does the substance warm as a liquid?
a)
First slope
b)
Second slope
c)
First flat
d)
Second flat
e)
Last slope
60.
What equation is used in sloped segments?
a)
q = mΔH
b)
q = mcΔT
c)
q = ΔH / m
d)
q = m / ΔT
e)
q = c / m
61.
What equation is used in flat segments?
a)
q = mcΔT
b)
q = mΔH
c)
q = m / ΔH
d)
q = ΔT / m
e)
q = c / ΔT
62.
How much energy is required to raise 1 g of water from –20 °C to 120 °C (all phases)?
a)
100 J
b)
418 J
c)
2500 J
d)
Varies by calculation
e)
Depends on pH
63.
Choose all equations used in heating curve calculations.
a)
q = mcΔT
b)
q = mΔH_fus
c)
q = mΔH_vap
d)
ΔH = q/m
e)
q = ΔT / c
64.
Which segment on the heating curve involves c_ice?
a)
First flat
b)
Second slope
c)
First slope
d)
Last flat
e)
Middle flat
65.
What is c_steam for water?
a)
2.1 J/g°C
b)
2.0 J/g°C
c)
4.18 J/g°C
d)
0.897 J/g°C
e)
3.5 J/g°C
66.
Fill in the blank: The flat segment at 100 °C in a water heating curve represents (a) .
67.
Why are specific heats different for each phase?
a)
Phase changes require different energies
b)
Mass varies
c)
Bond strength stays the same
d)
Temperature is constant
e)
Because of color changes
68.
Why is ΔH_vap larger than ΔH_fus for water?
a)
Water has more mass as gas
b)
More energy needed to overcome all IMFs into gas
c)
Vaporization is cooler
d)
Less energy required to freeze
e)
Fusion takes longer
69.
Which phase of water has the highest specific heat?
a)
Ice
b)
Water (liquid)
c)
Steam
d)
All equal
e)
None
70.
If the slope is steep, what does that suggest about the specific heat?
a)
High specific heat
b)
Low specific heat
c)
No energy used
d)
Constant heat flow
e)
Long phase change
71.
What does ΔH represent in thermochemistry?
a)
Change in mass
b)
Change in pressure
c)
Heat content change at constant pressure
d)
Bond strength
e)
Heat lost by surroundings
72.
In an exothermic reaction, what is the sign of ΔH?
a)
Positive
b)
Negative
c)
Zero
d)
Undefined
e)
It varies
73.
What is an example of an endothermic reaction?
a)
Burning wood
b)
Freezing water
c)
Boiling water
d)
Condensation
e)
Combustion
74.
Which of the following is a correct thermochemical equation format?
a)
CH₄ + O₂ → CO₂ + H₂O
b)
CH₄ + 2O₂ → CO₂ + 2H₂O + 890 kJ
c)
CH₄ + O₂ → CO₂
d)
C + O₂ → CO₂ – 393.5
e)
N₂ + O₂ → 2NO, endothermic
75.
If ΔH = –500 kJ, the reaction is:
a)
Endothermic
b)
At equilibrium
c)
Nonspontaneous
d)
Exothermic
e)
Neutral
76.
Choose all that describe exothermic reactions.
a)
ΔH is negative
b)
Heat is a product
c)
System loses energy
d)
Temperature of surroundings drops
e)
Products have lower enthalpy
77.
Fill in the blank: In a balanced thermochemical equation, ΔH is tied to (a) .
78.
If 2 mol of NH₃ releases –92.2 kJ, how much energy is released for 4 mol?
a)
–184.4 kJ
b)
–46.1 kJ
c)
–92.2 kJ
d)
0 kJ
e)
–230 kJ
79.
Which of the following is a product in an exothermic reaction?
a)
Heat
b)
Light
c)
Water
d)
CO₂
e)
All of the above
80.
Which variable is needed to calculate q from ΔH and moles?
a)
Specific heat
b)
Volume
c)
Mass
d)
Moles
e)
ΔT
81.
What is the enthalpy change if 3 mol of CH₄ is burned and ΔH_combustion = –890 kJ/mol?
a)
–890 kJ
b)
–2670 kJ
c)
890 kJ
d)
–1780 kJ
e)
–445 kJ
82.
In a bomb calorimeter, pressure may change but what stays constant?
a)
Mass
b)
Temperature
c)
Volume
d)
Enthalpy
e)
Bond energy
83.
How is % error in a lab typically calculated?
a)
Expected – actual
b)
Actual ÷ expected
c)
[(|actual – expected|)/expected] × 100
d)
Actual – error
e)
Absolute error only
84.
Which type of bond energy calculation supports estimating reaction ΔH without formation data?
a)
Bond enthalpy
b)
Ionization energy
c)
Calorimetry
d)
Kinetic modeling
e)
Mass spectrometry
85.
What does Hess’s Law state?
a)
Energy is always lost
b)
ΔH depends on path taken
c)
Total enthalpy change is path-independent
d)
Heat only flows one way
e)
Bonds always break first
86.
If you reverse a reaction, what happens to ΔH?
a)
Stays the same
b)
Becomes zero
c)
Changes sign
d)
Is halved
e)
Doubles
87.
When multiplying a reaction by 2, what do you do to ΔH?
a)
Divide by 2
b)
Square it
c)
Multiply ΔH by 2
d)
Leave it unchanged
e)
Subtract from 100
88.
Which operation is used when combining reactions in Hess’s Law?
a)
Add equations and ΔH values
b)
Multiply equations
c)
Subtract all products
d)
Reverse only
e)
Take ΔH average
89.
Choose all steps used in Hess’s Law problems.
a)
Reverse equations to cancel compounds
b)
Adjust coefficients
c)
Add ΔH values
d)
Divide all equations
e)
Use standard temp
90.
Fill in the blank: Hess’s Law is useful when (a) .
91.
How is enthalpy shown on a reaction energy diagram?
a)
As a slope
b)
As a vertical distance between products and reactants
c)
As width of curve
d)
As a peak
e)
As a wave
92.
What type of arrow direction indicates exothermic reaction?
a)
Upward
b)
Flat
c)
No arrow
d)
Downward
e)
Backwards
93.
What is a bond enthalpy?
a)
Heat change during boiling
b)
Energy released forming a gas
c)
Energy needed to break a bond in gas phase
d)
Total mass of atoms
e)
Mass lost in a reaction
94.
Which of the following is always true about bond breaking?
a)
It is exothermic
b)
It requires energy
c)
It releases energy
d)
It creates ions
e)
It lowers temperature
95.
Use bond enthalpies: H₂ + Cl₂ → 2 HCl; H–H = 436, Cl–Cl = 243, H–Cl = 431. What is ΔH?
a)
–249 kJ
b)
+249 kJ
c)
–431 kJ
d)
+431 kJ
e)
–100 kJ
96.
Which fuel has the highest energy density per gram?
a)
Octane
b)
Methane
c)
Propane
d)
Ethanol
e)
Butane
97.
Which equation estimates ΔH using bond enthalpies?
a)
ΔH = bonds made – bonds broken
b)
ΔH = products – reactants
c)
ΔH = bonds broken – bonds formed
d)
ΔH = mcΔT
e)
ΔH = mΔH_vap
98.
In molecular modeling, why are average bond enthalpies used?
a)
All molecules are identical
b)
Precise data is unavailable
c)
Bond strengths vary by context
d)
Only gases react
e)
They simplify math
100 %
