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WorksheetsEdexcel 6A 6B Notes Chemistry
Total questions: 101
Worksheet time: 2hrs 26mins
What does the symbol ΔH represent in thermodynamics?
Temperature change
Enthalpy change
Volume change
Pressure change
What is the standard temperature used when defining standard enthalpy of reaction?
273 K
298 K
300 K
310 K
Which of the following is a component of chemical energy?
Heat capacity
Temperature
Kinetic energy
Entropy
Which process transfers heat energy from the system to the surroundings?
Exothermic
Endothermic
Isothermal
Adiabatic
The heat energy change, ΔHΔHΔH, is measured at constant (a) .
Heat energy is directly proportional to the absolute (a) of a substance.
Enthalpy is the (a) energy of a system plus the energy required to make room for the system by displacing its surroundings.
(a) energy is the sum of the kinetic energy and potential energy of a substance.
Enthalpy change is the energy transferred between a system and its surroundings at constant volume.
True
False
Potential energy is related to the motion of particles in a substance.
True
False
Heat energy is a portion of the potential and kinetic energy of a substance.
True
False
Endothermic reactions transfer heat energy to the surroundings.
True
False
What term describes the heat energy transferred at constant pressure?
(a)
What type of reaction absorbs heat from the surroundings?
(a)
What is the standard pressure for measuring ΔHΔHΔH?
(a)
Which energy is responsible for the temperature of a substance?
(a)
Why does a cup of hot coffee get cold over time when left uncovered?
If water at 60°C is placed in contact with air at 20°C, in which direction will the heat transfer occur?
How can you identify an exothermic process in a chemical reaction?
A reaction occurs in a system where the surrounding temperature decreases. What type of reaction is this, and why?
Define enthalpy change in the context of biological reactions.
Provide an example of an exothermic biological process and explain why it is exothermic.
How does the concept of potential energy relate to enzyme-substrate interactions?
What is the enthalpy change (ΔH) of the reaction HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)?
+57.1 kJ mol⁻¹
-57.1 kJ mol⁻¹
+70 kJ mol⁻¹
-70 kJ mol⁻¹
Which of the following processes is an example of an exothermic reaction?
Melting of ice
Neutralization of HCl and NaOH
Evaporation of water
Photosynthesis
Which of the following is an exothermic process?
Melting ice
Combustion of petrol
Evaporating water
Photosynthesis
What is the recommended standard pressure for measuring enthalpy changes according to IUPAC?
1 atm
100 kPa
101.325 kPa
1 bar
What does the negative (−) sign of enthalpy change indicate?
Heat energy is absorbed
Heat energy is transferred to the system
Heat energy is transferred to the surroundings
No heat energy is transferred
The enthalpy change of a reaction is the heat energy transferred under (a) conditions.
Exothermic reactions release heat energy, resulting in an (a) in temperature of the surroundings.
Endothermic reactions require heat energy to be (a) from the surroundings.
The standard temperature commonly used for thermochemical measurements is (a) .
Combustion of petrol is an example of an endothermic process.
True
False
The enthalpy change for the reaction CaCO3(s)→CaO(s)+CO2(g) is +178 kJ mol−1.
True
False
Standard enthalpy change of reaction refers to enthalpy changes under standard conditions.
True
False
Evaporation of water is an example of an exothermic process.
True
False
What type of reaction transfers heat energy from the surroundings to the system?
(a)
What is the term for enthalpy change under standard conditions?
(a)
What type of reaction is the combustion of a hydrocarbon?
(a)
What is the SI unit for pressure used in standard conditions?
(a)
Why does the temperature of a reaction mixture increase when hydrochloric acid is added to aqueous sodium hydroxide?
Explain why photosynthesis is classified as an endothermic process.
A student finds the enthalpy change of a reaction to be positive. What does this indicate about the heat flow in the reaction?
Define standard enthalpy change of reaction (ΔH298⦵ΔH⦵_{298}ΔH298⦵).
Write the equation for the standard enthalpy change of formation of ammonia (NH3NH_3NH3) from nitrogen and hydrogen.
Suggest why standard enthalpy changes are measured at 100 kPa instead of 101.325 kPa as commonly used in the past.
Classify the following processes as exothermic or endothermic: Burning a candle wax, Baking bread.
What happens to the enthalpy of the system in an exothermic reaction?
It increases
It remains constant
It decreases
It fluctuates
Which of the following is true for an endothermic reaction?
H_products < H_reactants
H_products > H_reactants
Enthalpy change is negative
Heat is released to the surroundings
What is the value of ΔH for the reaction C(s) + O2(g) → CO2(g)?
+394 kJ mol^{-1}
-394 kJ mol^{-1}
0 kJ mol^{-1}
+234 kJ mol^{-1}
What is the correct direction for the arrow showing enthalpy change in an enthalpy level diagram?
Reactants to reactants
Reactants to products
Products to reactants
Products to products
The change in enthalpy ΔH
(a)
For an exothermic reaction, the enthalpy of the ______ is greater than the enthalpy of the ______.
(a)
In an enthalpy level diagram, the arrow must always point toward the (a) .
For an endothermic reaction, the value of \( \Delta H \) is (a) .
In an exothermic reaction, ΔH↓reactnts −> ΔHproducts
True
False
The direction of the arrow for \( \Delta H \) should be from products to reactants.
True
False
An enthalpy level diagram for an exothermic reaction shows the enthalpy of the system decreasing from reactants to products.
True
False
The combustion of carbon to form carbon dioxide has a negative enthalpy change of -394 kJ mol\(^{-1}\).
True
False
What type of reaction has a negative \( \Delta H \)?
(a)
What is the sign of \( \Delta H \) for an endothermic reaction?
(a)
In an enthalpy level diagram, where does the arrow point?
(a)
Which reaction involves heat transfer to the surroundings?
(a)
Explain why the enthalpy level diagram for an exothermic reaction shows the products at a lower energy level than the reactants.
How can you identify an endothermic reaction from its enthalpy level diagram?
If the enthalpy change for a reaction is positive, what does it indicate about the energy transfer?
Define the term enthalpy change (ΔH).
Why is it important to correctly label the arrow and sign of ΔH in an enthalpy level diagram?
Compare and contrast the enthalpy level diagrams for exothermic and endothermic reactions.
What is the enthalpy change (ΔH) for the reaction $ C(s) + CO_2(g) \rightarrow 2CO(g) $?
+172 kJ mol$^{-1}$
-172 kJ mol$^{-1}$
+394 kJ mol$^{-1}$
-394 kJ mol$^{-1}$
In an enthalpy level diagram, which of the following must be labeled?
Only the products
The vertical axis and reactants
The vertical axis and state symbols
Only the extent of the reaction
For the reaction $ CH_4(g) + 2O_2(g) \rightarrow CO_2(g) + 2H_2O(l) $, what is ΔH?
+890 kJ mol$^{-1}$
-890 kJ mol$^{-1}$
+172 kJ mol$^{-1}$
-394 kJ mol$^{-1}$
What does an enthalpy level diagram represent?
The relationship between energy levels and pressure
The enthalpy of reactants and products in a chemical reaction
The kinetic energy of molecules
The rate of reaction
The enthalpy level diagram shows the relationship between the ______ of the reactants and the ______ of the products.
(a)
The formula for both reactants and products in an enthalpy level diagram should include their ______ ______.
(a)
The value for ΔH must be given, including the (a) .
The activation energy is not essential in an enthalpy level diagram but should be shown in a(n) ______ ______ diagram.
(a)
The horizontal axis in an enthalpy level diagram must always be labeled.
True
False
The enthalpy change for CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) is -890 kJ mol⁻¹.
True
False
It is necessary to label the vertical axis in an enthalpy level diagram.
True
False
The enthalpy level diagram shows the activation energy of a reaction.
True
False
What is the sign of ΔH for an exothermic reaction?
(a)
In an enthalpy level diagram, what axis must be labeled?
(a)
What type of diagram is used to show the enthalpy change of reactants and products?
(a)
What is the enthalpy change (ΔH) for the reaction C(s) + CO₂(g) → 2CO(g)?
(a)
Why is it important to include state symbols in an enthalpy level diagram?
How would the enthalpy level diagram for an exothermic reaction differ from that of an endothermic reaction?
For the reaction CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l), explain why the ΔH value is negative.
If ΔH for H₂(g) → 2H(g) is +26.5 kJ mol⁻¹, explain the significance of the positive sign.
Define an enthalpy level diagram.
Draw an enthalpy level diagram for CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) with ΔH = -890 kJ mol⁻¹. Indicate whether the reaction is exothermic or endothermic.
Why is it not essential to include activation energy in an enthalpy level diagram?
What additional information can be derived from an enthalpy profile diagram that is not shown in an enthalpy level diagram?
94-108.
Answer the questions below after watching the video
What are the three primary methods through which thermal energy is transferred?
Evaporation, Condensation, Precipitation
Solidification, Vaporization, Sublimation
Compression, Expansion, Modulation
Conduction, Convection, Radiation
What is the term used to describe the transfer of heat through a solid object?
Convection
Insulation
Radiation
Conduction
How does heat transfer when objects are in direct contact?
Radiation
Convection
Conduction
Reflection
What everyday kitchen item exemplifies heat conduction when used on a stove?
Cup
Plate
Spoon
Kettle
What happens to the air inside a hot air balloon that causes it to rise?
It evaporates
It condenses
It cools down
It heats up and rises
What creates a convection current within a hot air balloon?
The sunlight hitting the balloon
The burner turning off and on
The rotation of the balloon
The rising of heated air
How does an air conditioner cool a room during a hot day?
By insulation
By convection
By radiation
By conduction
What is the role of matter in the transfer of heat by conduction and convection?
It blocks heat transfer
It is not necessary
It facilitates heat transfer
It converts heat into energy
How does the heat from the sun reach the Earth?
Through reflection
Through radiation
Through convection
Through conduction
What type of heat transfer occurs through electromagnetic waves?
Convection
Conduction
Reflection
Radiation
Which example illustrates radiation in a household setting?
Boiling water in a kettle
Using a microwave
Sitting by a fireplace
Cooking on a stove
What is a common source of radiation warmth experienced outdoors?
Shade from trees
Sunlight
Humidity
Wind
In the process of heating water in a kettle, what is the initial method of heat transfer?
Convection
Radiation
Expansion
Conduction
After conduction, what process takes over to move heat through the water in a kettle?
Radiation
Convection
Evaporation
Condensation
How does the heat finally leave the kettle and spread to its surroundings?
By conduction
By radiation
By convection
By insulation
Why does a wooden spoon not get hot when used for stirring boiling water?
It has a high density of free electrons
It is typically made of metals
It does not allow heat to flow through it easily
It is always cold to the touch
How is convection different from conduction?
Convection can transfer heat through a vacuum, but conduction cannot.
Conduction can transfer heat through a vacuum, but convection cannot.
Convection takes place only in liquid and gases, but conduction transfers heat in solids.
Convection takes place only in solids, but conduction transfers heat in liquid and gases as well
The air near the ceiling in a room is warmer than the air near the floor.
Conduction
Convection
Radiation
Heat is defined as
the transfer of thermal energy from one object to another due to temperature difference
the temperature of a solid, liquid, or gas
The kinetic energy of a solid, liquid, or gas.
Which of the following is true about radiation?
It requires a physical medium to transfer heat.
It is the only form of heat transfer that can occur in a vacuum.
It is most effective in solids.
It involves the movement of molecules from a hot region to a cooler one.
115-131.
Answer the questions below after watching the video
What is the primary direction of heat transfer in everyday situations?
From colder to hotter objects
From hotter to colder objects
Between objects of the same temperature
Randomly between objects
What is an example of a poor conductor?
Iron
Silver
Steel
Air
Which material is considered a good conductor of heat?
Wood
Styrofoam
Copper
Paper
What is conduction?
Movement of heat through fluids
Heat transfer through empty space
Transfer of heat through electromagnetic waves
Direct heat transfer between touching objects
Why is it safe to pick up wooden objects that have been in the sun compared to metal objects?
Wood is a poor conductor
Wood does not conduct heat
Wood absorbs less heat
Wood reflects all heat
What happens to a gas or liquid when it is heated?
It contracts and sinks
It expands and sinks
It contracts and rises
It expands and rises
What creates a convection current?
Heating and cooling of a fluid
Electrical energy
Magnetic fields
Rotation of the Earth
Which example illustrates the concept of radiation?
Boiling water in a pot
Freezing water into ice
Using a microwave to heat food
Mixing hot and cold water
How does radiation transfer heat?
Via convection currents
Through electromagnetic waves
Through direct contact
By mechanical means
If water at 60°C is placed in contact with air at 20°C, in which direction will the heat transfer occur?
What practical application benefits from understanding heat transfer?
Developing water filtration systems
Enhancing home heating and cooling systems
Designing better sports equipment
Improving vehicle aerodynamics
What happens to thermal energy in an exothermic reaction?
It is released to the surroundings
What is the unit for measuring enthalpy change?
What does Hess’s Law state about reversing a reaction?
Energy can neither be created nor destroyed in a chemical reaction. (True/False)
An endothermic reaction releases energy to the surroundings. (True/False)
True
The enthalpy of reaction is the sum of enthalpies of all smaller reactions involved. (True/False)
