Forms of Energy Quiz

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Questions and Answers

What does a positive value of work, w, represent in the system?

Friction between the piston and gas

Work done on the gas

Work done by the system (correct)

Compression of the gas

According to the first law, what does the heat energy q added to a system primarily do?

Maintain pressure

Cause friction

Decrease internal energy

Increase internal energy (correct)

What is the relationship between enthalpy and internal energy at constant pressure?

Internal energy is zero

Enthalpy is greater than internal energy

Enthalpy equals internal energy (correct)

Internal energy is negligible

In biochemical reactions, why is enthalpy change at constant pressure more relevant than internal energy change?

Pressure and volume changes are insignificant Signup and view all the answers

Why is the difference between ΔH and ΔU considered insignificant in most biochemical reactions?

Pressure and volume changes are minimal Signup and view all the answers

What aspect of enthalpy is of importance due to it being a state function?

Change in enthalpy between final and initial states Signup and view all the answers

What type of energy is converted when a heater is connected to the mains and placed in water?

Electrical energy Signup and view all the answers

What type of energy is converted when the chemical energy in ATP is used in skeletal muscles?

Mechanical energy Signup and view all the answers

What type of energy is released when liquefied petroleum gas is burnt in the kitchen?

Heat and light Signup and view all the answers

What type of energy holds atoms together in molecules?

Chemical potential energy Signup and view all the answers

What type of energy binds protons and neutrons in nuclei?

Nuclear energy Signup and view all the answers

What type of energy is converted in a Daniel cell?

Electrical energy Signup and view all the answers

What type of system allows for energy exchange but not matter exchange with the surroundings?

Closed system Signup and view all the answers

What is an example of a system that allows neither energy nor matter exchange with its surroundings?

Hot water in a tightly covered thermos flask Signup and view all the answers

What does an adiabatic process involve?

No heat transferred across the boundary Signup and view all the answers

Which type of change occurs at a constant temperature?

Isothermal change Signup and view all the answers

What happens to the temperature of a tightly covered thermos flask containing hot water over time?

The temperature decreases Signup and view all the answers

What is an example of a closed system?

Cold water in a corked bottle Signup and view all the answers

What type of reactions take place in the human body?

Isothermal reactions Signup and view all the answers

Which of the following correctly describes temperature?

Temperature measures the total amount of kinetic energy of a material Signup and view all the answers

Which of the following is an example of a state function?

The enthalpy change of a system Signup and view all the answers

What are the possible units for temperature mentioned in the text?

Kelvin or Fahrenheit Signup and view all the answers

What determines the enthalpy change in a system?

The initial and final states of the system Signup and view all the answers

What does the first law of thermodynamics state?

Energy can only be converted from one form to another Signup and view all the answers

Which of the following is an extensive property?

Volume Signup and view all the answers

In a galvanic cell, what type of energy conversion takes place?

Chemical energy is converted to electrical energy Signup and view all the answers

What is an intensive property?

A property that does not depend on the amount of material present Signup and view all the answers

Which mathematical formula represents the first law of thermodynamics as mentioned in the text?

$ΔU = q —w$ Signup and view all the answers

What is the enthalpy change when glucose is oxidized by burning it in oxygen and when it is oxidized in living cells?

The enthalpy change is the same Signup and view all the answers

What is given positive quantities in the sign convention used for heat and work?

Heat absorbed by the system and work done by the system Signup and view all the answers

Study Notes

Work and Energy in Systems

A positive value of work (w) indicates that energy is added to the system, enhancing its internal energy.
According to the first law of thermodynamics, heat energy (q) added to a system primarily increases its internal energy or does work on the system.

Enthalpy vs. Internal Energy

At constant pressure, enthalpy (H) is equal to internal energy (U) plus the product of pressure and volume (PV): H = U + PV.
In biochemical reactions, enthalpy change at constant pressure is more relevant than internal energy change due to the nature of biological processes occurring in open environments.

Change in Enthalpy and Internal Energy

The difference between ΔH (enthalpy change) and ΔU (internal energy change) is often negligible in biochemical reactions because pressure and volume changes are minimal.
Enthalpy is a state function, meaning its value depends only on the current state of the system, not the path taken to reach that state.

Energy Conversion Examples

When a heater is connected to mains electricity and placed in water, electrical energy is converted to thermal energy.
Using the chemical energy in ATP in skeletal muscles converts it into mechanical energy for muscle contraction.
Burning liquefied petroleum gas releases thermal energy, contributing to heating.
Chemical bonds hold atoms together in molecules, representing potential energy.
Nuclear energy binds protons and neutrons in atomic nuclei, providing stability.
Energy conversion in a Daniel cell transforms chemical energy into electrical energy.

System Types and Processes

A closed system allows for energy exchange, but not matter exchange, with its surroundings.
An isolated system neither allows energy nor matter exchange with its surroundings.
An adiabatic process involves no heat transfer to or from the system.
An isothermal change occurs at a constant temperature.

Thermodynamic Properties and Examples

Over time, the temperature of hot water in a tightly covered thermos flask gradually decreases as it approaches room temperature.
A typical example of a closed system is a sealed container of gas where energy can be exchanged but mass cannot.
The human body undergoes various exothermic and endothermic reactions to maintain homeostasis.
Temperature is a measure of the average kinetic energy of particles in a system and can be represented in units such as Celsius, Fahrenheit, or Kelvin.

Thermodynamic Principles

The enthalpy change in a system is determined by the heat flow and the work done during a process.
The first law of thermodynamics states that energy cannot be created or destroyed, only transformed.
The enthalpy change when glucose is oxidized differs between burning in oxygen and oxidation in living cells due to the controlled conditions in metabolism.
Positive quantities in the sign convention for heat and work denote energy being added to the system.

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Test your knowledge on different forms of energy including electrical, mechanical, chemical potential, and nuclear energy. Explore how energy is converted and transformed in various systems.