surroundings

Examples of surroundings in the following topics:

• Changes in the Entropy of Surroundings

  • Irreversible reactions result in a change in entropy to the surroundings.
  • Since the gas does no work on the surroundings in a free expansion (the external pressure is zero, so PΔV = 0,), there will be a permanent change in the surroundings.
  • The heat from the surroundings (entropy) goes into the ice water and the ice melts.
  • The entropy of the ice water increases while the entropy of the surroundings decreases.
  • Distinguish whether or not entropy of surroundings changes in various reactions

• The Three Laws of Thermodynamics

  • In order to avoid confusion, scientists discuss thermodynamic values in reference to a system and its surroundings.
  • Everything that is not a part of the system constitutes its surroundings.
  • The system and surroundings are separated by a boundary.
  • Everything outside of the boundary is considered the surroundings, which would include the container itself.
  • The boundary must be clearly defined, so one can clearly say whether a given part of the world is in the system or in the surroundings.

• Comparison of Enthalpy to Internal Energy

  • The outer edge of the system is referred to as its boundary, which often separates the system from the surroundings.
  • Exchanges of work, heat, or matter between the system and surroundings generally take place across the boundary.
  • In contrast, the internal energies of both open and closed systems can change because they can exchange heat and work with their surroundings.
  • Enthalpy (H) encompasses both the internal energy of a system and the energy associated with displacing the system's surroundings.
  • However, in open systems, the pressure of the system and the surroundings has stayed constant.

• Changes in Temperature

  • Reactions with positive enthalpies—those that absorb heat from their surroundings—are known as endothermic.
  • In contrast, reactions with negative enthalpies—those that release heat into their surroundings—are known as exothermic.
  • Endothermic reactions, on the other hand, will be shifted towards product formation as heat is removed from the reaction's surrounding environment.

• Changes in Energy

  • The state function has the important property that in any process where the system gives up energy ΔE, and its entropy falls by ΔS, a quantity at least TR ΔS of that energy must be given up to the system's surroundings as unusable heat (TR is the temperature of the system's external surroundings).
  • The difference in temperature between a warm room (the surroundings) and a cold glass of ice and water (the system and not part of the room) begins to equalize.
  • This is because the thermal energy from the warm surroundings spreads to the cooler system of ice and water.
  • However, the entropy of the system of ice and water has increased more than the entropy of the surrounding room has decreased.

• Volcanoes

  • Volcanic eruptions and lava can cause immediate danger to the surrounding area.
  • When either of these warnings happen, scientists monitor the volcano more carefully and may call for an evacuation of the surrounding towns.
  • Volcanoes can also have beneficial effects on the surrounding environment.

• Exothermic and Endothermic Processes

  • When a reaction proceeds, it either releases energy to, or absorbs energy from, its surroundings.
  • Since endothermic reactions draw in heat from their surroundings, they tend to cause their environments to cool down.
  • Therefore, the change in enthalpy is positive, and heat is absorbed from the surroundings by the reaction.
  • Therefore, the change in enthalpy is negative, and heat is released to the surroundings.

• Microstates and Entropy

  • In terms of energy, when a solid becomes a liquid or a liquid a vapor, kinetic energy from the surroundings is changed to ‘potential energy‘ in the substance (phase change energy).
  • This energy is released back to the surroundings when the surroundings become cooler than the substance's boiling or melting temperature, respectively.
  • Phase-change energy increases the entropy of a substance or system because it is energy that must be spread out in the system from the surroundings so that the substance can exist as a liquid or vapor at a temperature above its melting or boiling point.

• Free Energy and Work

  • Gibbs energy is the maximum useful work that a system can do on its surroundings when the process occurring within the system is reversible at constant temperature and pressure.
  • Energy that is not extracted as work is exchanged with the surroundings as heat.

• Spontaneous and Nonspontaneous Processes

  • This means a release of free energy from the system corresponds to a negative change in free energy, but to a positive change for the surroundings.
  • The increase in temperature of the reaction surroundings results in a sufficiently large increase in entropy, such that the overall change in entropy is positive.
  • That is, the ΔS of the surroundings increases enough because of the exothermicity of the reaction so that it overcompensates for the negative ΔS of the system.