Chem unit 4 part 1

Q: What characterizes an Open System?

A: It can exchange both matter and energy with its surroundings (e.g., boiling water in an open pot) (p. 1)

Q: What characterizes a Closed System?

A: It can exchange energy but cannot exchange matter (e.g., a sealed container in a water bath) (p. 1).

Q: What characterizes an Isolated System?-

A: It can exchange neither matter nor energy with its surroundings (e.g., an ideal thermos) (p. 1).

Q: What is a State Function?

A: A property that depends only on the initial and final states, not on the path taken

Q: What is a Path Function?.

A: A property that depends on the specific process or path taken to reach the final state (p. 1)

Q: What are the two specific conditions for 𝚫U and 𝚫H regarding heat

At constant volume 𝚫U = qv, at constant pressure 𝚫U = qp

Q: Define internal energy (𝚫U) and enthalpy (𝚫H)

A: 𝚫U is the total energy of a system, 𝚫H is heat at constant pressure

Q: Define entropy (𝚫S) and Gibbs Free energy (𝚫G)-

A: 𝚫S is a measure of disorder, 𝚫G is energy available to do work

Q: What is the difference between heat and work?-

A: heat is Energy transfer due to temperature difference, work is Energy transfer due to volume, pressure, or mechanical change (p. 1).

: What is the sign for heat and enthalpy in an ENDOTHERMIC process?

Positive (+). Energy is absorbed/entering the system. (p. 2)

What is the sign for heat (q) and enthalpy (𝝙H) in an EXOTHERMIC process?

Negative (-). Energy is released/leaving the system.

When is work (w) POSITIVE?

When work is done on the system (e.g., compression).

When is work (w) NEGATIVE?

When work is done by the system (e.g., expansion).

What is the core relationship equation for Gibbs Free Energy?

𝝙G = 𝝙H - T𝝙S

What is the sign of 𝝙G for a SPONTANEOUS reaction?

Negative (-)

Under what conditions is a reaction “Always spontaneous"?

When 𝝙H is negative (-) and 𝝙S is positive (+)

If a process is spontaneous only at HIGH temperatures, what are the signs for 𝝙H and 𝝙S?

both are positive - driven by entropy

What does a positive 𝝙S signify

disorder is increasing

what does a negative 𝝙S signify

disorder is decreasing (more ordered)

What is the main difference between Heat Capacity (C) and Specific Heat Capacity (c)?

Heat Capacity depends on mass; Specific Heat Capacity depends only on the substance's identity

What are the units for Specific Heat Capacity

J/g degrees C or J/g degrees K

What is the equation for calculating heat

q = m c 𝝙T

Does a substance with a LOW specific heat capacity heat up quickly or slowly

Quickly. It takes less energy to raise its temperature (e.g., metals like Lead)

Why does water have a very high specific heat (4.18 J/g * C)?

Strong hydrogen bonding

Between Water (4.18) and Copper (.384), which will reach a higher temperature if given the same amount of heat?

Copper. Its lower specific heat allows its temperature to rise much faster (p. 3)

What is the energy balance equation used in calorimetry

qlost = -qgained

m1c1𝝙T1 = - m2c2𝝙T2

What factors cause Heat Capacity () to increase?

Increasing mass and increasing intermolecular force (IMF) strength (p. 3).

What is the First Law of Thermodynamics?

Energy is conserved 𝝙Uuniv = 0

cannot be created or destroyed, only transferred

What is the relationship between the system and the surroundings?

𝝙U sys = -𝝙U surr (Energy lost by one is gained by the other)

What is the fundamental equation for internal energy (𝝙U)?

𝝙U = q+w

What are the 2 types of potential energy in a chemical system

Covalent bonds (chemical) and IMFs

What does enthalpy 𝝙H represent

heat flow at constant pressure (qp = 𝝙H)

When does 𝝙U = q (Internal energy equals heat)

at constant volume because no expansion work is done

What are the three forms of kinetic energy in molecular motion?

Translation, rotation, and vibration.

equation for enthalpy

𝝙H = 𝝙U + P𝝙V

definition enthalpy

state function that accounts for internal energy and PV work