Thermodynamics Flashcard

What three things happen in any chemical reaction?

Reactaants are consumed

 

Products are formed

 

There is a transfer of energy

Define:

 

Thermodynamics

The study of the changes in energy and transfer of energy that accompanies physical and chemical processes.
What are the three Laws of Thermodynamics?

1st Law: Conservation of Energy

 

2nd Law: Law of Entropy

 

3rd Law: Law of Absolute Zero

State the First Law of Thermodynamics.

 

(Law of Conservation of Energy)

This law suggest that energy can be transferred from one system to another in many forms but the energy cannot be created or destroyed.

State the Second Law of Thermodynamics.

 

(Law of Entropy)

Heat cannot be transfered from a cold body to a hot body. As a result of this fact of thermodynamics, natural processes that involve energy transfer must have one direction, and all natural processes are irreversible.

State the Third Law of Thermodynamics

 

(Law of Absolute Zero)

The third law of thermodynamics states that if all the thermal motion of molecucule (kinetic energy) could be removed, a state called absolute zero would occur. Absolute zero results in a Temperature of 0 Kelvins or -273.15° Celcius.

Define:

 

Energy

The capacity(ability) to do work.
What are the units associated with Energy?

joule (J)

kilojoule (kJ)

calorie (cal)

kilocalorie (kcal)

 

Note: calorie is denoted with a lower case “c”

What are the different forms of Energy?

How can Energy manifest itself?

Mechanical (car)

Electrical (electricity)

Radiant (light)

Nuclear

Chemical (hot/cold packs)

State the formula of Work and the unit associated with it.

Work = Force * Distance

 

Unit is joule (J)

or

Newton*meter (1N*m=1J)

 

Note: Work and Energy have the same unit.

Define:

 

Heat (q)

A measure of the internal energy that is absorbed or transferred from one body to another.

 

Represented by a lower case q.

 

(Not to be confused with Temperature)

Define:

 

Temperature

A relative measure of hotness or coldness.

Define:

 

Internal Energy (U or E)

The total kinetic energy and potential energy of all the molecules or an object.
What is Kinetic Energy
The energy of motion.
State the formula for determining Kinetic Energy.

KE=1/2mv2

 

Kinetic Energy=1/2 mass * velocity squared

 

Note:

All molecules and atoms are in constant motion so KEatom/molecule is >0

State the formula for determing Potential Energy.

PEgrav=mgh

 

m=mass

g=gravity

h=height

Define:

 

Potential Energy

Energy possessed by an object due to its postition or composition.
What are some examples of Potential Energy?

Gravitational

Tension or Compression(elastic)

Centrifigal

Magnetic

What is the formula for determing Internal Energy?

ΔU=q+w

Change of Internal Energy(ΔU) = heat + work

 

Note:

Internal Energy may be represented

by U or E

so you might see ΔU or ΔE in a problem.

How may Energy(E) be transfered?

In the form of heat

In the form of work

In the form of work and heat

Define:

 

System

Substances under investigation

 

Ex: Chemical reaction occuring in a beaker

Define:

 

Surroundings

The rest of the universe.

 

Every not being investigated.

Define:

 

Universe

(Not the Carl Sagan type)

System plus its surroundings.

Define:

 

Thermodynamic State of a System

A set of conditions that describe and define a system.

 

i.e.

1. number of moles or each substance

 2.physical state of each substance

3. temperature

4. pressure

5. volume

Define:

 

State Function

A property of a system that depends only on hte current state of the system and not how the system came to be in that state.

 

An Indepent property.

Define:

 

Enthalpy(H)

Enthalpy is the quantity of heat necessary to raise the temperature of a substance from one point to a higher temperature.

 

Enthalpy represented by H

State the formula for determining Enthalpy(H).

H = U + PV

 

Enthalpy = Internal Change + Pressure*Volume

Define:

 

Enthalpy Change(ΔH)

The change in the heat content of a system that accompanies a process which occures at a constant pressure.

What are the aliases associated with

Enthalpy Change(ΔH)?

Enthalpy Change(ΔH)

=

Heat change

=

Heat of reaction

State the formula for determing Enthalpy Change(ΔH).

ΔH = Hfinal system – Hinitial system = qp

 

Note:

qp= qconstant pressure

 

subscript p = constant pressure

What are the units associated with Enthalpy Change(ΔH)?
Typical unit is kJ/mole

Define:

 

Endothermic

The process of a system absorbing heat from its surroundings.

 

Endothermic = Enter

Define:

 

Exothermic

The process of a system releasing heat into its surroundings.

 

Exothermic = Exit

If an endothermic/exothermic process occures at a constant pressure what is ΔH equal to?

qp

 

Note:

exothermic = negative qp = negative ΔH

 

endothermic = positive qp = positive ΔH

Define:

 

Calorimetry

Experimental technique used to measure the heat released or absorbed during a reaction.

Define:

 

Calorimeter

A device used to measure the heat released/absorbed during a reaction.

Define:

 

Calorimeter Constant

The amount of heat gained by a calorimeter.

 

aka: the Heat Capacity of the Calorimeter.

 

Unit: J/oC

State the formula for determing the calculation heat released/absorbed by a system.

 

q=mcΔT

 

heat(J) = mass(g) * specific heat(J/g-oC) * ΔTemp

 

ΔT = Tfinal – Tinitial

 

pg 17 chap 5 .ppt

Define:

 

Specific Heat(J/g – oC)

The amount of heat needed  to increase the temperature of 1 gram of material by 1oC.

 

varies by substance

depents on the state of the substance

always a positive number

pg 17 ch5 .ppt

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