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# Force Energy Entropy Free Energy - PowerPoint PPT Presentation

Force Energy Entropy Free Energy. What is Force ?. F = m a. accel. force. mass. What is Force ?. S F = m a. “Sum of the forces on an object is (directions matter) is equal to the mass of that object multiplied by it’s acceleration”. What is Force ?.

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Force

Energy

Entropy

Free Energy

F=ma

accel.

force

mass

### What is Force ?

S F=ma

“Sum of the forces on an object is (directions matter) is equal to the mass of that object multiplied by it’s acceleration”

### What is Force ?

“Sum of the forces on an object is (directions matter) is equal to the mass of that object multiplied by it’s acceleration”

S F=ma

Fg=mg

### Gravitational

m

This is a special case.

When one of the two objects is Earth

m1m2

Fg=G

### Gravitation

r2

G = 6.67×10−11 N m2 kg−2

m2

m1

r

q1q2

q is the amount of charge on each object

Fe=ke

### Electrostatic

r2

Charge of an electron

e = 1.6 * 10-19 C

C= Coulomb a unit of charge

ke=9.0 x 109 Nm2/C2

q2

q1

r

What is Energy?

Capacity to do Work. … What does this mean?

EM Radiation

Light

X-rays

microwaves

Energy

Stored (Potential)

Chemical

Nuclear

Magnetic

Electrostatic

Mass

Motion (Kinetic)

Energetics of an Explosion

TNT

In what form is the energy?

Energetics of an Explosion

Bang!

In what form is the energy?

### ShakyNano Property #2:

All things shake, wiggle, shiver and move all around at the nanoscale.

Brownian Motion

In both cases the fluorescent particles are 2 microns in diameter. The left picture shows particles moving in pure water; the right picture shows particles moving in a concentrated solution of DNA, a viscoelastic solution in other words. The movies are 4 seconds of data, total; you can see a slight jump in the movie when it loops around. http://www.deas.harvard.edu/projects/weitzlab/research/brownian.html

Basic Thermodynamics

Zeroth Law: If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other.

First Law: Energy in the universe is conserved (it is also conserved in a closed system).

Second Law : Entropy increases

What is entropy ?

A count of the number of equivalent states of a system

Equivalent ?

States ??

TEMPERATURE

What is Temperature anyway?

What is it a measure of ?

MOTION

In specific Scientific Terms: Temperature is a measure of the average kinetic energy of the particles in a system.

Heat is nano-scopic motion

Very, Very cold

Warm

Hot

Thermal Energy

Ethermal=1/2 k * Temperature

k = Botzmann’s constant (1.38*10-23J/K)

Ethermal=1/2 kT

Average Energy of each degree of freedom in a system.

At room Temperature, Ethermal= 4*10-21 J

or 0.025 eV

Fahrenheit, Celsius, Kelvin

Kelvin

0

73

173

273

373

473

573

100

Celsius

0

-200

200

-100

300

-273

Fahrenheit

-459

-328

-148

32

212

392

572

Kinetic Energy

Ekinetic=1/2 (mass)*(velocity)2

Ekinetic= 1/2 mv2

We can set the thermal energy of an object equal to its kinetic energy to see how fast it is moving. This is appropriate for relatively “free” particles.

Ekinetic=Ethermal

1/2 mv2 = 1/2 kT

v=(kT/m)1/2

Thermally induced Kinetic Energy

v=(kT/m)1/2 (appropriate for a free particle)

Person 100kg 6*10-12m/s

Grain of Sand 10 mg 7*10-8m/s (10nm/s)

10 micron bead 4*10-12kg 20 microns/s

1 micron bead 4*10-15kg 700 micron/s

Virus 5*10-19kg 9 cm/s

Oxygen Molec. 5*10-26kg270 m/s

Entropy

DS < 0

Entropy

DS < 0

Entropy

DS > 0

### Bonding/Assembly

Bond Energy vs. Thermal Energy

x

Potential Energy

Transition State

Uactiv.

0

x

Ub

Eb=bond energy

Bonding / Assembling

x

Potential Energy

0

x

Ub

Disassociating

x

Potential Energy

0

x

Ub

Effects of thermal energy on Bond Strength

Thermal Energy affects the Dissociation Constant and Bond Strength.

Thermal Energy aids the dissociation of a bond.

Potential Energy

0

x

Ub

kBT

Bond Strength: Boltzman Factor

What is the probability that a bond will spontaneously dissociate????

kT at room temperature = 0.025 meV

P=e-Ub/kT

The rate of dissociation

rd = we-Ub/kBT

Rate of dissociation

Attempt frequency

Vibrational frequency of bond or

inverse relaxation time

Probability per attempt

Force, Energyand Bonding

A

B

DU = UB –UA < 0

Spontaneous & Stable

Thermodynamic Potential

Gibbs Free Energy

G = H - TS

Enthalpy

U + PV

Temp

Entropy

Helmholtz Free Energy

F = U - TS

Potential Energy (chemical typically)

Thermodynamic Potential

Helmholtz Free Energy

F = U- TS

DF=DU- TDS

Define System

When change in free energy is negative, process is spontaneous

DF=DU– TDS

DU = ? > or < 0 ?

DS = ? > or < 0 ?

When change in free energy is negative, process is spontaneous

Bond Strength: Boltzman Factor

What is the probability that a bond will spontaneously dissociate????

kT at room temperature = 0.025 meV

P=e-Ub/kT

The rate of dissociation

rd = we-Ub/kBT

Rate of dissociation

Attempt frequency

Vibrational frequency of bond or

inverse relaxation time

Probability per attempt

DU > or < 0 ?

DS > or < 0 ?

DF=DU- TDS

DU > or < 0 ?

DS > or < 0 ?

DF=DU- TDS

B

A

C

D

Which representative state of the fiber has highest entropy?

E