minooka atoms and elements part 1

Heat and EnergyHeat and Energy

What is Energy?What is Energy?

Petroleum products “Energy Crisis”It is at the very center of our

existenceEnergy is the ability to do work or

produce heat

Petroleum products “Energy Crisis”It is at the very center of our

existenceEnergy is the ability to do work or

produce heat

Two ClassificationsTwo Classifications

Potential EnergyKinetic Energy

Potential EnergyKinetic Energy

Potential EnergyPotential Energy

Energy due to position or composition

Energy stored in chemical bonds of petroleum products

Examples: Water stored behind a dam, calories in a chocolate bar, gas in a gas tankPE = mgh

Energy due to position or composition

Energy stored in chemical bonds of petroleum products

Examples: Water stored behind a dam, calories in a chocolate bar, gas in a gas tankPE = mgh

Kinetic energyKinetic energy

Energy due to motion of the objectEnergy released or absorbed in a

chemical reactionDepends on mass and velocity

KE=1/2 mv2

Energy due to motion of the objectEnergy released or absorbed in a

chemical reactionDepends on mass and velocity

KE=1/2 mv2

The internal motion of the particles in a body is its kinetic energy. Because these particles are vibrating back and forth they have a potential energy as well. The sum of the PE and KE of the particles is called the thermal energy of the object.

Remember that the kinetic theory says that a hot body has more thermal energy than a cold body.

The hot body has a higher total sum of PE and KE than a cold body.

Law of Conservation of Energy

Law of Conservation of Energy

Energy can be converted from one form to another….

But it can never be created or destroyed

Therefore, the energy of the Universe is CONSTANT

This is the First Law of Thermodynamics

Energy can be converted from one form to another….

But it can never be created or destroyed

Therefore, the energy of the Universe is CONSTANT

This is the First Law of Thermodynamics

WorkWork

Work is a force acting over a distance

Another definition is “the ability to resist a natural tendency”

w = fd

Work is a force acting over a distance

Another definition is “the ability to resist a natural tendency”

w = fd

State FunctionState Function

Important ideaIs a property of a system that changes

independently of it’s pathwayExample: You are traveling from Chicago

to DenverWhich property is a state function, Distance

traveled or change in elevation?

Important ideaIs a property of a system that changes

independently of it’s pathwayExample: You are traveling from Chicago

to DenverWhich property is a state function, Distance

traveled or change in elevation?

State Function Con’tState Function Con’t

Change in elevation is a state function because it doesn’t matter what path you take to get there

Distance traveled depends on the route you take, so distance traveled is not a state function

Change in Energy is a state function, work and heat are not.

Change in elevation is a state function because it doesn’t matter what path you take to get there

Distance traveled depends on the route you take, so distance traveled is not a state function

Change in Energy is a state function, work and heat are not.

Temperature and HeatTemperature and Heat

What is temperature?Temperature is a measure of the

random motions of the components of the substance

Must imagine this at the microscopic, molecular level

What is temperature?Temperature is a measure of the

random motions of the components of the substance

Must imagine this at the microscopic, molecular level

TemperatureTemperature

Two beakers of waterOne at 100 oC

Molecules moving fasterMore kinetic energy

One at 10 oCMolecules moving slowerLess kinetic energy

Two beakers of waterOne at 100 oC

Molecules moving fasterMore kinetic energy

One at 10 oCMolecules moving slowerLess kinetic energy

Same temp = same KE

Same temp = same KE

Heat vs. TemperatureHeat vs. Temperature

Heat is the flow of energy due to a temperature difference

Temperature is a measure of the average kinetic energy of the molecules

Heat is the flow of energy due to a temperature difference

Temperature is a measure of the average kinetic energy of the molecules

Heat flow is energy flowHeat flow is energy flow

Imagine two containers each holding the same amount of water. They are in contact with each other and heat can be transferred by water can not. No heat is lost to the surroundings. One side is at 100oC, and the other is at 10oC

Imagine two containers each holding the same amount of water. They are in contact with each other and heat can be transferred by water can not. No heat is lost to the surroundings. One side is at 100oC, and the other is at 10oC

Which way does heat flow?

Which way does heat flow?

When does heat stop flowing?

When does heat stop flowing?

Thermal EquilibriumThermal Equilibrium

When two objects in thermal contact cease to exchange energy by heat flow.

When two objects in thermal contact cease to exchange energy by heat flow.

Zeroth Law of Thermodynamics

Zeroth Law of Thermodynamics

Law of equilibriumTwo objects in thermal equilibrium

with each other are at the same temperature

Law of equilibriumTwo objects in thermal equilibrium

with each other are at the same temperature

Specific heat capacitySpecific heat capacity

Some definitions firstSystem: the part of the universe that

we are looking at (usually the chemical reaction)

Surroundings: everything else in the universe

Some definitions firstSystem: the part of the universe that

we are looking at (usually the chemical reaction)

Surroundings: everything else in the universe

Specific Heat Capacity Con’t

Specific Heat Capacity Con’t

The amount of energy required to change the temperature of a substance by 1 oC

Depends on the substanceDifferent substances respond

differently to being heatedExample: water, metal

The amount of energy required to change the temperature of a substance by 1 oC

Depends on the substanceDifferent substances respond

differently to being heatedExample: water, metal

The calorimetry equationThe calorimetry equation

Q = s x m x TWhere:

Q is the amount of heat energys is the specific heat of the substance

(must look this up)m is the mass (of the sample of the

substance)T is the CHANGE in TEMPERATURE

Q = s x m x TWhere:

Q is the amount of heat energys is the specific heat of the substance

(must look this up)m is the mass (of the sample of the

substance)T is the CHANGE in TEMPERATURE

What???? Come again??What???? Come again??

Q has units of Joules or Caloriess has units of J/g-oC, or Cal/g-oC, or

J/g K m has units of grams. If it doesn’t,

you must change it to grams in order to use the specific heat

T is the change in temperature in degrees Celsius or Kelvins

Q has units of Joules or Caloriess has units of J/g-oC, or Cal/g-oC, or

J/g K m has units of grams. If it doesn’t,

you must change it to grams in order to use the specific heat

T is the change in temperature in degrees Celsius or Kelvins

212o FA Lesson for Life

212o FA Lesson for Life

At 211o F water is very hot. It will burn.

At 212o F water becomes steam, andSteam can power a locomotive.The one degree makes all of the

difference.

At 211o F water is very hot. It will burn.

At 212o F water becomes steam, andSteam can power a locomotive.The one degree makes all of the

difference.