Laws and Specific HeatLaws and Specific Heat

February 18, 2014February 18, 2014

ObjectivesObjectives

1.1. State the three law of State the three law of thermodynamicsthermodynamics

2.2. Describe how Specific Heat capacity Describe how Specific Heat capacity affects our earth’s climateaffects our earth’s climate

3.3. Understand Thermal Expansion in Understand Thermal Expansion in terms of how ice and water reactterms of how ice and water react

Laws of ThermodynamicsLaws of Thermodynamics

1.1. First law states:First law states:

a.a. When heat flows in or out of a system When heat flows in or out of a system it is being neither created or destroyedit is being neither created or destroyed

b.b. It only transfers to a different placeIt only transfers to a different place

Laws of Laws of ThermodynamicThermodynamicss2.2. Second Law states:Second Law states:

a.a. Heat flows from a hot to a cold Heat flows from a hot to a cold substancesubstance

b.b. Has to be forced to move the opposite Has to be forced to move the opposite directiondirection

Laws of Laws of ThermodynamicsThermodynamics3.3. Third Law states:Third Law states:

a.a. No system can reach No system can reach absolute zeroabsolute zero

What is absolute zero?What is absolute zero?

How do we know where it is at if we can’t How do we know where it is at if we can’t reach it?reach it?

HEATHEAT

1.1. Heat is thermal energy in motionHeat is thermal energy in motion

2.2. Heat is measured = Joules/ CaloriesHeat is measured = Joules/ Calories

Specific Heat CapacitySpecific Heat Capacity

3.3. Different substance = different Different substance = different capacities for storing thermal capacities for storing thermal energyenergy

a.a. Require different amounts of thermal Require different amounts of thermal energy to raise temperatureenergy to raise temperature

Specific Heat CapacitySpecific Heat Capacity4.4. Specific Heat Capacity: Specific Heat Capacity: quantityquantity of heat of heat

required to change the temperature of required to change the temperature of a a unit mass unit mass by 1 degreeby 1 degree

a.a. Measure of thermal inertiaMeasure of thermal inertia

b.b. Matters ability to resist a Matters ability to resist a change in temperaturechange in temperature

Higher specific heat – stronger ability Higher specific heat – stronger ability to resist changeto resist change

Lower specific heat – low ability to Lower specific heat – low ability to resist changeresist change

Specific Heat CapacitySpecific Heat Capacity

5. Which has a higher specific heat 5. Which has a higher specific heat capacity, water or sand? In other capacity, water or sand? In other words which takes longer to warm in words which takes longer to warm in sunlight (or longer to cool at night?)sunlight (or longer to cool at night?)

Specific Heat CapacitySpecific Heat Capacity6.6. Waters specific heat capacity:Waters specific heat capacity:

a.a. Higher capacity for storing energyHigher capacity for storing energy

b.b. Absorbs a great quantity of heat for Absorbs a great quantity of heat for small rises in temperaturesmall rises in temperature

c.c. Takes much longer to cool, resistant to Takes much longer to cool, resistant to loosing thermal energyloosing thermal energy

Specific Heat CapacitySpecific Heat Capacityd. Water’s specific heat changes the d. Water’s specific heat changes the world’s climateworld’s climate

i. Currents carry warmer water to i. Currents carry warmer water to Europe’s Europe’s

west coast keeping it warmer than the west coast keeping it warmer than the cool coast’s of Canadacool coast’s of Canada

ii. Islands and peninsula’s do not ii. Islands and peninsula’s do not

have extreme temperatureshave extreme temperatures

7. Bermuda is close to North Carolina, 7. Bermuda is close to North Carolina, but unlike North Carolina, it has a but unlike North Carolina, it has a tropical climate year round. Why?tropical climate year round. Why?

Thermal ExpansionThermal Expansion

February 20, 2014February 20, 2014

Thermal Expansion

1. Thermal expansion - when a substance expands when heated and contracts when cooled

a. Different substances have different abilities to expand and contract

Bimetallic strips

Thermal expansion

b. When you can’t loosen a metal lid

on a glass jar, why is it that you

stick it under hot water to help you

out?

Thermal Expansion

2. Water’s Thermal expansion

a. Expands when heated

b. Between 0 and 4 degrees water particles contracts becoming more dense before freezing

Themal Expansiona. If you heat water at zero degrees it

actually contracts as the ice crystals start to collapse before it will expand at 4 degrees

Themal Expansion

3. When solid ice forms volume increases because of the ice crystals

Thermal Expansion

a. Since ice is less

dense it floats on bodies of water

b. Water at zero degrees is less dense as well and stays near the tops

c. Water at four degrees is more dense and will settle at the bottom keeping organisms warm all winter