Laws and Specific HeatLaws and Specific Heat

March 5, 2013March 5, 2013

ObjectivesObjectives

1.1. State the three law of thermodynamicsState the three law of thermodynamics

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

Laws of ThermodynamicsLaws of Thermodynamics

1.1. First law states:First law states:

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

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

Laws of Laws of ThermodynamicsThermodynamics2.2. Second Law states:Second Law states:

a.a. Heat flows from a hot to a cold substanceHeat flows from a hot to a cold substance

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 absolute No system can reach absolute zerozero

What is absolute zero?What is absolute zero?

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

Specific Heat CapacitySpecific Heat Capacity

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 Capacity3.3. Different substance = different capacities Different substance = different capacities

for storing thermal energyfor storing thermal energy

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

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

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

a.a. Measure of thermal inertiaMeasure of thermal inertia

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

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

Lower specific heat – low ability to resist Lower specific heat – low ability to resist changechange

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 words capacity, water or sand? In other words which takes longer to warm in sunlight (or which takes longer to warm in sunlight (or longer to cool at night?)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 small Absorbs a great quantity of heat for small rises in temperaturerises 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 Europe’s i. Currents carry warmer water to 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, but 7. Bermuda is close to North Carolina, but unlike North Carolina, it has a tropical unlike North Carolina, it has a tropical climate year round. Why?climate year round. Why?

Thermal Expansion

Objectives

• Understand Thermal Expansion in terms Understand Thermal Expansion in terms of how ice and water reactof how ice and water react

Eureka 19Eureka 19

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 Expansion3. 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