PHYSICS I

Temperature, Heat, Thermal Expansion, and Heat Transfer

Temperature

• defn: what a thermometer reads

• Average kinetic energy reading of a substance

• Fahrenheit, Celcius, Kelvin scales

Temperature Conversions

°F = (1.8 x °C) + 32°C = (°F – 32) ÷ 32K = °C + 273.15

HeatDefn: transfer of energy from one

object to another due to difference in temp.

Coffee mug examples 80°C coffee sitting on counter of

kitchen that is 26°C – what happens?What if cold (5°C) pop can sitting on

the counter of same kitchen?

HeatInternal Energy

A substance contains internal energy… NOT heat

There is more internal energy in a bathtub full of cold water than a red-hot pin (due to the higher number of molecules; therefore, bathtub has more kinetic energy)

But! Heat flows from red-hot pin to tub water

Measuring HeatHeat is a form energy (Joules)Calories:

calorie Calorie

Heat required to raise 1g of H2O by 1°C

Kilocalorie = heat required to raise 1kg of H2O by 1°C

Unit of energy Unit of energy

1 calorie = 4.184 joules Used on food labels

Specific HeatDefn: quantity of heat required to change

temperature of a unit mass of substance by 1°Water (discussion – see map next slides)

Jet Stream?

Water – What do these graphs tell us?

Thermal Expansion

As Temp. decreases => Substances contract (become more dense)

Except Water! H2O MOST dense at 4°C From 4°C to 0°C, water expands (becomes less dense) Which is why ice floats

Conduction

Heat transferred by successive collisions of atoms

Good conductors of heat and electricity: Metals - #1 Ag, #2 Cu, #3 Al…

Poor conductors: Wool, wood, styrofoam = insulators

In February you drive by a house with snow on its roof. Does the house have good insulation or poor? Explain.

ConvectionHeat transferred due to motion of fluid

Theory behind plate tectonics

Global Wind Currents

At night or during day? Explain. What happens during other half of earth rotation?

Explain.

Radiant Energy

Radiant Energy in form of Electromagnetic waves