HEAT UNIT

In the lab you will do the following: 1) Fill a 250 mL beaker with 150 mL of water 2) Record the initial temperature 3) Remove the thermometer and have one partner cup the beaker with both hands for exactly 3 minutes. 4) Record the temperature by having your partner place the thermometer in the water. 5) Repeat with all of your partners to see the change in temperature for each person.

What caused the water temperature to change in the previous experiment?

Kinetic Molecular Theory - Kinetic means "to move" This theory states that entities in solids, liquids, and gases are in constant, random motion.

Three ways particles can move: 1) Translational motion - the movement of na entity through space along a linear path. This occurs mainly in gases and liquids 2) Rotational motion - the spinning of an entity in place. This is found in gases and liquids, very limited in solids. 3) Vibrational motion - the back-and-forth vibration of entities. This is found in gases, liquids, and solids.

Strong attractions in substances limit motion Strong attractions in substances limit motion. Therefore most solids are limited to vibrational motion. Liquids exhibit all 3 types of motion. This is why liquid state is less ordered than solid state. For most practical applications, we may assume that there are no attractions between entities in a gas. As a result, the entities in gases exhibit all 3 forms of motion!

Solids Liquids Gases Types of Motion vibr. all 3 Strength of attraction Organization of entities strong highly organized medium medium level of organiz-ation weak least organized

So what makes an object hot? Thermal energy describes the total energy of the molecules within an object

Think of a helium balloon Think of a helium balloon. If you fill a balloon with helium, it will consist of billions of helium atoms that, by the kinetic molecular theory, are in constant motion.

If the helium balloon is left in the Sun, it will pop If the helium balloon is left in the Sun, it will pop. The balloon will expand because the energy from the Sun will cause the molecules to move faster which means higher collisions with the outside wall of the balloon.

If you place that same balloon in the fridge, it will shrink due to molecules slowing down causing less collisions with the outer wall.

Solid objects will VIBRATE more when they are heated which causes more thermal energy which in turn causes a higher temperature.

Therefore, a hot object will have MORE thermal energy than a COLD object.

Eventually, when two objects are in contact, they will want to reach THERMAL EQUILIBRIUM. The hot, energetic body will pass it's energy to the cold body until they both have the same amount of thermal energy.

CONDUCTION - the transfer of kentic energy when particles collide. CONVECTION - the motion of fluid in a liquid or gas cuased by temperature differences. Hot water rises as cold drops RADIATION - does not depend on matter! It's the transfer of energy by electromagnetic waves.

Temperature depends only on the average kinetic energy of the particles in the object. It does not depend on how many atoms are in the object (thermal energy takes into account how much energy each particle creates)

Temperature Scales: The Celsius scale (degrees C) Freezing point - 0 C Boiling point at sea level - 100 C

Absolute zero- this is the known temperature that any object can reach before the particles stop moving. THE LOWEST YOU CAN GO! - 273.15 degrees Celsius

The KELVIN SCALE is based on this value. This scale does not have negative values. Therefore it starts at -273 C which equals 0 K Therefore, TC + 273 = TK

Questions: Convert the following to Celsius: 1. 115 K 2. 172 K 3. 425 K 4. 212 K

What is the average temperature of the following in both Kelvin and Celsius? 1. room temperature 2. a typical fridge 3. a hot summer day in Saskatchewan d. a winter's night in Saskatchewan

Specific Heat - the amount of energy that must be added to the material to raise the temperature of a unit mass by one temperature unit. RED PHYSICS BOOK - Pg 318 variable = c unit = J/kgK or J/kgC

Look at waters specific heat. It has a value of 4180 Look at waters specific heat. It has a value of 4180. That means it takes 4180 Joules of energy to increase 1 kg of water by 1 degree of temperature. A JOULE is a unit of energy.

The heat gained or lost by an object depends on it's mass, specific heat, and change in temperature. Q = mc t

Example: A 5.10 kg cast-iron skillet is heated on the stove from 295 K to 450 K. How much heat had to be transferred to the iron? Pg 319 (# 3 and 5)