Temperature and the Phases of Matter

Key Question:What is temperature?

GPS:SP3. Students will evaluate the forms and transformations

of energy.

a. Analyze, evaluate, and apply the principle of conservation of energy and measure the components of work-energy theorem by

describing total energy in a closed system.

relating transformations of potential energy to kinetic energy.

f. Analyze the relationship between temperature, internal energy, and work done in a physical system.

ESSENTIAL QUESTION?Why does society spend a lot of resources on controlling thermal

energy?

Temperature and the Phases of Matter

In the Fahrenheit scale, water freezes at 32 degrees and boils at 212 degrees

The Celsius scale divides the difference between the freezing and boiling points of water into 100 degrees (instead of 180).

Converting temperatures

A friend in Paris sends you a recipe for a cake.

The French recipe says to bake the cake at a temperature of 200°C for 45 minutes.

At what temperature should you set your oven, which reads temperature in Fahrenheit?

Temperature and the Phases of Matter

Temperature measures the kinetic energy per atom due to random motion.

Phase changes When thermal energy is added or

subtracted from a material, either the temperature changes, or the phase changes, but usually not both at the same time.

Heat and Thermal Energy

Key Question:

What is the relationship between heat, temperature, and energy?

Heat and Thermal Energy

Temperature is NOT the same as thermal energy.

Thermal energy is energy stored in materials because of differences in temperature.

The thermal energy of an object is the total amount of random kinetic energy for all the atoms in the object.

Remember, temperature measures the random kinetic energy of each atom.

Heat and Thermal Energy

Imagine heating a cup of coffee to a temperature of 100°C.

Next think about heating up 1,000 cups of coffee to 100°C.

The final temperature is the same in both cases but the amount of energy needed is very different.

Heat and Thermal Energy

Heat is what we call thermal energy that is moving.

The joule (J) is the unit of heat (or thermal energy) used for physics and engineering.

The calorie is a unit of heat often used in chemistry.

Heat flows from the hot coffee to the cooler air in the room.

Specific Heat The specific heat is the quantity of heat

it takes to raise the temperature of one kilogram of material by one degree Celsius.

Specific Heat

The temperature of gold rises quickly compared with water because its specific heat is much less than the specific heat of water.

Heat Equation

E = mcp(T2-T1)

Specific heat (J/kgoC)

Mass (kg)

Heat energy (J)

Change inTemperature

(oC)

Calculate Heat One kilogram of water is

heated in a microwave oven that delivers 500 watts of heat to the water.

One watt is a flow of energy of one joule per second.

If the water starts at 10°C, how much time does it take to heat up to 100°C?

First Law of Thermodynamics

Energy loss is equal to energy gain.

Second Law of Thermodynamics

Application: The Refrigerator