Thermochemistry Chapter 10

Warm Up A deep underground cavern contains 2.24 X 10 6 L of methane gas at a pressure of 1.50 x 10 3 kPa and the temperature of 42 0 C. How many kilograms of methane gas does the cavern contain?

Rubber Band Demo Can you feel the heat?

Energy Transformation Fire, the sun’s rays, and rubbing your hands together all produce heat. Melting ice and boiling water also absorb heat!

A lot of Lava Lava flowing out of a volcano can be C to C. As it leaves the volcano, it cools. Why does lava cool more quickly in water than on land?

What is thermochemistry? Thermochemistry is concerned with the heat changes the occur during chemical reactions. But, really, what is energy—for real? Energy is the capacity to do work or supplying heat. Teenagers have tons of energy, but never wanna do work. Why is that?

The Nature of Energy Energy is the ability to do work or produce heat. Potential energy Energy of position Kinetic energy Energy of motion E = ½ mv 2

A. The Nature of Energy Law of conservation of energy –Energy can be converted from one form to another but can neither be created or destroyed.

Temperature is a measure of the random motions of the components of a substance. B. Temperature and Heat Hot water Cold water (90. o C)(10. o C)

Thermore Does energy have mass, weight, or odor. NO!!! Energy stored with the structural units or chemical substances is chemical potential energy. What are some substances that contain lots of potential energy?

What the heat? Heat is energy that transfers from one object to another because of a temperature difference between them. Heat, itself, cannot be detected by the senses or by instruments. Only the change can be detected. Heat always flows from a warmer object to a cooler object.

Heat is a flow of energy between two objects due to a temperature difference between the objects. Heat is the way in which thermal energy is transferred from a hot object to a colder object. B. Temperature and Heat Hot water Cold water Water Water (50. o C) (50. o C)

Hot OR Not??

EXO-thermic and ENDO-thermic All reactions and changes in physical state involve either the release or the absorption of heat. In heat studies, we use the word system and surroundings-system is the part of the universe you focus your attention and surroundings include everything else in the universe

Exo and Endo A major goal of studying thermochemistry is to examine the flow of heat from the system to its surrounding. A process of absorbing heat from its surroundings is called endothermic process. A process of releasing heat is an exothermic process.

Can you feel the burn? What does it mean to burn calories? During exercise your body generates heat, and this heat is measured in calories. The heat is generated as your body breaks down sugar and fats within your body.

C. Exothermic and Endothermic Processes System – part of the universe on which we focus attention Surroundings – everything else in the universe Burning a match

Calorie A calorie is defined as the quantity of heat needed to raise the temperature of 1 g of pure water 1 0 C. One dietary Calorie is actually equal to one kilocalorie or 1000 calories. The calorie is also related to the joule, the SI unit of heat and energy.

Which one would warm you up more when you are cold? Why?

Can you feel the heat? Bowl of water or bucket of water? Which one takes more energy to heat? So energy required depends on………

Specific Heat The specific heat capacity, or specific heat, of a substance is the amount of heat it takes to raise the temperature of 1 g of the substance 1 0 C.

Crank up the heat!! Heat affects the temperature of objects with high specific heat much less than those with low specific heat. Water takes in a lot of heat to raise the temperature and releases heat a lot of heat when it cools.

Warm Up What is thermochemistry and why is it important? Which direction does heat always flow? What is specific heat and why is it important in daily life?

Calculation To calculate the specific heat of a substance, you divide the heat input by the temperature change times the mass of the substance. C = q M XT C = specific heat M = Mass Q = heat (joules or calories)

Sample This !!!! The temperature of a piece of copper with a mass of 95.4 g increases from 25 0 C to C, when the metal absorbs 849 J of heat. Knowns M = 95.4 g Change in temperature= C Q = 849 J Unknowns C= Use the specific heat equation. Plug and chug!!! Answer =.387 (J/g x 0 C)