Thermodynamics
the study of energy changes in reactions Name __________________
Energy
Energy is the ability to do _____________________ or produce ______________________.
Energy is typically divided into two types: _____________________ energy and ____________________ energy.
Potential Energy is _________________ energy base on:
__________________ (gravity-related, like a skateboarder at the top of a half-pipe or a stretched rubber band)
__________________ composition (like the chemicals in food or a battery).
Kinetic Energy is energy of _________________This includes the constant, random motion of atoms and molecules Is proportional to temperature As temp increases, motion of particles increases
Chemical Energy - form of potential energy based upon chemical composition- stored in bonds between atoms, molecules, and ionic crystals - chemical energy of food powers your body - chemical energy of gas powers your car
Thermal Energy - Total internal energy of system: depends on both Heat and Temperature
Heat : Form of energy that ________________ from warmer to cooler object
Temperature: measure of the average KE of the particles
Energy can be _______________ between different forms of energy, but no matter how many times energy is converted the
 Law of Conservation of Energy: states that no energy can be _______________ or ______________.
Heat Energy: ____________ (q) is the energy that moves from hot to cold. Will continue to flow until temps are equal
The amount of heat is often measured as temperature does not directly measure heat.
Heat is quantified by measuring ___________________ in temp
calorie: To measure heat directly, the ______________________ (abbreviated cal) was defined as the amount of heat needed to increase the temperature of ______ gram of water by 1 °C.
Note: The Calories reported on food wrappers are measured as heat needed to increase the temperature of
_____________ grams of water by 1 °C,
1 Calorie (Cal) = 1000 calories (cal) = 1 kilocalorie (kcal)
Drinking a whole can of Pepsi actually means drinking 250 Cal = 250,000 calories! normal diet: 2000 Cal = 2,000,000 calories per day.
____________________________: measuring much heat energy
Calorimeter: device used to measure heat lost or absorbed during chemical reaction, including energy from food
Joules measure energy more accurately.
Calories are still used in the nutrition field, but in chemistry we will use the ________________ (J). 1 cal = 4.184 J
If my breakfast contains 230 Calories, how much energy in Joules will it supply?
Both the calorie and Joule are defined using water,

but other substances gain and lose heat at different rates – a factor called the_______________ ____________ (c) the amount of energy required to raise 1 gram of a any substance by 1°C
The metal of the pan has a ___________ specific heat b/c it can lose heat quickly. This heat would be absorbed by your finger!!! The cake contains a lot of trapped air and other materials with much higher specific heats. These objects lose heat _________________, allowing more time before your finger has absorbed enough heat to cause a burn.
____________ of a cake is much less than the density of the metal pan, so for the same surface area touched by your finger there are a lot more metal atoms that transfer heat energy than cake molecules. So… the __________ also has an affect on the amount of heat transferred
Plus… (old stuff)

Metals are good conductors of heat and electricity

While air is a poor conductor of heat and electricity (nonmetals)
To calculate the amount of heat that can be gained or lost by an object q = m × c × ∆T q = heat (J) m = mass (g) c = specific heat ∆T = Temp. final – Temp. initial, in °C
If the object is heating up, the final temp is ______________ than the initial temp, so ∆T is _____________ and amount of heat gained is positive.
If the object is cooling down, the final temp is __________ than the initial temp, so ∆T is ___________ and the amount of heat lost is negative.
If ∆T is ______________ the answer for heat is positive:heat is gained. If ∆T is ______________ the answer for heat is negative: heat is lost
Ex. 1) What is the heat absorbed by 100 g of water to raise it from 25 °C to 75 °C? The specific heat of water is 4.184
J/g°C. q = m × c × ∆T q = ________ x ________ x (________ - _______) q = _______________
Ex. 2) What is the heat given off by 100 g of iron to cool from 50 °C to 20 °C? The specific heat of iron is 0.449 J/g°C.
q = m × c × ∆T q = ________ x ________ x (________ - _______) q = _______________
Heat Movement The Law of Conservation of Energy states that heat energy cannot just appear out of nowhere and disappear to nowhere.
If an object warms up, that heat had to be _______________ from somewhere and if an object cools down, that heat had to be _______________ to something.
In the Earth's ecosystem heat is gained by the sun’s radiation and given off to space at night - This is why a cloudy night is typically warmer than a clear night – the heat gets trapped in by the clouds.
Heat can ______________ from one object to another by three ways: 1. Radiation 2. Convection 3. Conduction
The energy from the sun reaches earth by ________________,electromagnetic waves. The ________________ part of the electromagnetic spectrum is the “heat” form of radiation. Ex. of radiation: Heat from a fire, non-fluorescent
lightbulbs, and the coil in an electric oven that heats up to cook food.
_________________ is the movement of heat by circulating materials, so anything that is a ___________ (gases and liquids) can move heat by convection, often called convection currents. Ex. Most air-conditioning systems, the ocean
_____________, and the warm and cold “___________” the weather-person talks about on the news.
____________________ is the movement of heat between objects that are touching. Most common form of heat movement when ______________. The food touches a pan that’s touching a burner. As the pan absorbs heat from burner the food absorbs heat from the pan.

Heat energy will always _______________ move from an object with higher heat to an object with lower heat, regardless of the method of heat transfer
The Law of Conservation of Energy also tells us that the amount of heat _________ by the hot object must be equal to the amount of heat __________ by the cold object. Hot becomes cooler, and cold becomes warmer.
- q lost
= q gained
- (m lost
× c lost
× ∆T lost
) = m gained
× c gained
× ∆T gained
Phases or States of Matter: Solid, Liquid, Gas Sometimes when an object gains or loses heat, it is not just the temperature that changes but the ____________of the object can change.
The phase that an object currently exists in depends on how much _______________ energy is in the object, often measured by the temperature. The___________ form of any object is going to have lower temperature than the
______________ form, which will have lower temperature than the gas (vapor) form
Phase _____________ occur when sufficient heat energy is added or removed to change the object’s phase.
+q: heat is added or absorbed – Endothermic –q: heat is lost or released – Exothermic
From this heat curve (for ____________) we can see how the temperatures change and the phases change. Notice that the temperature _____________________ change during a phase change (the two flat lines).
Heat & Chemical Reactions: Thermochemical Equations: A balanced chemical equation that includes all physical states (s, l, g) and change in enthalpy (H) (heat content).
4 Fe(s) + 3O
2
(g) → 2Fe
2
O
3
(s) + 1625 kJ (heat released)
Heat can be written as either a ________________ or __________________ because every chemical reaction involves a change in energy: heat and/or light
If a chemical reaction feels cold, then the reaction is __________________ heat. When energy is absorbed it’s an
_______________________ reaction - energy in, and its written on the reactant side, and q is positive (+q)
If a chemical reaction feels warm, then it is _________________________ heat. When energy is given off it’s an
___________________ reaction- energy out, and it’s written on the product side, and q is negative (-q)
______________________ (a reactant) solid + energy (heat) → liquid heat _______________ the system from the surroundings This is why your skin gets cold when you hold ice; the
ice is pulling heat out of your skin to melt. System: ice Surrounding: your skin
_______________________ (a product) Iron + oxygen gas → iron(III) oxide + energy (heat)
Heat is _________________ from the system and is absorbed by the surrounding environment which is why
it’s used in instant hot pads. System: hot pad Surrounding: your skin
To separate water into hydrogen and oxygen (electrolysis) _____________________ is often used.
2H
2
O  2H
2
+ O
2
Is electrolysis of water endothermic or exothermic? Where does energy “go” in the equation?

The enthalpy of reaction (∆H) can be calculated to determine if heat is released or _____________
(STAAR Chart
) ΔH = ∆H f o (products) - ∆H f o (reactants)
∆H f o = standard enthalpy (heat) of formation from the formation of 1 mole of compound
If ΔH is +, then heat is absorbed, so it is an _________________________reaction
If ΔH is -, then heat is released, so it is an __________________________ reaction
Ex. 4) Find the ∆H rxn
for liquid ethanol, C
2
H
5
OH, undergoing combustion. Is this an endothermic or exothermic reaction?
C
2
H
5
OH + 3O
2
→ 2CO
2
+ 3H
2
O
Thermodynamic values table
Compound
C
2
H
5
OH
O
2
CO
2
H
2
O
∆H f o
-277.69 kJ/mol Per mole
0 kJ/mol
-393.509 kJ/mol
-285.830 kJ/mol
∆H f o (reactants): (-277.69) + 3(0) = -277.69 kJ
∆H f o (products): 2(-393.509) + 3(-285.830) =
ΔH = ∆H f o
-787.018 + (-857.49) = -1644.508 kJ
(products) - ∆H f o
ΔH is Neg = Exothermic
(reactants)
= (-1644.508) – (-277.69) = -1366.818 kJ
An additional way to show a change in enthalpy without a calculation is with an enthalpy diagram.
What is the key to knowing if the diagram shows exothermic or endothermic? Energy in or out
System System