THERMOCHEM
Study of the energy changes, specifically heat, that accompany chemical
reaction + physical transformations.
Here’s an example, a bank transaction:
Endothermic reactions Making a deposit, you take heat from
surroundings (wallet), and you put it in the system (bank). Surroundings
get colder (less cash)
Exothermic Making a withdrawal, system releases heat into
surroundings and surroundings get warmer.
Nature of energy:
Energy Ability to do work/transfer heat.
Work (w) Energy used to make smthn move.
Heat Energy transferred due to temp diff.
How is heat transferred?
1. Conduction Heat transfer thru direct physical contact
2. Convection Heat transfer by movement of fluid (liquid/gas) (hot
air rising)
3. Radiation Heat transfer thru empty space via electromagnetic
waves (feeling warmth of sun on skin)
Some important units:
Energy Joule (J)
Calorie (cal) 1 cal = 4.184 J. Is the energy needed to raise 1g of water
by 1°C.
Food cal 1 Cal = 1000 cal = 1 kcal. What is often seen on nutrition
labels?
DIFF TYPES OF ENERGY:
Energy is either kinetic or potential energy.
1. Kinetic energy: The energy of motion
Ek = (mv^2)/2
2. Potential energy: Energy due to height
Stored energy due to position, composition, or condition
There are 3 main types:
, a. Gravitational Potential Energy
Formula: P Egrav =mgh
b. Elastic Potential Energy: Energy stored in stretched/compressed
object (spring)
1 2
Formula: P Eelastic = k x
2
c. Chemical Potential Energy: Most important for chem, tis energy
stored in chemical bonds.
a. Breaking bonds REQUIRES energy, forming bonds RELEASES
energy.
A compressed spring has potential energy. When you release it, that
energy is let out. Similarly, the bonds in propane (C 3 H 8 ) and oxygen (O2)
are like compressed springs. When they react (the springs "uncoil"), they
form new, more stable bonds (C O2 and H 2 O ) and release a ton of energy
as heat and light.
SYSTEMS, SURROUNDINGS, AND FIRST LAW OF THERMYDYNAMICS
System Specific part of the universe we are studying (contents of
beaker)
Surroundings everything outside system (beaker)
Universe system + surroundings
There are 3 types of systems:
Study of the energy changes, specifically heat, that accompany chemical
reaction + physical transformations.
Here’s an example, a bank transaction:
Endothermic reactions Making a deposit, you take heat from
surroundings (wallet), and you put it in the system (bank). Surroundings
get colder (less cash)
Exothermic Making a withdrawal, system releases heat into
surroundings and surroundings get warmer.
Nature of energy:
Energy Ability to do work/transfer heat.
Work (w) Energy used to make smthn move.
Heat Energy transferred due to temp diff.
How is heat transferred?
1. Conduction Heat transfer thru direct physical contact
2. Convection Heat transfer by movement of fluid (liquid/gas) (hot
air rising)
3. Radiation Heat transfer thru empty space via electromagnetic
waves (feeling warmth of sun on skin)
Some important units:
Energy Joule (J)
Calorie (cal) 1 cal = 4.184 J. Is the energy needed to raise 1g of water
by 1°C.
Food cal 1 Cal = 1000 cal = 1 kcal. What is often seen on nutrition
labels?
DIFF TYPES OF ENERGY:
Energy is either kinetic or potential energy.
1. Kinetic energy: The energy of motion
Ek = (mv^2)/2
2. Potential energy: Energy due to height
Stored energy due to position, composition, or condition
There are 3 main types:
, a. Gravitational Potential Energy
Formula: P Egrav =mgh
b. Elastic Potential Energy: Energy stored in stretched/compressed
object (spring)
1 2
Formula: P Eelastic = k x
2
c. Chemical Potential Energy: Most important for chem, tis energy
stored in chemical bonds.
a. Breaking bonds REQUIRES energy, forming bonds RELEASES
energy.
A compressed spring has potential energy. When you release it, that
energy is let out. Similarly, the bonds in propane (C 3 H 8 ) and oxygen (O2)
are like compressed springs. When they react (the springs "uncoil"), they
form new, more stable bonds (C O2 and H 2 O ) and release a ton of energy
as heat and light.
SYSTEMS, SURROUNDINGS, AND FIRST LAW OF THERMYDYNAMICS
System Specific part of the universe we are studying (contents of
beaker)
Surroundings everything outside system (beaker)
Universe system + surroundings
There are 3 types of systems:
