section 3: Energy Flashcards
What is Energy?
The ability to change or move matter
What are the two types of energy?
Kinetic energy (KE) and Potential energy (PE)
What are the two types of potential energy?
Gravitational PE and chemical PE
Kinetic energy
Energy of motion or movement
Potential energy
Stored energy
Gravitational PE
Stored as the result of opposing a gravitational force
Chemical PE
Energy stored in chemical bonds
What is thermodynamics?
Moving energy
1st Law of Thermodynamics: Law of Conservation of Energy
- in a system energy cannot be created or destroyed (energy can be transferred and transformed but cant just disappear)
2nd Law of Thermodynamics:
- the entropy of the universe is increasing in any interaction
B) PE initial > PE final (true in any interaction) - universe prefers to go downhill (spread out)
-energy flows in one direction, not cyclical
What is entropy?
measure of disorder/ randomness
3rd Law of Thermodynamics:
- absolute zero is unattainable
a) at 0 K entropy is at its minimum
Why is absolute zero unattainable?
it is not possible to reach absolute zero in a finite # of steps, therefore impossible to reach absolute zero
Zeroth Law of Thermodynamics:
- if two thermodynamic systems are each in thermal equilibrium with a third, then they must be in thermal equilibrium with each other
a) if A=B and B=C, then A=C
What is Temperature?
It is the measure of the average KE of all the particles of an object
Celsius:
(°C) based on the boiling point (100) and freezing point (0) of water
-variable: t
Fahrenheit:
(°F) based on the freezing point of a concentrated salt water solution
-variable: TF
Kelvin:
(K) based on absolute zero
-variable: T
ºC ——> K (t —-> T)
T=t+273
K ——> ºC (T —-> t)
t=T-273
Heat:
the energy transferred b/w objects b/c of a difference in temperature
Thermal energy: energy in transfer
the sum of the KE and PE of the particles in an object
Joule (J)
The derived unit for energy
Joule
kg * m^2 / s^2
Energy transfer as heat can occur in 3 ways…
- Conduction
- Convection
- Radiation
Conduction
the transfer of energy as heat b/w particles as they collide within a substance or
b/w two objects in contact
Convection:
The transfer of energy by the movement of fluids (liquid + gas) with different temperatures
Convection currents:
the flow of a fluid due to heated expansion followed by cooling + contraction
Radiation:
the transfer of energy by electromagnetic waves (ex. sand on a beach heated bc of the sun)
A) does not require physical contact
Conductor:
A material through which energy can be easily transferred as heat
- solids are better conductors than gases b/c they are more dense
- metals are better conductors than nonmetals
Insulator:
A material that is a poor energy conductor
- Slow the transfer of energy as heat
- Wood and air are good insulators
What are R values?
R values indicate resistance to heat flow
If an R value is a high # then…
It is a better insulator
Data table:
info. displayed in organized rows and columns
Graphs:
Visual displays of info. or data
All graphs must be titled with a ______
Graph # and concise description
Bar graphs;
Used to show comparisons- 1 variable between several named categories
Line graphs:
Used to show trends or continuous change
extrapolation
method used to approximate values that are beyond data points on the graph
Interpolation
Method used to approximate values between data points on the graph
Circle graph
Used to show a fixed quantity broken into parts
Mechanical energy (ME)
The sum of the PE and KE of a system
Thermal energy
The sum of the PE and KE of an object/ substance
Specific heat
The amount of energy (transferred as heat) required to raise the temp. of 1 kg of substance by 1 K
Specific heat is ____
Constant to each substance
Thermal energy equation:
Q= c * m * change t
Kinetic theory of matter
All matter is made up of tiny particles in random motion
Solids:
- definite shape/ vol.
- enough KE to vibrate but not move out of position
- arranged in crystals (repeating geometric pattern)
Amorphous solids
Solid w/o true crystal structure (ex. Glass)
Liquids:
- definite vol. + indefinite shape
- enough KE to vibrate over and around e/o but particles are still close together
Gases:
- indefinite shape/ vol.
- can expand or shrink to fit container
- particles have enough energy to separate from e/o
Plasma:
- a gas like mixture of positive/negatively charged particles
- so hot that the electrons are stripped away from from the nucleus of the atom
- most common form of matter in the universe (sun)
- enough KE to collide violently with e/o causing them to break into smaller charged particles
Thermal expansion
Most matter expands when it gets hotter and contracts when it cools
Vaporization
Liquid to gas AT boiling point
Evaporation
Liquid to gas BELOW the boiling point
Sublimation
Solid to gas skipping over liquid (ex. Dry ice)
Deposition
Gas to solid skipping over liquid (ex. Frost on a window)
State changes occur when _____
The particles of the substance absorb/release a certain amount of energy
Heat of fusion
the amount of energy needed to change a material from the solid state to a liquid state
Heat of vaporization
The amount of energy needed to change a material from a liquid state to a gas
