01 Matter & Energy Flashcards
What is a subatomic particle
Particles that are smaller than an atom; among such particles protons, neutrons, and electrons are of special significance in chemistry
What are atoms composed of
Protons and neutrons held in the nucleus surrounded by an electron cloud
How are electrons and protons held together
By an attractive electrostatic force
Coulomb’s law
The force of interaction between two charged particles Q1 and Q2 is directly proportional to the product of the two charges and inversely proportional to the distance (d) between the charges squared, where k is the coulomb constant
F = k(Q1Q2/d^2)
What is an isotope
Atoms with the same atomic number but different number of neutrons
What are a, z and x standing for
A
X
Z
A: Mass number (protons + neutrons)
Z: Atomic number (protons)
X: atomic symbol
What is atomic weight
Average of the masses of all isotopes present
AW = (isotope mass) x (fractional natural abundance)
What is the law of conversion of mass
No atoms can be transformed into other atoms, and no atoms may be destroyed or created
- in chemical reactions the nuclei of atoms is unchanged
What is avgardos number
A conversion factor for relating grams to atomic mass units
The number of atoms in exactly 12g of carbon-12 is equal to 6.022 x 10^23: the number of particles in a mole of any surface
What is a mole
A collection containing avogadros number of objects
What is an anion
A negatively charged ion
(Gained an electron/s)
What is a cation
A positively charged ion
(Lost electrons)
Atoms combine to form…
Molecules or extensive solids
Molecular Compounds
A compound composed of atoms of two or mo
What is energy
The capacity to do work and transfer heat or the ability to make something happen
Potential energy
Related to the positioning of an object in relation to other objects
Kinetic
Related to the motion of objects
First law of thermodynamics
Energy can be converted from one form to another, but cannot be created or destroyed (aka law of energy conversion)
Electrostatic
Relating to interactions (force and energy) of stationary charges or fields
Which energies dominate chemical processes
Kinetic energy of particle motion and electrostatic potential energy
Types of potential energy
Electrostatic, nuclear, or gravitational energy
What does the change in internal energy of a system result from
The exchange of heat or work with the surroundings
Internal energy of a system
The total energy associated with the system, the sum of all sources of kinetic and potential energy
Internal energy changes (ΔE)
(Usually more important)
Directly connected to a physical or a chemical process under consideration
Internal energy changes formula
ΔE = q + w
-q
Removing heat from a system
-w
Having the system do the work
ΔE > 0
Q > 0 - heat is added to the system
W > 0 - work is done on the system
ΔE < 0
Q < 0 - heat is removed from the system
W < 0 - work is done by the system
What is a state function
Property that depends only on its present state of the system, and is independent of how the state was achieved
Examples: P(pressure), T(temperature), E(internal energy), and H(enthalpy)
Capital letters are used for state functions
What is enthalpy
The heat exchanged with the surroundings under constant pressure
In chemical and physical changes occuring under constant pressure, it is indeed quite common that the only work done by that system is due to…
Volume change
Endothermic
ΔH > 0
A process in which the system absorbs heat
Q > 0
Exothermic
ΔH < 0
Heat transfers to the surroundings
Q < 0
What is light
An electromagnetic wave
The “purest” form of energy as it may exist “outside” of matter
- on one hand it is an electromagnetic wave traveling with an enormous speed
- on the other hand it interacts with matter as a stream of energy packets or photons
What is a quantum
The smallest possible amount of a distinct quality
Wavelength
The distance between two adjacent peaks or troughs
The maximum amplitude of the waves is..
A measure of intensity of the radiation
What is radiation
The emission and transmission of energy through space in the form of electromagnetic waves
Frequency (v)
The number of cycles that pass a given point per second
Expressed as cycles per second or in hertz
Properties of waves depends on
Their wavelengths
Wavelength range of the visible light spectrum
400-750 nm
Photons
What light is a stream of
Quantized energy packets
Waves in order of increasing wavelength
Gamma rays < x-rays < UV rays < visible light < infrared < microwave < radio
Which is more energetic, long waves or small waves
Short waves (large frequency)
What is the photoelectric effect
The phenomenon in which only light of proper frequency can eject electrons from an illuminated metal surface
What is black body radiation
When solids are heated they emit radiation. The distribution of wavelengths of these electromagnetic waves depends on the temperature of the solid
- lower temps: infared frequencies
- increasing temps: starts emitting visible light
- brown -> red->orange->yellow->white
What do BBR and TPEE illustrate
That light can exhibit a “corpuscular” nature in its interaction with nature
What is spectroscopy
The study of how light interacts with matter
How does light interact with a clear object
All wavelengths of light are transmitted
How does light interact with a colored solution
The light of that color is transmitted and the waves of the light of the color absorbed by the medium
How does light interact with an opaque material
It reflects the wavelengths
What happens when light is emitted
Wavelengths are given off by the system
What is a spectrophotometer
A tool used to measure the absorption of light
Light energy absorbed by atoms or molecules is converted into…
Various forms of kinetic or potential energy
Changes that occur when gamma rays are absorbed
Ionizes atoms and molecules, breaks chemical bonds
Changes that occur when x-rays are absorbed
Ionizes atoms and molecules, breaks chemical bonds
Changes that occur when UV rays are absorbed
Ionizes atoms and molecules, breaks chemical bonds, promotes electrons to higher energy
Changes that occur when visible light is absorbed
Promotes electrons to higher energy
What changes occur when infrared rays are absorbed
Increases amplitude of vibrations
Changes that occur when microwaves are absorbed
Increases speed of molecular rotations
Changes that occur when radio waves are absorbed
Flips the nuclear spin
What is the only way that the earth can transfer energy back to space
Radiation
About how much incoming light is reflected back, out of the system into space
30%
What percentage of incoming light is absorbed by molecules in the atmosphere
19%
What percentage of incoming light reaches earths surface
51%
What is the greenhouse effect
The “trapping” of energy close to the surface due to greenhouse
What is global warming
A gradual increase in the average temperature of the earth due to an imbalance in earths energy cycle
When a component color is absorbed by an object, what color does the object appear to be
The complementary color
As temperature increases…
Increases: peak frequency, energy of the photon and light intensity
Decreases: peak wavelength
