Exam 1 Flashcards
1
Q
When to wear goggles in lab
A
all the time
2
Q
Where should reactions that give off fumes be done
A
fume hood
3
Q
when smelling
A
waft
4
Q
where is first aid kit
A
stock room
5
Q
where to dispose of organic liquids
A
organic waste carboy
6
Q
where to dispose solid chemicals
A
solid chemical waste jars
7
Q
neutralize acids with
A
sodium bicarbonate
8
Q
Neutralize bases with
A
citric acid
9
Q
scientific questions
A
testable or measurable through experimenting, observing, and measuring in a replicable way
10
Q
Models allow
A
prediction of what will happen under conditions you did not test
11
Q
A scientific theory
A
makes testable predictions and can be falsified - explains the phenomena - tells you why
12
Q
scientific law
A
describes the phenomena - tells you what
13
Q
AFM
A
Atomic Force Microscopy (picture of atom)
14
Q
SFM
A
scanning tunneling microscopy (Picture of atom)
15
Q
difference between AFM and SFM
A
AFM could detect each atom, whereas SFM could only detect every other
16
Q
Origin of first idea of atom
A
ancient greeks
17
Q
Hypothesis of the atom by Greeks
A
There are small particles that are “not to be cut.” that are in constant motion and are either of earth, wind, fire, or air domain based on the shape equating to element from the analogy to movement of specks - the random motion of atoms was later called Brownian Waves
18
Q
Earth atoms
A
cubic
19
Q
water actoms
A
spherical to slide over one another
20
Q
Iron atoms
A
spikey to make them stick to one another and, therefore strong
21
Q
Structure-Properties Relationship
A
molecular level structure of a substance determines observable properties
22
Q
Element characteristics
A
-The atom is the smallest unit of an element
-atoms of different elements are different
- 91-98 elements are naturally occuring
-elements ordered in periodic table
23
Q
top number on periodic table
A
atomic number which is the number of protons in the nucleus of each atom of that element
24
Q
Atoms vs Elements
A
Atoms: individual nanoscale entities, too small to see with eye
Elements: collection of atoms, macroscopic sample
** atoms and elements have very different properties
25
Dalton's Atomic Theory (1808)
1. Elements are composed of small indivisible, indestructible
particles called atoms. (not true-subatomic particle)
2. All atoms of an element are identical and have the same (not true-isotopes have different masses)
mass and properties.
3. Atoms of a given element are different from atoms of other
elements.
4. Compounds are formed by combinations of atoms of two or
more elements.
5. Chemical reactions are due to the rearrangements of atoms;
atoms (matter) are neither created nor destroyed during a
reaction.
26
Which subatomic particle was discovered first?
electron
27
who discovered the electron?
Joseph J Thompson
28
How did JJ Thompson discover the electron?
Using a particle accelerator (cathode ray tube):
High voltage was applied between a cathode (-) (made of non interfering metal) and an Anode (+) which emitted particles that are then subjected to two opposing electrically charged plates to which the particles would bend, exposing the charge - the metal of the cathode would be changed but the particles were identical regardless meaning all atoms contain electrons
- this also found that the mass of the particle was much smaller to that of the atom, solidifying the existence of subatomic particles
29
Thomson's model of the atom
"plum pudding" atoms contain electrons (-) "embedded" in a positively charged blob
30
Rutherford's experiment
shot alpha rays generated from a radioactive source at a piece of gold foil- if Thomson's idea of the atom was correct, the rays would go straight through, but some bounced back
31
Alpha particles
-2 protons and 2 neutrons
-it is the nucleus of a helium atom
-positively charged
32
what rutherford's experiment showed
-atom is mostly empty space (Greeks said this)
-small dense positive nucleus in the center of the atom
-big bang theory model (planetary) electrons circled the nucleus like a planet
33
Limitation of planetary model
In the planetary model of the atom, the electron should emit energy and spiral into the nucleus
34
When were neutrons discovered?
1932
35
Why are neutrons harder to detect?
- within nucleus
-neutral - can't be manipulated by magnetic or electric fields
36
which are heavier; protons or neutrons?
neutrons are slightly heavier than protons
37
Chemical symbols #/# letters
top number: atomic mass (#protons + #neutrons)
bottom number: atomic number (# of protons per atom of element)
letters: element symbol
- # of neutrons is found by subtracting the atomic number from the atomic mass
38
"Neutral element"
same number of protons as electrons
39
Atomic Mass u
u = mass of one atom of carbon-12 = 12 u
1.6605x10^-27 kg ~ 1 u
mass of proton ~ 1 u
mass of neutron ~ 1 u
mass of electron ~ 1/2000 u
40
Determining average atomic mass
Average atomic mass = (mass (u) of isotope a * relative abundance of isotope a) + (mass (u) of isotope b * relative abundance of isotope b) + (mass (u) of isotope c * relative abundance of isotope c) ...
41
Atom is electrically neutral
the number of protons (+) is the same as the number of electrons (-)
42
coulomb's law
explanation of how atoms interact using the idea that opposite charges attract and like charges repel
43
4 fundamental forces
gravity, electromagnetic, strong nuclear, weak nuclear
44
gravity
responsible for attraction between objects that have mass
45
electromagnetic
responsible for attraction/repulsion between objects that have electric charge
46
strong nuclear
short range interaction that occurs between objects made of quarks
47
weak nuclear
short range interaction that occurs between elementary particles; weaker than electromagnetic or strong force
48
newton's law of universal gravitation
F∝ (𝑀1𝑀2)/r^2
F= gravitational force
M1= mass of object 1
M2= mass of object 2
r= distance between 2 objects
as r increases, F decreases by a factor of 1/r^2
49
Gravitational fields
objects with mass are sources of gravitational fields and are affected by the gravitational fields of all other objects of mass
50
gravitational forces are mediated by gravitational fields
- gravitational forces require two or more objects
- gravitational forces are always attractive
51
Electromagnetic forces are mediated by electric and magnetic fields
- EM forces act at a distance
- EM forces can be attractive or repulsive
52
electrostatic force
a special case of the electromagnetic force- only electric fields and forces between charged particles
53
Coulomb's law -models the forces between attractive and repellent forces
𝐹 ∝ (𝑞1𝑞2)/r^2
F= electrostatic force
q1= charge 1
q2= charge 2
r= distance between charges
54
Gravitational Force vs. Electrostatic Force
-gravitational attraction between mass
-too weak to be detected at atomic/ molecular level
-attractive only
-electrostatic attraction between charged particles
-much stronger
-can be attractive or repulsive
55
if something is not moving
there is either no force acting on it OR the forces acting on it are equal and opposite
- ball in hand does not move because gravity is attractive and electrostatic is acting as repulsive
56
What is energy
we don't know
57
characteristics of energy
- any change in matter is accompanied by a change in energy
- changes in energy are caused by changes in force
- energy is conserved
-SI unit for energy - joule (J)
-- 1J = 1 (kg x m^2)/s^2
-- 1 Kcalorie = 1,000 calories = 4,184 J
58
energy changes
energy transfers between systems and surroundings
59
system
part of the universe you are looking as
60
surroundings
everything else in the universe
61
1st law of thermodynamics
energy is never lost, only transferred or transformed
62
Types of energy
kinetic and potential
63
Kinetic energy (KE)
energy associated with motion
- KE = 1/2 mV^2 (m=mass V=velocity)
64
Potential energy (PE)
-energy associated with the position of a system of objects in a field
-- must be two or more objects
-- must be a field (gravitational, electric, magnetic)
-- when the position of two objects in a field changes, so does the potential energy of the system
all forms of energy can be related to potential and kinetic at the molecular level
65
potential energy decreases as kinetic energy increases because the potential energy is being put into action and transforming into kinetic energy
66
as distance between two objects decreases what happens to the potential energy
it exponentially decreases
67
energy can be
transferred (from one object to another) via collisions
transformed (e.g., from potential energy to kinetic energy)
68
forces and energy in chemistry
-atoms are made up of charged particles (electrostatic force)
-we can understand atomic interactions in terms of coulombic attractions and repulsions
- clearly there must be come mechanism by which atoms stick together
-- to make molecules, solids from liquids, liquids from gasses
69
Noble gases
energetically stable
70
properties of helium
- (just like all noble gases) does not react with anything
- He melting point= 0.95 K (-272.2 degrees C)
- He boiling point= 4.5 K (-268.5 degrees C)
71
PE diagram for particles with opposite charges
attractive force: as distance decreases, potential energy decreases (it is transformed into Kinetic energy)
72
PE diagram for particle with same charges
repulsive force: as distance decreases, potential energy increases (kinetic energy is transformed into potential energy)
73
London Dispersion Forces (LDFs)
-caused by fluctuations of electron density in the molecule (for atom)
-adjacent atoms interact through electrostatic force
LDFs exist between ALL neutral atoms and molecules in the solid and liquid states (not gas bc too fat apart)
distorts the atom- creating partial charges and making it polar
74
Electrostatic Forces between He Atoms
larger r -> small F attractive
smaller r -> larger F attractive
smallest r -> largest F attractive
At very small r -> repulsive force is greater than attractive force
75
why don't the He atoms stay in the potential minimum?
too much energy
- need to remove some from system and into surroundings via collisions
76
how to add energy to a system from the surroundings?
increasing temperature
77
adding energy via increasing temerature
- kinetic energy is transferred to the atoms upon collision, causing them to move faster
- when a collision transfers enough KE to the two He atoms in our system, the attractive force between them is overcome and they fly apart (why gas is so far apart and doesn't have LDF interactions)
78
Thermal energy and Temperature
thermal energy= measure of the sum of the kinetic energies (1/2mv^2) of all the atoms -> depends on amount of substance
temperature (T)= directly related to average kinetic energy (1/2mn^2) of the atoms -> does not depend on amount
79
how the He atoms "know" the temperature has increased
the energy is transferred from other atoms that have collided with the walls of the container (that were directly heated)
80
Breaking attractive interactions
energy is absorbed -> the change from attractive to repulsive (low potential energy to high potential energy) breaks the interaction and pushes the exerted energy to get closer in the other direction, back to the atom itself
81
what does the position of the PE well on the x-axis tell you
the distance between the atom centers at their most stable point
82
what does the position of the PE well on the y-axis tell you
how much energy would be needed to overcome the interaction
83
Comparing LDFs between atoms
higher boiling points mean a lower potential energy well
84
size of two atoms
a greater atomic number means a greater amount of protons, and in neutral atom, a greater amount of electrons, creating a bigger electron cloud and overall the higher charge quantity
85
Polarizability comparison
the strength of LDFs depend on size of temporary dipoles, meaning a bigger electron cloud has a further distance between partial charges making them stronger
86
Helium vs Xenon PE diagram
Xe has a lower PE well that is at a further distance on the x-axis, He has a shallower PE well, closer to distance zero
87
internuclear distance
the distance between two nucleus of two atoms with electron clouds right next to each other
88
van der Waals Radii
description of atom "size" 1/2 distance between atoms at potential minimum (Internuclear distance)
89
London Dispersion Forces Trends
- increase with size of atom/molecule (number of electrons)
- increase with surface area
** trends allow for predictions but do not explain why certain elements/molecules would have stronger LDFs than another
part of a range of intermolecular forces (between particles)
90
Noble gases
-monoatomic
-interact through LDFs
-unreactive
91
what happens when two Hydrogen atoms approch
formation of a covalent bond
92
Hydrogen molecules (H2)
have different chemical and physical properties than hydrogen atoms (H)
other diatomic molecules: O2, N2, F2, Cl2, Br2, I2
93
which type of interaction is stronger LDF or Covalent bonds
covalent bonds
94
Interactions between atoms
Intermolecular forces and Bonds **Not the same thing, don't mix them up
95
Intermolecular forces (IMFs)
Include LDFs and other van der Waals interactions
-relatively weak
-occur between neutral molecules or atoms
96
Bonds
more permanent
-stronger + harder to break
-occur within molecules
97
Temperature to break He interactions
4K
98
temperature to break Hydrogen bonds
6,000K (melts at 10K, boils at 20K)
99
Breaking bonds
requires an input of energy into the system (absorbed), the energy is transferred into the system upon collision with other molecules
100
Forming bonds
releases energy from the system, energy is transferred out of the system upon collision with other molecules
101
Stoichiometry
relationship between the macroscopic and molecular level
allows us to calculate
-how much "stuff" can be produced in a reaction
-the relationship between any two components in a reaction
- dissection of the relationship between products and reactants of chemical reactions
102
to determine the number of atoms in one mole
-measure exactly 12.0000 g of C 12 diamond
-measure its volume precisely
-count the amount of atoms by geometry
-- 6.02214X10^23 carbon atoms = one mole
-- mass of one c 12 atom = 1.99265 X 10^-23 grams = 12 u or 1 u = 1.66054 X 10^-24 g
102
Molar mass
mass in grams of 1 mole
103
Mole relation to chemistry
-defined as 6.022 X 10^32 "things"
- "Avogadro's number"
-the mass of 1 mole of any substance is it formula mass in grams
-- the mass of 1 mole of Hydrogen atoms (H) is 1.008
-- Molar mass of H2 = 2.016 g/mol
104
what happens to mass during a chemical reaction
mass is conserved
105
solution
Homogenous mixture of 2 or more components
106
solute
minor component
107
solvent
major component
108
most solutions contain
a solid solute and a liquid solvent but not all ie air, broze, vodka
109
difference between solution and mixture
Solution
-homogenous- same composition all the way through the sample
-once solution is formed it (typically) will not "unmix"
-ex. salt water sugar water
Mixture
-heterogeneous- different composition depending on sample point
-relatively easy to "unmix"
-ex. sand + salt granite chocolate chip cookie
110
solution by mass
the exact sum of grams between the solute and the solvent
111
solution by volume
between the mass of solution and higher value between the two because of elements being closer together or not
112
How to make a solution
-Use volumetric flask
-add the solute to the flask and fill up to the required volume with solvent
-read the bottom of the meniscus
-why not just add the solute to the solvent? volume is not additive
113
aqueous solutions on paper
(aq)
114
concentrations of solutions-units
-Molarity (mol/L)
-- A 1 M solution contains 1 mol of solution dissolved to make 1 L of solution
-- Allows conversions between moles of solute and volume of solution
-Other units g/mL, ppm, ppb
115
Limiting reactant/reagent
reagent/reactant that limits the maximum amount of product that can be made
-- runs out first
-- done mathematically; compare how much of each reactant/reagent makes one product, smaller value is limiting
116
Isotope notation
mass number (Protons and Neutrons) over atomic number (protons) on left of atom
- ie 12/6 C or Carbon-12 (12 is atomic mass)
