CH 1.1-1.6 Flashcards
Molecule
Collection of atoms
STM
Scanning tunneling microscope; microscope that allows us to see atoms
2 fundamental concepts of chemistry
- Matter is composed of various types of atoms
- One substance changes to another by reorganizing the way the atoms are attached to each other
Scientific Method
- The basis on which a scientific enquiry is conducted.
1. Making observations (collecting data)
2. Suggesting a possible explanation (formulating a hypothesis)
3. Doing experiments to test the possible explanation (testing the hypothesis)
Qualitative observation
Descriptive observation
Quantitative observation
Measured observation, includes both a number and a unit
Theory
Aka model; a set of tested hypotheses that gives an overall EXPLANATION of some natural phenomenon; an interpretation
- a human invention
Observation
Something that is witnessed and can be recorded
Natural law
A statement that expresses generally observed behavior; SUMMARY of observed behavior
- A consistent set of observations that applies to many different systems
Law of Conservation of Mass
Mass is neither created nor destroyed
Robert Boyle
- 1st “chemist” to perform truly quantitative experiments
- measured the relationship between the pressure & volume of air
- The Skeptical Chymist
- Believed that an element is anything that cannot be betoken down into simpler substances
- Believed all theories must be proved experimentally before being regarded as true
Joseph Priestley
English clergyman & scientist that discovered oxygen gas by heating mercury oxide in a closed environment
- Gas was found to support light and burning
Antoine Lavoisier
French chemist that explained the true nature of combustion
- coined the Law of Conservation of Mass
- Discovered that life was supported by a process that involved oxygen (founded the correct name for oxygen)
- Elementary Treatise on Chemisty
- Wrote the 1st modern chemistry textbook
- Father of Modern Chemistry
- Found that heating lead sample makes it heavier while overall weight of sealed glass jar remained constant
Joseph Proust
Lavoisier’s student that coined the Law of Definite Proportion
Law of Definite Proportion
A given compound always contains exactly the same proportion of elements by mass
- Aka the Law of Constant Composition by Mass
John Dalton
Discovered that compounds are made of atoms & a given pair of atoms can form a variety of compounds
- Father of Atomic theory
Science
Study in which humans attempt to explain knowledge about themselves and their surroundings
Experimentation
Process that is used to explore repeatable and consistent observations and answer questions
Law
A concise, verbal statement that SUMMARIZES facts about a natural phenomenon
- Series of experiments that are consistent
- Doesn’t change
Measurement
Quantitative observation consisting of a number & a scale
Accuracy
agreement of a measurement (or a set of observations) with the true value
Precision
degree of agreement among several measurements of the same quantity, or the repeatability of a measurement
Error
the difference btwn the true value & measured value
Random/Indeterminate errors
Affect precision of measurement. Causes data to be more scattered around an average value
- Improved w/ instrument
Systematic/Determinate errors
Affect the accuracy of a result. Causes average of a set of data to differ from the true value.
- You can control
- Improve through technique
1 pound = … grams
454
1 inch = … cm
2.54
1 quart = … L
0.946
Tc –> Tk
Tc + 273.15
Tk –> Tc
Tk - 273.15
Tf –> Tc
(Tf - 32) x 5/9
Tc –> Tf
Tc x 9/5 + 32
Density formula
Mass/volume
Extensive property
Depends on the amount of matter
- Ex; volume, mass
Intensive property
Does not depend on amount of matter
- identifies product
- Ex; density, color, odor
Who was the first to attempt to provide a reason behind chemical reactions/equations & What did they believe
Greeks; Believed that all matter was composed of earth, air, fire, & water
Democritus theory
Believed all things were made up of things called “atoms.”
- Matter couldn’t be divided into smaller pieces forever
- Believed atoms were made of the same material but were different shapes & sizes
Phlogiston Theory
- All flammable materials contain phlogiston, which has no color, odor nor taste
- Phlogiston is set free by burning
- Inhibits burning
- Air is only capable to absorb a certain amount of phlogiston. Once air is saturated with phlogiston, burning ceases
- Phlogisticated air cannot support life. Importance of air for respiration: removal of phlogiston from the body
Law of Multiple Proportions
- John Dalton
- When 2 elements form a series of compounds, the rations of the masses of the second element that combine w/a fixed mass of the first element will always be in ratios of INTEGERS
Modern Atomic Theory
- grew out of observations & laws
1. Each element is made up of tiny particles called ATOMS. They cannot be created, divided into smaller particles, or destroyed (Law of Conservation of Mass).
2. Atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways
3. Chemical compounds are formed when atoms of different elements combine with each other in simple whole-number rations (Law of Multiple Proportions). A given compound always has the same relative numbers and types of atoms (Law of Definite Composition)
4. Chemical reactions involve reorganization of the atoms- changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction.
What are the 3 most important laws that led to the development & acceptance of the atomic theory?
- Law of Conservation of Mass
- Law of Definite Proportions
- Law of Multiple Proportions
Empirical formula
A chemical formula which displays the relative, not necessarily the absolute, number of atoms in a compound
Chemical/Molecular formula
A chemical formula that displays the symbols for the exact numbers and kinds of elements which compose the compound, with numerical subscripts that state the number of atoms of each element in the compound
Who prepared the first table of atomic masses (atomic weights)
Dalton
- However, they weren’t accurate & led to incorrect assumptions (didn’t account for diatomic molecules)
Joseph Gay-Lussac
- Measured volumes of gases that reacted w/each other under the same conditions of temp & pressure
The Law of Combining Volumes of Gases (Gay-Lussac)
When 2 gases react, the volumes that combine are in a ratio of small whole numbers (integers). The ratio of the volume of each gas is also in the ratio of small whole numbers
Is the volume of a gas conserved?
No
Amedeo Avogadro
- Linked Dalton’s Atomic Theory & Gay-Lussac’s Law of Combining Volumes
- Explained GL’s theory by assuming that @ the same temp & pressure, equal volumes of different gases contain the same # of molecules
- Hypothesized that elements may exist as “primal” molecules (diatomic or more)
Avagadro’s hypotheses
- Equal volumes of gases contain equal numbers of molecules
- Atoms of elemental gases may be joined together in molecules rather than existing as separate atoms
- Implies that the size or weight of the particle is irrelevant to the space that the particle occupies in the gas phase
Stanislao Cannizzaro
- stated that “the weights of equal volumes of gases are proportional to the relative particle weights” (atomic or molecular)
- Took all of the laws, made it official, & spread it
Mole concept
Small numbers (volumes) to represent large numbers (atoms & molecules)
- 1 mol of anything contains the same amount of particles
J.J. Thomson
English physicist that made the cathode ray tube
- Assumed the cathode ray comprised of particles or corpuscles (later named electrons) - measured their velocities
- Determined charge-to-mass ratio of an electron
(e/m = 01.76 x 10^8 C/g; e = charge of electron in coulombs)
- Concluded that there are particles lighter & smaller than an atom & that these particles were being emitted from atoms (electrons)
- Contradicted Dalton’s postulate
- Suggested that there must be positive charges balancing negative charges in atoms (a cloud)
- Plum Pudding model
Cathode ray tube
A vacuum tube
- Particles are ejected through the cathode (negative electrode) and moves to the anode (positive electrode)
- Cathode rays form when high voltage is applied across electrodes in a partially evacuated tube
- A stream of electrons
Heinrich Hertz
- Unable to deflect cathode rays electrostatically
- Concluded that the rays don’t carry an electric charge
- If it’s not a particle, it’s possibly an EM wave
1897 Cathode ray experiments
- wanted to prove that cathode rays were not EM waves (can CR penetrate right through matter or disperse by gas molecules? Measure the velocity)
- To proved cathode rays were negatively charged particles (deflect rays w/an electrical field. if rays bent towards + pole, then - charged)
What abilities did the cathode ray experiment allow?
- To calculate the charge to mass ratio
- Discovered there were particles
- Measure Deflection
Robert Millikan
- Wanted to determine charge of an electron
- Performed experiments involving charged oil drops (to determine magnitude of the charge on a single electron = mass of electron)
- calculated mass of electron as 9.11 x 10^-31
Determining the Charge of an Electron with Oil Droplets…
- Oil droplets ionized
- X-rays produce charges on the oil drops
- droplets pass through electrically charged plates (some enter the hole)
- Negative drops rise to positive plate
- Found velocity of charge when field was turned off, used to find mg. Using E & mg, the charge could be calculated (used charge/mass ratio from Thomson’s)
Plum Pudding Model
- J.J. Thomson
- Atoms are made of + charged cloud & - electrons are embedded at random
- Electrons were like currants
- Atom is neutral bc same number of + & - charges
Henri Becquerel
- Accidentally discovered radioactivity
Henri Becquerel
- Accidentally discovered radioactivity
Types of radioactive emission
- Gamma rays- High-energy “light”
- Beta Particles- High-speed electrons
- Alpha particles- possess a charge twice that of the electron, w/opposite sign & mass of the atom
Ernest Rutherford
- Learned physics in Thomson’s lab
- Noticed that ‘alpha’ particles were sometimes deflected by something in air
- Gold-foil experiment (hit atom @ different angles to discover shape of it)
- results interpreted that a particles interacted w/ very small & heavy particles within the atom (+ charge of atom is concentrated in a small volume (nucleus))
- positively charged particles in the nucleus were later called PROTONS
- the mass of an atom is > than the sum of the mass of its protons & electrons
- Noticed radium decays through a series of steps
Cation
When atoms turn into positive ions bc they are stripped of an electron
Anion
Atoms turned into negative ions bc they gain an electrion
Mendeleev 8 statements about his periodic table
- When arranged by atomic weight, the elements show a periodicity of properties
- Similar elements have atomic weights which are either very similar or which increase regularly
- The arrangement of the elements correspond to their valences
- Elements which are most common have small atomic weights
- The atomic weight can determines the character of an elements
- More elements will be discovered
- Atomic weight of an element may be corrected by comparison with adjacent elements
- Some properties of unknown elements can be predicted from their atomic weights
Dalton’s Atomic Theory
- Each element is made up of tiny particles called atoms
- Atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways
- Chemical compounds are formed when atoms of different elements combine with each other. A given compound always has the same relative numbers & types of atoms
- Chemical reactions involve reorganization of the atoms– changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction
Who prepared the first table of atomic masses?
Dalton
Atomic weight
The weighted average mass of the atoms in a naturally occurring element
Jons Jakob Berzelius
Developed modern symbols for the elements used in writing the formulas of compounds
- discovered the elements cerium, selenium, silicon, & thorium
Electrons
Negatively charged particle that moves around the nucleus of an atom
Radioactivity
The spontaneous decomposition of a nucleus to form a different nucleus
Nuclear atom
An atom having a dense center of positive charge (the nucleus) with electrons moving around the outside
Protons
A positively charged particle in an atomic nucleus
Neutrons
A particle in the atomic nucleus with mass virtually equal to the proton’s but with no charge
Why do different atoms have different chemical properties?
Different atoms have a different number and arrangement of electrons. These electron allow atoms to “intermingle” to form molecules
Isotope
Atoms of the same element (same # protons) with diff # of neutrons. They have identical atomic numbers but different mass numbers
- identical chemical properties
Ion
An atom or group of atoms that has a net positive or negative charge
Average atomic mass
((mass1 x %1) + (mass2 x %2))/100
Soddy
Conceived the idea of isotopes
Francis Aston
Designed the first mass-spectrometer
Mass spectrometer
took natural element & separated it by mass, found element has different isotopes
Factors which determine a particle’s path in the mass spectrometer
- Accelerating voltage, V
- Magnetic field strength, H
- Mass of the particle, m
- Charge on the particle, q
