Mid Year Flashcards
What is chemistry?
The study of all substances and the changes (physical and chemical) that they undergo.
List the types of chemistry
Organic Inorganic Analytical Physical Biochemical
What does organic chem deal with?
Substances containing carbon
What does inorganic chem deal with?
Substances without carbon
What does analytical chem deal with?
Composition of subtances
What does physical chem deal with?
Theories/experiments with chemical behavior
What does biochemical chem deal with?
Chemical processes in living things
Define scientific method
An orderly and systematic approach used to answer questions about the world around us
What are the steps of the scientific method?
1) observation –> question/purpose
2) form hypothesis
3) perform an experiment and analyze data
4) draw conclusions
5) communicate results, redo, and/or modify
What is the control in an experiment?
The group in an experiment that isn’t changed/isn’t tested for a variable and is used as a benchmark
What is the independent variable of an experiment?
Manipulated by the scientist
What is the dependent variable in an experiment?
Depends on the independent variable, the thing you measure
What are the parts of scientific notation?
A number between 1 and 10 and a power of 10
N * 10^x
To change from standard to scientific…
- Place the decimal point so there is one digit to the left of the decimal
- Number of places moved is the exponent
- If original number is less than 1, the exponent is negative. If it’s greater than 1, the exponent is positive
To change scientific to standard…
Move decimal point number of places in exponent. Positive= to the right. Negative= to the left.
All __________ digits in a measured number are significant.
Non-zero
________ in decimal numbers are never significant
Leading zeros
_____ zeros are significant
Sandwiched.
Between non-zero numbers
________ zeros in numbers without decimals are not significant
Trailing
Significant figure rule for adding and subtracting
The answer has the same number of decimal places as the measurement with the fewest decimal places
Significant figures for multiplying and dividing
Round (or add zeros) to the calculated answer until you have same number of sig figs as the measurement with the fewest sig figs
What is energy?
The capacity to do work or to produce heat
What are the types of energy (plus short description)?
Potential (stored)
Kinetic (in motion)
Radiant (heat, light)
How do we measure energy?
calories, BTUs, joules
What is a calorie?
Heat needed to raise one gram of water 1° centigrade
What is a BTU?
Heat needed to raise one pound of water 1° F
What is a joule?
The SI standard unit
Force of one Newton acting through one meter
A watt is…
Power of a joule of energy per second
1 BTU=
252 calories
1 calorie=
4.184 joules (J)
What is a Calorie?
1000 calories
1 kilocalorie
Sig figs in energy conversions
Sig figs in answer= sig figs in given
What is the law of conservation of energy?
Energy is neither created nor destroyed
What is temperature?
The measure of the kinetic energy of the atoms/molecules in an object
What are types of thermometers?
Bulb
Digital
Turkey popper
Galileo
What are the units of measurements for temperature?
Degrees (F and C)
Kelvins
°F to °C
°C=(°F-32) * 5/9
°C to °F
°F= (°C*9/5) +32
°C to K
°C+273= K
What are the states of matter?
Solid
Liquid
Gas
Plasma
Shape and volume
Kinetic Molecular Theory
Solids
Definite shape and volume.
Molecules are held close together and there is very little movement
Shape and volume
Kinetic Molecular Theory
Liquids
Indefinite shape, definite volume
Atoms/molecules have more space between them than a solid but less than a gas
Shape and volume
Kinetic Molecular Theory
Gases
Indefinite shape and volume
Molecules are moving in random patterns with varying amounts of distance between the particles
Plasma facts
Most common form.
Plasma In the stars and space between them makes 99% of visible universe. Used to water sterilization: no effect on taste or smell, 12 seconds
Physical change
Doesn’t change chemical composition. Changes state, form, or appearance
Water freezing into ice
Chemical changes
When a substance changes into something new. Signs: changes in density/melting point/freezing point, bubbling, foaming, etc.
Burning a match
Law of conservation of matter
Matter is neither created nor destroyed, it only changes state or molecules are rearranged into different substances
Intensive properties
Don’t depend on size of the sample of matter
Density, boiling point, color
Extensive properties
Do depend on quantity of sample
Mass, volume
What are the three classifications of substances?
Element
Compound
Mixture
What is a substance?
Cannot be broken down or purified by physical means. Each substance has its own properties different from any other substance.
Pure substances
Fixed composition and properties, can’t be separated into simpler substances by physical means. Compounds or elements.
What are compounds?
Can be decomposed into smaller substances by chemical changes, always in a definite ratio
What are elements?
Basic building block of matter. Cannot be decomposed into simpler substances by chemical changes
What is a mixture?
Two or more substances not chemically combined. Don’t have constant melting/boiling points.
Characteristics of mixtures
Variable composition
Components retain properties
May be separated by physical methods
Homogenous mixtures
Look the same, but still separated by physical means
Milk
Heterogenous mixtures
Relatively large pieces that are distinguishable that are easily separated by physical means
Fruit salad
Solutions
Homogenous mixtures. Something is completely dissolved in something else. Best separated by distillation or evaporation. Salt water.
Colloids
Like solutions. One substance trapped inside another. Identified by how they scatter light (fog). Air trapped inside the fat molecules of whipped cream
Gravimetric filtration
Filtration paper in funnel in metal stand. Differences in size of components relative to size of holes. Coffee grounds
Chromatography
Water creeps up strip of paper, different solubility/polarity means that some colors like to dissolve in water more and go higher up the paper. Mobile phase: water. Stationary phase: paper. Marker experiment.
Distillation
Heat under round bottom flask with liquid mixture to first boiling point. Component turns to gas, rises, enters condenser. Heat transfers to tube of cold water surrounding and substance turns back to liquid and drips out. Vodka on the rocks.
Centrifuge
Put vial in at angle, spin really fast, denser parts go to bottom. Blood: RBC at bottom
Atom
Smallest particle of an element that retains its identity in a chemical reaction, make up all matter
Democritus
Describe their model.
Greek 400 BC philosopher who said that atoms are tiny, indivisible, indestructible without experimental evidence. Just a circle
Dalton
Describe their model.
English chemist and schoolteacher performed experiments to make Atomic Theory:
- All elements are made of indivisible atoms
- Same=identical. Atoms of one element are different from another
- Came mix physically or chemically in ratios to form compounds
- Chem rxs occur when atoms separate, join, rearrange. Atoms of one element never change into another
What do you need to see it move an atom?
Nanotechnology called scanning tunneling electron microscopes
JJ Thomson
Electrons, 1897, cathode ray tube. Cathode ray attracted to positive magnet, deflected by negative magnet, so it must be a stream of negative particles. Also discovered charge to mass ratio. Plum pudding model with the actual atom being positive
Robert Millikan
Experimentally determined charge of an electron. Used Thomson’s ratio to mathematically calculate mass in 1916.
Eugene Goldstein
Discovered protons. Observed a positive particle go from positive anode to negative cathode in cathode ray tube in 1896
James Chadwick
Neutrons
No charge, mass equal to proton
Ernest Rutherford
Nuclear model through gold foil experiment. Passed large positive alpha particles through thin sheet of gold. Most passed, a small fraction bounced back. 1911
Atomic number
Number of protons
Mass number
Protons plus neutrons
Atomic mass
Average mass of all the isotopes
Complete chemical symbol
Element symbol
Upper left mass number
Lower left atomic number
Upper right charge
Shorthand notations of elements
Name-mass number
Symbol-mass number
Gold-197
Isotope
Same number of protons, different number of neutrons
3 isotopes of hydrogen
Hydrogen-1: 0 neutrons
Hydrogen-2: deuterium, 1 neutron
Hydrogen-3: tritium, 2 neutrons
What device determines mass?
Mass spectrometer
Amu
Atomic Mass Unit
1/12 the mass of a carbon-12 isotope used to define mass. A proton (and therefore a neutron) is approximately one amu
Niels Bohr’s Model
Electrons are in different energy levels like rungs on a ladder and move in a fixed orbit. Further from nucleus=higher energy=closer together. Quantum=amount of energy received/released to go up/down a level
Schrodinger
Made a mathematical equation to describe the behavior of electrons. Quantum mechanical model
Quantum mechanical model
Determines possible allowed energies and the probability of finding electrons in different locations around the nucleus. This is the electron cloud, where the electron is 90% of the time, because the exact location at any one instant can’t be found
S orbitals shape
Sphere
P orbitals shape
Peanuts
D orbitals shape
Double peanuts or donut around peanut
Max number of electrons in an energy level
2n^2
Electron configuration general definition
Arrangement of electrons in orbitals around nucleus
Aufbau principle
Electrons occupy lowest levels first
Pauli Exclusion Principle
Max of two electrons in each orbital spinning opposite directions
Hund’s Rule
Fill each orbital in a sublevel with one electron of the same spin first, then go back and add a second of the opposite spin
Dobereiner
Published a classification system of triads. The middle element had properties in between the other two
Ex: Li, Na, K reactions to water
Mendeleev
Table of 60 elements arranged by properties, increasing atomic mass. Was able to predict the properties of undiscovered elements and left spaces for them
The modern periodic table is organized by:
Atomic number
Periodic law
When electrons are arranged in order of increasing atomic number, properties repeat periodically
Columns, _____, or ________ share similar chemical properties
Groups
Families
Three classes of elements
Metals nonmetals metalloids
Metals
80% of elements Good conductors of heat and electricity Shiny Ductile, malleable Solid at rt
Nonmetals
Opposite properties of metals but bigger variation. Brittle, poor conductor. Most are gases at rt
Metalloids
In between, conditions, like presence of another element, cause them to act one way or another
Group 1A
Alkali metals
Group 2A
Alkaline earth metals
Group 7A
Halogens
Group 8A
Noble gases
Group 3B to 2B
Transition metals (d block)
Representative elements
Wide range of properties. All A groups
Inner transition metals
F block
