Exam 2 Flashcards
Mass
(g or kg) a measure of the amount of matter in an object, m=dv
Volume
(mL or cm^3) the space occupied by an object, v=m/d
Density
(g/mL or g/cm^3) amount of mass for every unit of volume, d=m/v
Metric Conversions
Kilo=1000 units Hecto= 100 units Deka= 10 units Base Unit Deci= 0.1 units Centi-= 0.01 units Milli= 0.001 units -King Henry Died By Drinking Chocolate Milk -Use dimensional analysis
Significant Figure Calculations
Purpose: to show the precision of your measurement tool.
When adding/subtracting, round the answer to the number of decimal places of the least precise measurement (ex: 20.1cm + 10cm= answer with no decimal places b/c 10 is the least precise)
When multiplying/dividing, round your answer to match the amount of significant figures in the least precise measurement (ex: 220.000g / 2mL= answer with 1 sig fig b/c 2 is the least precise measurement and has 1 sig fig)
Scientific Notation
a way to shorten very large and very small numbers to make them easier to work with.
ex: 2,500,000= 2.5 x 10^6
- move the decimal place to the space just before the last number furthest from the decimal.
Mole Conversions
One mole of anything is 6.022 x 10^23 particles
To perform Mole conversions use dimensional analysis:
ex:
How many molecules of water are in 6 mol?
(6mol / 1)(6.022x10^23 / 1mol) = 4 moles
How many moles is 8.74x10^23 atoms of platinum?
(8.74atoms / 1)(1mol / 6.022x10^23 atoms)= 1 mole
Democritus
- First person to propose that matter is composed of atoms
- atom model looked like a ball
- “Thought experiement”: if you took a material and kept dividing it in half, you should eventually reach a limit at the smallest particle, the atom
Dalton
- revived the idea that matter is composed of atoms, based on experimentation with gases
- atom model looked like a ball
- findings led him to propose the Law of Conservation of Mass
Crookes
-discovered the electron using Cathode ray experiments
Thomson
- experimented with a Cathode ray, showed that all atoms contain negative particles (electrons) along with Crookes
- put together the “plum pudding’ model, a ball with positive and negative particles scattered throughout it
- determined relative mass
Rutherford
- Gold foil experiments; shot alpha particles through the foil
- discovered the nucleus
- atom model has a nucleus in the center with electron particles around it, electron arrangement did not make sense because it portrayed an unstable atom
Bohr
- modified the Rutherford model
- model include electrons in orbitals, each orbital containing a certain number of electrons to create a stable atom
- discovered that electrons mo`ve in orbits around nucleus
Schrodinger
- made most accurate atom model today
- model features electron clouds surrounding a nucleus
Atomic Number
- equal to the amount of protons in an element
- identity of element
- 1/2 of the atomic mass
- located above each element symbol on the PT
Atomic Mass vs Mass Number
Atomic mass:
-also known as atomic weight
-the weighted average mass of an atom of an element based on the relative natural abundance of that element’s isotopes.
Mass number:
-total number of protons + neutrons in a given isotope of an atom
Relative Abundance of Isotopes
(mass of isotope x decimal form of abundance) + (mass of isotope x decimal form of abundance) + etc- add masses of each isotope together
Isotopic Notation
-At element symbol is featured big in the center
-Atomic Mass goes in the top left corner
-Atomic Number goes in the bottom left corner, technically unnecessary when given the symbol
-sometimes the charge is put in the top right corner
*Hyphenated isotope notation:
name of element- mass number of isotope
ex: Oxygen-16
Ions
- Atoms that have gained or lost electrons to become more stable
- To find an ion’s charge, add the electrons and protons together, incorporating their relative charges
Wave-particle duality of electrons and light
wave:
-Elements emit only specific colors of light when heated
-light is a form of electromagnetic radiation
-the longer the wavelength, the lower the frequency
The particle nature of light:
-quantum concept is the theory that matter can gain and lose energy only in small, specific amounts called quanta
-> concept developed by Max Planck- relates colors given off by elements to locations of electrons in discrete energy levels
3 properties of electromagnetic radiation
1) Wavelength
2) Frequency
3) Amplitude
Light Equations
As a wave: speed of light(c) = wavelength(lambda) x frequency(v)
As a particle: energy of one photon(E) = planck’s constant(h) x frequency(v)
A laser emits light of frequency 4.74 x 10^14 sec^-1. What is the wavelength of the light in nm? (1m = 1 x 10^9nm)
633 nm
A photon of light has a frequency of 1.50x10^14 Hz. Determine the wavelength and energy of the photon. Respect significant figures and write your answer in scientific notation.
wavelength: 2.00x10^-6 meters(m)
energy of the photon: 9.94x10^-20 joules(J)
