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MSU / Chemistry / CHEM 141 / What is the difference between atoms and molecules?

What is the difference between atoms and molecules?

What is the difference between atoms and molecules?


School: Montana State University
Department: Chemistry
Course: College Chemistry I
Professor: Christian bahn
Term: Fall 2016
Tags: General Chemistry, Exam 1, and Chemistry
Cost: 50
Name: Gen Chem 141
Description: This a study guide for the first exam of the semester and covers chapters 1 through 3 in depth, with details that are expected to be on the exam.
Uploaded: 09/18/2016
9 Pages 10 Views 13 Unlocks

Chemistry 141 Study Guide

What is the difference between atoms and molecules?

- The difference between atoms and molecules.  

o A molecule is a combination of two of more atoms in a definite arrangement that  is held together by chemical bonds and example would be one molecule of water  (H2O) which has 3 atoms

Hydrogen = atom

Hydrogen = atom

Oxygen = atom

H2O = Molecule

o An atom is the smallest constituent of ordinary matter that has the properties of a  chemical element.  We also discuss several other topics like econ1020

- The three main states of matter are solid, liquid, and gas

o Solid: particles in a solid are tightly packed, usually in a regular pattern. These  particles vibrate but do not generally move from place to place

o Liquid: particles in a liquid are close together but have no regular arrangement.  They move about and slide past each other.

What are the three main states of matter?

o Gas: particles in a gas are well separated with no regular arrangement. These  particles vibrate and move freely at high speeds.

- The difference between mixtures and pure substances; elements and compounds; and  heterogeneous and homogenous mixtures

o Mixtures and pure substancesDon't forget about the age old question of gy building iu

▪ Pure substances only have one kind of atom or molecule. An example  would be salt (NaCl)

▪ Mixtures have a number of different pure substances mixed together. An  example of this would be salt that has been dissolved in water (NaCl and  H2O)  We also discuss several other topics like aspeina

o Elements and compounds

▪ An element is a pure chemical substance made of the same type of atom.  An example would be things like iron (Fe), copper (Cu), silver (Ag), gold (Au), and nickel (Ni)

What is the law of conservation energy?

▪ A compound contains atoms of different elements that have been  

chemically combined together in a fixed ratio. An example would be water (H2O), salt (NaCl), and sodium bicarbonate (NaHCO3) If you want to learn more check out uh mece

o Heterogeneous and homogeneous

▪ Homogeneous mixtures are a mixture that are uniformly distributed throughout the mixture. The composition of the mixture is the same  

throughout, an example would be air, sugar water, vinegar, and  

dishwashing detergent.

▪ Heterogeneous mixtures is a mixture where the components of the mixture  are not uniform or have localized regions with different properties.  

Examples of this would be milk and cereal, pizza, soil, and mixed nuts - The law of conservation energy

o This law states that energy cannot be created or destroyed, but only changed from  one form to another or transferred from one object to anotherIf you want to learn more check out purdue biol 221

▪ An example of this would be when a moving car hits a parked car and  causes the parked car to move, energy is transferred from the moving car  to the parked car

- Conservation of mass

o This law states that for any system closed to all transfers of matter and energy, the  mass of the system must remain constant over time, as system mass cannot  change quantity if it is not added or removed. Don't forget about the age old question of mpf is a general regulator of the transition from

▪ Only applies to chemical and physical reactions, the total mass in a  reaction must be conserved

▪ Mass of reactants = Mass of product

- Correct units with measurements (SI)

o Length = Meter

o Mass = Kilogram

o Time = Second

o Temperature = Kelvin

o Amount of a substance = Mole

o Electric current = Ampere

o Luminous intensity = Candela

o SI modifiers

▪ Nano (n)

▪ Micro

▪ Milli (m)

▪ Centi (c)

▪ Kilo (k)

▪ Mega (M)

- The law of definite proportions

o This law states that in a pure compound the elements combine in definite  proportions to one another by mass. In other words, we know that water is always  composed of two hydrogens and one oxygen.

- The law of multiple proportions

o If elements A and B react to form two different compounds, the different masses  of B that combine with a fixed mass of A can be expressed as a ratio of small  whole numbers.

- The four postulates of Daltons atomic theory  

o Each element is composed of tiny, indestructible particles called atoms (No longer  true, atoms are destructible)

o All atoms of a given element have the same mass and same properties (same  properties is 99.99% true, however mass is not true due to isotopes)

o Atoms combine in simple whole number ratios to form compounds (Law of  Multiple proportions)

o Atoms of one element cannot change into another element

- J.J. Thompson’s experiments with the cathode ray tube

o Once the electron was discovered, models began to be proposed to fit the new  data

o Thomson proposed the plum pudding model (looks similar to a rasin cookie) - Robert Millikan’s oil-drop

o Robert Milliken determined the charge on an electron

▪ -1.6 x 10^-19 C (Colom – massive charge)  

▪ By combining this value with Thomson’s charge-to-mass ratio the mass of  the electron was determined

▪ = 9.1 x 10^-28g

- Understanding the terms

o Nucleus - A group of atoms bound in a structure, such as a benzene ring, that is  resistant to alteration in chemical reactions.

o Proton - a negatively charged particle in the center of the mass to counter the  negative electrons

o Neutron - a subatomic particle, symbol n or n0, with no net electric charge and a  mass slightly larger than that of a proton.

o Atomic mass unit - Masses are often expressed in atomic mass units (amu) o Atomic number – The number of protons in the nucleus, this is how the periodic  table is organized  

o Chemical Symbol – This is the abbreviation for the elements on the periodic table o Isotopes – atoms of an element have a different number of neutrons o Mass number – can be found by taking the number of protons, and adding the  number of neutrons

o Natural abundance - refers to the abundance of isotopes of a chemical element as  naturally found on a planet

- Full atomic symbol

o Anion – A gain of an electron(s) will lead to a negative ion

o Cation - A loss of an electron(s) will lead to a positive ion

- How ions are formed

o an atom that has obtained a charge

- Accuracy and Precision

o Accuracy – How close measurements are to an actual value

o Precision - the relative closeness of a set of measurements to each other of how  reproducible they are

- Systematic vs Random error

o Systematic – usually refers to errors related to how you are measuring something o Random - usually related to repeated attempts to measure the same quantity but  not getting the same answer each time

- Density

o Density = Mass (g)/volume (mL)

- Types of energy

o Kinetic energy – associated with motion

o Potential energy – associated with position (ball at top of hill) or chemical  composition (bombs)

o Thermal energy - the internal energy present in a system due to its temperature

- Moles and Avogadro’s number

o Moles - unit of measurement in the International System of Units (SI) for amount  of substance. It is defined as the amount of a chemical substance

o Avogadro’s number - number of units in one mole of any substance (defined as its  molecular weight in grams), equal to 6.022140857 × 1023 

- Converting between moles and atoms

o x moles * [(6.022 * 1023 atoms)/1 mole] = y atoms

o [ x atoms/ (6.022 * 1023 atoms/moles] = y moles

- Converting between moles and mass

o 1 mole/ # of grams = Moles

o # of grams/ 1 mole = Grams

- Macroscopic objects

o Objects on the length scale on which objects or phenomena are large enough to be  visible practically with the naked eye, without magnifying devices

- Electromagnetic radiation

o the radiant energy released by certain electromagnetic processes. Visible light is  electromagnetic radiation, as is invisible light, such as radio, infrared, and X-rays. o The light that we see with our eyes makes up the small portion of the EM  spectrum called visible light

- Amplitude, wavelength, and frequency

o Amplitude – is the related to vertical height of the crest and determine the  intensity of the light

o Wavelength – the physical distance between crests of the light wave

o Frequency - the number of crest that pass a point in a given time

- Converting between wavelength and frequency  

o C = Wave length * Frequency  

o C is our constant which is 3.00 x 108 m/s

- Interference and Diffraction

o Interference - The interaction of one light was with another depending on relative  phase

▪ Constructive interference, when the waves add to each other and the  amplitude grows  

▪ Destructive interference, when the waves cancel out from being out of  phase.

o Diffraction - The lending of a wave around on obstacle, circular in nature - Converting energy, wavelength, and frequency of electromagnetic radiation o De Broglie Wavelength

▪ This is the equation:

▪ h = Planck’s constant = 6.626 x 10-31J/s

▪ m = mass in kg

▪ v = velocity in m/s

o Schrodinger Equation

▪ H = Hamiltonian operator, E = Actual energy

o Rydberg

▪ E = actual energy  

▪ n2f – end, n2i – initial

- Orbital and wave function

o Orbital - the one (or two) electron wave functions (or probability distribution  functions for one or two electrons) in quantum mechanics

o Wave function - a probability amplitude in quantum mechanics describing the  quantum state of a particle or system of particles.

- Principal vs. magnetic quantum number

▪ n – returning from (Principal)

▪ m – returning to (Magnetic)  

- Nodes  

▪ What are they?

∙ Points of destructive interference between two waves

- Identifying the shapes of orbitals

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