Chem 31 Test 1

7 Major Groups on the Periodic Table

1) Alkali Metals, 2) Alkali Earth Metals, 3 )Transition Metals, 4) Halogens, 5) Noble Gases, 6) Lanthanides, 7) Actinides

Difference Between a Cation and an Anion

A cation is a positively charged ion due to the loss of one or more electrons). An anion is a negatively charged ion due to the gain of one or more electrons. "Cats have paws."

Define Exothermic Process

A change that releases energy. The reactants have more chemical potential energy than the products.

Define Endothermic Process

A change that requires and absorption of energy. The products have more chemical potential energy than the reactants.

Define Mixture

A combination of two or more pure substances. Has varying physical and chemical properties (boiling and melting point).

Difference Between a Group and a Period

A group runs in columns and elements share the same characteristics (example: number of valence electrons). A period runs in rows and elements do not share the same characteristics.

Formula for Determining Percent Abundance

(mass 1 * x) + (mass 2 * (1 -x)) = Average Mass. Average mass is obtained from the periodic table. Masses will be given.

PICTURE OF DIFFERENT WAY TO EXPRESS IONS!!!!

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Order of Scientists in Atomic Structure Theory

Dalton, Thomson, Rutherford.

5 Rules of Significant Figures

1) Anything not a zero is significant (1.234 = 4 sig figs). 2) Zero's in between non-zero numbers are significant (1002 = 4 sig figs). 3) Zero's to the left of the first non-zero number are not significant (0.001 = 1 sig fig). 4) Trailing zero's to the right of a decimal point are significant (0.0230 = 3 sig figs). 5) A number that ends in zero that is not to the right of the decimal point is ambiguous (190 could be 2 or 3 sig figs. Should be written in scientific notation for clarity).

2 Rules for Rounding When Following Sig Figs

1) When adding or subtracting count the fewest number of decimal places. 2) When multiplying and dividing use the lowest number of sig figs.

Define an Observation

A measurement of some aspect of nature.

3 Forms of Calculating Density

Always make sure units are in grams per milliliter! Density = Mass over Volume (d = m/v). Mass = Density times Volume (m = dv). Volume = mass over density (v = m/d).

Difference Between and Atom and an Ion

An atom is a basic unit of a chemical element. An ion is an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

Define a Hypothesis

An educated guess based on observation. Can be disproven, but not proven to be true.

What is Atomic Number?

Atomic Number = Number of Protons. Can be represented by "Z".

How are isotopes identified?

By their mass number.

C =

C = (F - 32) / 1.8

Define Pure Substance

Cannot be separated into any other kind of matter. Has constant physical and chemical properties (boiling and melting point).

What question do you ask to determine if a change is physical or chemical?

Did the composition change? If no, it's a physical property. If yes, it's a chemical property.

What did Thomson do?

Found that an atom is breakable and proposed that it is made of electrons suspended in a positively charged sphere that balanced the electron's negativity. Also proposed that the atom must be mostly empty space. The model was referred to as the "plum pudding" model. His experiment invalidated Dalton's assumption that an atom is unbreakable.

Formula for Heat Calculation

Heat = mass times specific heat capacity times change in temperature. Q = m * c * deltaT. Q is measured in Joules, mass is measured in grams, specific heat capacity is measure in Joules per gram degree Celsius, and change in temperature is measured in Celsius.

Define Specific Heat

Heat capacity of 1 gram of a specific substance.

K =

K = C + 273

Metric System Unit Conversion Chain

Kilo (k), Hecto (h), Deka (da), Unit, deci (d), centi (c), mili (m). King Henry Doesn't Usually Drink Chocolate Milk

Define a Law

Laws explain "what". Generalize a body of observations. Laws explain things, but do not describe them. Example: Newton's Law of Gravity. "What goes up must come down." This explains what will happen but doesn't explain why.

Define a Theory

Laws explain "why". Summarizes a group of hypotheses that have been supported with repeated testing. If enough evidence accumulates to support a hypothesis, then it is accepted as a good explanation of a phenomenon.

What is Mass Number?

Mass Number = Protons plus Neutrons. This a whole number and can be represented by "A".

Matter Tree

Matter is either a pure substance or mixture. Pure substances are either elements or compounds. Mixtures are either homogenous or heterogeneous.

Mega, mico, and nano Conversions

Mega (M) = Base x 10^6. mico (mew or mc) = Base x 10^-6. nano (n) = Base x 10^-9.

Define Heterogenous Mixture

Non-uniform appearance. Each substances presence can be seen (sand and water). Portions of a sample have different composition and properties.

Physical Properties

Observed or measured without changing composition. Examples: mass, volume, boiling point.

Chemical Properties

Observed when changing composition and describes the behavior of matter. Examples: Acidity, combustibility, reactivity.

What did Dalton do?

Proposed that each element is composed of unbreakable particles called atoms. All atoms of an element are identical. Atoms combine to form compounds.

Define Compound

Pure substances made of more than one kind of atom. All samples behave the same way, but the compound behaves differently than the individual elements it is make out of. Can be broken down into individual elements.

Define Elements

Pure substances made of one kind of matter. Cannot be broken down into simpler substances. Molecules may or may not form, but will always contain only one type of atom.

Solid (Shape, Volume, Compress, Flow)

Shape = Fixed; Volume = Fixed; Compress = No; Flow = No

Liquid (Shape, Volume, Compress, Flow)

Shape = Indefinite; Volume = Fixed; Compress = No; Flow = Yes

Gas (Shape, Volume, Compress, Flow)

Shape = Indefinite; Volume = Indefinite; Compress = Yes; Flow = Yes

What did Rutherford do?

Shot alpha particles at thin sheets of gold. Most particles went through, a few deflected, but a very small amount bounced off. This fact invalidated the plum pudding model. Proposed that there must be a nucleus that accounts for most of the mass of an atom and that electron weight is negligible. Protons must exist in the nucleus to balance the electron's charge.

Define Homogenous Mixture

Uniform in appearance. Substances appear to be one. All portions of the sample have the same composition and properties. Example: Tea and sugar.

Define Heat Capacity

The amount of heat a substance must absorb to raise its temperature by 1 degree Celsius.

Calculating Mass of Reactants or Products

The total mass will always be the same before and after the reaction.