chemistry exam

accuracy

closeness to the accepted value

precision

closeness of repeated measurements to each other

sig fig rules

1. all non-zero numbers are significant

2. leading zeros are NOT significant

3. zeros between non-zero numbers ARE significant

4. tailing zeros WITH a decimal ARE significant

5. trailing zeros WITHOUT a decimal are NOT significant

independent variable

the variable that you purposely change and test

dependent variable

the factor that may change as a result of your independent variable

controlled variable

keeping all conditions of the experiment the same except for the variables you are testing

matter

anything that has mass and takes up space

physical properties

can be observed or measured without changing the composition of matter or changing the identity of the substance. They are used to observe and describe matter. Include color, hardness, malleability, solubility, weight, and texture

intensive properties

a physical property that will be the same regardless of the amount of matter

ex. color, density, and conductivity

extensive properties

a physical property that will change if the amount of matter changes.

ex. mass, volume, and length

physical change

takes place without any changes in molecular composition. The same element or compound is present before and after the change. The same molecule is present throughout the changes.

ex. water freezing to become ice and ice melting to liquid, and cutting paper

chemical properties

describes its potenial to undergo some chemical change. The composition changes. Ability to change into a different substance.

ex. flammability, toxicity, combustion, and reactivity

chemical change

alters the composition of the original matter. Different elements or compounds are present at the end. The atoms in compounds are rearranged to make new and different compounds

solid

definite shape and volume

liquid

definite volume, and no definite shape

gas

no definite shape or volume

atomic number

number of protons, identifies the element, and never changes

mass number

protons + neutrons

neutrons

mass number — atomic number

element

a pure substance that cannot be broken doen into simpler substance by chemical means, and each element is made up of only one type of atom

compound

a substance made up of two or more elements that are chemically combined in a fixed ratio

atom

is the fundemental building block of all matter. The smallest particle of an element

cation

a positive ion, formed when an atom loses electrions, has more protons than electrons

anion

a negative ion, formed when an atom gains electrons, has more electrons than protons

nucleus

where is the proton (+) and neutron (0) located

electron cloud

where is the electron (—) located

horizontal rows

periods, tells how many energy levels

vertical columns

groups/families, tell how many valence electrons

staircase

seperates the metals (to the left) and nonmetals (to the right)

metalloids (semimetals)

straddle the line and have properties of both metals and nonmetals

atomic radius

the distance from an atom’s nucleus to its outermost electron shell

ionization energy

the energy required to remove an electron from an atom or ion

electronegitivity

an atom’s ability to attract shared electrons in a chemical bond

electron affinity

the energy needed when an electron is added to a neutral atom

ionization energy, electronegitivity, and electron affinity

what periodic trends increase left to right, and decrease top to bottom

Atomic Radius (2)

what periodic trend decrease from left to right across a period and increase down a group

ionic bonds

metal + nonmetal, electrons are transferred, and forms ions

covalent bonds

non-metal + non-metal, and electrons are shared

roman numeral

what do you need if you have a tranisition metal and a non-metal

prefixes

ex. mono, di, tri

what do you need if you have two non-metals

H+ ions

what do acids produce

OH ions

what do bases produce

Salt + Water

what are the products of a neutralixation reactions, Acid + Base

avogradro’s number

6.02 × 10²³

molar mass

sum of atomic masses

density

mass/volume=

mixture

two substances physically combined

heterogeneous mixture

visibly different parts

homogeneous

uniform composition

cohesion

attraction between same molecules

adhesion

attraction between different substances

surface tension

results from cohesion-insects can walk on surface of water

solid water is less dense

ice floats beacuse ________