honors chemistry exam 1

independent variable (IV)

factor the scientist manipulates

dependent variable (DV)

factor changing due to the IV changing

control/constants

factors that remain the same

control group

represents the norm

experimental group

represents a new change

dependent variable on a graph

y-axis

independent variable on graph

x-axis

accuracy

the degree to which the experimental results agree with the accepted value

precision

the degree to which measurements agree with one another

percentage error definition

shows how far off a measurement made in lab is from the commonly accepted value

percentage error formula

standard unit of length

meter=m

standard unit of mass

kilogram=kg

standard unit of time

seconds=s

standard unit of amount of substance

mole=mol

standard unit of temperature

kelvin=K

conversion factor definition

ratios of equivalent values (meaning that they equal 1): when you need a measurement in different units without changing the values

significant figures definition

the number of digits in a measurement that reflects how accurate the measurement is (numbers “read” from the tool)

what IS NOT a sig fig

placehold zeroes

what IS a sig fig

1. non-zero numbers

2. sandwiched zeros

3. trailing zeros

scientific notation definition

a technique used to rewrite very large or very small numbers in a format easier to read

steps of scientific notation

1. move decimal so that there is only 1 digit in front (to the left) of it

2. rewrite the number as #._____ with a x10 after.

3. add an exponent to represent the number of places you moved the decimal

4. make the exponent: + if you started with a big number or - if you started with a small number

matter

anything that has mass and volume

mass

a measure of the amount of matter

volume

a measure of how much space something takes up

atom

the building blocks of matter; the smallest unit of an element that maintains the identity of the elements

element

• a pure substance that cannot be broken down into simpler and more stable substances 

• on the periodic table

• cannot be broken down into anything simpler or more stable

• exist naturally as 1 atom (monatomic) or 2 atoms (diatomic)

compound

• a pure substance that can be broken down into simpler and more stable substances

• chemically combined atoms of 2 or more different elements

• fixed proportions, written as a formula

• can be chemically broken down into simpler or more stable substances (elements)

• have different properties as a compound than the parts that make it up

mixtures

• combination

• variable composition throughout

• each component retains its unique properties

homogeneous mixture

• even distribution, “same”

• appears blended

• can be physically broken down into different components

heterogeneous mixture

• uneven distribution, different

• can be physically broken down into different components and often easily

• components can often be seen or separate out over time

solutions

one substance (solute) is dissolved into another (solvent)

extensive property

depends on the amount of matter that is present

• mass, volume, and amount of energy

physical property

can be observed without changing the identity of the substance

• density, mass, boiling point, state, color

physical changes

change in a substance that doesn’t change its identity

• boiling, melting, dissolving, vaporizing, grinding, cutting

law of conservation of matter

matter is never created nor destroyed, it only changes forms

intensive property

do not depends on the amount of matter that is present

• density, melting point, specific heat

chemical property

can only be observed by changing the composition/ identity of the substance

• reactivity, ability to decompose, instability

chemical changes

change of a substance into another substance; when a chemical reaction occurs

• burning, oxidizing, rotting, corroding, fementing

• chemical changes do not have a change in the amount of matter

evidence of a chemical reaction

• release of light

• sudden temperature change

• sudden color change

• odor change

• gas given off

• sudden appearance of a solid

atomic theory definition

the idea that matter is made up of fundamental particles called atoms

subatomic particles definition

three particles that make up an atom

proton (p+)

positive particle in the nucleus

• identity

neutron (n0)

neutral particle in the nucleus with protons

• mass and holds protons together

electron (e-)

negative particle outside the nucleus in the electron cloud

• bonding behavior or chemically react

• volume

ions

atoms with more or less electrons than protons (has a charge)

mass number

• not on the periodic table

• tells the number of protons and neutrons in the nucleus of an atom (where most of an atom’s mass is located)

isotopes

atoms of the same element with different numbers of neutrons

• atomic number is same for both, mass number is different

• most stable when number of protons and number of neutrons are the same

hyphen form

name of element-mass #

nuclear form

^{mass #}Symbol

bohr model definition

simple diagrams that show the atomic structure of an atom

bohr model steps

1. determine the number of protons by the element’s atomic number

2. determine the number of neutrons by subtracting (mass number-atomic #)

3. place the protons and neutrons in the nucleus

4. use the number on the periodic table to determine the number of energy levels in the electron cloud; draw these around the nucleus

5. put the electrons on each level, filling from the inside out

6. check the number of valence electron is the same as the group number

nuclear chemistry

the study of changes to the nucleus

radioactive isotopes

have excess nuclear energy and thus are unstable and more likely to decay

radioactive decay

when particles are spontaneously emitted from an unstable nucleus