Chemistry Midterm Chapters 1-6 Vocab

Chemistry

the study of matter and the changes it undergoes

substance

also known as a chemical, is matter that has a definite and uniform composition.

mass

is a measurment that reflects the amount of matter

weight

is a measure not only of the amount of matter but also of the effect of Earth's gravitational pull on that matter.

model

is a visual, verbal, or mathematical explanation of experimental data.

scientific method

is a systematic approach used in scientific study, whether it is chemistry, biology, physical, or another science.

qualitative data

Information describing color, odor, shape, or some other physical characteristic

quantitative data

numerical information

Hypothesis

is a tentative, testable, statement or prediction about what had been observed.

experiment

a set of controlled observations that test the hypothesis

independent variable

in an experiment, the variable that the experimenter plans to change

dependent variable

in an experiment, the variable whose value depends on the independent variable

control

In an experiment, the standard that is used for comparison

conclusion

is a judgement based on the information obtained

theory

is an explanation of a natural phenomenon based on many observations and investigations over time.

scientific law

a relationship in nature that is supported by many experiments.

pure research

a type of scientific investigation that seeks to gain knowledge for the sake of knowledge itself.

applied research

a type of scientific investigation that is undertaken to solve a specific problem

base unit

a defined unit in a system of measurement that is based on an object or event in the physical world

second

SI base unit for time

meter

SI base unit for length

kilogram

SI base unit for mass

kelvin

SI base unit for temperature

derived unit

A unit defined by a combination of base units

liter

the metric unit for volume equal to one cubic decimeter

density

is a physical property of matter and is defined as the amount of mass per unit volume.

scientific notation

can be used to express any number as a number between 1 and 10 (known as the coefficient) multiplied by 10 raised to a power (known as the exponent).

dimensional analysis

is a systematic approach to problem solving that uses conversion factors to move, or convert, from one unit to another

conversion factor

is a ratio of equivalent values having different units

accuracy

refers to how close a measured value is to an accepted value

precision

refers to how close a series of measurements are to one another

error

the difference between the experimental value and the accepted value

percent error

it expresses error as a percentage of the accepted value

significant figures

it includes all known digits plus one estimated digit.

graph

is a visual display of data

states of matter

the physical forms in which all matter naturally exists on Earth- most commonly as a solid, a liquid, or a gas

solid

a form of matter that has its own definite shape and volume, is incompressible, and expands only slightly when heated

liquid

a form of matter that flows, has constant volume, and takes the shape of its container

gas

a form of matter that flows to conform to the shape of its container, fills the container's entire volume, and is easily compressed

vapor

Gaseous state of a substance that is a liquid or a solid at room temperature

physical property

a characteristic of matter that you can observe or measure without changing the samples composition - for example, density, color, taste, hardness, and melting point

extensive property

a physical property, such as mass, length, and volume, that is dependent upon the amount of substance present

intensive property

a physical property that remains the same no matter how much of a substance is present

chemical property

the ability or inability of a substance to combine with or change into one or more new substances

physical change

s type of change that alters the physical properties of a substance but does not change its composition.

phase change

a transition of matter from one state to another

chemical change

a process involving one or more substances changing into new substances; also called a chemical reaction

law of conservation of mass

states that mass is neither created nor destroyed during a chemical reaction but is conserved

mixture

a physical blend of two or more pure substances in any proportion in which each substance retains its individual properties; can be separated by physical means

heterogeneous mixture

one that does not have a uniform composition and in which the individual substances remain distinct

homogeneous mixture

one that has a uniform composition throughout and always has a single phase; also called a solution

solution

a uniform mixture that can contain solids, liquids, or gases; also called a homogeneous mixture

filtration

a technique that uses a porous barrier to separate a solid from a liquid

Distillation

a technique that can be used to physically separate most homogeneous mixtures based on the differences in the boiling points of the substances

crystallization

a separation technique that produces pure solid particles of a substance from a solution that contains the dissolved substance

Sublimation

the energy-requiring process by which a solid changes directly to a gas without first becoming a liquid

Chromatography

A technique that is used to separate the components of a mixture based on the tendency of each component to travel or be drawn across the surface of a fixed substrate.

element

A pure substance that cannot be broken down into other substances by chemical or physical means

periodic table

a chart that organizes all known elements into a grid of horizontal rows (periods) and vertical columns (groups or families) arranged by increasing atomic number

compound

a chemical combination of two or more different elements; can be broken down into simpler substances by chemical means and has properties different from those of its component elements

law of definite proportions

states that, regardless of the amount, a compound is always composed of the same elements in the same proportion by mass

percent by mass

a percentage determined by the ratio of the mass of each element to the total mass of the compound

Law of Multiple Proportions

states that when different compounds are formed by the combination of the same elements, different masses of one element combine with the same mass of the other element in a ratio of small whole numbers

Dalton's Atomic Theory

States that matter is composed of extremely small particles called atoms

atom

the smallest particle of an element that retains the properties of that element

cathode ray

radiation that originates from the cathode and travels to the anode of a cathode-ray tube

electron

a negatively charged, fast-moving particle with an extremely small mass that is found in all forms of matter and moves through the empty space surrounding an atom's nucleus

nucleus

The extremely small, positively charged, dense center of an atom that contains positively charged protons and neutral neutrons

proton

a subatomic particle in an atom's nucleus that has a positive charge of 1+

neutron

a neutral, subatomic particle in an atom's nucleus that has a mass nearly equal to that of a proton

atomic number

the number of protons in an atom

isotopes

Atoms of the same element that have different numbers of neutrons

mass number

the number after an element's name, representing the sum of its protons and neutrons

atomic mass unit (amu)

one-twelfth the mass of the isotopes of that element.

atomic mass

the weighted average of the masses of the isotopes of that element

Radioactivity

The process in which some substances spontaneously emit radiation

radiation

the rays and particles- alpha and beta particles and gamma rays- that are emitted by radioactive materials

nuclear reaction

A reaction that involves a change in the nucleus of an atom

radioactive decay

A spontaneous process in which unstable nuclei lose energy by emitting radiation

alpha radiation

Radiation that is made up of alpha particles; is deflected toward a negatively charged plate when radiation from a radioactive source is directed between two electrically charged plates

alpha particle

A particle with two protons and two neutrons, with a 2+ charge; is equivalent to a helium-4 nucleus, can be represented by a; and is emitted during radioactive decay

nuclear equation

a type of equation that shows the atomic number and mass number of the particles involved

beta radiation

Radiation that is made up of beta particles; is deflected toward a positively charged plate when radiation from a radioactive source is directed between two electrically charged plates

beta particle

a high-speed electron with a 1- charge that is emitted during radioactive decay

gamma rays

high-energy radiation that has no electrical charge and no mass, is not deflected by electric or magnetic fields, usually accompanies alpha and beta radiation, and accounts for most of the energy lost during radioactive decay

electromagnetic radiation

a form of energy exhibiting wavelike behavior as it travels through space; can be described by wavelength, frequency, amplitude, and speed

wavelength

the shortest distance between equivalent points on a continuous wave; is usually expressed in meters, centimeters, or nanometers.

frequency

The number of waves that pass a given point per second

amplitude

the height of a wave from the origin to a crest, or from the origin to a trough

electromagnetic spectrum

Includes all forms of electromagnetic radiation; the types of radiation differ in their frequencies and wavelengths

quantum

the minimum amount of energy that can be gained or lost by an atom

Planck's constant

6.626 x 10^-34 J*s, where J is the symbol for the joule

photoelectric effect

a phenomenon in which photoelectrons are emitted from a metal's surface when light of a certain frequency shines on the surface

photon

A particle of electromagnetic radiation with no mass that carries a quantum of energy

atomic emission spectrum

a set of frequencies of electromagnetic waves given off by atoms of an element; consists of a series of fine lines of individual colors

ground state

the lowest allowable energy state of an atom

quantum number

the number assigned to each orbit of an electron

de Broglie equation

predicts that all moving particles have wave characteristics and relates each particles wavelength to its frequency, its mass, and Planck's constant

the Isenberg uncertainty principle

states that it is not possible to know precisely both the velocity and the position of a particle at the same time

quantum mechanical model of the atom

an atomic model in which electrons are treated as waves; also called the wave mechanical model of the atom