CHEM Terms Ch 1-2

Chemistry

the science that seeks to understand the properties and behaviour of matter by studying the properties and behaviour of atom and molecules

Atoms

studying the properties and behaviour of atom and molecules

Molecules

two or more atoms attached together (using bonds) in a specific geometric arrangement

- different shapes and patterns

Qualitative Observations

uses your senses to make descriptive observations

Quantitative observations

measurable observations descriptive observations (numerical measurements)

- made with instruments (rulers, balances, graduated cylinders,

beakers and thermometers)

Physical property

properties of matter that can be determined without altering the chemical composition of the material

-characteristics that don’t change the substance

Chemical property

properties of matter that describe how the matter behaves in the presence of other substances

-can be determined only by changing the composition of the matter in some way

physical change

-processes that cause change in form of matter but not its chemical identity

-no new substance is formed

chemical change

-change involving one or more kinds of matter which are transformed into new matter or several kinds of matter

-a new substance is formed (change in composition)

energy changes

physical and chemical changes are usually accompanied by energy changes

Kinetic energy

energy associated with motion of an object

thermal energy

energy associated with temperature of an object

potential energy

energy associated with position or composition of an object

chemical energy

associated with the relative positions of electron and nuclei in atoms/molecules

Law of conservation of energy

-energy neither created or destroyed

-total amount of energy remains the same

mass

-measure of the quantity of matter present in an object

-kilogram,kg (SI unit)

temperature

measure of the average amount of kinetic energy (energy of motion) of atoms and molecules of matter

volume

-measure of the amount of space occupied

-any unit of length when cubed

Accuracy

How close a measurement is to actual value

Precision

How close repeated measurements are to each other (reproducibility)

density

ratio of mass (m) of substance to its volume (v)

intensive property

-property of substance independent of amount of substance

-properties depend on type of substance-not amount of it

extensive property 

property of substance dependent on amount of substance

temperature sensitive

heating an object generally causes it to expand; therefore, the density changes with temperature

Law of conservation of mass

In a chemical reaction, matter is neither created nor destroyed

Law of definite proportions

-all samples of a given compound, regardless of their source or how they were prepared

-have the same proportions (by mass) of their constituent elements

Law of multiple proportions

when two elements (call them A and B) form two different compounds, the masses of B that combine with 1g of A can be expressed as a ratio of small whole numbers

John Dalton

Came up with the Atomic Theory-theory based on ultimate, indivisible particles

J.J. Thompson

Made cathode ray tubes(mass-to-charge ratio of cathode ray particles) - discovery of the electron

Robert Millikan

Made oil drop experiment-determine charge and mass for an electron

Antoine Becquerel & Maria Curie

Worked together to discover radioactivity-the emission of small energetic particles from the core of certain unstable atoms

-3 types of radioactivity: alpha particles, beta particles, gamma rays

Ernest Rutherford

did the gold foil experiment-positive charge in the atom nucleus

Nuclear theory

• most of the atom’s mass and all its positive charge are contained in a small core-the nucleus

James Chadwick

Discovery of the neutron

natural relative abundance

the relative amounts of each isotope in a naturally occurring sample of a given element

ions

atoms that have gained or lost electrons to form +ve or -ve charged species

cations

positively charged ions -lost electrons

anions

negatively charged ions -gained electrons

atomic mass

average mass of the isotopes

mass spectrometry

instrument used to determine the masses of atoms and the percent abundances of isotopes