Chemistry – studies matter and the physical and chemical changes it undergoes

Branches of study include:◦ Organic – carbon compounds (DNA, etc)◦ Inorganic – non carbon cpds (medicines,etc)◦ Physical – matter/energy changes (atoms)◦ Analytical – material makeup (geometry of atoms)◦ Biochemistry – chemistry of living things◦ Theoretical – use of physics to understand

chemical phenomena (quantum chemistry)

Matter- anything that has mass and volume

Atom- smallest unit of an element that keeps the properties of element

Element- pure substance made of only one type of atom

Compound- substance made of 2 or more types of atoms that are chemically bonded

Molecule- type of compound in which bonds are covalent bonds

Element◦Composed of identical atoms◦Cannot be made simpler by chemical or

physical means◦EX: copper wire, aluminum foil

Compound

◦ Composed of 2 or more elements in a fixed ratio that are chemically combined

◦ Able to be separated by chemical means

◦ Properties differ from those of individual elements

◦ EX: table salt (NaCl)

Variable combination of 2 or more pure substances.◦ Not chemically combined and can be separated

through physical means

Heterogeneous Homogeneous

Homogeneous (solutions)◦ Very small particles◦ Particles don’t settle◦ Appear to be the same throughout◦ Examples: air, brass, salt water

Heterogeneous◦ Medium/large particles◦ Particles may/may not settle◦ Not the same throughout◦ Examples: concrete, cookie dough

Compound Mixture

One kind of piece-Molecules

More than one kind - Molecule or atoms

Making is a chemical change

Making is a physical change

Only one kind Variable composition

MATTER

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed?

noyesIs the composition uniform?

noyes

Characteristic properties of matter are used to classify substances

Types of Properties:◦ Extensive Property

depends on the amount of matter

Ex: volume, mass

◦ Intensive Property

does not depend on amount

Ex: density, boiling/melting point, ability to conduct heat/electricity

Examples:◦ boiling point

◦ volume

◦ mass

◦ density

◦ conductivity

intensive

extensive

extensive

intensive

intensive

Physical Property

◦ can be observed without changing the identity of the substance.

◦ Mixtures separated using physical properties

Chemical Property

◦ describes the ability of a substance to undergo changes in identity

◦ Chemical reactions are evidence

Examples:◦ melting point

◦ flammable

◦ density

◦ magnetic

◦ tarnishes in air

physical

chemical

physical

physical

chemical

Physical Change◦ Changes the form of a substance without changing its

identity

◦ Properties remain the same

◦ Phase changes, dissolving, cutting, bending, etc

◦ Mixtures separated with a variety of techniques (filtering, evaporation, boiling, etc)

Chemical Change◦ Changes the identity of a substance

◦ Products have different properties

◦ Combustion, production of odors, gases, light, rusting, precipitation, cooking,etc

Reactants – The substances that react in a chemical change (stuff you start with)

Products – The substances that are formed by the chemical change (what you make).

NEW PROPERTIES Not easily reversed

reactants product

carbon + oxygen → carbon dioxide

Signs of a Chemical Change

◦ change in color or odor

◦ formation of a gas

◦ formation of a precipitate (solid)

◦ change in light or heat

Examples:◦ rusting iron

◦ dissolving in water

◦ burning a log

◦ melting ice

◦ grinding spices

chemical

physical

chemical

physical

physical

Exothermic Reaction- reaction that gives off energy (feels warm on outside)

Endothermic Reaction- reaction that uses up energy (feels cold on outside)

Energy is always involved when physical or chemical changes occur.

Energy can be in various forms.◦ heat ◦ light

Law of Conservation of Energy.◦Energy can be absorbed or released in a

change, it is not destroyed or created.

Solids◦ very low KE - particles vibrate but can’t

move around

◦ fixed shape

◦ fixed volume

Liquids◦ low KE - particles can move around

but are still close together

◦ variable shape

◦ fixed volume

Gases◦ high KE - particles can separate and

move throughout container

◦ variable shape

◦ variable volume

Plasma◦ very high KE - particles collide with enough

energy to break into charged particles (+/-)

◦ gas-like, variable shape & volume

◦ stars, fluorescent light bulbs, CRTs

◦ Particles of matter are always in motion.

◦ As temperature increases, so does speed (Kinetic Energy) of particles

◦ KMT evidence exists in the presence of the four states of matter

Changing from any state to another state involves the addition or removal of energy from the system

Melting, freezing, vaporizing, evaporation, boiling, sublimation, condensation

Solid Liquid Gas

Melt Evaporate

CondenseFreeze

Groups (aka: families)◦ vertical columns◦ numbered 118◦ have similar chemical properties

Periods◦ horizontal rows◦ properties changes consistently across a period

Metals◦ an element that is a good

conductor of electricity◦ at room temperature, most

are solids◦ malleable- can be rolled or

hammered into sheets◦ ductile- can be made into wire◦ high tensile strength- can

resist breakage when pulled◦ most have silvery or grayish

white luster

Nonmetals◦ an element that is a poor conductor of heat and

electricity◦ many are gases at room temperature◦ some are solids: usually brittle, not malleable

Various nonmetal elements Various nonmetal elements (a) carbon, (b) sulfur, (c) phosphorus, and (d) iodine(a) carbon, (b) sulfur, (c) phosphorus, and (d) iodine

Metalloids◦ an element that has some characteristics of

metals and nonmetals◦ appear along staricase line◦ B, Si, Ge, As, Sb, Te◦ all are solids at room temperature◦ less malleable than metals but less brittle

than nonmetals◦ are semiconductors

Noble Gases◦ generally unreactive gases◦ in far right column of periodic table