Physical & ChemicalProperties & Changes

Physical Properties

� A physical property is a quality or condition that can be observed or measured without changing the composition or destroying the substance.

� Color, size, and texture are examples of physical properties.

Physical Properties

� Another physical property is the state that the chemical is in: Solid, Liquid, or Gas.

� Solid is a form of matter that has a definite shape and definite volume.

� Liquid is a form of matter that has an indefinite shape and a definite volume (takes the shape of its container).

� Gas is a form of matter that has an indefinite shape and an indefinite volume (takes both the shape and volume of its container).

States of Matter

Physical Change

�Physical change - properties of a material

change, but the composition does not

change.

�Physical changes can be classified as reversible or irreversible.

Physical Change

� All physical changes that involve a change from one

state to another are reversible physical changes.

� Solid to liquid – Melting

� Liquid to gas - Vaporization

� Gas to liquid – Condensation

� Liquid to solid – Freezing

� Solid to gas – Sublimation

� Gas to solid – Deposition

Physical Change

� Cutting hair, filing nails, breaking glass and cracking an egg are examples of irreversible physical changes.

Chemical Property & Change

� Chemical Property - ability of a substance to undergo a chemical change.

� Chemical properties can be used to identify a substance, but chemical properties can only be observed only when a substance undergoes a chemical change.

� Chemical Change – matter changes from one or more substances to one or more new substances

Chemical Change

� Possible clues to chemical change include:

� a transfer of energy – Gets hot or cold, produces light

� a change in color – metallic to brown, blue to white

� the production of a gas – see gas coming off, makes bubbles

� the formation of a precipitate – chunky stuff, a cloudy appearance

� Key words: Reacts, Oxidizes, Neutralizes, Combusts (burns),

Decomposes (rots)

Chemical vs Physical

�During a chemical change, the

composition of matter always changes.

�During a physical change, the

composition of matter never changes.

Physical vs Chemical Separation

�Physical – filter sand from water,

separating ink into pigments

�Chemical – Electrifying water, burning

coal

Chemical Change/Reaction

� A chemical change is also called a chemical reaction.

�Chemical reaction - One or more substances change into one or more new substances

� Begin with reactants, end with products.

� Reactants ���� Products

�Reactants to the left of the arrow, products to the right of the arrow

Law of Conservation of Mass

� The law of conservation of mass states that in any physical change or chemical reaction, mass is conserved.

� During any chemical reaction, the mass of the reactants is always equal to the mass of the products.

� Mass R = Mass P