Chem H Matter & Change

element

a pure substance made of only one kind of atom

compound

a substance made from the atoms of two or more elements that are chemically bonded

mixture

a blend of two or more substances, each of which retains its own identity and properties

atom

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

pure substance

a substance that has a fixed composition (elements and compounds are pure substances, mixtures are not)

homogeneous

matter of uniform composition; has the same proportion of components throughout (elements, compounds and some mixtures are homogeneous)

heterogeneous

a mixture that is not uniform throughout (some mixtures are heterogeneous)

solution

another term for a homogeneous mixture

precipitate

solid that is formed when two liquids are mixed

physical property

a characteristic of matter that can be observed or measured without changing the identity of the substance

examples of physical properties

physical state, boiling point, color, density

chemical property

a property that relates the ability of a substance to undergo changes that transform it into different substances

example of chemical property

flammability, corrosiveness, reactivity with acids

physical change

any change in matter that does not change its identity

example of physical change

cutting, crushing, melting, boiling, dissolving

chemical change

a change in which one or more substances are converted into different substances (that have different properties)

examples of chemical changes

burning, rusting, tarnishing, exploding

chemical reaction

another term for chemical change

kinetic theory of matter

molecules are always moving

solid

• matter that has a definite volume and shape

• particles have high attraction for each other

• particles packed together tightly and vibrate

liquid

• matter that has definite volume but not shape

• particles have high attraction for each other, but have more energy than a solid

• particles tumble past each other and “flow”

gas

• matter that has indefinite volume or shape

• exist as single particles that have no attraction for each other

• particles move rapidly in a straight line colliding with each other or the inside of the container that they are in

melting

• solid becomes liquid as heat energy is added

• temperature rises, particles speed up

melting point

the actual temperature where a solid turns into a liquid

freezing

• liquid becomes solid as heat energy is removed

• temperature drops, particles slow down

freezing point

the actual temperature when a liquid becomes a solid

boiling

• when a liquid becomes a gas as heat energy is added

• temperature rises, particles move faster

boiling point

the actual temperature where a liquid becomes a gas

condensing

• when a gas becomes a liquid

• particles slow down

factors that affect phase change

• temperature

• heat energy

• pressure

• mass of molecules

heat transfer

the movement of heat from substances or material to another

conduction

heat travels through solid objects (ironing clothes)

convection

heat traveling through fluids, gas/liquid (hot air rising)

radiation

heat traveling in the form of visible and invisible light (sunlight)

heat of vaporization

the amount of heat energy that must be absorbed by a liquid to turn into a vapor at a constant pressure

heat of vaporization formula

Q = mΔHvap

heat of fusion

the amount of energy needed to melt/freeze a substance under conditions of constant pressure at a specific temperature

heat of fusion formula

Q = mΔHfus

phase diagram

a graphical representation of the physical states of a substance at different temperature and pressures

critical point

the highest temperature and pressure at which a pure substance can exist in vapor/liquid equilibrium; the substance cannot exist at a liquid no matter the pressure

triple point

the temperature and pressure in which the substance exist as a solid, liquid, and gas

supercritical fluids (SCF)

highly compresses gases which combine properties of gases and liquids in an intriguing manner (CO2 & water)

heat (q)

the transfer of thermal energy

temperature

the measure of thermal energy (heat) of the molecules inside of the object

specific heat

the heat required to raise the temperature of the unit mass of a given substance by a given amount (usually one degree)

specific heat of water

4.18 J/g°C

specific heat formula

Q = mcΔT