GEN CHEM FIRST PERIODIC EXAM

Solid

Particles are tightly packed in an orderly or fixed arrangement. they vibrate in place, fixed shape, fixed volume, has very low compressibility

Liquid

particles are close together but can move and slide past one another, takes the shape of its container, fixed volume, has low compressibility

Gas

particles are far apart and move rapidly in random directions, no fixed shape, no fixed volume, have high compressiblity

Democritus

matter consists of tiny indivisible particles called atomos moving through empty space

thales

proposed water as the basic or primordial substance

anaximenes

proposed air as the fundamental substance

heraclitus

emphasized fire and continual change

Empedocles

proposed four roots, earth, air, fire and water

property

is a characteristic used to describe or identify a substance.

physical property

observed or measure without chemical identity

chemical property

describes how a substance reacts to form new substances

Malleability

ability of a material to be hammered or rolled into sheets, example, aluminum sheet

ductility

ability of a material to be drawn into a wire, example, copper electrical wire

density

mass per unit volume, helps predict whether an object floats or sinks in a fluid

specific gravity

ratio of a substance’s density to the density of a reference substance, usually water for solid/liquid. it has no unit

biodegradable

can be broken down by microorganisms. cardboard/cellulose is an example

flammability

ability to catch fire or burn, a chemical property

electrical conductivity

ability to conduct electric current, a physical property when no chemical change occurs

physical change

form or state changes, chemical identity remains the same, example, water boiling into steam

chemical change

one or more new substances form, example, iron rusting, vinegar reacting with baking soda

exothermic

releases energy, commonly heat, to the surroundings. example, combustion, the rusting example as described in the exam

endothermic

absorbs energy from the surroundings, example, the vinegar and baking soda scenario

element

pure substance containing one type of atom, example copper, oxygen

compound

pure substance containing two or more elements chemically bonded in a fixed, example, pure water, iron sulfide

homogeneous mixture

uniform composition throughout appears as one phase, example, salt water

heterogeneous mixture

non uniform composition, different parts or phrases can be observed, example, granite, muddy water

solution

very small dissolved particles uniform, do not settle, do not show the tyndall effect, example, saltwater

colloid

intermediate sized particles dispersed throughout, do not readiity settle, example, scatter light, milk or gelatin

suspension

larger particles, may settle on standing, can often be separated by filtration, example, muddy water

filtration

separates an insoluble solid from a liquid. sand is trapped by filter paper, dissolved salt passes through with the water

distillation

separates a liquid from dissolved substances by vaporizing the liquid and condensing the vapour. it can recover water from saltwater

magnetic separation

uses a magnet to remove a magnetic component, such as iron fling, from a mixture

sepatating funnel

separates immiscible liquids such as oil and water. the denser bottom layer is drained first

paper chromatography

separates components such as ink pigments based on their different movement with a solvent

Accuracy

describes how close a measurement is to an accepted or true value

precision

describes how close repeated measurements are to one another

random error

unpredictable variation from trial to trial

systematic error

a consistent bias that shifts measurements in one direction

parallax error

a scale is read from above or below the correct eye level

zero offset

an instrument gives a non zero reading when it should be read zero

unstable digital reading

a value is recorded before the display settles