Ch. 1 Flashcards
Hypothesis
a tentative explanation/prediction in accord with current knowledge
Law
a concise verbal or mathematical statement of a behavior/relation that seems always to be the same under the same conditions
Theory
a well-tested, unifying principle that explains a body of facts and the laws based on them
capable of suggesting new hypotheses that can be tested experimentally
where someone has made a guess/an idea is not yet substantiated
How are laws established?
once a theory has been tested thoroughly and is accepted
based on results from many experiments by many different scientists over time
Solids
rigid shape and fixed volume
particles are packed closely together, vibrate back and forth
large net forces of attraction
Liquids
fixed volume and takes on shape of container (fluid, no definite shape)
particles arranged randomly, not confined to specific locations
medium net force of attraction
Gases
fluid and volume depends on size of container (varies more than liquid)
particles move rapidly, not constrained by neighbors and colliding with each other and container walls
small net force of attraction
Solution
a homogeneous mixture of one or more solutes dissolved in solvent
Pure substances
set of unique properties
fixed composition, cannot be further purified
Mixtures
two or more pure substances that can be separated by physical techniques
composition can be varied
Homogeneous mixtures
uniform composition throughout (two or more substances in the same phase)
often called solutions
Ex: air, gasoline, sugar water, steel
Heterogeneous mixtures
nonuniform composition
uneven texture of material can often be detected by naked eye
properties in one region are different from those in another region
Ex: milk, oil and water, sandy water
Atoms
smallest particle of an element that retains the characteristic chemical properties of that element
Elements
cannot be subdivided by chemical or physical processes
substances composed of only one type of atom
Molecule
particles consisting of more than one atom in which atoms are held together by chemical bonds
Compound
elements united in fixed ratio
substance which is composed of two or more DIFFERENT elements held together by chemical bonds
properties different than those of constituent elements
Law of definite proportions
(law of constant composition)
a compound has a definite composition (by mass) of its combining elements
Physical properties of common substances
color
state of matter
melting point
boiling point
density
solubility
electric conductivity
malleability
ductility
viscosity
Chemical changes
one or more substances (reactants) are transformed into one or more different substances (products)
Physical changes
identity of substance is preserved even though it may have changed its physical state
does NOT result in new chemical substance being produced
Chemical properties of common substances
Ex: Hydrogen gas reacts violently with oxygen gas
Types of kinetic energy (energy associated with motion)
thermal: motion of atoms, molecules, or ions at submicroscopic level
mechanical: motion of macroscopic objects
electrical: movement of electrons in a conductor
acoustic: compression/expansion of the spaces between molecules in the transmission of sound
Types of potential energy (results from an object’s position or state)
gravitational: energy possessed by ball held above floor and by water at top of water wheel
energy stored in an extended spring
chemical: energy stored in fuels
electrostatic: energy associated with the separation of electrical charges
Law of conservation of energy
energy cannot be created or destroyed
total energy of the universe is constant
