S1 Flashcards
elements
primary constituents of matter, which cannot be chemically broken down into simpler substances
compounds
consist of atoms of different elements chemically bonded together in a fixed ratio
mixtures
contain more than one element or compound in no fixed ratio, which are not chemically bonded and so can
be separated by physical methods
kinetic molecular theory
a model to explain physical properties of matter (solids, liquids and gases) and
changes of state
temperature
measure of average kinetic energy of particles
What are the properties of solids?
fixed shape
fixed volume
cannot be compressed
What are the properties of liquids?
no fixed shape, take shape of their container
fixed volume
can flow
cannot be compressed
What are the properties of gases?
no fixed shape, take shape of their container
no fixed volume, take up volume of their container
can flow
can be compressed
Mixtures can be further categorised as being either
homogeneous or heterogeneous
heterogeneous
has visible phases or boundaries such as those that can be seen between the oil and the water. The composition of a heterogeneous mixture is non-uniform, meaning that different parts of the mixture have a different composition
Homogeneous
do not have visible phases or boundaries. They have a uniform composition meaning that the components of the mixture are equally distributed and in the same state, making the composition the same throughout the mixture. An example of a homogeneous mixture is the air that we breathe.
convert between values in the Celsius and Kelvin scales
K = C + 273
isotopes
atoms of the same element with different numbers of neutrons
emission spectra are produced by
atoms emitting photons when electrons in excited states return to lower energy
levels
the line emission spectrum of hydrogen provides evidence for
the existence of electrons in discrete energy levels,
which converge at higher energies
the main energy level is given an integer number, n, and can hold a maximum of
2n2 electrons
a more detailed model of the atom describes the division of the main energy levels into
s, p, d and f sublevels of
successively higher energy
continuous spectrum shows
all the wavelengths or frequencies of visible light from red to violet.
emission line spectrum only shows
specific wavelengths or frequencies of light. These are shown as coloured lines on a black background that converge at high energy
formation of an emission line spectrum
Electrons emit energy as they transition from higher to lower energy levels.
mole (mol)
SI unit of amount of substance
one mole contains
exactly the number of elementary entities given by the Avogadro constant
masses of atoms are compared on a scale relative to
12 C and are expressed as relative atomic mass (Ar) and relative
formula mass (Mr)
empirical formula of a compound gives
simplest ratio of atoms of each element present in that compound
the molecular formula gives the
actual number of atoms of each element present in a molecule
molar concentration is determined by
amount of solute and the volume of solution
Avogadro’s law states that
equal volumes of all gases measured under the same conditions of temperature and
pressure contain equal numbers of molecules
Avogadro’s law applies to
ideal gases.
an ideal gas consists of
moving particles with negligible volume and no intermolecular forces; all collisions between
particles are considered elastic
real gases deviate from
the ideal gas model, particularly at low temperature and high pressure
the molar volume of an ideal gas is
constant at a specific temperature and pressure
