Introductory Concepts Flashcards
Kinetic theory of gases
− Gases particles in constant random motion
− Attraction and repulsion in gases is minor
− particles of a gas are widely spaced, the total volume of particles is minor compared to the volume the gas occupies
− have kinetic energy (Ek) given by, Ek(particle) = ½mv2, where the particles have a speed of motion, v and mass, m
− average kinetic energy is proportional to its temperature
− Particle collisions are elastic
Ideal Gases
− ideal gas have negligible volume real gases do occupy space volume can be significant when compared to the volume occupied by the gas as a whole
− ideal gas have negligible attraction, real gases do have forces of attraction for one another
Some cases we see differences in real gases behavior versus that predicted for an ideal gas
− At a temperature of zero kelvin an ideal gas would have zero volume. A real gas would never have zero volume as its particles do occupy space
− If a real gas is cooled and/or compressed it will condense to a liquid. due to the weak interparticle attraction that exists. Ideal gases would never condense as its particles always have minor attraction for one another.
Mixtures & Compounds
− Compounds are chemically combined while mixtures are not
− Elements & compounds are pure substances, fixed composition
− Mixtures are not pure
− Mixtures are separated by filtration, distillation of chromatography
Homogeneous
− Homogeneous – mixed evenly, also known as solutions
Heterogenous
− Heterogeneous – mixed unevenly
Atomic Number/Mass
Z = N(p) Z= atomic number N(p) = number of protons in atom
A = N(p) + N(n) A= mass of atom N(n) = number of neutrons in atom
N(e) = (Np) N(e) = number of electrons in atom
John Dalton
− Elements are composed of atoms
− All atoms of a given element are identical having the same size, mass and chemical properties. (Opposite for dif)
− Atoms are not created nor destroyed or changed into different types during a chemical reaction
− A chemical reaction involves only separation, combination or rearrangement of atoms
− Compounds are formed when atoms of more than one element combine in a specific ratio
J.J. Thomson
− Showed that electrons have an estimated mass of 1/1000
− New model that accounted for observations
− Numerous very small negatively charged electrons embedded within a much larger uniform positively charged sphere.
− Plum Pudding
− Short lived due to the work of Ernest Rutherford
Ernest Rutherford
− Tested Thomson’s theory
− All alpha particles passed through gold foil unaffected but a small number were deflected significantly or even turned back in the original direction
− Improved the model
− Atom consisted of mostly empty space occupied by electrons
− Electrons orbit around nucleus (protons)
− Explains why most alpha particles passed through the gold foil
− Undeflected alpha particles had passed through empty space
− Particles that passed the positively charged nucleus would show deflection
Sir James Chadwick
− Rutherford’s model didn’t account for all of the atoms mass
− Ernest Marsden and Hans Geiger showed that the number of protons equaled half the mass
− Searching for neutral particles was difficult as techniques only worked on charged particles
− Identified neutrons as a product of the alpha particle bombardment of the metal Beryllium
Niels Bohr
− Solved problem of the unstable electron orbits while precisely accounting for the line of spectrum of hydrogen gas
− Model proposed that electrons moved about the central nucleus in circular orbits, as was first proposed by Rutherford
− Proposed that electrons could orbit without losing energy
