Class Test 1 Flashcards
(43 cards)
Relationship aming particles depends on
1) avg distance between particles
2) Degree of organization of particles
3) Kinds of interactions among particles
Why do solids have high bp and mp
**Because of the strong packing of the particles (strong attractive forces , KE < Attractive forces)
T/F: Solids have high desnity
True
MP & BP of a solid depends on 2 things:
1) the strength of the attractive forces in the solid
2) Polar higher MP than non polar (Polarity)
What is an amorphous solid + examples
An amorphous solid is one with** no organized structure**/orderly pattern
Example: candle wax , gel , fat tissue
T/F: Amorphous solids have exact MPs
False, They gradually melt over a range of temperatures because the strength of the bonds holding the particles is not the same
What are crystalline solids ?
They are solids with an orderly pattern
Define molecular crystalline solids , give examples and state their characteristics
Molecular crystalline solids are made up of covalent compounds and are held together by 1)London Dispersion forces 2)Dipole-Dipole interactions(makes them easily evaporated 3)H-bonding. Characteristics: low MP , poor conductors , soft , volatile (evaporate easily). Examples: dry ice , water ice , sugar
Define ionic crystalline solids , give examples and state their characteristics
Ionic crystalline solids are made up of ionic compounds (+ - charge). Held together by electrostatic forces. They’re extremely hard , brittle , have high MPs, soluble in H2O and other polar solvents. Example: chalk , NaCl, limestone, magnesium sulfate(Epsom salt).
Covalent crystalline solids: give examples and state their characteristics
Are hard , brittle , insoluble in most solvents , have very high MPs. Example: diamonds and silicon.
Define metallic crystalline solids , give examples and state their characteristics
Comprised of metal atoms held together by metallic bonds. Their orbitals overlap causing regions of high electron densities. Electrons can move from one atom to another because of the overlapping orbitals –> makes them great electrical conductors. Example: copper and silver. They are easily shaped.
Why are liquids intermediate in character ?
Because the atoms are closely held together like solid atoms , but are disordered like gas atoms.
Why do gases have low densities ?
Becaise gases have low M/V because they’re moslty empty space.
Kinetice Molecular Theory of Gases 6 statements
1)atoms are in constant and random motion
2)atoms are seperated by large distances **
3)behave independently** (no attractive/repulsive forces)
4)collide with each other & walls of the container without losing energy
5)energy is transferred from one atom to another during collisions (results in random changes in direction
6)avg KE is proportional to absolute temp
When do gases ideally behave ?
At low pressure and high temprature
T/F: Gases exert pressure on their containers
True
Define 1)Boyle’s Law 2)Charles Law 3)Avogadro’s Law
1) V&P are inversly proportional PiVi= PfVf
2) T&V are directly proportional (T in kelvin) Vi/Ti=Vf/Tf
3) Equal volumes of any gases contain the same number of moles (if measured under the sam circumstances) Vi/ni = Vf/nf
What are: 1) the combined gas law 2) the ideal gas law
1) Boyle + Charles PiVi/Ti= PfVf/Tf
2) Boyle + Charles + Avogadro PV= nRT (R= 0.0821 L x atm x K^-1 x mol^-1 )
What are intensive and extensive properties ?
Intensive: Independant on the quantity of substance (BP , MP, Density, Specific gravity)
Extensive: Dependent on the quanitity of the sample(Mass and Volume)
What is a pure subtance ? Gives examples of its types
A pure subtance has only one component, fixed composition, and unique set of properties.
1) Element: charcoal -> carbon , (carbon is the building block of life) copper used in electrival wiring &water pipes, mercury (used in barometers and nanometers because of its high density, and used to form amalgam (Ag-Hg-Sn)used in filling teeth.
2) Compound: H20 etc.. You can resolve a compound by heating or electrolysis (if it’s a liquid)
What are mixtures ?
Mixures are a combination(not chemically combined) of 2 or more substances. Each substance retains its own identity. Mixtures have** variable composition.**
Differentiate between homogenous and hetergoneous mixtures.
1)Homogenous: 1-layer mixture, unifrom composition,particles are throroughly intermingled, solvents are most commonly liquid. (Alcohol+water, air, soda+water)
2)Heterogenous: 2-layer solution, non-uniform composition (salt+pepper, concrete which is mixture of various types and sizes of stones + cement)
What is an atom ?
It is the basic structural and smallest unit of an element which retains the chemical properties of that element.
Mass (amu) of e- , p+, and n
E: 5.486x10^-4
P: 1.007
N: 1.009
