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midterm exam Flashcards

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1
Q

what is chemistry?

A

the study of the composition and structure of matter in the changes they undergo

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2
Q

briefly explain the scientific method

A

observe- collect data, experiment, communicate

theory- tests are always done with theories

test- observing, testing and theories can go back and forth if more/new data is needed

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3
Q

what is the difference between an endothermic and exothermic reaction?

A

endothermic- absorb energy, feels cold

exothermic- release energy, feels hot

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4
Q

list one intensive and one extensive physical property of a sample of water

A

intensive- color

extensive- heat

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5
Q

which piece of equipment do you use to find the mass? Which piece of equipment do you use to find the volume?

A

use a balance to find the mass, use a graduated cylinder to find the volume

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6
Q

list the indicators of a chemical reaction

A

unexpected change in color
a gas is released
energy is released or absorbed
the formation of a precipitate

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7
Q

List the units to measure heat in the units to measure temperature. are heat and temperature of the same thing?

A

heat- J
temperature- °C

no

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8
Q

what is an atom? what one factor determines an atom’s identity?

A

the smallest particle of an element that retains the chemical identity/properties of that element

atomic number

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9
Q

John Dalton wrote the first atomic theory. what two points in his three were later prove to be false? explain why each is false

A

atoms are not subdivided created or destroyed and a chemical reaction- changed to: atoms cannot be subdivided created or destroyed. (this was because of nuclear reactions

atoms of a given element have the same size, mass, and other chemical properties- changed to: atoms of the same element have the same chemical properties (this was because of isotopes which differ in mass and size)

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10
Q

how did Thompson use the cathode ray tube experiment to determine that electrons have a negative charge?

A

The cathode ray was repelled by negative charge, meaning the cathode ray had a negative charge

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11
Q

how did Thompson use the cathode ray to be experiment to determine that electrons are particles?

A

when a paddle wheel was placed on the cathode ray it spun, showing it was made of particles

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12
Q

how did Millikan use the oil drop experiment to determine the charge of an electron?

A

he adjusted the voltage so the charge drop would stay in mid air between the two plates

force~(charge on drop)(voltage charge) to find it; where force and voltage charge were given and you could solve for charge on drop

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13
Q

how did Millikan determine the mass of the electron?

A

he used the charge and Dalton’s ratio (in the oil drop experiment)

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14
Q

after the cathode ray tube and oil drop experiments, scientists knew that atoms are neutral yet electrons are negative. what conclusion regarding atoms could they draw from this?

A

there must be something positive in the atom that could balance out the negative electrons and make the atom neutral

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15
Q

briefly explain the plum pudding model of the atom

A

it modeled an atom with a positive charge spread throughout it with the negative electrons scattered. alpha particles passed by without repelling

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16
Q

what would have been observed in the gold foil experiment if the plum pudding model were true?

A

alpha particles would pass by without interruption or repelling

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17
Q

how did Rutherford determine that the nucleus has a very large mass?

A

the alpha particle bounced back after hitting the nucleus, (the nucleus had to be large enough for it to bounce back)

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18
Q

how did Rutherford determine that the nucleus is positive?

A

positive alpha particles repelled from the nuclei as they passed, things with like charges repel from one another

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19
Q

how did Rutherford determine that the nucleus is very small?

A

it only hit 1 out of 8,000 times, if it were much larger it would hit a lot more often

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20
Q

list the three subatomic particles with their masses, charges, and locations

A

protons- charge: +1, mass (amu): 1, location: nucleus

neutrons- charge: 0, mass (amu): 1, location: nucleus

electron- charge: -1, mass (amu): 0, location: electron cloud

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21
Q

what what is the strong nuclear force?

A

the force that holds the nucleus (of an atom) together

22
Q

why are decay equations not written for gamma decay?

A

no particles are released in gamma decay, (only energy is released)

23
Q

list the types of electromagnetic radiation in order from highest frequency to lowest frequency

A 
gamma radiation
x-rays
ultraviolet radiation
visible light
infrared radiation
micro waves
radio waves
24
Q

what is wavelength? what is frequency? which variable does the energy of a wave depend on?

A

wavelength- the distance from one crest of a wave to another

frequency- how many waves pass a given point per second

the energy of a wave depends on the frequency of a wave

25
Q

briefly explain Einstein’s photoelectric experiment. what was his conclusion?

A

he shone red light and purple light on metal. if the red light was a wave, the metal would have. soaked up enough energy to create a current (but it didn’t); only the purple light had enough energy to conduct a current

he concluded that light came in the form of particle streams

26
Q

how do quanta and photons compare

A

quanta and photons compare because a quanta is a finite amount of energy, and a photon. is a quanta of light

27
Q

what is the difference between quantized and continuous? is energy quantized or continuous?

A

quantized- only specific, certain values (are accepted)

continuous- all values (are accepted

energy is quantized

28
Q

explain the activity of electrons when heated in a flame

A

electrons reach a higher energy level and go into an excited state when heated in a flame

29
Q

what is spectroscopy?

A

the identification of atoms through the emission spectra

30
Q

the Bohr Model of the atom seems to make sense. what was its problem

A

it only worked for hydrogen; it could not explain the line spectra of elements with more than one electron; it treated electrons as particles

31
Q

what is the difference between an orbit and an orbital?

A

orbit- an exact, definite location of an electron outside the nucleus

oribitz- a predictable, but not definite location on an electron outside the nucleus

32
Q

list the four quantum numbers with their descriptions and possible values

A

principle quantum number- describes: the energy level of an orbital, possible values: 1, 2, 3, 4, 5, 6, 7, 8

orbital quantum number- describes: the shape of an orbital, possible values: s, p, d, f

magnetic quantum number- describes: the orientation of the orbital on the x/y/z axis, possible values: x, y, z

spin quantum number- describes: the spin of the electron(s), possible values: +1/2, -1/2

33
Q

which group is the most reactive? which group is the least reactive?

A

most reactive- alkali metals

least reactive- noble gases (are nonreactive)

34
Q

what is ionization energy? which group has the largest ionization energy?

A

the energy required to remove one electron from an atom

largest IE: group 18

35
Q

equation for first ionization energy. which group has the lowest first ionization energy?

A

A + energy —> e- + A+

lowest group

36
Q

what happens to ionization energy as you move down a group? explain

A

IE decreases because you are removing electrons further and further from the positive nucleus

37
Q

write the equations for the second and third ionization energies

A

second IE: A+ + energy —> e- + A^2+

third IE: A^2+ + energy —> e- + A^3+

38
Q

what is electron affinity? write the equation for negative electron affinity

A

the energy charge that occurs when adding an electron to an atom

negative EA equation: A + e- —> energy + A-

39
Q

which group has the highest positive electron affinity? why?

A

highest positive EA: group 18

because it already has a full octet

40
Q

what is electronegativity?

A

an atom of a compound’s tendency to draw electron towards it

41
Q

which group has the highest electronegativity values? what happens to electronegativity as you move down a group?

A

highest EN values: group 17

as you move down a group, EN decreases

42
Q

what happens to atomic radius as you move across a period? explain

A

as you move across a period, atomic radius decreases. this is because no new energy levels are added and the nuclear charge increases, so the electrons are being drawn in towards the nucleus

43
Q

what is a cation? how does its size compare to a neutral atom?

A

a positive ion

it is always smaller in size compared to its neutral atom

44
Q

what is an ionic bond? what is a covalent bond?

A

ionic bond- the force of attraction between oppositely charged ions, no electrons are shared

covalent bond- a bond in which electrons are shared/distributed

45
Q

two elements form a compound. assuming there are partial charges present, how can you tell which atom has the partial negative charge?

A

whichever atom has the highest electronegativity, or pull on electrons, has the partial negative charge

46
Q

in terms of electrons, what is the difference between a polar covalent bond and a nonpolar covalent bond

A

polar covalent bond- a bond where electrons are evenly distributed

nonpolar covalent bond- a bond in which electrons are evenly shared

47
Q

what is the main reason that elements and compounds undergo chemical reactions?

A

so that atoms can become more stable

48
Q

why must chemical reactions be balanced?

A

because atoms cannot be lost or gained in a chemical reaction

49
Q

what is a mole?

A

the amount of a substance that contains 6.022x10^23 particles

50
Q

what is molar mass? what is formula mass?

A

molar mass- the mass, in grams of one mole of a substance

formula mass- the mass, in amu, of one particle of a substance

51
Q

compare and contrast one mole of magnesium and one mole of aluminum

A

one mole of magnesium and one mole of aluminum have the same amount of atoms (6.022x10^23 atoms), but have different masses (Mg = 24.305 g, Al = 26.982 g)

chemistry (16 decks)

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