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Tufts - Ch > Final Exam > Flashcards

Final Exam Flashcards

1
Q

Allotropes

A

Allotropes: different forms of same element

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2
Q

Pure substance:

A

constant & uniform composition

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3
Q

Pure substance: ELEMENT vs. COMPOUND

A

Element: molecules contain only 1 type of atom [O2]

Compounds: combining different atoms [H2O] –> can be decomposed into 2+ atoms

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4
Q

Mixture:

A

2+ types molecules can be separated by physical changes (ie. evaporation)

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5
Q

Mixture: Homogenous vs Heterogeneous

A

Homogenous mixture: uniform composition - solutions & air (“solution” ie. air)

Heterogeneous mixture: composition varies from point to point

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6
Q

Physical properties:

A

observed without changing substance into another, reversible

(mass, volume, density, boiling pt, solubility, color)

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7
Q

Physical properties: intensive vs extensive

A

Intensive: independent amount substance (boiling pt, density, color)

Extensive: depend amount substance (weight, mass, length)

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8
Q

Chemical properties:

A

undergoes change chemical composition

(flammability, corrosiveness, reactivity with acid)

Key words: reacting, changing, burning

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9
Q

Changes in matter: physical vs chemical

A

Physical change: don’t change composition of substance and no new substance is formed (wax melts, magnetizing solids)

Chemical change: result in formation of new substance with different chemical properties (combustion, oxidation)

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10
Q

Significant figure rules

A

All non-zero digits = significant

Zeros:
Left = not significant
Middle = significant
Right = significant after decimal point

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11
Q

Rounding numbers rules

A

Adding/subtracting: same # decimal places as the # with least decimal places

Multiplying/dividing: same # of digits as # with least sig figs

If digit dropped < 5 (round down) if > 5 (round up)

If digit dropped = 5 (round up or down whichever yields an even value for the retained digit)

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12
Q

Accuracy

Precision

Exact numbers

A

Accuracy: variation from accepted value

Precision: how similar results are when repeated in the same manner

Exact numbers: counting, definition, unit conversion (infinite # sig figs, no uncertainty)

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13
Q

Density

A

desnity = mass / volume
[g/ml = g/cm^3]

Used to identify unknown substance
Determine density of irregular object: use volume water displaced in beaker

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14
Q

Atom

A

Atom: smallest unit of an element that can participate in chemical change (indivisible)

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15
Q

Element vs molecule

A

Element: 1 type of atom, in which mass is a characteristic feature

Molecule: 2+ atoms joined by chemical bonds

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16
Q

Dalton’s atomic theory:

A

WRONG, but laid foundation for future work

  • All matter is made up of tiny particles called atoms (indivisible & indestructible)
  • Atoms given element are identical in size, mass, chemical properties
  • Atoms combine to form compounds in whole number ratios
  • Atoms of element cannot change into atoms another element (only rearrange)
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17
Q

Cathode ray tube, J.J. Thomson

A

DISCOVERED: electrons negative, charge to mass ratio

Plum pudding model atom

18
Q

Oil drop experiment, Millikan:

A

DISCOVERED charge of an electron

19
Q

Alpha-ray scattering, Rutherford

A

DISCOVERED nucleus in atoms (disprove plum pudding)

Nucleus has protons & neutrons (which are much much heavier than electrons) → nucleus accounts for most of an atom’s mass but very little of its size

20
Q

Rutherford’s model of atom:
- 3 main points
- limitations

A
  • All + charge & mass concentrated inside nucleus (tiny region)
  • Negatively charged particles revolve around nucleus in circular path
  • Electrostatic force attraction between proton & electrons holds atom together

LIMITATIONS: failed to explain
- Stability of an atom
- Electronic structure of atom (how electrons arranged inside nucleus)

21
Q

Atomic number (Z):

A

protons in nucleus (found in periodic table)

Neutral atom: electrons = protons = Z

22
Q

Mass number (A):

A

protons + neutrons

23
Q

Nuclear symbol:

A

represents nucleus of an isotope

Atomic number (Z): protons
Mass number (A): protons + neutrons

24
Q

Empirical formula:

A

molecular formula expressed in lowest whole number ratio

25
Q

Mole:

A

number of atoms/molecules in a bulk sample of matter

26
Q

Avogadro’s number

A

Number of particles per mole

27
Q

Isotopes:

A

atoms with same atomic number (Z) but different mass number (A)

carbon 12, 13, 14

28
Q

Percent abundance of isotope

A
29
Q

Atomics mass:

A

weighted average of isotopic masses (mass spectroscopy)

30
Q

Electromagnetic (EM) radiation:

A

oscillating electric & magnetic field perpendicular to each other & direction propagation → quantized (units: photons)

31
Q

Wavelength (λ):

A

distance between 2 consecutive peaks/troughs

[m, nm]

32
Q

Frequency (v)

A

cycles pass through given point / second

[Hz = 1/sec]

33
Q

Amplitude

A

height of peak, corresponds to brightness/intensity

34
Q

All types of EM radiation travel at what speed?

A

Speed of light

3 x 10^8 m/s

35
Q

Electromagnetic spectrum:

A

microwave → infrared → visible → ultraviolet → x-ray → gamma ray

36
Q

Wavelength range of visible light:

A

(LOW frequency) ROYGBIV (HIGH frequency)

37
Q

Photoelectric effect:

A

light wave is particulate in nature, consisting of small packets of energy called photon

CORRECT
- Electrons ejected from metal when light has frequency greater than threshold (>0)
- Energy proportional to number of photons

38
Q

Wave theory (classical physics):

A

WRONG

  • Energy light should correspond to intensity, nothing to do with frequency
  • Kinetic energy of electron shouldn’t change with frequency, change with intensity of EM radiation:
  • KE electrons should increase linearly with intensity of light
  • # electrons should be independent of intensity & brightness incident light
39
Q

Photoelectric effect: threshold frequency (v0)

A

min frequency of light needed to eject electron

40
Q

Continuous vs discontinous spectrum

A

Continuous spectrum: contains all wavelengths of visible light

Discontinuous spectrum: missing/discontinuous wavelength (line spectra)

41
Q

Line spectra vs absorption spectra

A

Line spectra (emission): atoms release energy

Absorption spectrum: atoms absorb energy

42
Q

Bohr’s model of atom:

A

combines classic & quantum physics:

  • Stationary states: electrons move around nucleus in ORBITS
  • Quantization of angular momentum: electron revolves around nucleus only in specific orbits in which angular momentum of electron is an integral multiple of h/2π
  • Energy levels: unequal spacing (radius decreases by n^2), closer electron is to nucleus = smaller energy
  • When electrons jump lower → high orbit (absorbs energy), higher → lower (emit energy)

Tufts - Ch (2 decks)

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