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Chemistry ATAR U1 > Materials & Atoms > Flashcards

Materials & Atoms Flashcards

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1
Q

What are materials

A

Substances used to make objects

Eg. Wood, Paper, Nylon

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2
Q

What are Properties of Materials

A

Melting Point: Temperature to change state to liquid

Boiling Point: Temperature to change state to gas

Reactivity: Tendency of substance to undergo chemical reactions

Hardness: Ability of material to resist deformation from force

Density: Measure of materials mass per volume

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3
Q

What are Pure Substances

A

Made up of one type of substance

Cannot be physically separated

Uniform & Definite composition throughout substance

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4
Q

What are Elements

A

Made up of one type of atom

Cannot be separated by chemical processes into simpler substances

Eg. Carbon (C), Gold (Au), Silver (Ag)

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5
Q

What are Compounds

A

Two or more atoms chemically combined

Formula indicates number of atoms of each element in compound

Name and formula depend on bonding type

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6
Q

What are Mixtures

A

Two or more substances physically mixed, can be separated

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7
Q

What are Homogenous Mixtures

A

Same proportions of components throughout mixture

Eg. Solution

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8
Q

What are Heterogenous Mixtures

A

Composition not uniform throughout mixture

Eg. Vegetable Soup

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9
Q

What are Properties of Metals

A

High tensile strength, ductility, malleability, shiny lustre, high melting points, thermal & electrical conductivity

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10
Q

What are Alloys

A

Mixture with other metals, or small amounts of non-metals

Refine physical properties of metal

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11
Q

What are Properties of Polymers

A

Low density, corrosion resistant, electrical insulators, biological polymers have good compatibility with human tissue

Molecular structure of repeating smaller units bonded together

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12
Q

What are Properties of Ceramics

A

Hard, high compressive strength, withstand high temperatures

Metal, non-metal, metalloid elements held together by ionic & covalent bonds

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13
Q

What are Properties of Composites

A

Combination of two or more distinct metals, with different physical & chemical properties

Resultant material has range of properties

Eg. Reinforced concrete, steel bars counter low tensile strength of concrete

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14
Q

What is Filtration

A

Separate insoluble solids from liquid or gas

Depends on components of mixture having different solubilities

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15
Q

What Properties Does Filtration Use to Separate

A

Particle Size, Solubility

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16
Q

What is gravitational filtration

A

Uses weight of mixture to push through filter paper

Paper catches larger particles, smaller particles pass through

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17
Q

What is sieving

A

Mesh screen, allows smaller materials through, leaving larger particles

Eg. Flour sieve

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18
Q

What is decantation

A

Pour liquid from one container to another, leaving sediment behind

Difficult for complete separation

Eg. Pouring clean water from muddy water

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19
Q

What properties does decantation use

A

Insolubility, Density

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20
Q

What is centrifugation

A

Spins mixture rapidly, separates finer particles

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21
Q

What is solvent extraction

A

Two unmixable liquids shaken to disperse one in the other

  • Solutes migrate from one solvent to other

Requires separation funnel to drain solution separately

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22
Q

What properties does centrifugation use

A

Density

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23
Q

What properties does solvent extraction use

A

Density

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24
Q

What is crystallisation

A

Solvent boiled off, recovering solute (Was dissolved)

Water lost to atmosphere

Faster the liquid boiled = Smaller crystals

Eg. Evaporating sea water for sea salt

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25
Q

What properties does crystallisation use

A

Boiling Point

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26
Q

What is distillation

A

Solvent boiled off, recovering solute (Was dissolved)

Vapor collected & cooled, pure liquid (Distillate)

Example: Perfume

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27
Q

What properties does distillation use

A

Boiling point

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28
Q

What is fractional distillation

A

Separate mixable liquids with similar boiling points

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29
Q

What is chromatography

A

Substances in mixture are dissolved in solvent, travel with solvent through medium

  • Different solutes chemically attracted to medium by varying amounts
  • Move at different sppeds through medium
  • Each component moves different amount over time period
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30
Q

What properties does chromatography use

A

Adsorption, Solubility

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31
Q

What is gas chromatography

A

Separates organic mixtures

Separated components pass out at different times, detected in ionisation chamber

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32
Q

What did John Dalton do

A

Revised concept of atoms

Based theory on others’ experimental data

In chemical reactions, atoms are rearranged not changed

Atoms of different elements combine in simple proportions to make compounds

Made billiard ball model
- Each element is uniform, indivisible, solid sphere (Atom)

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33
Q

What did JJ Thomson do

A

Discovered electrons
- Mass smaller than hydrogen, is negative particles within atoms

Did Cathode Ray Tube experiment:
- Shined a beam of negative particles (Beta), which bent towards positive plate
- Proposed atoms must have positive particles to cancel negative

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34
Q

What did Ernest Rutherford do

A

Discovered nucleus
- Dense, positive charge in center
- Majority of mass
- Tiny

Did Gold Foil experiment
- Hit positive alpha ray into thin gold foil

  • Some rays bounced back, means atoms have positive part
  • Majority of atoms went through = Empty space

Made Nuclear Model:
- Dense, positive nucleus, surrounded by negative electrons

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35
Q

What did Niels Bohr do

A

Discovered energy levels:
- Electrons exist in specific energy levels
- Make up electron shells

Did Bright-Line Spectrum experiment
- Where there was presence of specific colours in Hydrogen’s emission spectrum

  • Each line was a different energy level

Made Planetary Model:
- Electrons in circular orbits, in electron shells

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36
Q

What did James Chadwick do

A

Discovered neutrons:
- Z, A values didn’t match
- Bombarded neutrons into Nitrogen gas, found the mass
- Found neutrons were from nucleus

STILL NEED TO FINISH

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37
Q

What is the structure of an atom

A

Cloud of negatively charged electrons, which is most of the volume

Nucleus, which holds protons & neutrons

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38
Q

What are the three subatomic particles, their charge, and relative mass

A

Neutron, neutral, 1
Proton, positive, 1
Electron, negative, 1/1836

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39
Q

What is the nucleus

A

Protons & neutrons, held together by nuclear force

Positive charge in center of atom

99.9% mass, is 100,000x smaller then whole atom, dense

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40
Q

How is the nucleus held together

A

Electrostatic forces push protons away from each other

Nuclear force attracts nucleons together, regardless of charge (Only a short distance)

To be stable, there needs to be a balance of the two forces

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41
Q

What is the electron cloud

A

Where the electrons move, large space

Negatively charged, move around nucleus by electrostatic forces

Each shell holds fixed number of electrons (Eg. 2,8,8,2)

42
Q

What is atomic number

A

Atom identity determined by number of Protons in nucleus

Neutral atom, number of protons = number of neuytrons

Periodic table, elements sorted by atomic number

43
Q

What is mass number

A

Mass Number = n(Protons) + n(Neutrons)

Lighter atoms, number of protons = number of neutrons

Heavier atoms, more neutrons than protons

44
Q

What are isotopes

A

Same atomic number, different number of neutrons

45
Q

What are the properties of isotopes compared to other isotopes

A

Same chemical properties (Eg. Same number of electrons)

Different physical properties (Eg. Density, Boiling Point), due to different mass

Larger isotopes have unstable nucleus, therefore radioactive

46
Q

What is the nuclear notation for isotopes

A

AZX

A = mass number
Z = atomic number
X = chemical symbol

47
Q

What is mass spectrometry

A

Determines abundancy of each isotope in element

48
Q

What are the steps in mass spectrometry

A

Vaporisation
Ionisation
Acceleration
Deflection
Detection

49
Q

What is vaporisation in mass spectrometry

A

Where a sample is heated to a gas

50
Q

What is ionisation in mass spectrometry

A

Electron gun hits atom/molecule, removes some electrons, cation forms

51
Q

What is acceleration in mass spectrometry

A

Where the atoms are accelerated by negatively charged plates

52
Q

What is deflection in mass spectrometry

A

Ions deflected by magnetic field, greater mass : charge ratio deflected more

Lighter mass = Deflected more, higher charge = Deflected more (Mass : Charge)

53
Q

What is detection in mass spectrometry

A

Particular mass : charge, detected by device, counts number of ions (Abundancy)

Records proportions of each isotope

54
Q

Why does mass spectrometry happen under vacuum

A

Ions have free run through machine without hitting air molecules

If hit air molecules, alter pathway of some ions, could go undetected, giving inaccurate result

55
Q

What is relative atomic mass

A

Mass of an atom, compared to (1/12) the mass of a Carbon-12 atom

Unitless

56
Q

What is the formula for relative atomic mass

A

Ar = ( (% abundance of isotope a) * Ar(a) + (% abundance of isotope b) * Ar(B) ) / 100

57
Q

How are the electrons in the bohr model of an atom

A

Orbit the nucleus in fixed, circular orbits

Orbits correspond to fixed energy levels / shells

Large the radii, higher the energy

Cannot exist between energy levels

58
Q

What is the outermost electron shell in an atom

A

Valence shell

Electrons in valence shell = Valence electrons

  • Involved in chemical reactions

Atoms with full valence shell = Very stable (Octet Rule)

Is possible to move between shells, by absorbing / emitting energy

59
Q

What is electron configuration

A

Number of electrons in each shell, separated by a comma

Starts with lowest energy shell

60
Q

What is atomic radii

A

Distance between adjacent atomic nuclei, divided by 2

Is the radius of an atom

61
Q

What are the patterns of atomic radii

A

Atomic radii increasing as it goes to left of periodic table

Atomic radii increasing as it goes down periodic table

62
Q

What are the two principles to explain the trend in atomic radii

A

Principal Quantum Number

Effective Nuclear Charge

63
Q

What is principal quantum number

A

Number of electron shells

64
Q

What is effective nuclear charge

A

Net charge experienced by valence electrons towards nucleus

More shells = Less electrostatic attraction to nucleus than core electrons (Electrons closer to nucleus)

Zeff = Atomic Number - (# of core electrons)

65
Q

What is the trend down a group in periodic table of atomic radii

A

More electron shells down a group = Increasing atomic radii

66
Q

What is the trend across a period in periodic table of atomic radii

A

More protons in nucleus, means more pull on valence electrons towards nucleus, decreasing atomic radii

67
Q

What are ions

A

Where n(Protons) doesn’t equal n(Electrons)

Atoms lose/gain electrons in chemical reactions, to have full outer shell

Lose electrons = Cation (Positive)

Gain electrons = Anion (Negative)

When lose/gained, written as power, followed by charge

68
Q

What is quantisation of energy

A

Where every energy level / shell is quantised

Cannot exist between energy levels

Can move between energy levels by absorbing / emitting electromagnetic radiation

69
Q

What is an electron in ground state

A

Lowest energy state, in first shell

70
Q

What is an electron in excited state

A

Atom absorbed electromagnetic radiation, moved to higher energy level

Unstable, exists for short amount of time, then back to ground state, releasing electromagnetic radiation

71
Q

What is electromagnetic radiation

A

Visible light on electromagnetic spectrum

Described with frequency, wavelength, energy

Observed through emission spectra / absorption spectra

72
Q

What is absorption spectra

A

Electron excited through electromagnetic radiation
- Jumps to higher energy level

Atoms only absorb certain colours = Absorption lines
- All absorbed lines on full spectrum = Absorption spectrum

73
Q

What is emission spectra

A

Excited electron returns to lower energy level shortly after through various possible transitions

  • Photon / light emitted, energy equal to amount initially absorbed
  • Different jumps between energy levels produce different colours

Individual colours of light emitted = Emission lines

  • All emission lines = Emission spectrum
74
Q

How is emission spectrum different to every atom

A

Different number of electrons, different number of electron shells

Photon emitted energy equal to difference in energy between levels

Therefore photons emitted unique to each element (Characteristic)

75
Q

What is spectroscopy

A

Study of interaction between matter and electromagnetic radiation

76
Q

What is flame test

A

Determines metallic elements in compound

Shown by emission spectrum

77
Q

What is process for flame test

A

Sample heated, electrons in metal atom excited, moves to higher energy level

  • Returns ground state shortly after, releases photons unique to element
  • Causes flame to change colour
78
Q

What is atomic absorption spectrum

A

Finds amount of element in a substance

79
Q

What is process for atomic absorption spectrum

A

Lamp made out of element being tested for

Substance vaporised in flame to produce free atoms (Gaseous element)

Light shined through sample from lamp, element being tested for absorbs light, electrons in it become excited state

The light is focused through a slit, which enters monochromator that separates wavelengths

1 wavelength is analysed, where intensity is measured to see amount of light not absorbed = Absorbance value

80
Q

What is Beer’s Law

A

Linear relationship between absorbance value & concentration

Used to determine concentration of element

81
Q

What is ionisation energy

A

Energy (Joules) required for complete removal of 1 mole of electrons from 1 mole of gaseous atom/ion

  • Knocks out most weakly held electron (Valence electron)
82
Q

What is pattern of ionisation energy down a group

A

Decreases down a group

  • Shells increase down group, so valence electrons further from nucleus, decreasing attraction
  • Easier to remove electrons
83
Q

What is pattern of ionisation energy across a period

A

Increases across a period

  • Valence electrons pulled closer, as there are more protons, so atom more positively charged
  • Harder to remove electrons
84
Q

What is the explanation of trend of ionisation energy

A

Related to atomic radii (Opposite)

Energy used to remove electron, must overcome attraction to nucleus, related to atomic radius

Uses same two principles

1) Principal Quantum Number (n)

2) Effective Nuclear Charge (Zeff)

85
Q

What is successive ionisation energies

A

Removing more moles of electrons after 1st one

Requires more energy, removing negative electron from positive cation

Massive jump in energy for next shell, as it’s closer to nucleus

86
Q

What is electronegativity

A

Relative scale of ability of atom to attract shared electrons in covalent bond (Unitless, baseline hydrogen)

More electronegative = Stronger pull of shared electrons

87
Q

What is pattern of electronegativity down a group

A

Decreases down a group

  • Effective nuclear charge lower
  • Tendency to attract electrons decreases, decreasing electronegativity
88
Q

What is pattern of electronegativity across a period

A

Increases across a period,

  • Effective nuclear charge higher
  • Tendency to attract electrons increases, increasing electronegativity
89
Q

What is explanation of trend of electronegativity

A

Inversely related to its size

If its tendency to attract electrons is larger, then it would attract the shared electrons more

90
Q

What is periodic table

A

Arrangement of elements by atomic number

91
Q

What is the rows in periodc table

A

Periods

Same row = Same number of shells

Valence electrons increase left to right

92
Q

What are the columns in periodic table

A

Groups

Same valence electrons

Electron shells increase down a group

Similar chemical properties

93
Q

Why are neutrons last to be discovered

A

As they have no charge, so they couldn’t use the same method they used to discover protons & neutrons

94
Q

Why does each element have unique absorption/emission spectrum

A

Different atoms have different number of Protons, and different electron arrangement, so need different amounts of energy for the atom’s electrons to move between energy levels.

Different wavelengths have different amounts of Energy, therefore have different absorption spectras.

95
Q

What are properties of alkali metals

A

Solft, silvery colored metals

Very reactive

96
Q

What are properties of alkaline earth metals

A

Silvery-White metals

Fairly reactive

97
Q

What are properties of transition metals

A

Most good conductors of electricity

Malleable (Easily bent/hammered into wires/sheets)

98
Q

What are properties of metalloids

A

Share properties with metals & non-metals

99
Q

What are properties of non-metals

A

Brittle

Don’t conduct electricity

100
Q

What are properties of halogens

A

Fairly reactive

Salt-Forming

101
Q

What are properties of noble gases

A

Unreactive

Gases at room temperature

Exist in Earth’s atmosphere

Chemistry ATAR U1 (5 decks)

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