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Chemistry > 1) Principles of chemistry > Flashcards

1) Principles of chemistry Flashcards

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1
Q

Three states of matter

A

-solids
-liquids
-gases

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2
Q

Solid characteristics

A

-very close together
-regular pattern
-vibrate around a fixed point
-low energy

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3
Q

Liquid characteristics

A

-particles are close
-randomly arranged
-move around each other
-higher energy

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4
Q

Gas characteristics

A

-widely spaced
-randomly arranged
-move quickly in all directions
-highest energy

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5
Q

Interconversions between states of matter - heating up

A

Solid –melting–> liquid –boiling/evaporation–> gas
solid –sublimation–> gas

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6
Q

Interconversions between states of matter - cooling down

A

gas –condensing–> liquid –freezing–> solid
gas –deposition–> solid

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7
Q

Boiling vs evaporation

A

-at boiling point - all particles have enough energy
-at lower temperature - only surface particles have enough energy

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8
Q

Practical: dilution of coloured solutions

A
  1. When potassium manganate (VII) crystals are dissolved in water, a purple solution is formed
  2. A small number of crystals produce a highly intense colour
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9
Q

Dissolving potassium manganate (VII) explanation

A

Water and dye are moving randomly and particles can slide over each other
-particles can easily mix together
-diffusion in liquids is slower than in gases because the particles in a liquid are closely packed together and move more slowly

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10
Q

Practical: diffusion of gases

A

-When ammonium gas and hydrogen chloride gas mix, they react together to form a white solid - ammonium chloride
1. A cotton wool pad was soaked in ammonia solution and another in hydrogen chloride solution
2. Two pads put into opposite ends of a dry glass tube at the same time

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11
Q

Diffusion of ammonia gas and hydrogen chloride - explanation

A

-ring of ammonium chloride forms close to the hydrochloric acid end because ammonia particles are lighter than hydrogen chloride particles and therefore travel faster
-particles move in random directions and will collide with air particles in the tube

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12
Q

Solvent definition

A

The liquid in which a solute dissolves

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13
Q

Solute definition

A

The substance which dissolves in a liquid to form a solution

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14
Q

Solution definition

A

The mixture formed when a solute is dissolved in a solvent

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15
Q

Saturated solution definition

A

A solution with the maximum concentration of solute dissolved in the solvent

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16
Q

Soluble definition

A

Describes a substance that will dissolve

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17
Q

Insoluble definition

A

Describes a substance that won’t dissolve

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18
Q

Solubility definition

A

A measurement of how much a substance will dissolve in a given volume of a liquid
-g of solute per 100g of solvent

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19
Q

Solubility of gases - temperature and pressure

A

Pressure increases, gases become more soluble
Temperature increases, gases become less soluble

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20
Q

Solubility curves

A

Solubility (g of solute per 100g) - y-axis
Temperature - x-axis

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21
Q

Practical: Investigate the Solubility of a Solid in Water at a Specific Temperature

A
  1. Pour deionised water into a 250 cm3 beaker
  2. Use a water bath to heat to desired temperature
  3. Add known masses of the solid bit by bit until solution is saturated
  4. Record the mass of solid that was soluble.
  5. Repeat steps 1-4 with the water at different temperatures
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22
Q

Element definition

A

A substance made up of atoms that all contains the same number of protons and cannot be split into anything simpler

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23
Q

Compound definition

A

A substance formed when two or more elements are chemically bonded together. Cannot be separated by physical means

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24
Q

Mixture definition

A

Two or more substances that are not chemically bonded together. Can be separated by physical means

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25
Q

Pure substance - cooling curve

A

-horizontal line where the compound has a sharp melting point
-is a pure substance as they melt and boil at specific and sharp temperatures

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26
Q

Impure substance - cooling curve

A

-produce a gradual decrease in temperature
-mixtures have a range of melting and boiling points as they consist of different substances that tend to lower the melting point and broaden the melting point range

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27
Q

Different separation techniques

A

-simple distillation
-fractional distillation
-filtration
-crystallisation
-paper chromatography

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28
Q

Simple distillation

A

-used to separate a liquid and soluble solid from a solution or a pure liquid from a mixture of liquids
1. The solution is heated, and pure water evaporates producing a vapour
2. The vapour passes through the condenser, where it cools and condenses, turning into the pure liquid that is collected in a beaker
3. After all the water is evaporated from the solution, only the solid solute will be left behind

29
Q

Fractional distillation

A

-Used to separate a mixture of different liquids that have different (but very similar) boiling points
1. The solution is heated to the temperature of the substance with the lowest boiling point
2. This substance will rise and evaporate first, and vapours will pass through a condenser, where they cool and condense, turning into a liquid that will be collected in a beaker
3. All of the substance is evaporated and collected, leaving behind the other components(s) of the mixture

30
Q

Fractional distillation - fractionating column

A

-fractionating column is full of little glass rod - large surface area
-evaporating substance comes into contact with glass rods, which are cooler than their boiling point
-condense back into liquid form and fall back into the flash
-only pure methanol falls into the beaker

31
Q

Filtration

A

Used to separate an undissolved solid from a solution
1. filter paper funnel above a beaker
2. A mixture poured
3. The filter paper allow small liquid particles to pass through
4. Solid particles are too large to pass stay behind as a residue

32
Q

Crystallisation

A

Separate dissolved solid from a solution, when solid is much more soluble in hot solvent than cold
1. Heat solution, evaporate solvent, leave saturated solution behind
2. Test if saturated: dip clean, dry, cold glass rod into solution, crystals will form on the glass rod
3. cool solution slowly
4. Crystals begin to grow as solids will come out of solution due to decreasing solubility
6. filtering the solution, washed, dry

33
Q

Paper chromatography

A

Technique is used to separate substances that have different solubilities in a given solvent
1. Take a piece of filter paper and use a pencil to draw a line at the bottom of the sheet - baseline
2. Add sample of ink to the pencil line
3. Add a shallow amount of solvent to a beaker
4. Put filter paper inside
5. Wait for solvent to seep up the paper. Different dyes in inks will dissolve in the solvent and move up in it
-different substances separate out

34
Q

Calculate Rf value

A

Reference value - always the same value of a compound but dependent on the solvent used
-allows chemists to identify unknown substances by comparing Rf values of known substances under the same conditions
-between 0-1 - close to 1 - more soluble
distance travelled by substance/ distance travelled by solvent

35
Q

Atom definition

A

Smallest particles of an element that consists of electrons surrounding a nucleus that contains protons and neutrons

36
Q

Molecule definition

A

A group of two or more atoms chemically bonded together

37
Q

Structure of the atom

A

-consists of a central nucleus
-composed of protons and neutrons
-surrounded by electrons
-atoms are neutral as the number of electrons and protons are equal

38
Q

Proton - mass and charge

A

Mass: 1
Change: +1

39
Q

Neutron - mass and charge

A

Mass: 1
Change: 0

40
Q

Electron - mass and charge

A

Mass: negligible (1/1836)
Charge: -1

41
Q

Atomic number definition

A

The number of protons in the nucleus of an atom

42
Q

Mass number definition

A

The sum of the number of protons and neutrons in the nucleus of an atom

43
Q

Isotopes definition

A

Atoms of the same element that contain the same number of protons and electrons but a different number of neutrons
-same atomic number but different mass number

44
Q

Relative atomic mass definition (Ar)

A

Weighted average mass of the isotopes of an element relative to the mass of 1/12th of a carbon-12 atom

45
Q

Calculate relative atomic mass

A

[(% of isotope A x mass of isotope A) + (% of isotope B x mass of isotope B)]/ 100

46
Q

Periodic table - periods

A

Horizontal rows that show the number of shells of electrons an atom has and are numbered from 1-7

47
Q

Periodic table - groups

A

Vertical columns that show how many outer electrons each atom has and are numbered from 1-7
-final group is called group 0 - noble gases - full outer shell

48
Q

Electron configuration

A

-electrons orbit the nucleus in shells
-further away from the nucleus, more energy a shell has
-first shell: 2 electrons
-second, third shell: 8 electrons each
-outmost shell: valence shell
–an atom is much more stable if the outer shell is full
–if shell is not full, atoms react with other atoms to achieve a full outer shell of electrons or lose electrons to empty the shell

49
Q

Metal vs nonmetal - conductivity

A

Metal - good conductors of electricity
Nonmetal - poor conductors of electricity

50
Q

Metal vs nonmetal - acid-base character of oxides

A

Metal - oxides that are basic - react with acids to give salt and water
Nonmetal - have oxides which are acidic or neutral

51
Q

Identify a metal/ non metal on the periodic table

A

-search up periodic table

52
Q

Elements with similar chemical properties

A

-same group in the periodic table
-as they have the same number of outer electrons so will react and bond similarly

53
Q

Noble gases

A

-elements in group 0
-have full outer shells - extremely stable
-unreactive and inert

54
Q

Noble gas characteristics

A

-all non-metal
-monatomic (exist as single atoms)
-colourless
-non flammable gases at room temperature

55
Q

Ionic equations

A

-in aqueous solutions, ionic compounds dissociate into their ions
-separate into component ions that formed them
-e.g. HCl (aq) → H+ (aq) + Cl-(aq)

56
Q

Relative formula mass (Mr)

A

Mass of a molecule or compound
-calculated by adding up the relative atomic masses (Ar) of all the atoms present in the formula
-molar mass

57
Q

Calculating percentage by mass of an element in a compound

A

[(Ar x number of atoms of the element) / Mr of the compound] x 100

58
Q

Mole definition

A

The unit for the amount of substance

59
Q

Avogadro constant

A

Number of atoms/ molecules/ ions in a mole of a given substance
-6.02 x 10^23 per mole
e.g. one mole of Na contains 6.02 x 10^23 atoms of sodium

60
Q

Moles - mass calculations

A

mass = mole x Mr

61
Q

Calculate reacting masses

A
  1. Write balanced equation
  2. Fill in mass you know and ? mass you need
  3. Write down Mr
  4. Calculate mol from mass/Mr
  5. Compare molar ratio from equation to find other moles
  6. Find mass
62
Q

Calculate percentage yield

A

(actual yield/ theoretical yield) x 100

63
Q

Empirical formula

A

Shows the simplest whole number ratio between atoms/ ions in a compound

64
Q

Molecular formula

A

Formula that shows the number and type of each atom in a molecule

65
Q

Calculate molecular formula from empirical formula

A
  1. Calculate relative mass of empirical formula
  2. Divide actual relative mass by mass above
  3. Equals how many times bigger the molecular formula is compared to the empirical formula
66
Q

Calculate empirical formula

A
  1. List the symbol for each element
  2. Write down the masses for each element
  3. Divide by their relative atomic mass
  4. Divide all numbers by the smallest of these numbers to get a ratio
  5. Should be 1:__
67
Q

Calculating concentrations of solutions

A

moles = concentration x volume (dm3)

68
Q

Avogadro’s law

A

At same conditions of temp and pressure, equal amounts of gases occupy the same volume of space
-one mole of gas is 24dm3
-molar gas volume at RTP (room temp and pressure - 20C and 1atm)

Chemistry (6 decks)

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