C3 - Atoms, elements and compounds Flashcards

1
Q

Element

A

A pure substance made of only one kind of atom (e.g. He)

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2
Q

Atom

A

The basic unit of a chemical element (e.g. O2)

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3
Q

Compound

A

A substance made up of atoms of two or more different elements joined by chemical bonds (e.g. NH3 - ammonia)

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4
Q

Molecule

A

A group of atoms bonded together (can be of a single type of element, or of multiple types)

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5
Q

Mixture

A

A combination of two or more substances that are not chemically combined

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6
Q

Physical changes

A

A type of change that alters the physical properties of a substance but does not change its composition
- no movement of atoms
- change in form or appearance that can be undone

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7
Q

Chemical changes

A

Changes that alter the composition of matter
- movement of atoms
- formation of new substances that cannot be undone

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8
Q

Properties of chemical changes (name 3)

A
  • gas produced (no addition of heat)
  • change in composition
  • change in temperature (without heat)
  • cloudiness
  • change of colour (without heat)
  • formation of solid
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9
Q

Properties of physical changes (name 3)

A
  • same composition
  • change in temperature only when manually heated
  • change in colour only when manually heater or cooled
  • gas produced when heated manually to boiling point
  • solid formed when frozen
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10
Q

Sublimation

A

solid to gas

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11
Q

Deposition

A

gas to solid

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12
Q

Boiling

A

liquid to gas

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13
Q

Condensation

A

gas to liquid

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14
Q

Melting

A

solid to liquid

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15
Q

Freezing

A

liquid to solid

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16
Q

Solvent

A

A liquid substance capable of dissolving other substances
- in which the solute dissolves
- in the highest proportion in solution

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17
Q

Solute

A

The substance that is dissolved within a solvent
- found in lower concentration in solution

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18
Q

Solution

A

A homogeneous mixture of two or more substances (solvent, solute)

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19
Q

Proton

A

A subatomic particle found within the nucleus of an atom
- CHARGE: positive
- RELATIVE ATOMIC MASS: 1

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20
Q

Electron

A

Subatomic particles distributed along the shells of an atom
- CHARGE: -1
- RELATIVE ATOMIC MASS: 0.0005 / 0

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21
Q

Neutron

A

A subatomic particle found in the nucleus of an atom
- CHARGE: neutral/0
- RELATIVE ATOMIC MASS: 1

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22
Q

Reading the periodic table (periods, groups, proton number, atomic mass)

A

Periods: show the number of shells of a single atom of that type of element
Groups: show the number of electrons on the outer shell of an atom of that element
- proton number/atomic number: the number of protons and the number of electrons (same amount)
- atomic mass: protons + neutrons

23
Q

Isotopes

A

Atoms of the same element that have different numbers of neutrons
- with the same properties because they have the same number of electrons

24
Q

Types of hydrogen isotopes

A
  • protium (1P, 0N)
    • used in hydrogen fuel cells and the production of plastics
  • deuterium (1P, 1N)
    • used in nuclear fusion
  • tritium (1P, 2N)
    • used in thermonuclear fusion weapons
25
Q

Nuclide

A

A type of isotope
- refers to a specific nucleus that contains a certain number of protons and neutrons

26
Q

Metals (properties in terms of atoms)

A

Found on the left side of the periodic table (few electrons on their outer shells)
- when they react they lose one or more electrons from their outer shell
- they form positively charged ions (cations)

27
Q

Non-metals (properties in terms of atoms)

A

Found on the right side of the periodic table
- when they react they gain one or more electrons onto their outer shell OR they share electrons
- they gain to form negatively charged ions (anions) OR they share to form neutral molecules

28
Q

Properties of metals (3)

A
  • high melting and boiling points
  • good conductors of heat and electricity
  • they are all solid (except mercury)
29
Q

Properties of non-metals (3)

A
  • lower melting and boiling points
  • often found as gases
  • generally do not conduct heat or electricity
30
Q

Metal alloys

A

a mixture of the metals and other materials
- change a metal’s properties

31
Q

Aluminium (uses)

A
  • a metal alloy
  • low density makes it suitable for use in manufacturing aircrafts
  • other uses: armour plating for military vehicles
32
Q

Steel (types and uses)

A

Alloys of iron that contain carbon and other elements
- high carbon steels: strong but brittle
- uses: making cutting tools and blades
- low carbon steels: soft but malleable
- uses: making car bodies
- stainless steel (contain chromium and nickel): strong and resistant to corrosion
- uses: cooking utensils and cutlery

33
Q

Bronze (uses)

A
  • an alloy of copper and tin
  • adding tin increases the hardness of the material
  • uses: making coins, electric hardware and statues
34
Q

Brass (uses)

A
  • alloy of copper and zinc
  • adding zinc makes the material more malleable
  • uses: door fitting and water taps
35
Q

Gold (uses)

A
  • pure gold is soft so jewellers will add other metals like silver, zinc and copper to produce a more resilient substance
  • carats provide a measure for the purity of an alloy of gold
  • 24 carats = 100%
36
Q

Ion

A

An electrically charged atom or group of atoms formed by the loss or gain of one or more electrons

37
Q

Ionic bond

A

A chemical bond resulting from the attraction between oppositely charged ions
- found in compounds made between a non-metal and a metal atom

38
Q

Ionic compound

A

Composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal

39
Q

Metallic bonds

A

An attraction between positively charged ions and negatively charged, delocalised electrons
- made between at least two metal atoms

40
Q

Covalent bonds

A

Bonds created by sharing electrons with other atoms
- made between two non-metal atoms
- found in most non-metal elements and compounds of non-metals

41
Q

Properties of ionic compounds (name 3)

A
  • high melting and boiling points due to many strong bonds between the ions which takes a lot of energy to overcome
  • when they are solids they cannot conduct electricity because the ions are held in place
  • when they are liquid or dissolved in water they can conduct electricity because the ions are free to move
  • they dissolve in water easily
42
Q

Small covalent molecules

A
  • have weak intermolecular forces meaning they have low melting and boiling points
  • often liquids or gases at room temperature
  • don’t contain delocalised electrons and so cannot conduct electricity
  • e.g. chlorine
43
Q

Bigger covalent molecules

A
  • bigger molecules attract other molecules with stronger intermolecular forces meaning they have higher melting and boiling points than small molecules
  • don’t contain delocalised electrons and so can’t conduct electricity
  • e.g. sucrose
44
Q

Macromolecules

A

A very large organic molecule composed of many smaller molecules

45
Q

Properties of giant covalent structures (name 3)

A
  • no specific formula because the structure can be any size
  • very high melting points and boiling points because high temperature and a lot of energy is needed to break covalent bonds
  • bonds make them solid at room temperature
  • have no intermolecular forces because they are just one large molecule
  • strength of bonds: strong
  • do not conduct electricity
46
Q

Diamond

A
  • an allotrope of carbon each carbon atom is bonded to 4 other carbon atoms by strong covalent bonds
  • creates a giant covalent structure
47
Q

Properties of diamond (name 3)

A
  • does not conduct electricity because of no delocalised electrons
  • insoluble in water
  • high melting point because of strong bonds
  • hard because of strong bonds
  • can be used as a cutting tool for other materials
  • lustrous (shiny)
48
Q

Graphite

A
  • an allotrope of carbon in which each carbon atom forms 3 bonds
  • 1 electron from each carbon atom is delocalised
  • carbon atoms form layers of hexagonal rings with each layer held together by weak intermolecular forces
49
Q

Properties of graphite (name 3)

A
  • conducts electricity because of delocalised electrons
  • soft since hexagonal layers can slide over one another easily
  • makes it useful as a lubricant and as pencil lead
  • lustrous
  • opaque
  • slippery
  • high-melting point
  • soluble in water
50
Q

Uses of diamond (name 3)

A
  • jewelery making
  • construction (saw blades, drill bits etc.)
  • minor industrial applications
  • surgeries
51
Q

Uses of graphite (name 3)

A
  • stationary
  • lubricants
  • nuclear reactors
  • industries
52
Q

Silicon (IV) dioxide

A
  • tetrahedral macromolecular structure
  • each silica atom is covalently bonded to 4 oxygen atoms and each oxygen atom is covalently bonded to 2 silica atoms
  • the formula is SiO2
  • each oxygen atom has two non-bonded (lone) electron pairs
  • localised; cannot move freely
  • there are no delocalised electrons
53
Q

Properties of silicon dioxide (name 3)

A
  • cannot conduct electricity
  • rigid and hard
  • high melting and boiling point
  • is a semi-conductor