topic 2 - bonds, structures + properties of matter Flashcards
(42 cards)
1
Q
what are the three states of matter?
A
- solids
- liquids
- gases
2
Q
describe the arrangement of solids
A
- solids are extremely hard to compress
- this is because the particles in a solid are packed together in a regular pattern
- solids have a fixed shape and they cannot flow from place to place
- this is because, in a solid, the particles can vibrate but they cannot move from place to place
3
Q
describe the arrangement of liquids
A
- liquids are extremely hard to compress
- this is because the particles are close together with not many spaces between them
- unlike solids, liquids take the shape of their container and they flow from place to place -> particles in a liquid can move
4
Q
describe the arrangement of gases
A
- gases are extremely easy to compress
- this is because the particles in gases are widely spaced
- gases spread out and fill the space of their container
- that is because the particles in a gas move quickly and randomly
5
Q
why do elements react?
A
to achieve a full outer energy level
6
Q
what is an ion?
A
an atom with an overall charge
7
Q
what is ionic bonding?
A
- ionic bonding takes place in compounds formed from metals combined with non-metals
- the outer electrons are transferred from the metal atom to the non-metal atom
- ionic bonding produces ions which have the electronic structure of a noble gas
8
Q
how are ionic compounds held together?
A
- ionic compounds are held together in a giant lattice
- the electrostatic forces of attraction between positive and negative ions hold the structure together
-> these electrostatic forces are also known as ionic bonds
9
Q
what are giant ionic lattices?
A
- three-dimensional structures where positive ions are surrounded by negative ions
- giant ionic lattices have very strong forces of attraction between the positive and negative ions
- scientists call these electrostatic forces
10
Q
what are the properties of ionic compounds?
A
- ionic compounds have very high melting and boiling points
-> the strong electrostatic forces require a great deal of heat energy to break - ionic compounds cannot conduct electricity when they are solids
-> this is because the ions cannot move. they are locked in place by the strong electrostatic forces of attraction - ionic compounds can conduct electricity when they are melted or dissolved in water
-> the ions can now move and carry the charge
11
Q
what is a covalent bond?
A
- a covalent bond is a shared pair of electrons between two atoms
- this occurs between non-metals
12
Q
what are properties of small covalent bonds?
A
- small covalent molecules have low melting and boiling points
-> they are usually gases or liquids at room temperature - small covalent molecules do not conduct electricity
-> this is because the molecules do not have an overall electric charge
13
Q
why do small covalent molecules have low melting/boiling points?
A
- there are weak intermolecular forces between the molecules which do not require a lot of energy to break
14
Q
how do intermolecular forces change as the mass/size of the molecule increases?
A
- as the size of the molecule increases, the intermolecular forces increases
- this causes melting/boiling points to increase as well
15
Q
what are the properties of giant covalent molecules?
A
- giant covalent molecules are always solids at room temperature
- giant covalent molecules have millions of strong covalent bonds
- they always have high melting and boiling points
16
Q
why are diamonds made from?
A
diamonds are formed from the element carbon
- each carbon atom forms four strong covalent bonds
17
Q
why do diamonds have a high melting point?
A
- each carbon atom forms four strong covalent bonds
- diamonds have a huge number of covalent bonds and these have to be broken when the diamond is melted
18
Q
can diamonds conduct electricity?
A
- diamonds cannot conduct electricity
- this is because there are no free electrons to carry electrical charge
19
Q
what are the properties of graphite?
A
- graphite has a high melting and boiling point
- graphite is soft and slippery
- graphite is an excellent conductor of both electricity and heat
20
Q
how is graphite formed?
A
- graphite is formed from the element carbon
- each carbon atom forms three covalent bonds
- the carbon atoms form hexagonal rings
21
Q
why does graphite have a high melting point?
A
- because graphite has many strong covalent bonds, it takes a great deal of energy to break these so graphite has a high melting and boiling point
22
Q
why is graphite slippery?
A
- the hexagonal rings are in layers
- there are no covalent bonds between the layers so they can slide
- this makes graphite slippery
23
Q
why is graphite a good conductor of both electricity and heat?
A
- only 3 out of 4 of carbon’s four outer electrons are used in bonds, so each carbon atom has one electon that’s delocalised (free)
- delocalised electrons can move. This means they can conduct thermal energy and electricity
24
Q
what is graphene?
A
- graphene is a single layer of graphite
- graphene is one atom thick, making it a two-dimensional compound
25
what are properties of graphene?
- graphene is an excellent conductor of electricity because it has delocalised electrons
- graphene is extremely strong
26
what are fullerenes?
- fullerenes are molecules of carbon atoms with hollow shapes
27
how are fullerenes formed?
- fullerenes are mainly made up of hexagonal rings of carbon atoms
- however, fullerenes can also have rings of five or seven carbon atoms
28
what was the first fullerene to be discovered
- buckminsterfullerene was the first fullerene to be discovered
- its got the molecular formula C60 and forms a hollow sphere
29
what are uses of fullerenes?
- pharmaceutical delivery
- lubricants
- catalysts
30
what are carbon nanotubes?
- nanotubes are small carbon cylinders which are formed by fullerenes
31
what are properties of carbon nanotubes?
- carbon nanotubes have high tensile strength (can be stretched without breaking)
- carbon nanotubes are excellent conductors of heat and electricity
32
what are uses of nanotubes?
- nanotubes can be used in electronics or to strengthen materials without adding much weight, such as in tennis racket frames
32
what is a molecule?
a group of atoms chemically bonded together
33
what is a polymer?
millions of small molecules joined together in a chain to form a large molecule
34
what is a single molecule called?
a monomer - monomers are often alkene molecules e.g. ethene
35
what are properties of polymers?
- most polymers are solids at room temperature
- the intermolecular forces of attraction between polymer molecules are relatively strong
36
describe the structure of metals
- metals consist of a giant structure of atoms arranged in regular layers
- in a metal, the electrons in the outer shell of each atom are delocalised
- there is a strong electrostatic attraction between the sea of delocalised negative electrons and the positive metal ions
- scientists call the electrostatic attractions in metals a metallic bond and metallic bonds are strong
37
what are the properties of metals?
- metals have got high melting and boiling points because a great deal of energy is required to break the strong metallic bonds
- metals are excellent conductors of heat and electricity
- metals are malleable
38
how do metals conduct heat?
- metals are excellent conductors of heat and electricity because the delocalised electrons can move
- because electrons are charged, these moving electrons can carry an electric current
- the moving electrons can carry thermal energy which allows metals to conduct heat
39
how are metals malleable?
- the layers of atoms in a metal can slide over each other
40
what is an alloy?
a mixture of metals
41
why are alloys harder than pure metals?
- the different sizes of atoms distorts the layers, making it more difficult for them to slide over each other.
