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Chemistry > Topic 2 - Structure and bonding > Flashcards

Topic 2 - Structure and bonding Flashcards

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1
Q

Where is energy transferred to and from in melting and boiling?

A

From the surrounding, to the substance

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2
Q

Where is energy transferred to and from in freezing and condensing?

A

from the substance, to the surroundings

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3
Q

How can you tell what state a substance will be at room temperature?

A

if the temperature’s below the melting point of a substance, itll be a solid. if its above the boiling point, itls be a gas. if its between the two points, then its a liquid.

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4
Q

Properties of a solid

A

Regular lattice arrangement, fixed position, vibrate on a spot, keep a definite shape + volume, strong forces of atraction between each particle.

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5
Q

Properties of a liquid

A

random arrangement, close together, free to move around, take the shape of the container, dont keep a definite shape.

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6
Q

Properties of gas

A

random arrangement, far apart, move constantly with random motion, fill a volume, weak forces of attraction between particles, can be compressed.

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7
Q

What does it mean if the forces between each particles in a substance are strong?

A

More energy is needed to break the bonds so the melting and boiling point of the substances increases.

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8
Q

Why can gas be compressed?

A

Because there is lots of space between gas molecules. This space allows us to put pressure on gas, and force it in a smaller container.

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9
Q

What happens when metals form ions?

A

They loose electrons from their outer shell to form positive ions

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10
Q

What happens when non- metals form ions?

A

they gain electrons into their outer shell to form negative ions.

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11
Q

What is ionic bonding?

A

occurs between a metal and a non-metal. it is an electrostatic force of attraction between oppositely charged particles (ions).

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12
Q

Why does ionic bonding occur between metals and non-metals?

A

Because metals want to give up electrons whereas non- metals want to gain electrons.

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13
Q

describe an ionic compound structure

A

the ions form a closely packed regular lattice arrangement and there are very strong electrostatic forces of attraction between oppositeley charged ions, in all directions in the lattice.

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14
Q

Properties of ionic compounds

A
  • high melting and boiling points
  • when solid they cant conduct electricity but when melted the ions are free to move and theyll carry electrical charge.
  • when dissolved in water they can conduct electricity
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15
Q

what is covalent bonding?

A

when non- metal atoms bond together, they shair pairs of electrons to make covalent bonds.

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16
Q

Where does covalent bonding occur?

A
  • compounds of non- metals
  • non- metal elements
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17
Q

Advantages and disadvantages of a dot and cross diagram

A

advantages:
- show which atoms the electrons in a covalent bond come from

Disadvantages:
- dont show the relative sizes of the atoms
- doesnt show how the atoms are arranged in space

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18
Q

Advantages and disadvantages of a displayed formula

A

Advantages:
- shows how atoms are connected in large molecules

Disadvantages:
- doesnt show the 3d sructure of the molecule
- doesnt show which atoms the electrons in the covalent bond have come from

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19
Q

Advantages and disadvantages of particle diagram

A

Advantages
-it provides a reasonable explanation for the behaviour of matter

disadvantages
-does not take into accountthe size and shape of particles
-the space between particles.
- forces of attraction between particles

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20
Q

What is a simple molecular substance?

A

made up of molecules containing a few atoms joined together by covalent bonds

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21
Q

Examples of simple molecular substances

A

hydrogen ( h2)
chlorine (Cl2)
oxygen (O2)
nitrogen (N2)
water (h2O)

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22
Q

Properties of simple molecular substances

A
  • simple molecular structure
  • atoms are held together by strong covalent bonds but the forces of attraction between the molecules are very weak
  • low melting and boiling point
  • most are gas or liquid at room temperature
    as they get bigger, the strength of the forces increase
  • dont conduct electricity
23
Q

What is a polymer?

A

Lots of small units linked together to form a long molecule that has repeating sections.

24
Q

At what state are polymers at room temperature?

A

Most are solid

25
Q

Properties of giant covalent structures

A
  • atoms bonded to eachother by strong covalent bonds
  • very high melting and boiling points
    -dont conduct electricity
26
Q

Properties of a diamond

A
  • rigid giant covalent bonds. this makes it really hard
  • very high melting and boiling points
  • doesnt conduct eletricity
27
Q

Properties of graphite

A
  • each atom forms 3 covalent bonds to create layers of hexagons
  • each atom has one delocalised electron
  • soft and slippery
  • high melting and boiling point
    -nconducts electricity and thermal energy
28
Q

What are fullerenes?

A

molecules of carbon shaped like closed tubes or hollow balls

29
Q

Uses of fullerenes

A
  • ‘cage ‘ other molecules to deliver a drug into the body (hollow structure)
  • catalysts ( large surface area)
  • lubricants (because it’s round spherical, the molecules can roll)
30
Q

Properties of nanotubes

A
  • strong
  • light
  • conduct electricity
31
Q

What is nanotechnology?

A

Technology that uses very small particles such as nanotubes.

32
Q

uses of nanotubes

A
  • electronics
  • strengthen materials without adding much weight, such as a tennis racket frame
33
Q

What is graphene and what are its properties?

A

A layer of charbon atoms joined in hexagons ( a layer of graphite)
- light
-strong
- can be added to composite materials to improve strength
- 2 dimensional
- conducts electricity

34
Q

Why do nano particles have such a huge surface area to volume ratio?

A

As particles decrease in size, their surface area increases in relation to their volume. this causes the surface area to volume ratio to increase.

35
Q

Uses of nanoparticles

A
  • catalysts
  • could be used to deliver drugs right into the cell when needed
  • could be used in tiny electric circuits for computer chips
  • could be added to polymer fibres that are used to make surgical masks
  • can be used in cosmetics to improve moisturisers whithout making them really oily
  • used in suncream
36
Q

Disadvantages of using nanoparticles

A
  • if they get in your body, they could damage cells
  • could damage the environment
37
Q

What is metallic bonding?

A

The attraction of the positively charged ions in a giant metallic lattice and the delocalised electrons that flow around them. occurs between 2 metals.

38
Q

What is an alloy?

A

a mixture of 2 or more elements where at least one of the elements is a metal

39
Q

Examples of alloys

A
  • stainless steel (iron and chromium)
  • bronze (copper and tin)
  • brass (copper and zinc)
40
Q

Why are alloys harder than metals?

A

They are a mixture of different elements which also mean that they are made up of different sized atoms. this makes the layers rigid and harder to slide over eachother which makes the alloy stronger. Disrupts the regular structure.

41
Q

Describe how metallic bonding occurs

A

metallic bonding occurs between two metals. metal atoms loose their electron in order to obtain a full outer shell and become stable. this means that the metal atom becomes a positive ion and the electrons become delocalised and form a pool of delocalised electrons. There is now an electrostatic force of attraction between the negative electrons and positive ions which holds everything together in a regular structure.

42
Q

Properties of mettalic bonds

A
  • high melting and boiling points
  • good conductors of elecricity and heat (delocalised electrons carry electrical current and thermal energy througout the structure)
  • malleable (layers slide over eachother because of regular structure)
43
Q

Magnesium loses electrons to become an ion. Complete the equation below:

___➔Mg2++_e-

A

Mg
2

44
Q

Fill in the blank:
Atoms ingroup 5have_electrons in their outer shell. This means they need to gain_electrons to be stable, forming an ion with a charge of__.

A

5
3
-3

45
Q

Fill in the blank
Atoms can g___or l____electrons to become charged particles called i___.

A

gain
loose
ions

46
Q

Diamond and graphite are examples of_____covalent molecular structures.

Both are made from the element______ arranged into a large regular repeating ________.

A

giant
carbon
lattice

47
Q

In diamond, each______atom is bonded to_other atoms via covalent bonds.

This forms a regular 3D lattice which is very strong, and has very _____melting and boiling points.

A

carbon
4
high

48
Q

Unlike diamond, the carbon atoms in graphite each bond to_other carbon atoms.

This arranges the graphite into 2D _______ made up of repeating ________.

A

3
layers
hexagons

49
Q

Explain why methane is a gas at 20 degrees

A

It has a very low melting and boiling point (below room temperature) because the intermolecular forces (between each molecule of methane) is very weak so little energy is required to break them.

50
Q

explain why graphene in strong (3 mark)

A
  • covalently bonded
  • hexagonal shape bonded to 3 other atoms
  • a lot of energy is required to break the bonds (strong covalent bonds)
51
Q

Explain why graphene can conduct electricity (2 mark)

A
  • bonded to three other atoms which mens one electron is delocalised into a pool of electrons which move around the structure and carry a charge
52
Q

Explain why graphene is a lubricant (2 mark)

A
  • layers of graphite with weak forces of attraction between them
  • allow to slide over eachother smooth layers
53
Q

Explain why chlorine is a gas at room temperature but sodium chloride is a solid ( 6 mark)

A

Chlorine
-low melting and boiling point
-weak intermolecular forces between chlorine atoms (little energy required to break them)
- energy in chlorine goes into breaking the weak intermolecular forces not the strong covalent bond
-bonded to only one type of atom (simple molecular structure)

sodium chloride
- each ion bonded to oppositely charged ions in all directions
- large ionic structure
-melting and boiling point high
-lots of energy required to break the strong ionic bonds
- solid at room temperature.

Chemistry (7 decks)

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