AQA Topic 2 - Bonding, Structure and Properties of Matter 9-1

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  • Created by: Grace
  • Created on: 26-04-18 10:08
When are ions made?
When electrons are transferred
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True or False: Ions only exist as charged single atoms
False, they can also be groups of atoms
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How do you know what charge is going to be on an ion?
The number of electrons lost or gained is the same as the charge on the ion i.e if 2 electrons are lost the charge is 2+
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What is an ionic bond?
When a non-metal + metal react together, the non-metal gains electrons to form a negatively charged ion and the metal loses electrons so becomes a positively charged ion. The opp charged ions are strongly attracted to 1 another by electrostatic force
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What is the advantage and disadvantages of dot and cross diagrams?
Advantage - Useful for showing how ionic compounds are formed, Disadvantage - Doesn't show the structure of compounds, the size of the ions or how they're arranged
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What is the structure of ionic compounds?
A giant ionic lattice
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Define an ionic lattice
The ions form a closely packed regular lattice arrangement and there are very strong electrostatic forces of attraction between opp charged ions in all directions in the lattice
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What is useful about a ball and stick model?
It shows the regular pattern of an ionic crystal and shows how all the ions are arranged.
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Explain why ionic compounds have similar properties
They are have high melting/boiling points due to many strong bonds between the ions so it takes lots of energy to overcome this attraction. When the ions are melted they can carry electric current because the ions are free to move
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How can you find the empirical formula?
1. If its a dot and cross diagram, count up how many atoms there are of each element 2. If its a 3D Diagram use it to work out what ions are in the ionic compound
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Why do covalent bonds stay together?
The positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces which makes covalent bonds very strong
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Why do atoms atoms share electrons in their outer shells?
Because its their highest energy levels
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What does each single covalent bond provide?
One extra shared electron for each atom
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Give 7 examples of simple molecular substances
Hydrogen, Chlorine, Oxygen, Nitrogen, Methane, Water and Hydrogen Chloride
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Give the relative formula for Methane
CH4
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If Nitrogen covalently bonds with hydrogen how many covalent bonds does it need and why?
Nitrogen has five outer electrons so needs three to have a complete electron configuration. It needs to form 3 covalent bonds to make up the extra 3 electrons needed
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What is a double covalent bond?
When two non-metals share two pairs of electrons with each other they form double covalent bonds
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Why are the melting and boiling points of simple molecular substances very low?
The atoms within the molecules are held together by very strong covalent bonds however the forces of attraction between these molecules are very weak (intermolecular) so it does not take much energy to break the bonds
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Complete the sentences: As molecules get ____ the strength of the ____ forces ____ so more _____ is needed to break them so melting/boiling points ____
1. Bigger 2. Intermolecular 3. Energy 4. Increase
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What are molecular substances at room temperature?
Gases or liquids due to their low melting and boiling points
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Why don't molecular compounds conduct electricity?
Because they aren't charged so there aren't any free electrons or ions to carry the charge
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Define a polymer
A polymer is a long chain of repeating units
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Why are polymers solids at room temperature?
The intermolecular forces between polymer molecules are larger than between simple covalent molecules so more energy is required to break them
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Why do polymers generally have lower boiling points than ionic compounds?
The intermolecular forces are weaker than ionic or covalent bonds so the boiling point is generally lower
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Define giant covalent structures
Macromolecules where all the atoms are bonded to each other by strong covalent bonds
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Why do giant covalent structures have high boiling/melting points?
Lots of energy is required to break the strong covalent bonds between the atoms
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Why don't giant covalent structures conduct electricity?
They don't contain charged particles so they don't electricity, even when molten
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Give 3 examples of giant covalent structures
Diamond, Silica and Graphite
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Describe the properties of graphite
Graphite's carbon atoms each form three covalent bonds to create layers of hexagons, each carbon atom has one delocalised electron so can conduct electricity and thermal energy
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Describe the properties of diamond
Diamond's carbon atoms each form four covalent bonds which makes diamond hard. The strong covalent bonds given diamond a very high melting point and it does not conduct electricity because it has no free electrons or ions
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Describe the properties of silicon dioxide
Silicon dioxide is formed of covalent bonds between silicon and oxygen, each grain of sand is one giant structure of silicon and oxygen. This is also known as SILICA
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Define an allotrope
Allotropes are different structural forms of the same element in the same physical state, diamond and graphite are allotropes of carbon
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Explain why graphite is a good lubricant
Because graphite's carbon atoms only form three bonds they create the structure of sheets. There aren't are covalent bonds between graphite's layers so they are only held together weakly + are free to move over each other. This makes it soft + slippy
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What is graphene?
One layer of graphite and as the sheet is only one atom thick it is a 2D compound
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Why is graphene useful?
The network of covalent bonds makes it very strong but also light so it can be added to composite materials to improve their strength without adding considerable weight, it can also be used in electronics due to its electric conductivity
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What are fullerenes?
Fullerenes are molecules of carbon shaped like closed tubes or hollow balls
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Describe the structure of fullerenes
Mainly made up of carbon atoms arranged in hexagons but can also contain pentagons or heptagons
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Why are fullerenes good in the medical industry?
Fullernes can be used to cage other molecules as the structure can form around another atom or molecule which becomes trapped inside, this can then be used to deliver a drug into the body
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Why are fullerenes good in industrial aspects?
Fullerenes have a large surface area is they could help make industrial catalysts as individual catalyst molecules can be attached to the fullerenes. They also make good lubricants
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What is a buckminsterfullerene?
The first fullerene to be discovered, it has the molecular formula of C60 and forms a hollow sphere
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Describe nanotubes
Fullerenes can be used to form nanotubes (tiny carbon cylinders). The ratio between the length and diameter of nanotubes is high and can conduct both electricity and heat. They have a high tensile strength and is used in nanotechnology
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What does metallic bonding involve?
Delocalised electrons
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Describe the structure of metals
Metals consist of a giant structure with the electrons of the outer shell of the metal atoms being delocalised. There are strong forces of electrostatic attraction between the pos and neg, these forces hold the atom together in a reg structure
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True or False: Metallic bonding is the strongest bonding
True
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What produces all the properties of metals?
The delocalised electrons in the metallic bonds
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Why are metals solid at room temperature?
Because the bonds between the metal atoms and the delocalised sea of electrons is very strong so needs lots of energy to be broken i.e very high boiling and melting points so they're solid at room temp
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Name two properties of metals and explain why
CONDUCTOR OF ELECTRICITY AND HEAT - The delocalised electrons carry electrical current and thermal energy through the whole structure, MALLEABLE - The layers of atoms in a metal can slide over each other which means it can be bent or hammered etc
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Explain why pure metals are not always suitable for certain jobs
Pure metals can be too soft
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Define an alloy
An alloy is a mixture of two or more metals or a metal and another element that are mixed to make the product harder
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Why are alloys harder than pure metals?
Different elements have different sized atoms, so when an element is mixed w/ a pure metal the new metal atoms will distort the layers of metal atoms which makes it more difficult for them to slide over one another
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What determines what state a material is at room temperature?
The forces of attraction between the particles of the material because weak forces = low melting point etc
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Name the three things that forces of attraction depend upon
Temperature, Pressure and Material (the structure of the substance and the type of bonds holding the particles together i.e covalent or ionic)
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Define the particle theory
The kinetic particle theory explains the properties of the different states of matter. The particles in solids, liquids and gases have different amounts of energy. They are arranged differently and move in different ways.
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Use the particle theory to describe solids (1)
There are strong forces of attraction between the particles which holds them close together in a fixed position to form a regular lattice arrangement. The particles don't move from their positions so all solids keep a definite shape and volume i.e
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Use the particle theory to describe solids (2)
don't flow like liquids. The particles vibrate about their positions so the hotter the solid becomes the more they vibrate which causes solids to expand slightly when heated
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Use the particle theory to describe liquids (1)
There are weak forces of attraction between the particles, which are randomly arranged and free to move past each other but closely. Liquids have a definite volume but not shape so will flow to fit the bottom of a container. The particles are
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Use the particle theory to describe liquids (2)
constantly moving with random motion. The hotter the liquid gets the faster they move which causes the liquid to expand slightly when heated
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Use the particle theory to describe gases (1)
There are very weak forces of attraction between the particles which means they are free to move far apart from each other. The particles in gases travel in straight lines. They have no definite shape/volume so fill the container they're in. They
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Use the particle theory to describe gases (2)
move constantly with random motion, the hotter the gas gets the faster they move. Gases either expand when heated or their pressure increases
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What do physical changes do to an element?
Changes the arrangement of a particle or their energy not change the particles themselves
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How does a solid go to a liquid? What is this called? (1)
A solid is melted when the particles gain more energy as they're heated, the more energy the particles get the more the vibrate which weakens the forces that hold them together. At the melting point the particles have enough energy to break free
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How does a solid go to a liquid? What is this called? (2)
from their positions, therefore the state changes from a solid to a liquid - MELTING
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How does a liquid turn into a gas? What is this called?
As the particles are heated they gain energy, the energy makes the particles move faster which weakens + breaks the bonds holding it together. At the boiling point the particles gain enough energy to break their bonds + turn into a gas - BOILING
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How does a gas turn into a liquid? What is this called?
As a gas cools the particles do not have enough energy to overcome the forces of attraction between hem, bonds form between the particles, at the boiling point so many bonds have formed that the gas turns into a liquid - CONDENSING
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How does a liquid turn into a solid? What is this called?
Liquid cools = less energy = particles move around less. Not enough energy to overcome the attraction between the particles so more bonds form between them. At the melting point so many bonds have formed that the particles are held in place- FREEZING
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What does the amount of energy needed for a substance to change state depend on?
How strong the forces between particles are as stronger forces = more energy to break them = higher melting/boiling point of substance
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What is 1nm in metres?
1 x 10 to the power of -9
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Name the three different types of particles, starting with the biggest
Coarse Particles (dust), Fine Particles and Nanoparticles
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State the equation for surface area to volume ratio
Surface area to volume ratio = surface area ÷ volume
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Why is the surface area to volume ratio important?
It can affect the way a particle behaves
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What happens when particles decrease in size?
The size of their surface area increases in relation the their volume which causes the surface area to volume ratio to increase
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What does having a high surface area to volume ratio mean?
That the surface area is very large compared to the volume
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Do nanoparticles have a high surface to volume ratio? What does this cause?
Yes, it causes the properties of a material to change depending on whether it is in bulk or a nanoparticle. For example you'll need less of material that's made of nanoparticles to work as an effective catalyst compared to a 'normal' material
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Describe different uses of nanoparticles
CATALYSTS - bc of large surface area to volume ratio, NANOMEDICINE - Fullerenes are absorbs easier than most particles i.e drug delivery, SILVER NANOPARTICLES - Have antibac properties and can be added to polymer fibres for surgical masks + dressings
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What are the cons of nanoparticles?
Their effects on health aren't fully understood and people are worried that products containing them have been mad enviable before the effects on human health have been investigated properly as we do not know what long-term impacts on health will be
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True or False: People do not believe products containing nanoparticles need to be thoroughly tested
False, because the health side effects are not fully understood it is important that any new products are tested throughout to minimise risks
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Why are nanoparticles used in sunscreen?
They have been shown to be better than traditional sun creams at protecting skin from UV Rays, they give better skin coverage but unsure if they damage skin cells. It is also possible that when they are washed away they might damage the environment
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Card 2

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True or False: Ions only exist as charged single atoms

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False, they can also be groups of atoms

Card 3

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How do you know what charge is going to be on an ion?

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Preview of the front of card 3

Card 4

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What is an ionic bond?

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Card 5

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What is the advantage and disadvantages of dot and cross diagrams?

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