Chemistry Unit 2 Revision Flash Cards Additional Science Produced by Mr P Scutt.

Chemistry Unit 2 Revision Flash CardsAdditional Science

Produced by Mr P Scutt


Describe the sub-atomic particles and their characteristics (12 marks)


Describe the sub-atomic particles and their characteristics (12 marks)

Sub-Atomic Particle

Mass Charge Where found in the atom

Proton +1 +1 Nucleus

Neutron +1 No charge Nucleus

Electron Very small -1 Shells/Orbits


What does the periodic table tell you about an element and its atomic structure?


What is a compound?


What does the periodic table tell you about an element and its atomic structure?

The Group tells you how many outer electrons an atom has, e.g. Group I metals all have 1 outer electron i.e. Na, Li, K.

The atomic symbol tells you:

2311Na

23 – This is the mass number of the element. This is made up of protons and neutrons.11 – This is the atomic number and indicates how many protons are in the atoms.

So in this example, Na has 11 Protons and 12 Neutrons.

An atom is uncharged and so the number of protons is equal to the number of electrons. Therefore, this atom of Na has 11 electrons.


What is a compound?

A compound is where two or more elements are chemically combined together.

E.g. carbon dioxide, water, ammonia.

It is very difficult to separate these into their original elements.


What is an Isotope? Give an example. (4 marks)


How is an IONIC bond formed and what properties does it have?


What is an Isotope? Give an example. (4 marks)

An isotope is a different form of the same element. Therefore it has the same number of PROTONS and a different number of NEUTRONS.

Example is Carbon:

C-12 and C-14

Carbon- 12 has a mass of 12 and atomic number of 6, so has 6 protons, 6 neutrons and 6 electrons.

Carbon-14 has a mass of 14 and atomic number of 6, so has 6 protons, 8 neutrons and 6 electons.


How is an IONIC bond formed and what properties does it have?

In an ionic bond, elements have either lost or gained electrons. This makes them become ions.

A negative and positive ION can then attract (electrostatic attraction) each other to form a strong bond, e.g. Na+Cl-

Good examples are Group 1 metals donating their electron to Group 7 metals. The group 1 metal becomes positive (lost a negative electron) and the group 7 metal becomes negative (gains a

negative electron). These attract each other very strongly and form giant ionic lattices.

They have high melting points, high boiling points – due to lots of energy being needed to break these strong bonds.

They don’t conduct electricity when solid – as the ions are fixed firmly in position. They DO conduct electricity when molten or dissolved as the IONS can move.


What is an ion and how are they formed?


Draw the bonding between Na and Cl to form NaCl.


What is an ion and how are they formed?

An atom can lose or gain an electron to become a charged ION.

If an atom GAINS an electron (a negatively charged particle) it becomes a negative ION.

If an atom LOSES an electron (a negatively charged particle) it becomes a positive ION.

The reason for becoming an ION is that the ion has a structure like a noble gas, i.e. a full outer shell of electrons.

Group 1 elements form 1+ Ions. Group 2 elements form 2+ Ions. Group 6 elements form 2- Ions.Group 7 elements from 1- Ions.


Draw the bonding between Na and Cl to form NaCl.

Ions are shown is square brackets to highlight that they are IONS and not atoms. It is good to use different colours or dots and crosses for electrons belonging to different

elements. It is then clear what has happened to the electrons.

http://www.google.co.uk/url?sa=i&rct=j&q=sodium+chloride+ionic+bond&source=images&cd=&cad=rja&uact=8&docid=Dorpxy9v-kwzbM&tbnid=--sWJcRmjKCkCM:&ved=&url=http://scienceaid.co.uk/chemistry/fundamental/bonding.html&ei=MCtWU--IBObe7AbCmYCgCg&bvm=bv.65177938,d.ZGU&psig=AFQjCNE6js42Y_IooZEQ2Vjqn8Nd-LMmXQ&ust=1398242480573332


How is a covalent bond formed and what properties do simple covalent structures have?


Give three examples of giant covalent structures and summarise their properties.


How is a covalent bond formed and what properties do simple covalent structures have?

This is where atoms share electrons. By doing so they have a full outer shell (like a noble gas).

Examples: hydrogen, water, methane, ammonia

Bond between atoms is very strong, but between molecules it is weak, i.e. between the two hydrogen atoms it is a strong bond, between hydrogen molecules it is weak.

They have low melting points as require low amount of energy to break bonds. They have low boiling points as require low amount of energy to break bonds.

Most are gases or liquids at room temperature. Do not conduct electricity as there are NO ions.


Give three examples of giant covalent structures and summarise their properties.

No charged IONSStrong covalent bonds

Very high mpVery high bp

Don’t conduct electricity (except graphite)

Graphite – made of 3 covalent bonds of carbon. Forms layers which slide over each other. They are slippery, soft. The layers slide off when using a pencil on to a page. They conduct electricity as have

free delocalised electrons (as only use 3 electrons out of a possible 4).

Diamond – forms 4 covalent bonds with carbon. Very hard material. Very rigid structure.

Silica – what sand is made up of. Each grain of sand is one giant structure of silicon and oxygen.


Describe the structure of metals and their properties.


How is an alloy different from a metal?


Describe the structure of metals and their properties.

Metals are giant structure.Held by electrons holding them in a regular structure.

Strong electrostatic forces between metal ions.

They conduct electricity as they have ‘free-electrons’. These free-electrons are from the outer shell of atoms only.

These free-electrons are free to move and conduct heat and electricity.

Can be bent as layers can slide over each other.


How is an alloy different from a metal?

An alloy has 2 or more metals together.

The elements are different sizes and so distort the layers.

This means that the layers do not slide over each other as easily and so alloys are harder than metals.


What are SMART materials and where are they found?


What are nanoparticles and where are they found?


What are SMART materials and where are they found?

Materials that behave differently depending on conditions, e.g. Temperature.

e.g. glasses frames. Bend them and then pop them in hot water and they reform their shape.

Dental braces – mouth warms them and they try and reform their shape to pull the teeth back into place.


What are nanoparticles and where are they found?

Very tiny particlesA few hundred atoms per particle

Include fullerenesDifferent properties from the atom they are made from.

Huge Surface area to volume ratio

Make industrial catalystsSensors to test water purity

Stronger, lighter building materialsSun tan creams

Deodorants – stop white marks Lubricants

Electrical circuits


What is a plastic made up of and what are the different types of properties that plastics can have?


How is the relative atomic mass of an atom determined?


What is a plastic made up of and what are the different types of properties that plastics can have?

Plastic is a polymer made up of long chains joined together between chains by bonds. There are two types of bond:

Weak bonds – form tangled chains that can slide. These are found in thermosoftening plastics – they form a new shape on heating and so can be remoulded.

Strong bonds – form strong crosslinks and so held firmly, so cant slide. These form themosetting plastics that when heated don’t soften. They are hard, rigid and strong.

There are two types of polymer:Low density: Heat ethene at 200C and under high pressure. Its flexible.

High density: made at lower temperature and pressure, with a catalyst. More rigid – used for drainpipes.


How is the relative atomic mass of an atom determined?

From the periodic table, this is the mass of the element and is made up of the total number of protons and neutrons.

It is the mass compared to Carbon-12.


How is the relative formula mass calculated?


How do you calculate the percentage mass of an element in a compound?


How is the relative formula mass calculated?

This is the combined mass of all the elements in the compound, e.g.

MgCl2

Mg – Ar is 24Cl – Ar is 35.5

(Ar = Relative Atomic Mass)

So the formula mass is 24 + 35.5 + 35.5 = 95


How do you calculate the percentage mass of an element in a compound?

If you know what elements make up a compound then use the equation:

Ar x Number of atoms of that element Mr of whole compound x100

e.g.

MgCl2

Mg – Ar is 24Cl – Ar is 35.5

So percentage of Mg in compound is 24/95*100 = 25%


If 44.8g of iron oxide is produced from iron and 19.2g of oxygen, what is the empirical formula for iron oxide?(Ar of Fe = 56, O = 16)


What is meant by percentage yield and how is it calculated?


If iron oxide is produced from 44.8g of iron and 19.2g of oxygen, what is the empirical formula for iron oxide?(Ar of Fe = 56, O = 16)

This is the simplest formula using whole numbers. You need to carry out the following steps:

Elements: Fe OMasses: 44.8g 19.2g

Divide mass by Ar: 44.8/56 19.2/16=0.8 =1.2

Multiply by 10: 8 12Simply ratio: 2 3

Empirical formula is: Fe2O3


What is meant by percentage yield and how is it calculated?

Compares the actual yield with the predicted yield.

Yield is the amount of product formed.

This may not always be 100% because:- Not all reactants are used.

- Some product is lost/escapes.- Some reactions are reversible.

Percentage yield = actual yield/predicted yield x 100


How do you perform the process of chromatography?


How do you perform the process of gas chromatography?


How do you perform the process of chromatography?

Use chromatography paper. Draw a pencil line 1cm from base of paper.

Place a drop of the mixture to be test on the line. Place paper in a beaker with less than 1cm depth of solvent (e.g. water, ethanol)

Leave for the solvent to seep up the paper. Compare final chromatogram with known samples to identify substances in mixture.


How do you perform the process of gas chromatography?

Gas can be used to carry substances through a columnSubstances travel at different speeds through the tube

The time taken to reach detector is called retention time. A graph can be drawn with peaks showing retention time.

This can be used to work out the relative molecular mass of substances.


What affects the rate of reaction?


How can you measure the rate of a reaction?


What affects the rate of reaction?

TemperatureConcentration

Presence of a catalystSurface area


How can you measure the rate of a reaction?

The time taken for a product to from

The time taken for reactants to be used up.

The change in mass per unit time.

The volume of gas produced per unit time.

The amount of solid formed, per unit time.


Why does surface area affect rate of reaction?


Why does concentration affect rate of reaction?


Why does surface area affect rate of reaction?

Greater the surface area the more area for collisions between particles to occur so greater the rate of reaction.


Why does concentration affect rate of reaction?

With more particles (a greater concentration) the is more chance of collisions and so faster rate.

In gases the concentration can be changed by increasing the pressure so the particles have less space to move in.


Why does temperature affect rate of reaction?


Why does a catalyst affect rate of reaction?


Why does temperature affect rate of reaction?

Higher the temperature the faster the rate

As particles gain kinetic energy and so move around more

Therefore, a greater number of collisions.

Collisions are also more likely to be successful as the minimum amount of energy needed for the reaction to occur has been reached – i.e. activation energy.


Why does a catalyst affect rate of reaction?

A catalyst helps reactants come together and so speeds up the reaction.

The catalyst is not used in the reaction and so can be recycled.


What is the difference(s) between exothermic and endothermic reactions?


What happens in a neutralisation reaction?


What is the difference(s) between exothermic and endothermic reactions?

Exothermic- energy (heat) leaves a reaction and goes into the surroundings. The cooler the surroundings the faster the reaction, e.g. combustion, oxidation, neutralisation

Endothermic – energy (heat) goes into the reaction from the surroundings. So the hotter the surroundings, the faster the reaction. E.g. sports injury packs


What happens in a neutralisation reaction?

Acid + Base salt + water

The H+ ions in acids react with the OH- ions in alkali to form water.

H+ + OH- H2O

This forms a neutral solution.

Metal oxides and Metal hydroxides are bases, e.g. sodium hydroxide, zinc oxide.


What is formed when a metal reacts with an acid?


What happens in electrolysis?


What is formed when a metal reacts with an acid?

Metal + Acid Salt + Hydrogen

Hydrogen can be tested using the “pop” test where a lit splint is held at the top of the test tube and a pop sound is heard.

Hydrochloric acid form chloride salts, e.g sodium chloride. Sulfuric acid forms sulphate salts, e.g. magnesium sulphate.


What happens in electrolysis?

Electrolysis is the splitting up using electricity.

An electric current is passed through an ionic substance that is dissolved or molten. The free ions move to opposite electrodes.

The ion movement means the solution conducts electricity.

Reduction occurs when electrons are gained.Oxidation occurs when electrons are lost.

Remember: OIL RIG

When more than 2 free ions are around, the metal ions stays in solution and H+ ion forms at the electrode instead forming hydrogen gas (as long as it is less reactive).


Describe the process of extraction of aluminium.


Describe the process of electroplating.


Describe the process of extraction of aluminium.

Electrolysis removes Al from its ore.

Its ore is bauxite – aluminium oxide

It has a high mp of 2000C

Carbon electrodes are used

Molten state is used so don’t have to melt

Al forms at the negative electrode Oxygen at the positive electrode – reacts with the Carbon electrode to form carbon

dioxide. Therefore, the electrode needs replacing frequently.


Describe the process of electroplating.

Electrolysis is used to coat the surface of a metal with another metal.

Metal object is at the negative electrode.

Pure metal is at the positive electrode.

Electrolyte (the solution) has ions of the plating metal.

This is used for decoration and to improve conductivity in electric circuits and computers.

Chemistry Unit 2 Revision Flash Cards Additional Science Produced by Mr P Scutt.

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Transcript of Chemistry Unit 2 Revision Flash Cards Additional Science Produced by Mr P Scutt.