Post on 08-Mar-2018
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Your stomach contains hydrochloric acid. This aids digestion and allows the stomach to kill any harmful bacteria. The acid has a pH of ~2.
If to much acidic foods are eaten it can result in indigestion, heartburn and acid reflux. This causes pain in the stomach and in the oesophagus.
OH Na
Sodium hydroxide
Cl H
Hydrochloric acid
The sodium replaces the hydrogen from HCl
Cl Na
Sodium chloride
H2O
Water
acid + base salt + water
Neutralisation
•The technique of titration is used to find out accurately how much of a chemical substance is
dissolved in a given volume of a solution.
•The technique uses a particular set of apparatus with which volumes of solutions can be measured to an
accuracy of greater than 0.1cm 3
What is Titration?
Titration demonstration B Use the funnel to help you to pour
some hydrochloric acid into the burette. Put the
beaker under the burette and open the tap to let
some acid into the tip of the burette. Close the tap
again and pour the acid in the beaker down the sink. C Fill the burette up to just below the zero mark with hydrochloric acid – this does not have to
be exact. D Use the measuring cylinder to pour
exactly 10 cm3 sodium hydroxide solution into to
the conical flask. Add a few drops of indicator and
swirl it so that the liquids mix. Stand the flask under the burette. E Read the volume of acid in the burette and write it down. F Add the acid from the burette to the flask a little at a time – about 1 cm3 each time is
about right. Swirl the flask gently each time you
add some acid. Stop when the indicator turns red and stays red. G Record the volume of acid in the
burette. Work out how much acid has been added and write it down. H Wash out the conical flask with water
and repeat steps D to G. This time, add acid about
1 cm3 at a time until you have nearly added the
same amount as before. Then add acid in much smaller amounts – drop by drop.
Copper (II) oxide is a _________, which reacts with sulfuric acid to make a ________ and __________. A soluble base is called an ________. This is called a ______________ reaction.
Applying ideas…….
Must remember……. METAL + ACID → SALT + HYDROGEN METAL OXIDE + ACID → SALT + WATER METAL CARBONATE + ACID → SALT + WATER + CARBON DIOXIDE
Zinc + hydrochloric + acid
• Use the general equation to finish of the word equations below metal + acid a salt + hydrogen
iron + nitric acid +
calcium + sulphuric
acid
+
iron nitrate
calcium sulphate
zinc chloride
hydrogen
hydrogen
hydrogen
magnesium + sulphuric
acid
+ magnesium sulphate
hydrogen
Activity
Metal oxides and acids
Metal oxide + acid a salt + water
• Most metal oxides are not soluble. • i.e. They are bases but not alkalis.
This means they are often slower and may need heating to make them react
Acid
Oxide
water + copper sulphate
sulphuric acid
+ Copper oxide
Reactions of metal oxides with acid A metal oxide is a compound containing a metal and oxide. They are sometimes called BASES. For example:
Mg O Na
Na O
O
Al
Al O
O
Magnesium oxide Sodium oxide Aluminium oxide
METAL OXIDE + ACID SALT + WATER
Copy and complete the following reactions:
1) Magnesium oxide + hydrochloric acid
2) Calcium oxide + hydrochloric acid
3) Sodium oxide + sulphuric acid
Mg O
H Cl
Mg Cl Cl
H H O H Cl
Sulfuric acid + copper carbonate
When your base is a carbonate, carbon dioxide
Gas is also made!!!
Base + acid a salt + water
1. Hydrochloric acid + sodium hydroxide
2. Hydrochloric acid + calcium carbonate
3. Sulfuric acid + copper oxide
4. Sulfuric acid + iron carbonate
5. Nitric acid + ammonia
6. Phosphoric acid + iron oxide
Task - write out and complete these half equations
C
1. Sodium chloride + water
2. Calcium chloride + water + carbon dioxide
3. Copper sulfate + water
4. Iron sulfate + water + carbon dioxide
5. Ammonium nitrate + water
6. Iron phosphate + water
Must remember……. METAL + ACID → SALT + HYDROGEN METAL OXIDE + SALT → SALT + WATER METAL CARBONATE → SALT + WATER + CARBON DIOXIDE
Extracting metals from ores Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Copper
Silver
Gold
Platinum
Metals ABOVE CARBON, because of their high reactivity, are extracted by ELECTROLYSIS and this needs a lot of energy
Metals BELOW CARBON are extracted by heating them with carbon in a BLAST FURNACE
These LOW REACTIVITY metals blatantly won’t need to be extracted because they are SO unreactive you’ll find them on their own, not in a metal oxide
Fill in the gaps
• A solid compound cannot conduct _______. This is because the particle are not free to move. When we dissolve or melt the compound the _________ are free to move so can conduct ________ .
Electrolysis of copper sulphate
Negative electrode cathode
Positive electrode anode
electrolyte
+
Cation, copper
-
Anion, oxygen
+ -
Electrolysis Electrolysis is used to extract a HIGHLY REACTIVE metal.
= sulphate ion
= copper ion
When we electrolysed copper sulphate the
negative sulphate ions moved to the positive
electrode and the positive copper ions moved to the
negative electrode – OPPOSITES ATTRACT!!!
What substances can we split up?
• We can separate compounds like: –Zinc chloride
–Lead bromide
–Aluminium oxide
–Nickel sulphate
They must be liquids
Write a sentence to explain what electrolysis is and write what will be made during electrolysis of these chemicals.
What happens at the electrodes
• At the positive electrode the negative anions are attracted to it. They give electrons to the electrode to lose their charge
+
-
e-
What happens at the electrodes
• At the negative electrode the positve cations are attracted to it. They take electrons from the electrode to lose their charge
-
+
e-
Hydrogen chloride and hydrochloric acid have the formula HCl
Hydrogen chloride → hydrogen + chloride
HCl → H + Cl
HCl → H2 + Cl2
2HCl → H2 + Cl2
• Chlorine gas was used as a weapon in WW1.
• The gas dissolves the moisture in the eyes and lungs.
• The cholrine then forms an acid.
• The victim usually died very painfully within a few days.
Chlorine gas in the First World War
Electrolysis of brine
• When NaCl dissolves in water, it’s ions become free to move. So the solution can be electrolysed.
• In water some of the molecules of water will naturally split apart.
Watch the demonstration of the electrolysis of brine
Product Test for substance
Hydrogen Blows out a lighted splint
and makes a squeaky
pop.
Chlorine Damp litmus paper goes
from blue to red then
bleaches white
Sodium hydroxide Goes dark blue or purple
when universal indicator
is added.
Electrolysis of salt 1
Cl2 2Cl- - + 2e- Chlorine gas is formed
Negative ions
• Salt consists of sodium ions (Na+) and chloride ions (Cl-).
• Chloride ions go to the anode where they lose an electron
• The neutral chlorine atoms produced join up into pairs
Electrolysis of salt 3
• Na+ ions move to the cathode but do not accept electrons.
• It is the hydrogen ions that gain electrons
• As a result hydrogen gas is formed at the cathode.
2H+ + 2e- H2
How does the sodium hydroxide form? Sodium chloride solution has four types of ions:
What is the overall equation for the electrolysis of a sodium chloride solution?
The Cl- ions form chlorine at the positive electrode and the H+ ions form hydrogen at the negative electrode. So, what’s left?
Na+ and OH- ions are left behind and so a solution of sodium hydroxide (NaOH) is formed.
2NaCl (aq) + 2H2O (l) H2 (g) + Cl2 (g) + 2NaOH (aq)
Na+ and Cl- ions from the sodium chloride H+ and OH- ions from the water.
Sodium + water→ sodium + hydrogen + Chlorine
Chloride hydroxide
NaCl + H2O → NaOH + H2 + Cl2
2NaCl + 2H2O → 2NaOH + H2 + Cl2
Compound Anode Cathode
Sodium Bromide
Potassium Iodide
Calcium Fluoride
Magnesium Oxide
Lithium Chloride
Half Equations
• The half equation shows what happens at each electrode e.g.
3Al3+ + 3e- 3Al • The aluminium ions collect 3 electrons at the
cathode to form aluminium atoms. 2Cl- Cl2 + 2 e-
• The chlorine ions drop off electrons at the anode to form chlorine atoms (which in turn react to form a chlorine molecule (covalent bonding)
Balance the following half equations.
1. Cl2 + e- → Cl-
2. Al3+ + e- → Al
3. H+ + e- → H2
4. Pb2+ + e- → 2Pb
5. O2- - 4e- → O2
The Reactivity Series
The Reactivity Series lists metals in order of reactivity:
Make a pneumonic to help you remember this
Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Lead
Copper
Silver
Gold
The premier league of reactivity •Think about it like a football league. If the team near the bottom played the team near the top, who would
you expect to win?? It’s the same for the reactivity series, if an element
near the top of the reactivity series is mixed with an ore from the bottom, the element displaces the less
reactive metal from it’s ore.
V
Explain why we need different methods of extraction depending on the reactivity of the metal Objective:
Displacement reactions
Mg
Magnesium
SO4 Cu
Copper sulphate
The magnesium DISPLACES the copper from copper sulphate
SO4 Mg
Magnesium sulphate
Cu
Copper
A displacement reaction is one where a MORE REACTIVE metal will DISPLACE a LESS REACTIVE metal from a compound.
Magnesium + copper sulphate magnesium sulphate + copper
Some example reactions… Reaction Prediction Observations
Zinc + copper sulphate
Zinc + lead nitrate
Copper + lead nitrate
Copper + silver nitrate
Extension work – write down the equations for these reactions
4. Aisha placed small samples off four different metals on a spotting tile. She added drops of copper sulphate solution to each metal.
Aisha repeated the experiment with fresh samples of the four metals and solutions of different salts. She recorded some of her results in a table. shows that a reaction took place X shows that no reaction took place.
copper iron magnesium zinc
spotting tile
coppersulphate
ironsulphate
magnesiumsulphate
zincsulphate
solutionsmetals
copper iron magnesium zinc
×
×
×
× ×
×
×
×
(a)The four metals have different reactivities. (i) Use the information in the table to put the four metals in a reactivity series. 1 mark (ii) Use the reactivity series to complete the table by writing in √ or X in the three empty boxes. 2 marks (b) Copper reacts with silver nitrate solution. (i)Complete the word equation for the reaction: Copper + silver nitrate → ...........................+........................... 2 marks (ii) Platinum does not react with silver nitrate.
Put the metals platinum, copper and silver in the correct order according to their reactivity. (iii) 1 mark (c) In many houses the hot water pipes are made from copper and the boiler is made from iron. Which of these metals will corrode first? Explain your answer. 1 mark Maximum 7 marks
Rocks and Minerals
Objective: Recall that most metals are extracted as ores from the earth’s crust
•Rocks in the earth’s crust are very rarely pure substances •If the minerals in rocks contain metals then they are called ores. •Unreactive metals are found in their pure state and not as an ore.
•Can you think of any unreactive metals? •Metals vary in cost depending on the availability of the ore, how much metal is contained in the ore and the method of extraction. •You are going to try one method of extraction today.
bauxite(Aluminium)
haematite(iron)
cinnabar(mercury)
Galena(lead)
malachite(copper)
Match the metal ore to the picture
Starter Activity
bauxite(Aluminium)
haematite(iron) cinnabar(mercury)
Galena(lead)
malachite(copper)
Match the metal ore to the picture
Answers
Which method of extraction?
Objective: Explain why we need different methods of extraction depending on the reactivity of the metal
•There are two main methods for the extraction of metals from their ores: •Chemical reduction (like you’ve carried out in class) •Electroysis •The method used for extraction depends on the reactivity of the metal you are trying to extract. •Scientists use something called the reactivity series to help them decide which method to use, the higher the metal, the more reactive it is.
Extracting metals from ores Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Copper
Silver
Gold
Platinum
Metals ABOVE CARBON, because of their high reactivity, are extracted by ELECTROLYSIS and this needs a lot of energy
Metals BELOW CARBON are extracted by heating them with carbon in a BLAST FURNACE
These LOW REACTIVITY metals blatantly won’t need to be extracted because they are SO unreactive you’ll find them on their own, not in a metal oxide
Oxidation
A reaction where the products contain more oxygen than the original fuel. Adding more oxygen to a substance is called ‘oxidation’.
Gloss paint Iron nails
Burning
Oxidation Fuels like carbon when burnt are oxidised.
C CO2
S SO2
It has had oxygen added to it.
Iron has been oxidised to make iron oxide (rust).
Reduction
Removing oxygen from a chemical is called reduction. It reduces the amount of oxygen in the substance.
Reduction Reduction can occur when burning iron oxide.
3C + 2Fe2O3 4Fe + 3Co2
The iron oxide gives its oxygen to the carbon.
What can we say has happened to the Carbon?
Redox reactions
Although some fuels gain oxygen some will also lose oxygen. Thus oxidation and reduction are happening at the same time. These are known as REDOX reactions.
Write a word equation for methane (CH4) reacting with oxygen. State what where redox
is occurring.
Comparing the electrical conductivity of metals:
• Are all metals good conductors?
• Are some better than others?
• How could we investigate this?
Monday, 16 March 2015
What are the advantages of recycling metals?
• Make metals last longer • Less energy needed to
recycle compared to extracting ore
• Reduces the need to mine ores – less damage to the environment
• Less pollution produced • Less waste materials put
into landfill
Monday, 16 March 2015
What are the disadvantages of recycling metals?
• Costs and energy
involved in:
– Collecting materials
– Sorting materials
– Transporting
materials
• Can be more expensive to recycle
Monday, 16 March 2015
An alloy is a mixture of a metal with at least one other element.
The final alloy may have very different properties to the original metal.
What is an alloy?
Steel is a common example of an alloy. It contains iron mixed with carbon and other elements. Adding other elements to a metal changes its structure and so changes its properties.
What types of alloys are there?
brass: an alloy of copper and zinc.
solder: an alloy of tin and lead
amalgam: an alloy of mercury and
silver or tin.
Other well-known alloys include:
Steel is an alloy of iron and other elements, including carbon, nickel and chromium.
Steel is stronger than pure iron and can be used for everything from sauce pans… …to suspension bridges!
What is steel?
When other elements are added to iron, their atoms distort the regular structure of the iron atoms.
The atoms in pure iron are arranged in densely-packed layers. These layers can slide over each other. This makes pure iron a very soft material.
Why is steel stronger than iron?
It is more difficult for the layers of iron atoms in steel to slide over each other and so this alloy is stronger than pure iron.