KS3 Acids and Alkali’s
Revision activity from BBC
Revision test from BBC

Recognise some problems with acidic properties.
Check and complete the safety symbols on your workbook on p.33.

Bring your materials to test how acidic or how alkali they are.
ex) cleansing soap, liquid soap, lemon juice, vinegar, milk, blood, toothpaste, bleach, washing soda, oven cleaner, etc

Acid rain from epa.com

Describe alkalis as the chemical opposite of an acid.
What are the meaning of acids and alkalis?
Acid: A sour substance that can attack metal, clothing or skin.(Acidic)
Alkali: A soapy feeling substance that dissolves grease.(Alkaline)
Acids change litmus to a red colour.
Acid particles make other particles change.
Lots of acids become dangerous.
Uses: Metal cleaner. Vitamin C
Alkalis make litmus blue.
Alkalis have different active particles. They are often used to destroy grease. Oven cleaner is a strong alkali. Alkali particles taste bad. Lots of alkalis are also dangerous.
Uses: Cleansing soap/liquid.
Acidus in Latin means sour.
Most of acids are corrosive liquids that fizz when they come into contact with solids and burn when they touch the skin.
Alqaliy in Arabic means the ashes.
A concentrated solution of an alkali is corrosive and can burn the skin. Even dilute solutions of alkali react with fat on the surface of the skin and change it into substances found in soap. Alkalis such as many household cleaners must be handled with great care.
Acids found in plants and animals(Refer to your text page 146)
Acids with plant origins
Acids with animal origins

Alkalis around us: text page 149.

Do Science workbook 1 page 32, 33.

Bases are compounds which react with acids. All metal oxides, metal hydroxides and metal carbonates are bases. Bases which dissolve in water are called alkalis(e.g. sodium hydroxide)

Prepare indicators using crushing and filtering techniques.Use their prepared indicator on some acids.
Indicator: A dye that changes colour when added to an acid or alkali.

LITMUS paper changes its colour from red to blue in alkali and blue to red in acid.
RED CABBAGE INDICATOR: It changes its colour into pink in acids and greenish blue in alkalis.Red cabbage indicator from About.com chemistry
1. Making own indicator and testing everyday substances.ppt
1. Making own indicator and testing everyday substances.ppt
1. Making own indicator and testing everyday substances.ppt


Read the following article and write a letter to Ms. Lee explaining to her about hydrangeas and soil pH.
Ms. Lee loves blue. Explain to her how to turn the flowers blue. Explain why this method works.
‘Hydrangeas are amazing plants and you can actually change the colours of the
flowers. The flower colour in most hydrangeas relates to the pH of the soil. In soil that has a pH of more than 5 the flowers are pink or red. In
acidic soil (pH 5 or less) the flowers are blue. You can buy a ‘blueing tonic’ which contains aluminium and acid and will turn pink or red hydrangeas blue. It should be applied once a month in March and April and then again in August, September and October. A cup of calcium carbonate added to the soil in spring will turn
blue hydrangeas pink. White flowering hydrangeas will stay white no matter what the pH of the soil is.’

Compare between weak and strong acids.
Distinguish strong and weak acids and alkalis.
Draw the figure 10.10 on page 151.
The pH scale is a scale for measuring acidity. The pH number match to a colour chart of universal indicator.

The pH scale.jpg
The pH scale.jpg

Image from www.naturalalliance.org

Use Universal Indicator.
Universal indicator is a mixture of dyes that goes different colours according to how concentrated/strong the acid or alkali in a solution is.
Universal indicator.JPG
Universal indicator.JPG

Detecting acids and alkalis:
Hydrangeas have pink flowers in a soil containing lime(calcium hydroxide/alkali) while blue flowers in acidic soil (acid/ PH 5 or less).

Describe the use of neutralisation to solve a problem. Eg bee stings/ indigestion.
2 neutralisation students PPT research.ppt
2 neutralisation students PPT research.ppt
2 neutralisation students PPT research.ppt
Neutralisation from www.s-cool.co.uk

Prepare a neutral solution.
Prepare crystals of common salt.
Prepare other chlorides by the same method.
Complete your workbook page 34 and 35.
2. Neutralisation.ppt
2. Neutralisation.ppt
2. Neutralisation.ppt

Acids + Alkali => Salts + water
sodium hydroxide + hydrochloric acid → sodium chloride + water
hydrochloric acid + potassium hydroxide => potassium chloride + water
sodium hydroxide + sulphuric acid => sodium sulphate + water
nitric acid + potassium hydroxide => potassium nitrate + water
Neutralisation: A metal oxide or a metal hydroxide reacts with an acid to form water and a salt. This reaction is called neutralisation.
If neutralisation has occurred can be checked by using universal indicator.
Name some common including hydroxides, sulphates and carbonates.
Reactions of Acids and Metals
Pop test
Aim: To investigate which product are made when metals react with acids.
Apparatus: hydrochloric acid, sulphuric acid, magnesium strip, zinc strip
Safety: 1. Wear eye protection. 2. Take care handling acids. Wash it off if you get any on yourself.

1. Quarter fill (about 2 ~ 3 cm depth) a test tube with dilute hydrochloric acid and add some finely granulated magnesium.
2. Put your thumb loosely in the top of the tube. As the magnesium reacts with the acid, the bubbles rise up.
3. Light a splint.
4. Bring the splint near to the neck of the tube as you take your thumb away.
5. Repeat the experiment using different metals and acids.
Results: Write word equations for the reaction between metals and acids.
magnesium + hydrochloric acid
magnesium + sulphuric acid
zinc + hydrochloric acid
zinc + sulphuric acid →
1. What can you tell when you put a piece of metal strip in an acid solution?
2. How can you tell if it is physical or chemical reaction?
3. What test did you do to test the gas produced? Put a flame on the mouth of test tube to see if the gas is flammable or explosive.
4. Did you hear any sound? You hear a ‘pop’, which is a small explosion. Hydrogen is a very explosive gas.
5. Can you tell the name of the gas? If flammable, it is oxygen. If explosive, it is hydrogen.
6. What can you tell about the gas produced during the reaction? a. hydrogen does not dissolve in water. b.hydrogen floats. c. hydrogen is explosive.
When metal reacts with acids, hydrogen gas, a salt and heat are produced.
Hydrogen is lighter than air and is an explosive gas that does not dissolve in water.


Some of the hydrogen may have escaped into the air before you had time to test it. Can you think of a better method of collecting the gas?

Acids + Metal Salts + Hydrogen gas
1. hydrochloric acid + magnesium magnesium chloride + hydrogen
2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)
2. hydrochloric acid + zinc zinc chloride + hydrogen
2HCl(aq) + Zn(s)→ H2(g) + ZnCl2(aq)
3. magnesium + sulphuric acidmagnesium sulphate + hydrogen
Mg (s) + H2SO4 (aq) -> MgSO4 (aq) + H2 (g)
4. Sulphuric acid + Zinc → Zinc sulphate + Hydrogen
Zn + H2SO4 → ZnSO4 + H2
5. nitric acid + magnesium → magnesium nitrate + hydrogen
2HNO3 + Mg → Mg(NO3)2 + H2
6. aluminium + hydrochloric acid → aluminium chloride + hydrogen
2 Al + 6 HCl → 2 AlCl3 + 3 H2
7. nitric acid + potassium → potassium nitrate + hydrogen
2K + 2HNO3 → 2KNO3 +H2

Acids + Metal carbonates => Salts + Carbon dioxide + Water
3. Reactions of Acids metals carbonates.ppt
3. Reactions of Acids metals carbonates.ppt
3. Reactions of Acids metals carbonates.ppt

To investigate the properties of CO2 in terms of density, flammability, and the reaction with lime water.
To understand that an acid react with metal carbonate, it produces carbon dioxide.
To deduce the name of the salt formed in the reaction.
To be able to name of the several carbonate compound. sodium carbonate, iron carbonate, ...

Test 1: Add 1 small spatula of calcium carbonate powder into a test tube with 2cm Hydrochloric acid in it. Collect the gas produced into a flask with lime water in it.
Test 2: What is gas produced? What happens when CO2 bubbles pass through lime water. Record your observations.
Test 3: Put a burning splint into a test tube of CO2. Record your observations.
Test 4: Try putting a splint out by "pouring" CO2 over it.

Carbon dioxide is heavier than air and is a non-flammable, colourless and odourless gas that dissolves in water.

Why does lime water go cloudy when carbon dioxide is bubbled through it? from www.gcsescience.com

Lime water is a solution of calcium hydroxide. When carbon dioxide dissolves in water, it forms an acid which can react with the calcium hydroxide. The products of this reaction are calcium carbonate solid (the same chemical as chalk) and water

calcium hydroxide + carbon dioxide => calcium carbonate + water

Ca(OH)2 + CO2 => CaCO3 + H2O

If you were to keep bubbling carbon dioxide through cloudy limewater, it would go clear again. It is because the calcium carbonate, chalk reacts with water and carbon dioxide to form a new compound called calcium hydrogen carbonate that is soluble in water. This water is known as hard water.

Metal carbonates and acid
1. Fill in the gaps
Metal Carbonate + acid >> _ + _ + ___
2. Describe how you would test for carbon dioxide and what you would see.
3. How could you tell a chemical reaction had taken place?
4. What salt did you make when you added copper carbonate to sulphuric acid?
5. Write a word equation to summarise the reaction that took place.
6. Complete the word equations below:
Sulphuric acid + Zinc Carbonate zinc sulphate + water + carbon dioxide
H2SO4(aq) + ZnCO3(s) → ZnSO4 (aq) + H2O (l) + CO2 (g)
Hydrochloric acid + Magnesium Carbonate Magnesium chloride + Carbon dioxide + Water
2HCl + MgCO3 → MgCl2(aq) + H2O (l) + CO2 (g)
Nitric Acid + Calcium Carbonate calcium nitrate + water + carbon dioxide
2HNO3 + CaCO3 → Ca(NO3)2 +H2O (l) + CO2 (g)

7. Using the following information construct symbol equations for the word equations written in questions 5 + 6:
(Zinc Carbonate = ZnCO3 Hydrochloric acid = HCl, Sulphuric acid =H2SO4, Nitric acid =HNO3)

1. iron carbonate + sulphuric acid →Iron sulphate + carbon dioxide + water
Iron(II) carbonate + Sulphuric acid Iron(II) sulphate + Water + Carbon dioxide
FeCO3 + H2SO4 → FeSO4 + H2O + CO2
Iron(III) carbonate + Sulphuric acid Iron(III) sulphate + Water + Carbon dioxide
Fe2(CO3)3 + 3 H2SO4 → Fe2(SO4)3 + 3 H2O + 3 CO2
2. zinc carbonate + hydrochloric acid → zinc chloride + carbon dioxide + water
ZnCO3(s) + 2HCL(aq) → ZnCl2 (aq) + H2O(L) + CO2(g)
3. potassium carbonate + nitric acid potassium nitrate + carbon dioxide + water
K2CO3 + 2HNO3 → 2KNO3 + H2O + CO2
4. Sodium hydrogen carbonate + hydrochloric acid sodium chloride + carbon dioxide + water
NaHCO3(aq) + HCl(aq) → NaCl(aq) + CO2(g) + H2O(l)
5. lithium carbonate + nitric acid → lithium nitrate + water + carbon dioxide
Li2CO3 + 2HNO3 → 2LiNO3 + H2O + CO2
6. calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water
CaCO3 + 2HCl → CaCl2 + H2O + CO2

Extension reactions of acids from BBC bitesize acids and alkalis from gcsescience

Physical and Chemical Changes
Distinguish physical and chemical changes
AIM : To find out if the given task is a physical or chemical change

1. Collect 5-10 crystals of Iodine into a petri dish and leave it out in the sun. Check the Petri dish for observations after 20 minutes.

2. Place two spatulas of sucrose into a test tube. Then gently warm using the Bunsen burner.

3. Place a 2 cm depth of acid into a test tube. Then add a small marble chip (calcium carbonate).

4. Observe the appearance of the mixture of sulphur and iron. Separte the mixture, ask the teacher for apparatus that you may need.

5. Place a 2 cm depth of sodium carbonate solution into a test tube. Carefully add a further 2 cm depth of iron chloride solution.

6. Place a 2 cm depth of copper sulfate solution into a test tube. Carefully add a further 2 cm depth of dilute ammonia.


Task 1
Task 2
Task 3
Task 4
Task 5
Task 6
Physical change

Chemical change


Physical changes: A physical change does not produce a new substance. The physical change is often reversible.
Starting products are equal to the ending products after the change.
Chemical changes: A chemical change produces a new substance and the change is usually non reversible. It often accompanies with light, heat or colour changes. Starting products are not equal to the ending products after the change.

Examples: Making a sheet of paper into smaller pieces by cutting or tearing it. Melting ice cubes(Phase change). Breaking a beaker. Crushing a can.
Examples: Mixing acid and base, rusting of an iron nail. cooking eggs.
Burning bread. Digesting food.
Key words for reaction:
The process of oxidizing; the addition of oxygen. A reaction when a substance burns in air with reaction of oxygen.
A chemical change, especially oxidation, accompanied by the production of heat and light.
A chemical reaction in which a substance, usually a fuel, takes part in a fast reaction with oxygen to release heat energy.
fuel + oxygen >> carbon dioxide + water
The formation of reddish-brown flake of rust(ferric oxides) on iron by oxidation in the presence of water. It is exothermic reaction but as the reaction is slow the heat is produced in small amounts.
Iron + oxygen >> iron oxide
When water vapour in the air condenses on iron/steel, it makes film on the surface of the metal. Oxygen dissolves in the water and reacts with the metal to form iron oxide.
A process in which a substance reacts with oxygen to give heat and light and a flame develops in the reaction.
The process in which energy is released from food and produce carbon dioxide and water.
glucose + oxygen >> carbon dioxide + water
Oxidation occurs in respiration where the carbon in glucose is oxidised to carbon dioxide.
Physical change:
A change in size/shape or reversible reaction without a change in chemical composition.
Chemical change:
A process in which one or more substances are changed by the atomic and molecular composition into others. Many chemical reactions are non-reversible changes.
A substance that participates in a chemical reaction, esp a substance that is present at the start of the reaction.
A substance that is formed/resulting from a chemical reaction.
A chemical reaction of two or more compounds, usually to form one other compound
Separation of a substance into two or more substances that may differ from each other and from the original substance
A violent release of energy such as heat and light resulting from a rapid chemical or nuclear reaction
If coal dust is hot and heated, it produces a flame and explodes in air. The heat produced by this fast reaction causes the air to expand rapidly.

Describe burning
A process in which a substance reacts with oxygen giving heat and light with a development of flame.

Recognize that the process of burning gives out heat.
Burning: Exothermic reaction which gives out heat when a substance react with oxygen.
Natural gas is hydrocarbon which is made of carbon and hydrogen. When it burns, carbon dioxide and water are produced.
methane + oxygen >> carbon dioxide + water
CH4 + 2O2 => CO2 + 2H2O

Compare melting and burning
Melting: A process of the change of states from solid to liquid such as an ice cube to water. It is a physical change and heat is taken in during the process.
Burning: A process of chemical reaction with oxygen in general. It is a chemical change and heat gives out during the chemical reaction.

Describe some reactions which happen relatively quickly.
Baking soda and vinegar.
Calcium carbonate with acetic acid.
Acids with ..
Your own examples...

Rapid combustion with a fine powder( cornflour in a tin with a lighted candle).
When the flour is blown with a straw the explosion can blow the lid off the tin. This is a danger in mills, coal mines etc.

Describe some reactions which happen relatively slowly.
Examine some food which contain antioxidants.
Your own examples...
Your own examples...
Wild blueberry, Cranberry, Blackberry, Raspberry, Strawberry, Smith apple, Pecan, Plum, Apple

Slow oxidation of fats and oils takes place turning them rancid.

Oxidation reaction between fats and oils in food and oxygen in the air makes food.

State the conditions necessary for the formation of rust
Both water and oxygen must be presented for the formation of rust.

Explain that rusting is an oxidation process (addition of oxygen)
Iron + Water + Oxygen => Hydrated Iron Oxide
Oxygen is compulsory element for rusting to take place. If there is no oxygen, the process above does not take place so rusting does not happen.

State the factors which increase the rate of rusting
What other factors do you think will increase the rate of rusting?(Science text 2 p.152)
Rusting speeds up if the reactants are warmed. The presence of salt in the water on the metal also speeds up rusting.

Aim: To investigate if other factors such as temperature and presence of salt in the water affect to the rate of rusting.

State ways of preventing rust.
How can you not expose iron materials to water?
By keeping oxygen and water away from the contact with iron/steel, rust does not form.
Painting, greasing, galvanising, plastic coating can prevent rusting of metal but if the oil dries up or the paint becomes chipped, rust can begin to form again.

Suggest where we can find an example of the applications to be most appropriately used.
Suggest how different parts are protected from corrosion.
A bicycle with a painted frame.
A steel used to build office blocks and bridges is coated in zinc in a process of galvanising.
Steel can be also protected by covering the surface with tin.

Recognize other examples of corrosion.
Your task: Research the uses of iron and suggest why it is used even though it rusts.

State that oxides can be prepared by combustion.
Combustion is a chemical reaction with oxygen oxidation.The simplest reaction is the combustion of elements to form oxides.
It can be weighed before and after to show addition of oxygen. Iron and copper can be burned in oxygen.

State the three requirements needed for a fire to start/remain alight.
Oxygen, fuel, fire

Compare the values of different fuels.
Suggest the best fuel for a purpose.
diesel oil
natural gas

Briefly describe the link links with respiration and photosynthesis.
Respiration is a process of producing energy along with carbon dioxide and water from food when glucose reacts with oxygen.
glucose + oxygen => carbon dioxide + water ------> Energy released during the process

Image from education.ti.com

Photosynthesis vs Respiration.jpg
Photosynthesis vs Respiration.jpg

Image from revisionworld


Image from co2crc

photosynthesis and respiration.ppt
photosynthesis and respiration.ppt
photosynthesis and respiration.ppt

Photosynthesis a process of producing food and oxygen in a plant leave using water and carbon dioxide. It requires energy from the Sun.

carbon dioxide + water => glucose + oxygen ------> Energy required during the process