KS3+Acids+and+Alkalis

[|Revision activity from BBC] Revision test from BBC
 * KS3 Acids and Alkali’s **

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 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. || 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. || media type="youtube" key="DupXDD87oHc" width="448" height="251"
 * 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.
 * //Acidus// in Latin means __ sour. __
 * [|Acids and bases] from TED Ed youtube.com**
 * 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. Examples)

Do Science workbook 1 page 32, 33.

media type="youtube" key="IAJsZWhj6GI" width="560" height="315" [|All about that base from youtube.com] 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) [|Acids and Bases] definition from chemistry.about.com [|Bases andd Alkalis] from BBC Bitesize Prepare indicators using crushing and filtering techniques.Use their prepared indicator on some acids. I__ ndicator __: A dye that changes colour when added to an acid or alkali.
 * Bases**

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

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. 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.’ ||
 * ‘Hydrangeas are amazing plants and you can actually change the colours of the

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.

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.

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

​ Describe the use of neutralisation to solve a problem. Eg bee stings/ indigestion. [|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.

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 If neutralisation has occurred can be checked by using __ universal __ __ indicator __. Name some common including hydroxides, sulphates and carbonates.
 * Neutralisation**: A metal oxide or a metal hydroxide reacts with an acid to form water and a salt. This reaction is called neutralisation.
 * 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.
 * Diagram: **

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. 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.
 * Method: **
 * Results: Write word equations for the reaction between metals and acids. **
 * Conclusion:**


 * Evaluation:**

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) → MgCl 2 (aq) + H 2 (g) 2. hydrochloric acid + zinc → zinc chloride + hydrogen 2HCl(aq) + Zn(s)→ H 2 (g) + ZnCl 2 (aq) 3. magnesium + //sulphuric acid// → //magnesium// sulphate + hydrogen Mg (s) + H 2 SO 4 (aq) -> MgSO 4 (aq) + H2 (g) 4. Sulphuric acid + Zinc → Zinc sulphate + Hydrogen Zn + H 2 SO 4 → ZnSO 4 + H 2 5. nitric acid + magnesium → magnesium nitrate + hydrogen 2HNO 3 + Mg → Mg(NO 3 ) 2 + H 2 6. aluminium + hydrochloric acid → aluminium chloride + hydrogen 2 Al + 6 HCl → 2 AlCl 3 + 3 H 2 7. nitric acid + potassium → potassium nitrate + hydrogen 2K + 2HNO 3 → 2KNO 3 +H 2

Acids + Metal carbonates => Salts + Carbon dioxide + Water

Aim: To investigate the properties of CO 2 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 CO 2 bubbles pass through lime water. Record your observations. Test 3: Put a burning splint into a test tube of CO 2. Record your observations. Test 4: Try putting a splint out by "pouring" CO 2 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 => CaCO 3 + H 2 O

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**. [|Thermal decomposition of calcium carbonate] from BBC Bitesize Metal carbonates and acid 1. **Fill in the gaps ** Metal Carbonate + acid >> ___ +__ _ + ___ ………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………… 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)
 * 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? **
 * <span style="font-family: &#39;Comic Sans MS&#39;;">5. Write a word equation to summarise the reaction that took place. **
 * <span style="font-family: &#39;Comic Sans MS&#39;;">6. Complete the word equations below: **

<span style="font-family: &#39;Comic Sans MS&#39;;">(Zinc Carbonate = ZnCO 3 <span style="font-family: &#39;Comic Sans MS&#39;;"> Hydrochloric acid = HCl, Sulphuric acid =H 2 <span style="font-family: &#39;Comic Sans MS&#39;;">SO 4 <span style="font-family: &#39;Comic Sans MS&#39;;">, Nitric acid =HNO 3 <span style="font-family: &#39;Comic Sans MS&#39;;">) <span style="font-family: &#39;Comic Sans MS&#39;; font-size: 16px;">…………………………………………………………………………………………………………………………………………………………………………………
 * <span style="font-family: &#39;Comic Sans MS&#39;;">7. Using the following information construct symbol equations for the word equations written in questions 5 + 6: **

acid || + || calcium carbonate || => || calcium chloride || + || carbon dioxide || + || water || 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
 * hydrochloric

Lab1: Table of various chemical reactions
 * Extension** [|reactions of acids] from BBC bitesize [|acids and alkalis] from gcsescience

Lab2: Types of chemical reactions practical

Distinguish physical and chemical changes <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">AIM : To find out if the given task is a physical or chemical change
 * Physical and Chemical Changes **

<span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">Tasks: <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">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.

<span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">2. Place two spatulas of sucrose into a test tube. Then gently warm using the Bunsen burner.

<span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">3. Place a 2 cm depth of acid into a test tube. Then add a small marble chip (calcium carbonate).

<span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">4. Observe the appearance of the mixture of sulphur and iron. Separte the mixture, ask the teacher for apparatus that you may need.

<span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">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.

<span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">6. Place a 2 cm depth of copper sulfate solution into a test tube. Carefully add a further 2 cm depth of dilute ammonia.

<span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">OBSERVATION TABLE:
 * || <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">Task 1 || <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">Task 2 || <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">Task 3 || <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">Task 4 || <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">Task 5 || <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">Task 6 ||
 * <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">Physical change ||  ||   ||   ||   ||   ||   ||
 * <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">Chemical change ||  ||   || <span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">v ||   ||   ||   ||

<span style="font-family: &#39;Lucida Console&#39;,Monaco,monospace;">CONCLUSION: 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.
 * **Physical changes:** A physical change does not produce a new substance. The physical change is often r __ eversible __.

[] || Burning bread. Digesting food. || Oxidation: The process of oxidizing; the addition of oxygen. A reaction when a substance burns in air with reaction of oxygen. Combustion: A chemical change, especially o xidation, 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 Rusting: 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. Burning: A process in which a substance reacts with oxygen to give heat and light and a flame develops in the reaction. Respiration: 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. reactant: A substance that participates in a chemical reaction, esp a substance that is present at the start of the reaction. product: A substance that is formed/resulting from a chemical reaction. Combination: A chemical reaction of two or more c ompounds, usually to form one other compound Decomposition: Separation of a substance into two or more substances that may d iffer from each other and from the original substance Explosion: 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.
 * __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.
 * Key words for reaction: **

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 CH 4 + 2O 2 => CO 2 + 2H 2 O

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. Calcium carbonate with acetic acid. || Acids with .. || Your own examples... || 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. ||
 * Baking soda and vinegar.
 * ||  || Rapid combustion with a fine powder( cornflour in a tin with a lighted candle).

Describe some reactions which happen relatively slowly. Oxidation reaction between fats and oils in food and oxygen in the air makes food.
 * 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. ||  ||   ||

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. In the presence of water, iron combines with oxygen in the air to slowly form rust. 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.

**Experiment** Aim: To investigate if other factors such as temperature and presence of salt in the water affect to the rate of rusting. Hypothesis: Apparatus: Method: 1. 2.  3.  4.  5.  6.  7.  8.  9.  10. Result: Conclusion

State ways of preventing rust. By keeping oxygen and water away from the contact with iron/steel, rust does not form. __ P ainting, 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.
 * How can you not expose iron materials to water? **

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.
 * Suggest where we can find an example of the applications to be most appropriately used.**
 * Suggest how different parts are protected from corrosion.**

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.
 * Fuel || coal || charcoal || oil || diesel oil || petrol || natural gas || wax || wood ||
 * Uses ||  ||   ||   ||   ||   ||   ||   ||   ||

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 **r** eleased during the process Image from [|education.ti.com] || Image from [|revisionworld] ||
 * [[image:Respiration.jpg width="434" height="235"]]
 * [[image:Photosynthesis vs Respiration.jpg width="437" height="158"]]
 * [[image:Photosynthesis.jpg width="444" height="604"]] ||



__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 r equired during the process