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Chemicals In Our Daily Life - 1I

Chemistry 8th GradeChapter - 12

Content

1. Chlorine

2. Sulphur dioxide

3. Sodium Bicarbonate

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We have learnt in the past about Elements and the Periodic Table, and we know that the building blocks of all the matter that exists on earth are found there.

Q: Can you think of one element that is involved in keeping your water safe to drink, your swimming pools healthy and clean, is found on your dinner table, and even in cell phone and solar panels?

Yes, the element is Chlorine!

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Activity 1: In Pairs with your partner do the followingChlorine is used to manufacture each of the following products. Circle the products you have used or seen used in the past month.

luggage telephones air conditioners photographs toys

umbrellas perfume toothpastes paint removers cosmetics

shoes soft drink bottles fire extinguishers plastic bags

fireworks soft drinks newspaper compact discs mirrors

paper towels paint plastic bottles refrigerators raincoats

What can you say about Chlorine after this exercise?

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What do we know about Chlorine already?

1.What is its symbol?

2. What is its Atomic Number and weight? 3. What is its Atomic configuration?

4. Which family does it belong to?

5. So what type of ion does it form?

Cl

17 ,atomic weight of 35.435.

The Halogens

2,8,7

A negative ion, receiving one electron into its outermost shell to acquire the highly stable electronic configuration.

More about Chlorine:The naturally occurring isotopes of chlorine are 35 and 37. It is highly reactive, and greenish yellow with a noxious odor and is poisonous to humans if inhaled even in small quantities.

Chlorine : History• Chlorine was discovered

in 1774 by Swedish Chemist Carl Wilhelm Scheele.

• In 1810, Sir Humphry Davynamed the gas Chlorine fromgreek word ‘chloro’ meaning ‘Pale Green’.

Chlorine – Occurrence in nature

• Chlorine is found in Common Salt, Rock Salt.

• In Oceans, mainly in the Dead Sea.

• As HCl in our stomach.

• Some common Chloride minerals include Halite, Sylvite, Carnalite etc…

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Interesting Facts:

The most common natural chlorine compound on Earth is sodium chloride or table salt.

Chlorine is the 21st most abundant element in the Earth's crust

Chlorine is the 3rd most abundant element in the Earth's oceans

Chlorine gas was used as a chemical weapon during World War I. Chlorine is heavier than air and would form a deadly layer in low-lying trenches.

Chlorine leaks are detected using ammonia, because Ammonia reacts with the chlorine to form a white mist above the leak. What might this compound be?

Commercial Preparation of ChlorineCommercially Chlorine is prepared by electrolysis of an aqueous solution of Sodium Chloride (NaCl) where Cl2 is evolved at the anode and H2 at the Cathode.

222 222 ClHNaOHOHNaCl

Laboratory Preparation Of Chlorine

Chlorine is also prepared in the labaratory in smaller quantities. These methods are different from the way it is made commercially.

1. Using Manganese Dioxide (MnO2)

2. Using Potassium Permanganate (KMnO4)

Preparation Of Chlorine1. From Manganese Dioxide

OHClMnClHClMnO 2222 24

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Q1. Why is the gas evolved passed through water first?To dissolve any lingering Hydrochloric Acid.

Q2. Why is the gas evolved passed through Concentrated Sulphuric Acid next?Concentrated Sulphuric Acid is a drying agent and removes moisture from the gas.

Q3. Why is the gas collected by the upward displacement of air?Chlorine gas is heavier than air and will settle at the bottom of the gas jar.

Q4. Why are the ends of the tubes, that enter the Conc. Sulphuric Acid and Water, made to dip into them?Because then the gas will be forced through the liquid in the bottle for better reaction.

Preparation Of Chlorine2. From Potassium Permanganate

08522162 22224 HClMnClKClHClKMnO Potassium Permanganate removes Hydrogen from Hydrochloric Acid in the above reaction.What type of a reagent could we call it? Explain in your own words.

Chlorine : Physical Properties

.Colour - Pale Green Gas

Formula – Cl2

Heavier than airCombines with both Metals and Non-Metals.

Chlorine: Physical propertiesActivity 2: In PairsThe following experiments were done with these observations. What would the Inferences be?

EXPERIMENT OBSERVATION INFERENCE

Introduce a burning candle into a jar of chlorine gas

Burns with a dull sooty flame

Introduce few rose petals (soaked in water) into a jar of chlorine

decolourization

Introduce rose petals into another jar but without water

Slow decolourization

Hold wet blue litmus separately in chlorine jar

Blue litmus becomes red

Collect chlorine in a jar Pale greenish yellow

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Chemical Properties Of Chlorine

• Chlorine reacts with Magnesium to form Magnesium Chloride.

• Chlorine reacts with red phosphorus in different conditions to give different products.

(Less Chlorine)

(More Chlorine)

22 MgClClMg

32 232 PClClP

52 252 PClClP

Name the 2 compounds formed.

Chemical Properties of Chlorine

• Sodium burns vigorously with Chlorine to produce fumes of Sodium Chloride.

• Aluminium reacts with Chlorine to give Aluminium Chloride. A bright white light is observed during the reaction. What can you infer from this?

• When Chlorine is dissolved in water it forms Hypochlorous acid which is not very stable. It releases nascent Oxygen (Oxygen in its atomic state) which is a powerful oxidising agent. This is responsible for its bleaching and sterilising properties.

NaClClNa 22 2

32 232 AlClClAl

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Chlorine and Drinking Water

Q: Why is chlorine added to drinking water?A: Chlorine destroys disease-causing germs and helps make water safe to drink. It helps to virtually eliminate waterborne diseases like cholera and typhoid fever. The WHO drinking water standard states that 2–3 ppm chlorine should be added in order to have satisfactory disinfection and acceptable residual concentration.

Besides killing dangerous germs like bacteria, viruses and parasites, chlorine helps reduce disagreeable tastes and odors in water. Chlorine also helps eliminate slime bacteria, molds and algae that commonly grow in water supply reservoirs, on the walls of water storage tanks.

Q: How is chlorine added to drinking water?A: Water treatment may use either chlorine gas, liquid sodium hypochlorite solution (bleach) or dry calcium hypochlorite. Each of these disinfectants unleashes the power of chlorine to destroy disease-causing germs in water.

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Activity 2:2 Questions you should discuss and answer

1. What do you think will happen if chlorine levels in natural water sources such as rivers and lakes was high?

2. How do you think the chlorine level in the water indicates the quality of the water?

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Where can you find chlorine?Swimming PoolsHave you ever gone swimming? People put chlorine in the pool to kill bacteria and other disease producing organisms. It is also used to control the growth of slime and Algae in pipes and Storage tanks

Making PaperChlorine is used to make paper white. It bleaches the paper of all color, which results in the white colour.

BleachWhenever you wash white clothes you use bleach. That's chlorine you're using! It also takes the color out of darker clothes, so you have to take care. Used in the manufacturing of Bleaching powder.

Water PurificationChlorine is use to clean the water that comes to your house to control widespread of diseases like Typhoid, Cholera.

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Table SaltThe salt on your table is made up of chlorine. The Sodium Chloride of salt comes from the ocean.

PlasticsThink about sprinkler systems. Whenever you put sprinklers in a garden people use plastic pipes for the water. Those pipes are made with a special plastic called PVC. That's poly-vinyl-chloride.

Medical and other applicationsNaCl is the basic component of intravenous saline injections, used in the preparation of Chloroform,

Used in the preparation of pesticides like Benzene hexachloride, DDT etc…

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QUIZQ: Chlorine has a distinctive color in its normal gaseous form. That color is:

greenish blue, greenish yellow, bright orange, dark red

Q: Chlorine is a member of the….

halogen group, noble gas group, alkali metal group, semi-metal group

Q: Chlorine is element number….

9, 16, 8, 17

Q: Chlorine has two stable isotopes.

True , False

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Project work(In groups of 4)

Make a visit to your local Water Treatment plant and make a Chart on the process followed there.

2. Sulphur DioxidePriestley prepared Sulphur Dioxide by heating Sulphuric Acid with Mercury and called it ‘Vitriolic Air’.

Sulphur dioxide comes from both human activities and natural sources.

Burning coal and other fossil fuels is the largest source of sulphur dioxide from human activities.

Volcanoes and forest fires are the major natural contributors. Sulphur dioxide is a pollutant, and plays a role in climate change. Once in the atmosphere, sulphur dioxide can easily form sulfate ions, which readily combine with water vapor in the atmosphere to form small droplets of sulphuric acid (H2SO4) which comes down as ‘acid rain”.

When a volcano erupts huge amounts of sulphur dioxide are thrown into the stratosphere and converted to sulfates. These tiny droplets of sulphuric acid stay in the atmosphere and reflect incoming solar radiation. This reduces the amount of energy reaching the lower atmosphere of the Earth's surface. In turn, this results in a cooling of the lower atmosphere and Earth's surface and so the climate changes.

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Sulphur Dioxide: OccurrenceIn egg yolk, raddish, onion, garlic.

In our hair, nails and skin.

Released into the air by electric utilities that burn coal, petroleum refineries, cement manufacturing, paper manufacturing and metal smelting and processing facilities. Locomotives and large ships with diesel equipment burn high sulphur fuel and release SO2 into the air. In nature, volcanic eruptions release sulphur dioxide into the air.

Sulphur Dioxide- Commercial Production

• Mercurous sulphide (also called cinnabar) is one of

the many ores that has Sulphur. The sulphide ore

burns in air and sulphur dioxide is obtained as a

byproduct.

HgS + O2 ----- Hg + SO2

• Zinc from Zinc Sulphide (also called Zinc Blend)

2ZnS + 3O2 ---- 2ZnO + 2SO2

Sulphur Dioxide- Laboratory preparation.

Copper turnings and conc. Sulphuric are used in the

préparation of sulphur dioxide.

Cu + 2 H2SO4 ---- CuSO4 + SO2 + 2H2O

Sulphur Dioxide- Physical properties

Activity 3: If the following tests were done and the

observations made, what inferences could you draw?

EXPERIMENT OBSERVATION INFERENCE

Introduce a burning candle into a jar of Sulphur Dioxide gas

Flame is extinguished.

Pass sulphur dioxide for about five minutes into 400ml beaker half filled with water. Dip wet blue litmus.

Blue litmus turns red

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Activity 3a: With your partner complete the inferences you could make.

EXPERIMENT OBSERVATION INFERENCE

Introduce few rose petals (soaked in water) into a jar of chlorine

decolourization

Take the rose petals and introduce it to air

Colour regained

Introduce rose petals into another jar of sulphur dioxide but without water

No change

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Sulphur Dioxide- Think about it• Why is the bleaching action of sulphur dioxide temporary?

Because the bleaching happens by a process of reduction which

gets easily reversed, unlike the bleaching action of Chlorine.

• When a burning magnesium ribbon is kept inside a sulphur

dioxide jar, it continues to burn, leaving behind yellow particles.

2Mg + SO2-------- 2MgO + S

If Sulphur dioxide does not burn and also does not help in burning

then how does Magnesium burn?

What are those yellow particles?

Did you know? - Sulphur dioxide

• Sulphur dioxide dissolves easily in water to form sulphuric

acid. Sulphuric acid is a major component of acid rain.

Acid rain can damage forests and crops, change the acidity

of soils, and make lakes and streams acidic and unsuitable

for fish.

• Sulphur dioxide also contributes to the decay of building

materials and paints, including monuments and statues.

Uses of sulphur dioxide

1. In the manufacture of sulphuric acid used in making

detergents, fertilizers , paints and many medicines.

2. It prevents growth of microbes- used to increase

shelf life of foods.

3. Used in sugar industry for deodourizing and

decolourizing.

4. Used to prevent decolorization of dried fruits.

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5. Bleaching agent (wool, straws, sponges, wood-pulp in the manufacture of paper).

6. Fumigating agent in houses to kill insects (i.e. black ants)

7. Preservation of some liquids (i.e. orange juice).

8. Refrigerant.

3. Sodium bicarbonateIn what connection have you heard of this compound?

In connection with baking as an agent that makes the dough rise.Many food products such as bread, cakes and buns have a honeycomb structure which contains many bubbles. During cooking these bubbles are formed by a gas and the mixture ‘rises’. The most common chemical used to do this is sodium hydrogen carbonate, NaHCO3 (more commonly called sodium bicarbonate, or baking soda).

Sodium bicarbonate, is a base (alkaline in nature) that is formed when sodium carbonate is mixed with a solution of carbonic acid: Na2CO3 + H2CO3 = 2 NaHCO3Sodium Carbonate Carbonic Acid Sodium Bicarbonate

Commercial production

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Sodium Bicarbonate

Activity 5:Watch Video 1. Inpairs discuss what you see and try and explain the chemistry behind what is happening.

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On heating

2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(l)

On reacting with an acid, such as hydrochloric acid (HCl)

NaHCO3(s)+ HCl(aq) → NaCl(aq) + CO2(g) + H2O(l)

In both cases we see that Carbon dioxide is released.

• Prepare solutions of the following substances:

• washing soda, calcium hydroxide, bleaching powder,

vinegar, detergent, baking soda and soda water.

• Put a drop of each of the above solutions on a watch glass

and test by dipping red and blue litmus paper in it.

• What happens? Why?

Activity 6:Watch your teacher demonstrate the following and answer the questions below.

Observe the teacher demonstration and answer the questions.

•Take a spoon of baking soda. Observe its colour and physical

state.

•Put a red litmus into the solution of baking soda. What happens?

•Squeeze a piece of lemon on sodium bicarbonate in a test tube.

What happens? Pass the gas through lime water. What happens?

Uses of sodium bicarbonate

1. Baking powder is used to make bakery items.

2. Used in medicine as an antacid to treat excess of

acid formed in the stomach.

3. Mild cleaning agent

4. Prepare aerated water (soda water).

SOAPS AND DETERGENTSWhat are they ? Are they the same or different?

Soap- Cleaning substance made of animal or vegetable oil

is called soap.

Detergent- Cleaning substance made using petroleum is

called detergent.

Oil/Fat+ Sodium Hydroxide = Soap + Glycerol

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How soaps and Detergents work

Activity 6: In your groups of 4 watch the Video 2. Then make a chart to show your understanding of how Soaps work.

Use words like : Surfactants, Saponification, triglyceride, Alkali, grime, Hydrophobic, hydrophyllic, soap micelle. Display the chart.

All groups go around and examine the charts to look for accuracy of information.

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Activity 7: How Soap is made in the laboratory.

Watch Video 3 to observe the process and the precautions necessary while working with Sodium Hydroxide (or Lye).

Soaps and detergentsHow to make soap in the laboratory

•Take 30ml of vegetable oil in a beaker. •Dissolve 20gm of sodium hydroxide in 100ml of water in another beaker.•Take 60ml of this solution and add to 30ml of oil•Heat the mixture slowly.•Add 5 gms of sodium chloride to the boiling mixture (after 10-15 min).•Stir well!•It begins to thicken into a slurry. Here any desired perfume may be added. •Pour it out into moulds and cool for 24 hours.•Your soap cakes are ready!

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RECAP

Cl2+H2O→HOCl+HCl

1.Name the compounds formed. What is the significance of this reaction?→4H

2. Solve and balance the following equations

H2S+Cl2+H2O→3. Write the electron configuration for Chlorine.

4. What are the naturally occurring Chlorine isotopes?O2

5. Which fuels release sulfur dioxide when they burn?

6.How does sulfur dioxide in the air become acid rain?

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Complete the reaction. Why is it important?7. Na2SO3(s) + 2HCl(aq) →

8. Sulphur dioxide is formed when sulphur and sulphur-containing compounds burn. What environmental problem does sulphur dioxide contribute to?

9. Give two practical consequences of this problem.

10. C2H4O2 + NaHCO3 = NaC2H3O2 + H2O + CO2acetic acid sodium bicarbonate sodium acetate water carbon dioxide

What would you do if you wanted to make more carbon dioxide? Could you just keep adding more and more baking soda to the same amount of vinegar (acetic acid) to get more carbon dioxide? Why or why not?

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