Keywords

• Allotropes
• Autotrophy
• Fuels
• Global warming
• Hard water.
• Renewable

By the end of this chapter, you will be able to

(a) Understand how and why carbon compounds are used as fuels.

(b) Know and appreciate the difference between renewable and non – renewable fuels and understand that non – renewable fuels are not sustainable.

 (c) Know and appreciate the impact of burning carbon – based fuels on the environment.

(d) Understand the process of making charcoal, but recognize that the use of charcoal as a fuel is cheap, efficient, and sustainable only if it is made from wood that can be regrown easily

(e) Know and appreciate the physical properties and uses of carbon dioxide.

 (f) Understand how the increase in carbon dioxide in the air can cause the atmosphere and the oceans to get warmer.

(g) Understand what greenhouse gases are, where they come from and how they are affecting climate.

(h) Understand the origin of hard water in limestone areas and investigate how it can be softened.

(i) Understand how the properties and uses of the allotropes of carbon relate to their structures

Competency

You should be able to investigate the diversity of carbon compounds in the environment.

4.1 Introduction

 Most of us are familiar with ‘ charcoal ‘ or ‘ firewood ‘. Charcoal and firewood are used in everyday life as fuel for cooking the food we eat. Figure 4.1 shows the use of firewood for cooking.

 How many people know the actual chemical composition of charcoal and firewood in terms of the elements? Do you?

Both charcoal and firewood contain an element called carbon. Thus, carbon is all around us in many different forms and in many compounds that we use most often.

In this chapter, you will find out more about the different forms of carbon and how useful they are. You will also look at some carbon substances used as fuels , different forms of fuel , how some fuels are made and which form of fuel is cheaper and why .

In addition, you will also look at some compounds of carbon, their preparation, properties and uses.

Figure 4.1: Cooking the food we eat using firewood

4.2 What are fuels?

 Carbon is very useful to us because of its special properties. Carbon is an element. Do you recall what an element is? You may refer to Book One for help.

We have already mentioned that both charcoal and firewood contain carbon and that the two substances are commonly used as fuel.

 Now, what do you think fuels are? Can you name the other substances commonly used as fuels in your country and the elements present in the fuel?

Look at the pictures in Figure 4.2 which show common modes of transport in Uganda.

Figure 4.2: Common modes of transport in Uganda

A car

 Train

A ferry

An aero plane

 Group discussion

In small groups:

1. Suggest what you think the pictures in Figure 4.2 have in common.

2. Share your ideas with the other groups in class.

Activity 4.1 Finding out more about fuels what do you know about fuels?

 In this activity, you will work in groups to find out more about fuels.

What you need

• Library or internet

What to do

1. Carry out research from the library or the internet about fuels.

2. Use the following questions as your guideline:

1. What is a fuel?
2. What are the common substances we use as fuel in our communities or country?
3. Using word equation (s), explain what happens to the elements in the fuels named when the fuel is burnt in air. What are the elements that make up the fuels named in?
4. Apart from cooking, which is already mentioned as one of the uses of fuels, what are the other uses of the fuels named in (b)?

3. Write a report on your findings and present it in class.

4.3 Sources of our fuels and different forms of fuel

Most of our fuels come from the Earth itself. Fuels can be classified as non – renewable and renewable fuels.

Group discussion

In small groups:

1. Differentiate between renewable and non – renewable fuels.

Hint: You may use the dictionary to look up for the meaning of the term renewable.

2. List down examples of fuels that can be classified as: a) renewable. B) Non – renewable.

3. Suggest reasons why the named fuels in ( 2 ) ( a ) and ( 2 ) ( b ) are classified as renewable and non – renewable fuels , respectively .

4. Share your ideas with the other groups in class.

 In the following activities, you will find out more about some of the common fuels we use in our daily life.

Activity 4.2 Finding out more about the fuels in our communities

What to do

1. In groups, using the explanation using the explanation of what fuel are, brainstorm the different forms of fuel that are commonly used in your community. State whether the fuel is renewable or non – renewable. You may use a table of the form.

 Table 4.1: Examples of common fuels in Uganda

Fuel	Renewable or non – renewable	Use(s)

2. Using the library or internet (if available), carry out research about the fuels we get from crude oil.

Your findings should include the following:

• Names of the fuels and their uses.
• Name of the method used to obtain the fuels from crude oil and the reason for the choice of the method.
• Other product (s), if any, from crude oil.
• Whether the fuels are renewable or non-renewable.

3. In your view:

 a) Is it cheaper to rely on the fuels obtained from crude oil?

 b) What are some of the dangers associated with over – dependence on the fuels from the crude oil?

4. Share your findings with the class during the lesson.

Assessment 4.1

1. Charcoal is a form of carbon commonly used as a fuel. State what is meant by the term fuel. Using carbon, differentiate between incomplete combustion and complete combustion.

 2. Name any other three forms of fuel that are commonly used in your community.

4.4 Making charcoal

In Uganda, many people cook food using fire from burning wood. This practice was and is still being used in many different parts of Uganda.

The use of wood for cooking was widespread because in the past, wood was still abundant and supplies seemed to be inexhaustible.

Nowadays, some areas have almost no trees because they have been cut down for several reasons.

Look at Figure 4.3.

Figure 4.3: a): Making charcoal

Figure 4.3 b): Bags of charcoal ready for marketing.

Video link showing how charcoal is made locally

https://youtu.be/m3hOH7qcKpA?si=G8NzPUdIQivVrygv.

 Group discussion

 In small groups:

1. List down reasons why trees are being cut down by people in your community
2. . What are the alternative sources of fuel for cooking in your homes?
3. Share your ideas with the other groups in class

With the trees almost no more in many parts of the country, people have shifted to using charcoal as fuel instead of firewood

The only challenge with this alternative source is that much of it also comes from wood, as we shall see in the next activity.

The table 4.2 below shows the charcoal production trend in Uganda from 1961-2010.

 Table 4.2: Wood charcoal production trend in Uganda from 1961-2010

Year	Wood charcoal produced (tonnes)
1961	187160
1965	208292
1970	272269
1975	338733
1980	448283
1985	507627
1990	560789
1995	642806
2000	713381
2005	813508
2010	931466

Activity 4.3 Finding out more about wood charcoal production in Uganda

 What to do

1. Using the data in Table 4.2, plot a suitable graph to show the wood charcoal production trend in Uganda from 1961-2010.

2. What:

a) Does your graph reveal about the wood charcoal trend production in Uganda? Suggest reasons for your answer.

b) Are some of the negative impacts of over – dependence on wood charcoal?

c) Do you think the government should do to make the use of wood charcoal sustainable?

• Share your findings with your classmates.

From Activity 4.3, we have seen that wood charcoal use Uganda has been increasing and it is still increasing. The increase is attributed to various reasons already mentioned In Uganda , wood charcoal use is mainly in the urban areas The wood charcoal comes mainly from the rural areas .

Can you suggest why this is so?

Wood charcoal is made by heating pieces of wood covered with damp soil in a limited supply of air. Heating removes moisture and other volatile components from the wood and leaves charcoal behind.

 Activity 4.4 Making charcoal on a small scale

 What steps are taken when making charcoal?

CAUTION: WEAR HAND AND NOSE PROTECTION GEAR. A LOT OF SMOKE IS PRODUCED AND MAY CAUSE SERIOUS IRRITATION TO THE EYES. ENSURE THAT YOU HAVE A BUCKET OF WATER / SOIL JUST IN CASE OF A FIRE OUTBREAK.

In this activity, you will work in groups to make wood charcoal on a small scale.

 What you need

• Pieces of hardwood cut into small pieces.
• A medium – sized metal drum with a lid.
• Small twigs or paper.
• A box of matches / lighters.

What to do

1. Light a fire in the bottom of the metal drum with the small twigs / paper and some small bits of wood. Wait until the fire set is good and strong enough.

2. Once the fire is good and strong enough, add some pieces of wood and let it catch fire before adding more pieces. Continue adding the pieces of wood, a little at a time, until all the pieces have been added.

Figure 4.4: Processes involved in making wood charcoal           

Pieces of wood on fire ready for covering with a lid

Pieces of wood in a filled in drum with fire set at the bottom

Home ready – made charcoal

3. After all the pieces of wood have been added into the metal drum, wait until you can see that all the wood is starting to burn and blacken and then put the lid on to the metal drum

4. Allow the metal can to stand for around 24 hours or longer if needed and then remove the lid to check if the wood has finished smouldering. (If is it not quite ready, replace the lid and leave it for several hours longer before removing the lid again.)

5. When the fire is completely out and the barrel has cooled, remove the lid to get your home – made charcoal.

Results and discussion

• Why do you think?
• hardwood is preferred to softwood for charcoal making?
• It is recommended to add pieces of wood a little at a time?
• It is advisable to wait to see the wood starting to blacken before covering the metal drum with a lid?
• What is the use of placing the lid on the metal drum once all the wood is starting to burn and blacken?
• If you were a forestry officer, what advice would you give to the community on charcoal making?
• In your view:

 a) Which one is a better fuel (economically) and why? Is it charcoal or crude oil products?

Hint: Your comparison should base on: the availability, quantity of heat produced, pollution effects, transportation and storage.

                b) What are some of the qualities of a good fuel?

• Discuss your findings with the other group members.
• Prepare a summary of your findings and ask your teacher to comment on it.

Assessment 4.2

1. Charcoal making is associated with good and bad effects. Discuss.
2. Charcoal is a cheap but expensive source of fuel. Explain.

CHARCOAL FROM WASTE ORGANIC PRODUCTS

In Bwaise, Kampala and other places, people are engaged in making charcoal from the different waste materials. The charcoal made from this way is called charcoal briquettes. A briquette is a block of compressed coal dust, dust, sawdust, wood chips or biomass and is used as a fuel charcoal in stoves and boilers.

Figure 4.5 a): Charcoal briquettes being dried

Figure 4.5 b): Ladies making charcoal briquettes

 Figure 4.6 : From left – right : honey – comb briquette ( made by hydraulic press ) ; non – carbonized straw briquette ( made by piston extruded ) ; carbonized charcoal dust ( made by roller press ) ; hand – made charcoal dust briquettes

Many different types of briquettes exist for a variety of applications (see Figure 4.6). Briquettes have the potential to be a source of energy if they are made from sustainably harvested biomass or waste agricultural residues in this section, we shall investigate how charcoal briquettes are made from the waste materials.

Activity 4.5 Making charcoal briquettes from locally available materials

 What steps are taken when making charcoal briquettes?

CAUTION: WEAR HAND AND NOSE PROTECTION GEAR! CHARCOAL DUST CAUSES INCREASED INCIDENCE OF HEART AND RESPIRATORY DISEASES LIKE ASTHMA AND LUNG CANCER. PUT ON OLD CLOTHING.

In this activity, you will work in groups to make charcoal briquettes from locally available materials.

What you need

• Soil, preferably clay.
• Smashed charcoal / charcoal dust.
• Water.
• Basin / large bucket / cemented (or a clean) floor / large appropriate tray.
• Plastic cup / an appropriate beaker.

What to do

1. Using a plastic cup / beaker, transfer 6 parts of charcoal dust and 3 parts of soil into a basin / large container and thoroughly mix them.

2. Add water, a little at a time, to the mixture in the basin as you carefully mix it with your hands until a moist paste of the mixture is formed. (Take care not to add too much water.)

3. Using hands mould the moist paste formed into small round balls or any shape that is suitable for you.

 4. Keep the balls in a shade or indoors for about 5 days and then put them in the sun for further drying. Keep the briquettes away from rain as they dry.

Figure 4.7: Processes involved in making charcoal briquettes

Raw materials being thoroughly mixed

 Charcoal briquettes being spread out to dry

Ready – made charcoal briquettes

Results and discussion

• State the purpose of using soil during the making of charcoal briquettes.
• Why is the use of sandy soil more ideal than all the other forms of soil?
• Sometimes in the absence of soil, cow dung or cassava flour may be used. State the disadvantages of using cow dung or cassava flour in making briquettes.
• If you were a forestry officer, what advice would you give to the community on charcoal briquette making?
• Wood charcoal or charcoal briquettes; which of the two is economically better and why?

Hint: Your comparison should be based on: the cost, availability, quantity of heat produced, pollution effects, transportation and storage.

• Describe what happens when the charcoal briquettes are burnt.
• Discuss your findings with the other group members.
• Prepare a summary of your findings and ask your teacher to comment on it.
• https://drive.google.com/file/d/1FrQMeqk8Yg8MjH7OVO_hmE9SR4mcfrWW/view?usp=drivesdk link to the video showing how to make briquettes

ENERGY – SAVING CHARCOAL STOVES

 There are different forms of energy – saving charcoal stoves in Uganda.

In Uganda, the energy – saving charcoal stove factories are located in Mbarara and Mokono districts. However, there are other small – scale energy saving stove makers in some other parts of Uganda.

The energy – saving charcoal stoves vary depending on whether they are for home, school, hospital, restaurant or factory use, at the factories, the smallest available stove goes for about Shs13, 000.

These have advantages and disadvantages over the traditional charcoal stoves.

Look at the pictures below:

Can you tell which one is better: energy – saving charcoal stoves or the traditional charcoal stoves and why?

Figure 4.8 a): An energy – saving stove being constructed

 Figure 4.8 b): A modern energy – saving stove

Figure 4.8 c): Traditional charcoal stove

In this section, you make a choice between the two forms of charcoal stoves.

Activity 4.6 Finding out how energy – saving charcoal stoves are made

 In this activity, you will work in groups to find out how energy saving stoves is made.

What you need

• Note book, pencil / pen and markers
• Video clips / internet (if available) and library.
• Manila paper.

What to do

1. Carry out research on:

a) How energy – saving charcoal stoves are made.

b) Why the energy – saving charcoal stoves are being made in Uganda.

                c) The challenges the manufacturers are currently facing.

2. Prepare a summary of your findings.

3. Share the summary of your findings with your teacher and other group members in class.

 Project work 4.1

Making energy – saving charcoal stoves

 In Activity 4.6, you found out how energy – saving charcoal stoves are made in Uganda. Can you recall the steps and challenges involved in making energy – saving charcoal stoves?

 In this project, you will work in groups to make an energy saving charcoal stove. Thereafter, each group will present its report to the teacher and then, the classmates.

What to do

1. Basing on the information and knowledge you have gained so far, try to make energy – saving charcoal stove
2. You should be innovative and try to use any cheap local material that is available within your environment.
3. .Make a list of the materials you intend to use for the project.
4. Design the procedure you will follow to make energy saving charcoal stoves.
5. Present your ideas to your teacher so that he / she can advise you where possible.

CRUDE OIL

Crude oil, like many other natural resources, is not found in all parts of the world.

In Uganda, deposits of oil have been discovering in Bunyoro region. However, the production of oil has not taken off as many necessary things associated with its production are still underway.

Uganda imports refined oil and much of it comes through Mombasa port.

Figure 4.9: An oil refinery in Mombasa

 It is important to note that fossil fuels give out a lot of heat. But the worst is that they are non – renewable and cause pollution, with coal being the worst culprit.

 At present, Uganda depends on both charcoal and products of crude oil as sources of energy. However, crude oil being a non – renewable natural resource, its reserves is diminishing. In fact, this partly contributes to the ever – rising oil prices experienced in Uganda today.

The rise in oil prices has recently had serious impacts on our economy in terms of sharp increase in fares and the prices of commodities , and hence a higher cost of living .

In fact , some experts say we have approximately 60 years ‘ supply of crude oil remaining , depending on the way in which it is extracted and the rate at which it is used , but maybe more . But there is probably enough coal to last several hundred years (See table 4.3).

 Table 4.3: Estimates of how long our fossil fuels will last

Fossil fuel	Estimated date it is expected to run out
Natural gas	2110
Oil	2080
Coal	2500

 Therefore, it is important to use non – renewable fuels very carefully and to consider alternative renewable sources of. Energy for use now and in the future

The amounts of refined oil used by Uganda are still small compared to some other countries such as the USA and France. However, this amount is ever increasing day by day.

Can you guess why this is so? There is rapid population growth and this increases the demand for oil.

Figure 4.10: Graph showing the consumption of oil from 1980-20-13

Currently, research is being conducted to find:

 a) New oil reserves in different parts of the world.

b) A cheap, plentiful and probably renewable energy source to replace crude oil

Activity 4.7 Investigating crude oil production and use in a particular country

How crude oil is produced used in a country?

 In this activity, you will work in groups to investigate crude oil production and use in a particular country.

 What you need

• Note book, squared book / graph paper and a pen / pencil.
• Video recorder / internet / library.
• Ruler.
• Calculator

What to do

1. Collect ten years ‘ figures or more on crude oil production and consumption for a country of your choice.

2. Carefully study the figures and decide whether or not the country has used more than it has produced, each year.

3. Uing a horizontal axis for the ten or more years ‘ period; plot a graph of each set of figures

4. From your graph, state whether there is.

a) an regular increase or decrease in the figures.

b) an irregular increase or decrease in the figures.

5. Suggest reasons for your findings in 4.

6. From your graph, predict the production and consumption figures for that country in the year 2080.

7. is the prediction in 6 easy or not? Explain your answer. 7.

Assessment 4.3

1. In a table, list down the common fuels used in your country and for each fuel; state its sources along with its advantages and disadvantages.

2. With specific examples, state what is meant by the following terms:

a) Non – renewable energy sources.

b) Renewable energy sources.

4.5 Laboratory preparation and properties of carbon dioxide

We have already learnt in the previous section that carbon can be converted into carbon dioxide.

 Also in the atmosphere, the amount of carbon dioxide is 0.03 % by volume of the atmospheric gases (you may refer to Book One). In the laboratory, we can prepare carbon dioxide by reacting carbonates with acids.

Figure 4.11: Carbon dioxide from soda

 The most convenient pair is calcium carbonate (in the form of marble chips) and dilutes hydrochloric acid. This is because the reaction occurs at a controllable rate.

Activity 4.8 Preparing carbon dioxide and testing some of its properties

CAUTION: ACIDS ARE CORROSIVE! HANDLE WITH CARE. MARBLE CHIPS CAN CAUSE THE FLASK TO BREAK.

Why do you think carbon dioxide is important to us? In this activity, you will work in groups to prepare carbon dioxide gas.

What you need

• Marble chips, dilute hydrochloric acid, limewater and water.
• Conical flask with a side – arm (any available and appropriate flask), thistle funnel (or dropping funnel / tap funnel), gas jar, delivery tubes, deflagrating spoon and gas jar covers.
• Splints (a burning candle) and litmus paper (universal indicator).
• Internet (if available) / library.

What to do

1. Slide (do no drop) marble chips into the flask
2. Arrange the apparatus as shown in Figure 4.12 Collect the gas over water.
3. Pour dilute hydrochloric acid through the funnel into the flask containing the chips. Ensure that the acid covers the chips.

What do you observe in the flask?

Can you write a word equation for the reaction taking place in the flask? (You may refer to Chapter 1 for help.)

4. Collect about four gas jars of carbon dioxide. What can you say about the smell (odour) and colour of the gas collected?

Figure 4.12: Preparation of carbon monoxide

5. Basing on the choice of the method of gas collection used, what can you say about the density of the gas? Is the gas lighter or denser (heavier) than air

6. Carry out the following tests on the gas collected:

•  (i) Add about 15cm² of limewater and shake. What happens to the limewater? Is there any colour change?

                 (ii) What do you think is the use of the reaction that took place in Chemistry?

 b) (i) lower a burning candle / burning splint by means of a gas jar spoon into the jar of carbon dioxide

                (ii) What happens to the flame? What does the observation indicate about carbon dioxide?

                (iii) Can you suggest one use of carbon dioxide as a result of the observed property?

c) (i) Add about 20 cm³ of water into the gas jar and shake. Then add 2-3 drops of universal indicator (or you may drop the litmus papers)

(ii) What do you observe? What can you say about the solubility of the gas in water and its chemical nature?

7. Basing on the chemical nature identified in (6) (c), suggest some dangers associated with having high levels of carbon dioxide in our atmosphere.

8. Suggest with reasons (where applicable) some other uses of carbon dioxide apart from the one identified in (6) (b) you may use internet / library / handouts from your teacher for help

9. Share your findings with your classmates in the presence of your teacher.

4.6 The effects of carbon dioxide on the environment

We already mentioned in Book One. Chapter 7 that air pollution is one of the main environmental issues being talked of all over the world. Several measures are being put in place to address the issue.

One major contributor is the fuel we use that contains carbon.

 When the fuel is burnt, the carbon forms carbon dioxide which goes into the air.

The more we use the fuels, the more carbon dioxide is put in the air.

The next activity provides some of the ways in which the use of carbon – based fuels has impacted negatively on the environment in Uganda and worldwide, and some of the measures being taken to address the issues arising from the continued use of carbon – based fuels.

Figure 4.12: Preparation of carbon dioxide dilute

Activity 4.9 investigating the negative effects of carbon – based fuels on our environment and the world at large

Do you think the use of carbon – based fuels has done more harm than good?

In this activity, you will work in groups to investigate the effects of carbon – based fuels on the environment.

What you need

• Note book, pencil / pen and markers.
• Video clips / internet and library.
• Manila papers.

What to do

1. Carry out research on the negative effects of the use of carbon – based fuels. Your findings should include :
2. Condition (s) under which the products are formed.
3. Ways in which the amounts of the products from carbon – based fuels increase in the atmosphere.
4. Ways in which each of the products negatively impacts on the environment.
5. Product (s) arising from the use of carbon based fuels.
6. The necessary diagrams / photographs / illustrations (where applicable) of the key concepts of the impacts. •
7. Ways in which different countries, including Uganda, are trying to reduce or even prevent the increasing use of carbon – based fuels.
8. A poster with a message to the community about the dangers of increasing carbon dioxide in the atmosphere.

2. Prepare a summary of your findings.

3. Share your findings with other group members and then with your teacher

Assessment 4.4

1.            (a) Write a word equation for the reaction between calcium carbonate and dilute nitric acid.

b) How can the gaseous product in (a) be identified?

c) What colour change occurs when litmus paper is dipped into water saturated with carbon dioxide?

d) In what ways is the gaseous product in (a) useful to us?

2. How is carbon dioxide?

a) Removed from the atmosphere?

b) put back in the atmosphere?

3. Explain why the amount of carbon dioxide in the atmosphere stays about the same.

4.            a) Why might burn of carbon – based fuels lead to an increase in the Earth’s temperature?

 b) In what ways does the increase in the Earth’s temperature affect us?

c) How has the increase in the Earth’s temperature been minimized in your country?

4.7 Water hardness

One other most important natural resource we have apart from air is water.

Group discussion

In small groups:

• List down common sources of water in your community.
• List down some common substances that make water impure? You may refer to Book One, Chapter 8 for help on water pollution.
• Why do you think rainwater in a clean town is often regarded as the purest?
• Share your ideas with the other groups in class.

Each source is associated with a certain degree of purity. The purest water in a clean environment is rainwater.
Water contains dissolved salts ( like sodium chloride , calcium salts , potassium salts and magnesium salts ) and dissolved gases ( like carbon dioxide and oxygen )
 It is important to note that the dissolved X salts usually are not harmful and can , in fact , be good for us  
In what ways do you think the dissolved salts in water are useful to us ? Hint: You may refer to Chapter 2 for help.
 Look at the composition of one of the brands of bottled water that we drink.

Figure 4.13: Bottled water

What do you notice that the water contains? Of what use are they to us?
We use water daily for drinking, cooking and washing among others.

Group discussion

In small groups:

1. List downs the effects of the dissolved salts on the different uses of water, for example, washing.
2. List down the sources of these salts.
3. Briefly describe how these salts enter water.
4. Share your findings with the other group members.

 In this section, we shall deal with the effect of dissolved calcium and magnesium salts in water during washing. You must have noticed or heard that when washing using some water samples; a lot of soap is required to form lather.

Group discussion

In small groups:

1. List down the water samples which:

a) Easily form lather with soap when washing

b) Do not easily form lather with soap when washing.

2.Share your findings with the other group members

In the following activity, you will find out the effects of some salts on the water during washing.

 Activity 4.10 investigating the effect of soap solution in different water samples

How do we know that a given water sample is hard or soft?

In this activity, you will work in groups to investigate the effect of soap solution on different water samples.

CAUTION: GLASSWARE CAN EASILY BREAK IF NOT HANDLED WELL. TAKE GREAT CARE.

What you need

• 60 cm³ of each of the following water samples : Borehole water , distilled water , deionized water , sea water ( or river / lake water ) , rainwater , well ( spring ) water and tap water .
• 250 cm³ of soap solution.
• Measuring cylinder (50 ml / 100 ml), retort stand, burrito. Conical flask, cork and filter funnel.
• White tile / plain piece of white paper.
• Library / internet (if available).

What to do

1. Fill a burette with soap solution and note the level of the meniscus.

 2. Measure about 20 cm of distilled water into a clean conical flask.

 3. To the flask containing the water sample, add about 1 cm³ (or about 5 drops) of soap solution, cork the flask, and shake the mixture. What do you observe? Does the lather formed persist unbroken for about 2 minutes or does it disappear?

Figure 4.14: Investigating the effect of soap solution on different water samples water sample

4. If the lather formed persists / is unbroken for about 2 minutes, the titration is complete.

Note and record the burette reading in the table below.

5.However , if the lather formed in step 3 is broken / disappears , continue adding soap solution in the intervals of 1 cm³ ( or about 5 drops ) and shaking until permanent lather is formed

Note and record the burette reading in the table 4.4 of results below.

Note: If no permanent lather is formed after adding about 25 cm³ of soap solution, stop the addition. Note and record the burette reading in the table below.

6. Rinse the flask and repeat procedures 1 to 5 for the samples of water available.

Burette readings

 Table 4.4: Table of results

Water sample	Burette readings		Volume of soap solution used
	Initial burette reading	Final burette reading
Distilled water
Rainwater
Borehole water
Sea water/lake water/river water
Distilled water
Deionized water
Well/Spring water
Tap water

7. Answer the following questions:

1. Why do you think in some case the addition of soap solution was stopped when about 25 cm of soap solution had been added?
2. Which of the water samples readily formed lather with soap?
3. Can you suggest reasons for your answers in (b) and (c)?
4. What general name do we give to the water samples in (b) and (c)?
5. What do you think makes certain water samples not to readily form leather with soap?
6. Which of the water samples do not readily form leather with soap?
7. Suggest ways in which the water samples identified in (7) (c) can be made to form lather with soap solution more easily.

8. Prepare a summary of your findings.

9. Share your findings with other group members and then with your teacher.

HOW WATER BECOMES HARD

We have already seen the effects of magnesium sulphate, calcium sulphate, magnesium hydrogencarbonate and calcium hydrogencarbonate in water during washing using soap. The questions are: Where do these salts come from and how do they enter water?

In the next activity, we shall explore the sources and how they enter water.

Activity 4.11 Finding out how water becomes hard

In this activity, you will work individually or in pairs to find out how water becomes hard.

What you need

• Notebook, pencil / pen and markers.
• Video clips / internet (if available) and library.  Manila papers.

What to do

1 Carry out research and write a report on how rainwater becomes hard. Your findings should include:

• Sources of salts that make water hard.
• The relevant chemical reactions leading to water becoming hard.

2. Share your findings with your teacher and then the other members of class.

REMOVAL OF HARDNESS IN WATER

We earlier mentioned that the presence of calcium and magnesium salts dissolved in water is a real problem. One such problem associated with hard water is soap wastage.

Thus, making water free from the hardness means removing the calcium and magnesium ions present in the dissolved salts in water. Basing on Activity 4.10, can you suggest one way through which water can be made soft? The next activities provide some ways through which hard water can be made soft.

Activity 4.12 Investigating if boiling can make hard water samples soft

Which water sample becomes soft on boiling?

 CAUTION: GLASSWARE CAN EASILY BREAK IF NOT HANDLED WELL. TAKE GREAT CARE.

 In this activity, you will work in groups to investigate which hard water samples can be made soft by boiling.

What you need

• 100 cm³ of water samples labeled A and B.
• Water sample A containing calcium (or magnesium) hydrogencarbonate and water sample B containing calcium (magnesium) sulphate.
• 200 cm³ of soap solution.
• Measuring cylinder (50 ml / 100 ml), retort stand, conical flask, cork, spatula and filter funnel.
• White tile / plain piece of white paper and access to a heat source.
• Internet (if available) / library.
• Manila and markers.

What to do

1. Measure about 25 cm³ of water sample A into a clean flask. See Figure 4.15.

2. Fill a burette with soap solution and note the level of the meniscus. See Figure 4.15.

3. To the flask containing water sample A, add about 1 cm³ (or about 5 drops) of soap solution, cork the flask and shake the mixture.

What do you observe? Does lather form?

Figure 4.15: Investigating how hard water can be made soft water

4. If the lather formed in step 3 persists unbroken for about 2 minutes, the titration is completed

Note and record the burette reading in Table 4.5 below.

5.However , if the lather formed in step 3 is broken ( or disappears ) , continue adding soap solution in the intervals of 1 cm³ ( or about 5 drops ) and shaking until permanent lather is formed .

Note and record the burette reading in Table 4.5 of results.

Note: If no permanent lather is formed after adding about 30cm³ or slightly more of soap solution, stop the addition. Note and record the burette reading in the table 4.5 below

 6. Rinse the flask and measure about 25cm³ of water sample A into a clean flask. Heat the water to boiling.

What do you observe?

7. Repeat procedures 2 to 5 with a boiled sample of water A.

8. Repeat procedures 1 to 7 with water sample B and record your results in Table 4.6 of results.

Table 4.5: Table of results

Water sample A	Burette readings		Volume of soap solution used
	Initial burette reading	Final burette reading
Before boiling
After boiling

Table 4.6: Table of results

Water sample B	Burette readings		Volume of soap solution used
	Initial burette reading	Final burette reading
Before boiling
After boiling

Results and discussion

• Which of the water samples becomes soft after boiling?
• Using a word equation, explain the effect of boiling on the water samples, if any.
• Basing on burette readings for results after boiling both water samples, suggest with a reason which water sample can be said to have:
  • temporary hardness.
  • permanent hardness.
• Suggest one disadvantage of using boiling as a method of removing hardness in water.
• Name the substances responsible for causing:
  • temporary hardness in water.
  • permanent hardness in water.
• Differentiate between temporary hardness and permanent hardness.
• Prepare a summary of your findings.
• Share your findings with your teacher and then other group members in class.

Activity 4.13 Investigating if sodium carbonate can make hard water sample soft

Which hard water sample becomes soft upon the addition of sodium carbonate?

CAUTION: GLASSWARE CAN EASILY BREAK IF NOT HANDLED WELL. TAKE GREAT CARE. IN THIS ACTIVITY, YOU WILL WORK

In groups to investigate which hard water samples become soft upon the addition of sodium carbonate.

What you need

• 100 cm³ of water samples labelled A and B. Water sample A contains calcium (or magnesium) hydrogencarbonate while water sample B contains calcium (magnesium) sulphate
• Sodium carbonate crystals.
• 200cm of soap solution.
• Measuring cylinder (50 ml / 100 ml), retort stand, cork, spatula and filter funnel.
• White tile / plain piece of white paper.
• Internet (if available) / library.
• Manila and markers.

What to do

1. Note and record in Tables 4.5 and 4.6, the volumes of soap solution required to form permanent lather with water samples A and B without boiling, as noted in Activity 4.12.

2. Fill a burette with soap solution and note the level of the meniscus, as shown in Figure 4.15.

 3. Measure about 25 cm³ of water sample A into a clean flask. Add a few crystals of sodium carbonate, and shake until they all dissolve. What do you observe?

4. To the flask containing water sample A, add about 1 cm³ (or about 5 drops) of soap solution from the burette. Cork the flask and shake the mixture. What do you observe? Does lather form?

5. If the lather formed in step 4 persists unbroken for about 2 minutes, the titration is complete.

Note and record the burette reading in Table 4.7.

6.However , if a lather formed in step 4 is broken ( or disappears ) , continue adding soap solution at intervals of 1cm² ( or about 5 drops ) and shaking until permanent lather is formed .

 Note and record the burette reading in Table 4.7 of results.

Note: If no permanent lather is formed after adding about 30cm³ or slightly more of soap solution, stop the addition. Note and record the burette reading in Table 4.7 below.

7. Repeat procedures 2 to 6 with water sample B and record your results in Table 4.8 of results.

Table 4.7: Of results

Water sample A	Burette readings		Volume of soap solution used
	Initial burette reading	Final burette reading
Before adding sodium carbonate
After adding sodium carbonate

Table 4.8 : Of results

Water sample B	Burette readings		Volume of soap solution used
	Initial burette reading	Final burette reading
Before adding sodium carbonate
After adding sodium carbonate

Results and discussion

• Which of the water samples becomes soft after the addition of sodium carbonate? Volume of soap solution used
• Using word equations, explain the effect of the addition of sodium carbonate on the water samples, if any. Using your findings in this activity and Activity 4.12, what are some of the other ways of making hard water soft?
• Prepare a summary of your findings and share your findings with other group members in class.

Assessment 4.5

1. Suggest the advantages of using the ion exchange method to remove hardness in water over the methods identified in Activities 4.12 and 4.13.

2. Explain why use of distillation method to remove hardness in water is too expensive on a large scale

Much as we have mentioned that using hard water during washing is a real problem, hard water has several applications in everyday life.

In the following activity, you will find out the advantages and disadvantages of hard water.

Activity 4.14 Finding out advantages and disadvantages of hard water

What do you think about hard water as to whether it is good or bad for us and our environment?

In this activity, you will work in groups to discuss the advantages and disadvantages of hard water.

·         What you need

• Notebook, pencil / pen and markers.
• Video clips / internet and library.
• Manila papers.

What to do

1. Carry out research on the advantages and disadvantages of hard water.

 2. Your findings should include necessary diagrams / photographs / illustrations and word equations, where necessary.

3. Prepare a summary of your findings.

4. Share the summary of your findings with your teacher and other group members in class.

 Assessment 4.6

1. Water containing calcium chloride does not form lather with soap. Explain.

 2. Make a list of the main methods of making hard water become soft. In each case, where necessary, write reactions involved. Suitable word equation (s) to summarize the chemical

3. One of the substances found in some samples of temporary hard waters is magnesium hydrogencarbonate. Write word and balanced chemical equations to show the effect of heat on this substance in an aqueous solution.

4.8 Different forms of carbon

We have already mentioned that carbon is around us in several forms. One of them is charcoal.

 Can you now name the other forms of carbon that exist?

 The next activity will help you discover the different forms of carbon that exist apart from charcoal and how useful the different forms are to us.

 Activity 4.15 Finding out about the different forms of carbon

What are the different forms of carbon?

 In this activity, you will work in groups to find out the different forms of carbon.

What you need.

• Notebook, pencil / pen and markers.
• Video clips / internet and library.
• Manila paper.
• One used dry cell.

What to do

1. Study the pictures below showing the different uses of certain elements and answer the questions which follow:

Figure 4.16: Common things we use

Drill bits

Tiger Head dry cells

Diamond ring

Pencils

a) Observe the things in the picture in Figure 4.16.

b) What is the element?

(i) present in pure charcoal?

 (ii) used to make the pencil lids?

 (iii) used in making rings?

 (iv) used as a black rod in dry cell batteries?

Hint: Carefully open a used up dry cell battery to see the black rod. Wear gloves during this process or your teacher will provide the rod.

2.  Carry out research on the different forms of carbon your findings should include:

a) The necessary diagrams / photographs (where applicable) of the forms of carbon.

b)  Properties of the different forms of carbon. Your properties of the allotropes should include the following: appearance, hardness, density and conductivity, if any (heat and electricity).

 c) Uses of the different forms of carbon.

(Where need be, you may ask your teacher to help and provide some forms of carbon present in the laboratory). You may use the following table for help in your summary.

Table 4.9: Properties and uses of allotropes of carbon

Allotropy	Properties	Uses (if any) as a result of the property

3. Using suitable locally available materials develop a model for some forms of carbon. You may discuss with your teacher the suggestions and the approach you intend to follow and the models for help.

4. Prepare a summary of your findings.

5. Share your findings with your teacher and then the other group members in class.

Assessment 4.7

1. Explain the term ‘ allotropes.  
2. Explain the following:
3. Diamond is hard but graphite is soft.
4. Graphite conducts electricity but diamond does not.
5. Graphite is used as a lubricant whereas diamond is used in drill bits.
6. Write a word equation to show how graphite burns in plenty of air. 4. How would you test for the product formed in (3)?

Chapter Summary

 In this chapter, you have learnt that:

• Carbon – based substances are around us and are commonly used as fuel.
• fuels are substances which can be used as a source of energy and that they release energy in the form of heat when they undergo combustion.
• The common fuels can be firewood, charcoal or fossil fuels. Fossil fuel is produced from the dead plants and animals which lived millions of years ago.
• The fuels can be renewable (can be easily replaced, e.g. firewood and charcoal) or non – renewable (cannot be replaced e.g. fossil fuels)
• Most fuels burn in air (oxygen) according to the following equation:

fuel + oxygen →→→ carbon dioxide + water + energy

• Burning carbon – based fuels is one of the major causes of the air pollution and global warming. Global warming is the way in which the Earth could warm, causing changes in the weather.
• Carbon dioxide levels in the atmosphere are slowly but alarmingly increasing. This could have catastrophic effects on the environment leading to climate change.
• Charcoal making can only be sustainable if we replant trees that grow faster.
• Carbon dioxide can be prepared from marble chips and dilute hydrochloric acid.
• Carbon dioxide gas has the following properties:
  • Is colourless.
  • Is denser than air.
  • Does not burn, neither does it support burning.
  • Is slightly soluble in water and forms carbonic acid.
  • Turns limewater milky.
• carbon dioxide has several uses which may include : as a fire extinguisher since it does not burn / does not support burning / heavier than air , as a preservative , making soft drinks and mineral water , making rain , baking , manufacture of washing soda , and as solid carbon dioxide , it is used to create special effects on stage .
• The water samples available can either be soft water or hard water.
• The hardness in water is due to dissolved calcium or magnesium salts from the soils and rocks.
• The hardness in water can be either permanent or temporary depending on the effect of boiling on the water.
• The amount of soap solution can tell us the type of water sample. Hard water can be made soft by distillation, boiling, ion exchange and the addition of washing soda.
• Carbon exhibits allotropy, i.e. the existence of an element in several forms in the same physical state.
• There are several forms of carbon which include diamond, graphite and amorphous carbon. The several forms of carbon are in the same physical state and are called allotropes.
• All forms of carbon have similar chemical properties in spite of their physical differences.

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