Chemical combinations - Login Department of Educationlrr.cli.det.nsw.edu.au/legacy/Science/31701_cc_set1.pdfChemical combinations Set 1 i Chemical combinations Here are the names of

Science Stage 5

Set 1: Lessons 1 to 5

NEW SOUTH WALES

DEPARTMENTOF EDUCATIONAND TRAINING

ChemicalcombinationsSet 1: Working as a chemist

Number: 31701 Title: Chemical combinations

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Chemical combinations Set 1

i

Chemical combinations

Here are the names of the lessons in this unit.

☞ Set 1 Working as a chemistLesson 1 A chemical investigationLesson 2 What happened?Lesson 3 Metal or not?Lesson 4 Copper, zinc and ?Lesson 5 Black and blue

Set 2 Describing some chemical reactionsLesson 6 Reactants and productsLesson 7 Taking a closer lookLesson 8 Another close lookLesson 9 Chemical equationsLesson 10 What is in it?

Set 3 Why do chemicals react?Lessons 11 and 12 Why do elements react?Lessons 13 and 14 How do compounds react?Lesson 15 Some important reactionsRevision lesson The last word


ii

Set 1: Working as a chemist

Contents

What will you learn in Set 1? ................................................................... iii

What do you need for Set 1? .................................................................... iv

Lesson 1 A chemical investigation...................................... 1

Lesson 2 What happened? ................................................... 7

Lesson 3 Metal or not? ........................................................ 15

Lesson 4 Copper, zinc and ? .............................................. 19

Lesson 5 Black and blue ..................................................... 25

Suggested answers ................................................................................... 31

Send-in pages ............................................................................................ 35


iii

What will you learn in Set 1?

In Set 1, you will have opportunities to:

Lesson 1 • make observations and describe somechemical substances

• recall and use the definitions of element,compound, pure, impure, mixture, solution,solute and solvent

Lesson 2 • set up and use a filtration apparatus

• interpret results of an ammonia test forcopper in solution

• suggest what may have formed in the reactionso that you can plan more investigationsto test your ideas

Lesson 3 • compare the electrical conductivity ofdifferent samples

Lesson 4 • use litmus paper to test a solution to see if it is an acid

• plan a controlled experiment comparing different metalsin acid

• identify dependent, independent and controlled variables

• identify zinc and copper by testing samples andcomparing your results with their known properties

Lesson 5 • observe and compare the results of an experiment

• summarise reactions from several lessons

• interpret a flow chart


iv

What do you need for Set 1?

Lesson 1

• measuring cylinder

• 2 pieces of zinc

• 1 piece of copper

• 1 teaspoon of copper sulfate

• 2 beakers

• plastic spoon

• marker pen or labels

• plastic wrap

Lesson 2

• filter funnel

• retort stand

• retort ring

• beaker

• 1 piece of filter paper

• clock glass

• 1 piece of zinc


• your set up experiment from Lesson 1

Lesson 3

• battery holder

• 3 leads with alligator clips

• light globe

• socket for light globe

• battery clip


• 1 piece of zinc

• 2 ‘AA’ batteries

• ‘lead’ from HB pencil

• dried residue from Lesson 2

Lesson 4

• 1 piece of blue litmus paper

• 1 piece of zinc


• copper oxide

• white vinegar

• dried residue from Lesson 2

• 2 beakers

• plastic spoon

• marker pen or labels

Lesson 5

• your set up experiment from Lesson 4


1

Lesson 1

A chemical investigation

A chemist can be a bit like a detective. First, the chemist watcheswhat happens when chemicals are combined. Does a chemical change,called a chemical reaction, occur? Or is it a physical change only?

Then the chemist studies any substances that are formed.What are they? How can they be tested? Why did they form?What could they be used for?

In this way, the chemist makes and organises observations,identifies and tests patterns in the observations and suggestsexplanations for what happens. The chemist must be very logical andorganised in the study of a reaction to solve the chemical puzzle.

In Set 1, you are going to conduct a chemical investigation.You’ll need to be objective as you make observations so thatyou see what really happens and not what you expect to see.You’ll need to be curious and creative to find out what was formedin the reactions. And, you’ll have to be very logical to pull togetherall the clues in the investigation to identify the chemicals thatare formed. You’ll also need to be organised.There are many experiments for you to do in this set!

Are you ready to begin?


2

Metal in solution

In this investigation, you will put zinc metal into a solution ofcopper sulfate. You will observe this experiment for two lessonsso it’s important that you find a place to leave the equipment set upso it won’t be disturbed.

What you will need:

Collect the equipment listed below.• 2 pieces of zinc• piece of copper• 1 teaspoon of copper sulfate• 2 beakers• plastic spoon• measuring cylinder• marker pen or labels• plastic wrap.

CAUTION Be careful!

Copper sulfate is a poisonous substance.Make sure your experiment is out of the reach of small children.Do not eat while you are carrying out this activity.

What to do:

Now that you have collected the things you need,follow the instructions below.

1. Make a copper sulfate solution by placing a teaspoon of coppersulfate into a beaker. Do not use all the copper sulfate supplied.Add 100 mL of water. Stir to dissolve.

2. Divide the solution into two by pouring half into another beaker.Label one beaker experiment and the other control.

3. In Question 1 and Question 2 on the next page, describe zinc metaland copper metal and then describe copper sulfate solution.

4. Place one piece of zinc into the beaker labelled experiment.Put the other piece of zinc and the piece of copper beside thebeakers.

5. Leave the beakers to stand overnight. (Remember to leave themin a place that small children can’t reach.)


3

Observations

Describe the appearance of the metals and solution at the beginning ofyour investigation. This will allow you to see if there are any changes tothe chemicals.

zinc copper sulfate solutioncopper

control

1. Write a description of the two metals.

copper:

zinc:

2. Describe the copper sulfate solution in the beaker labelled control.

Complete these descriptions after the experiment has been left overnight.

3. Look in the beaker labelled experiment. Describe any changes.

4. What do you think has happened?

Please check your descriptions in the answer pages.


4

You will be checking your explanation in the lessons that follow.Leave the experiment set up because you’ll come back to it inthe next lesson. You’ll use the solution in the beaker called controlin Lesson 2 and again in Optional Lesson 6. For now, cover itwith a lid or with plastic wrap so that nothing falls into it.Put the control somewhere safe and away from childrenuntil you need it again.

Before you continue, there are a number of terms that areused in chemistry that you may need to revise.

A review

Read the information below and try to answer as many questionsas you can to refresh your memory.

Pure substances

There are a large number of metals that we use in our lives.The metals you are observing in this activity are copper and zinc.These are both pure substances.

What are the two different kinds of pure substances?

The two kinds of pure substances are elements and compounds.

Are copper and zinc elements or compounds?

Copper and zinc are both elements.

Copper is made of copper atoms only. Zinc contains zinc atoms only.Now write a sentence explaining what elements are.

Elements are pure substances made up of one type of atom only.


5

Elements, such as copper and zinc, have chemical symbols.Can you remember the symbols for copper and zinc?Write them below.

The symbol for copper is Cu. The symbol for zinc is Zn.

The copper sulfate you dissolved in water is also a pure substance.Copper sulfate contains copper atoms, sulfur atoms and oxygen atoms.Is copper sulfate an element or a compound?

Copper sulfate is a compound (because it contains atoms of more than one elementthat have been chemically combined together).

Compounds such as copper sulfate have chemical formulas.Can you recall the formula for copper sulfate? Write it below.

The chemical formula for copper sulfate is CuSO4.

The formula for copper sulfate shows you the elements thatcopper sulfate contains. You might have expected a compoundcontaining copper, sulfur and oxygen to have a different name.However, a sulfur atom and four oxygen atoms form a special,stable unit that tends to stay together. Therefore this specialcombination of sulfur and oxygen is given its own name, sulfate.

Circle the sulfate part in the formula below.

CuSO4

Did you circle the part that is SO4? Remember, sulfate refers to one sulfur atomchemically combined with four oxygen atoms.

Compounds are different from elements. Can you describethis difference? Write a sentence about how they differ.

Compounds contain more than one type of atom whereas elements containone type of atom only.


6

Impure substances

There are a large range of solutions that you come into contactwith regularly. Things like sea water, household bleach, urine,lemonade, vinegar, battery acid and petrol are all examplesof solutions.

Are solutions pure or impure substances?

Solutions are impure substances.

Solutions are mixtures of various substances. In this activity,you made a solution of copper sulfate. How do you know thatyour copper sulfate solution is impure?

You made it by mixing together two compounds – water and copper sulfate –so the solution must be impure.

When copper sulfate dissolves in water:

(a) which substance is the solute? ___________________________________________________

(b) which substance is the solvent? _________________________________________________

A small amount of copper sulfate dissolves in water so copper sulfate is the solute.This means that water is the solvent.

What have you learned in this lesson?

Tick the box if you can:

❑ make observations and describe some chemical substances

❑ recall and use the definitions of element, compound, pure,impure, mixture, solution, solute and solvent.

Exercise 1

Now that you have refreshed your memory, turn to the send-in pagesand do Exercise 1. This will show your teacher that you understandeach of the terms you have used so far.


7

Lesson 2

What happened?

Your experiment has been standing overnight.What has happened to it?

In this lesson, you will observe and test chemical substancesto see if there have been any changes.

First impressions

Write down your first impressions.Compare the contents of the experiment beaker with the controlbeaker. What do you see? What do you think has happened?

This is a record of your thinking that you can look back towhen you have finished testing the substances.

Filtration

To get a good look at what has happened in the beaker labelledexperiment, you need to filter the mixture. To do this, you will need thefollowing pieces of equipment:

• filter funnel

• retort stand

• retort ring

• beaker

• 1 piece of filter paper

• clock glass.

You will also need a piece each of copper and zinc.


8

Folding filter paper

Begin by folding your filter paper.

Make a cone

Step 3

Fold filter paperin half again

Step 2

Fold filter paperin half

Step 1

Step 5 Moisten filter paper with water

Step 4

Place cone infilter funnel

Filtration apparatus

Then set up the filtration apparatus.

exp

erim

ent beaker labelledexperiment

filter paper

residue

beaker

filtrate

retort ring

filter funnel

retort stand

stirring rod


9

1. Once you have filtered the contents of the beaker markedexperiment, carefully examine the residue (the solid that remains)in the filter paper. Describe what you see.

2. Compare the solids left in the filter paper with a piece of copperand a piece of zinc. Are they similar in any way?

3. What do you think the solids from the beaker are?

Are you thinking like a chemist?You need to predict what substances have formed in the reaction so that you can decide how to test them.

You’ll be able to compare your answers with the answers of other studentsas you continue through Set 1.

Now follow these instructions

You need to pack up carefully so that you keep the substancesthat you need for other lessons.

• Put the filter paper with the residue on the clock glass andset it aside to dry. You will use it again in Lesson 3.

• Thoroughly wash the beaker labelled experimentthen wash your hands.

• DO NOT discard the copper sulfate solution in the beaker markedcontrol. You will need it again in this lesson.

• DO NOT discard the filtrate. (It is the colourless solutionin the beaker.) You will use it later in this lesson.


10

Now compare your description with the logbook entry that Year 10student, Max, wrote after doing this part of the experiment.

Metal in solution

The solution in the beaker is still clear but now it is colourless.

The things in the bottom of the beaker are hard to see so

we need to filter it.

After we filtered the mixture in the beaker, we ended up

with a clear, colourless solution and a mixture of solids in

the filter paper.

The clear, colourless solution looked different from the

clear, blue solution in the beaker labelled control. My

partner thinks that the blue had faded so we will test it

using ammonia solution later.

We had a closer look at what was left in the filter paper,

the residue. Anyway, there was a variety of solid bits that

were black, silvery and pinkish orange.

The black stuff looks like carbon. The silvery stuff looks

like some zinc left over from when we put it in the jar.

The pinkish orange stuff looks like copper.

We need to test the solids to see if they are carbon, zinc

and copper. Maybe we’ll think of how to test them by

tomorrow.

Max

Were your observations and thoughts similar to these?

What substances does Max think have been made in the reaction?Underline their names (or their descriptions if they are not named)in the report above.

There are answers in the answer pages.


11

Testing the solution

Compare the copper sulfate solution in the beaker labelled controlwith the filtrate. The filtrate is in the unlabelled beaker.

Describe the difference between the filtrate and the copper sulfatesolution in the jar labelled control.

The copper sulfate solution is blue but the filtrate is colourless.

Now you can empty and thoroughly wash the beaker of filtrate.Then wash your hands.

DO NOT discard the copper sulfate solution in the beaker markedcontrol. You will need it later in this lesson.

What has happened?

Max’s laboratory partner thinks that the blue solution fadedovernight. Max tried to explain that the solution in the control beakerdidn’t change so it couldn’t have faded but his partner remainsunconvinced. They have decided to test the solutions.

What test do you think Max and his partner used?

A test using ammonia solution.

Adding ammonia solution is a test for copper in a solution.Ammonia solution is colourless. When it is added to a solution thatcontains copper, the mixture turns dark blue.

What do you think would happen if the mixture does not containcopper in solution?

There is no colour change if the solution does not contain copper in solution.


12

Using the ammonia test

Max added ammonia solution to the control and to the filtrate.The results are shown below.

1. Before

controlfiltrate

clear, colourlesssolution pale blue solution

2. After ammonia solution is added

filtrate control

clear, colourlesssolution dark blue solution

What do you think? Do both these solutions contain copper?

You can see from the results that the solution in the control beakergoes darker when ammonia solution is added. The control beakercontains a solution of copper sulfate so there is copper in solution.

However, the colour of the filtrate doesn’t change colour withammonia solution. Therefore the filtrate doesn’t contain copper.Where did the copper that was in the solution in the experiment beakergo? What you think could have happened to it?

Look back at this answer that you’ve just written when Max and hispartner attempt to explain their observations in Lesson 3 and Lesson 4.


13

Testing the solids

Let’s now devise some tests that can be carried out on the solidsto see what they might be. To do this, you could follow the stepsset out below.

1. List the features or properties of each ‘suspect’ substance.

2. Test the properties of the substance(s) present.

3. Compare the results for these tests with the properties ofknown substances.

You’ll carry out Step 2 and Step 3 in the next two lessons.But you can do Step 1 now.

The first step

Can you remember any features, or properties, of the three elements,carbon, copper and zinc?

Complete the table below by listing some properties of these elements.

Properties of three ‘suspects’

‘Suspect’substance

Some properties

carbon

copper

zinc

How did you go? Please look at my answers in the answer pages.

In the next lesson, you will test each substance in the residueto determine some of its properties.


14



❑ set up and use a filtration apparatus

❑ interpret results of an ammonia test for copper in solution

❑ suggest what may have formed in the reaction so that you canplan more investigations to test your ideas.


15

Lesson 3

Metal or not?

In Lesson 2, you separated solids from a solution by filtering.There are a number of possible ‘suspects’ that these solids could be.You may have suggested that they are carbon, copper and zinc.In this lesson, you’ll begin testing the solids to determine their identity.

Testing conductivity

Metals like copper and zinc conduct electricity. Carbon is alsoan electrical conductor even though it is a non-metal. Let’s nowseparate out pieces of each ‘suspect’ substance and test them.If they conduct electricity then they are metals or carbon.

The carbon you will test is the ‘lead’ in an HB pencil.Pencils do not have the metal lead in them.The black, solid substance is graphite, the form of carbonthat conducts electricity.

What you will need:

Collect the following items:

• battery holder

• 3 leads with alligator clips on both ends

• a small light globe

• a socket to hold the light globe

• a battery clip

• 2 ‘AA’ batteries

• a piece of copper

• a piece of zinc

• the ‘lead’ from a pencil

• dried residue from Lesson 2.


16

What to do:

First connect your electrical equipment. If you haven’t done thisfor a while or haven’t used this equipment before, you may need torefer to the diagram below.

Testing electrical conductivity

RE

AD

Y

NE

VE

RE

AD

Y battery holder

battery clip light globe

socket

lead

alligator clip

'AA' battery

place substanceto be tested here

NE

VE

RE

AD

Y

Test that your circuit works by tapping the free alligator clips together.Next, test each type of substance for electrical conductivity.The substance is a conductor if the light globe shines.Write your results into the table below.

Substance tested Electrical conductor?

black substance in residue

carbon in a pencil

silvery substance in residue

zinc

pinky-orange substance in residue

copper

Note: Keep all the substances listed in the table aboveas you will use them again, later in this set.


17

What do your results tell you about the electrical conductivity of each substance?Which substances do you think might match (be the same chemical)? Why?

Do you need to do some further testing?

Compare your results with the ones below that Max and his partner gotwhen they did the same experiment.

Does it conduct?

We tried the copper first then the pinkish orange solid.

They both conducted electricity because the light globe

worked when we put them into the electrical circuit.

Next we tried the zinc and the silver solid.

They both conducted electricity.

Lastly we tried the carbon and the black solid.

The carbon conducted electricity but the black solid

from our reaction didn’t.

From carrying out these tests, we think that there are

two metals in the residue: silvery-coloured zinc and

pinkish orange copper. We’re not sure about the

black substance but it is not carbon.

We’re going to look for extra information about

what the black substance could be in a textbook.

Max


18

In the next lesson, you will be further testing the three solids thatyou filtered from the reaction mixture. What tests can you think ofthat might help you to decide what they are?



❑ compare the electrical conductivity of different samples.


19

Lesson 4

Copper, zinc and ?

So far, you can probably say that the solids from the beaker markedexperiment were copper, zinc and a black substance that isn’t carbon.In this lesson, you will carry out one more test on the metals andinvestigate the identity of the black substance.

Metals in acid

Let’s have another look at the metals that you suspect are copper andzinc. You will put the metals into an acid. You can identify an acidbecause it changes the colour of litmus paper from blue to red.Litmus paper is an example of a chemical indicator because it can beused to show if a substance is an acid.

Some metals, magnesium for example, produce bubbles of gas whenthey are in acid. Other metals, such as gold, don’t produce anythingwhen they are in acid.

In this activity, you will compare what happens when copper andthe pinky-orange substance, and zinc and the silvery substance,are placed into acid.

What you will need:

For this experiment, you need the following items:

• 2 beakers

• piece of blue litmus paper

• piece of copper

• piece of zinc

• pinky-orange substance from your residue

• silvery substance from your residue

• white vinegar.


20

What to do:

Once you have collected your equipment, you need to check thatvinegar is an acid. How would you do this?

Pour some vinegar into a beaker. Dip a piece of blue litmus paper into thevinegar. If the litmus paper turns red then the solution is an acid.

Try this test. Is your vinegar an acid? ________________________________________________

Next, you are going to test the copper and the pinky-orange substancethat you suspect is copper with acid (vinegar). You need to plana controlled experiment so that you can compare them.What do you think you should do? Describe a suitable experiment.

What are you testing in your experiment?This is your independent variable because it is the thing you decideto change in the test.

What are you observing in your experiment?This is your dependent variable because the results depend onthe experiment you have planned.

What are some variables you will control (or make constant)in your experiment?

Turn to the answer pages and compare your answers with mine.Make any changes to your experiment plan above that are needed.


21

Now perform your experiment. Describe what happens.

Did the copper and the pinky-orange substancebehave in the same way as each other? _________________________________

Take the copper and the pinky-orange substance out of the beakersand rinse them in water. Tip the vinegar out of the beakers butDON’T rinse them.

Next, you are going to test the zinc and the silvery substance thatyou suspect to be zinc with acid (vinegar).

Exercise 4.1

Turn to the send-in pages and plan the test you will perform.Answer all the questions in send-in Exercise 4.1 before you continue.

Conduct your experiment. Describe what happens.

Did the zinc and the silvery substancebehave in the same way as each other? _________________________________

Do you think that the metals in the residue are copper and zinc?Why?


22

Compare your results and conclusion with Max and his partner’s.

Metals in acid

Results:

copper

pinkish orange substance

zinc silvery substance

MetalsBehaviour in acid

no bubbles

no bubbles

bubbles of gas

bubbles of gas

Conclusion:

The pinkish orange metal is the same colour as copper

and behaves the same way as copper in acid.

(It also conducts electricity like copper.)

We think it is copper.

The silvery metal is the same colour as zinc and

behaves the same way as zinc with acid.

(It also conducts electricity like zinc.)

We think it is zinc.

Do you agree with this conclusion?

Now that you have established the identity of the two metalsin the residue, it’s time to investigate the identity of thatthird substance.


23

Max and his partner have been busy looking up informationin a chemistry book. This is what they found.

Most metals that are left

exposed to air tarnish.

This means that oxygen

in air combines with the

metal to form a compound

called an oxide.

Tarnishing results in a dull

surface. Some metals are

coated in a white oxide layer

while others have a black

oxide coating.

Copper in air

Copper, when exposed to

the air, becomes black.

This is due to copper

combining with oxygen

to form copper oxide.

Copper oxide is a

black substance that

dissolves in acid.

The solution formed

is blue.

Metals in air

What do you think Max and his partner might do next?That’s right. Max and his partner are going totest the black substance in acid.


24

Is the black substance copper oxide?

Now it’s time to set up the experiment.

What you will need:

• 2 beakers

• black substance from the residue

• copper oxide from your minikit

• white vinegar

• plastic spoon

• marker pen or labels.

What to do:

1. Label one beaker A and the other beaker B.Pour the same amount of vinegar into each beaker.

2. Add half a teaspoon of copper oxide to the vinegar in beaker A.Stir the mixture.

3. Add some of the black substance from the residue to beaker B.Stir the mixture.

CAUTION4. Leave the two beaker to stand in a place where the experiment

won’t be disturbed (or accidentally thrown out or drunk!).

You will observe the results of this experiment in the next lesson.



❑ use litmus paper to test a solution to see if it is an acid

❑ plan a controlled experiment comparing different metals in acid

❑ identify dependent, independent and controlled variables

❑identify zinc and copper by testing samples andcomparing your results with their known properties.

Exercises 4.2 and 4.3

Now complete send-in Exercise 4.2 about indicators andExercise 4.3 about working scientifically.


25

Lesson 5

Black and blue

It’s time to observe and interpret the results of the experimentyou set up to identify the black substance.

What happened?

Look closely at the mixtures in the two beaker that you set upin Lesson 4.

1. Describe what has happened in beaker A.

2. Describe what has happened in beaker B.

3. What do you think the black substance from the residue was?Explain your answer.

Please check your answers.

Max and his partner thought that the black substance was copper oxidebecause both the black substance and black copper oxide producedblue solutions. What do you think these blue solutions may contain?

The solutions may contain dissolved copper.


26

Max and his partner tested two solutions for the presence of copperin Lesson 2. Do you remember what they did?

A blue solution containing copper goes dark blue when ammonia solutionis added to it.

Max and his partner tested for copper in both the solutionsmade by reacting copper oxide and vinegar.What do you predict the results to be?

The results of their tests are shown below.

Testing for copper in solution

add colourlessammonia solution

add colourlessammonia solution

copper oxide

Beaker A

pale blue solution

Beaker B

pale blue solution

black substancefrom residue

dark blue solution

dark blue solution

You can see that both solutions turned dark blueso both solutions contain copper.


27

Organising the results

Here is a list of the chemical combinations that you haveconsidered so far. Fill in the missing information in the listby looking back through Set 1.

Activity on Chemicals combined What formed?

page 2 solidcopper sulfate and water

page 2 copper sulfate solution and _ _ _ _ _ _ _ _ _ _

mixture ofthree solids and

colourlesssolution

page 12 copper sulfate solution and

_ _ _ _ _ _ _ _ _ _

solution dark blue solution

page 12 _ _ _ _ _ _ _ _ _ _ and ammonia solution no change

page 20 copper and acid

page 21 zinc and acid

page 25 copper oxide and acid

page 26 copper oxide and acid and

ammonia solution

There is a completed table in the answer pages.

Near the beginning of Set 1, you tried to predict what you madein the reaction between copper sulfate solution and zinc.You have been creatively and logically working through the evidenceto find an answer to the problem.

Do you think you have worked it out?

Max and his laboratory partner had the same puzzle.They thought it seemed like a huge task so they decidedto draw a flow chart to help them organise their results.

Their flow chart is on the next page.


28

Max’s flow chart

filter

stir

leave to stand

physical separation

conductor?

add acid add acidadd acid

conductor? conductor?

black silvery pinkish orange

pinkish orangemetal

copperzinc

blacknot a metal

copper oxide

water copper sulfate

clear, blue coppersulfate solution

zinc

clear, colourless solutionwith a mixture of solids

clear, colourless solution mixture of solids

silverymetal

This looks fairly complicated so let’s go through it.

Layout

1. The words in the boxes are names or descriptions of chemicals.

For example,

copper oxide is the black substance in the residue.

2. The words beside the arrows tell you what the experimenter didat each step of the experiment.

For example,

add acid means acid was added to the residue.


29

Steps

Max is having trouble explaining the flow chart to his partner.The diagram below shows Max going through the steps inthe investigation. Each step is labelled as A, B, C, D or E.As he explains, he points to the place on the flow chart thatshows each step.

D The three solids weretested for electricalconductivity to determineif they were metals.

C The mixture of solidswas separated from thecolourless solutionby filtration.

B Zinc was put into

the copper sulfate solution

and left to stand.

A The threesolids were testedwith acid.

E Copper sulfate was

dissolved in water to

make a blue solution.

??

??

?

1. Max is not explaining the steps (A to E) in the correct order.No wonder Max’s partner is having trouble understanding!Write the letter of each step where it is shown in the flow charton page 28.

2. Write the letters representing the steps of the experiment,in order, on the lines below. Add a brief description for each.

Step 1: ______________________________________________________________________________________

Step 2: ______________________________________________________________________________________

Step 3: ______________________________________________________________________________________

Step 4: ______________________________________________________________________________________

Step 5: ______________________________________________________________________________________


30

3. On Max's flow diagram, what words are used to identify:

the filtrate? _______________________________________

the residue? _______________________________________

Check all your answers in the answer pages.

Did you notice that the controls were not included in the flow chart?This is because the controls don’t actually change.They are used for comparison so that you can recognisewhen there is a chemical change in an experiment.

Another thing that was left out of the flow chart was the testto see if the filtrate had copper in solution. Remember,this was when Max and his partner added ammonia solutionto a copper sulfate solution and to the colourless filtrate.The filtrate didn’t contain copper so it isn’t shownbecause we are more interested in what the solution israther than what it’s not.



❑ observe and compare the results of an experiment

❑ summarise reactions from several lessons

❑ interpret a flow chart.

Exercises 5.1 and 5.2

Show your teacher what you have learned by completing thesesend-in exercises.


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Suggested answers

Lesson 1 A chemical investigation

Page 3 Observations

1. copper: Copper is a pink or orange-coloured solid. It has a shiny surface and is hard but easily bent.

zinc: Zinc is a silvery solid. It is shiny and hard, but is easy to bend into shapes.

2. The copper sulfate solution in the control beaker is blue in colour.The solution is clear (you can see through it).

3. The zinc was covered with a black substance. If you look carefully,you can see some orange material on the surface of the zinc.

4. You will have your own ideas about what might have happened.You will test some ideas as you continue through the lessons in this set.

Lesson 2 What happened?

Page 10 Metal in solution

The substances that Max thinks were made in the reaction are:

• the clear, colourless solution

• a mixture of solids – black stuff that looks like carbon, silvery stuff thatlooks like zinc and pinkish orange stuff that looks like copper.

Page 13 The first step

‘Suspect’ substance Some properties

carbon (graphite) Carbon is a black solid which breaks easily.It is a conductor of electricity although it does notconduct as well as metals. Carbon is an insulatorto heat (it does not conduct heat very well).

copper Copper is a pinky-orange solid. It is shiny anda good conductor of heat and electricity.

zinc Zinc is a silvery, shiny solid. It is a goodconductor of heat and electricity.


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Lesson 4 Copper, zinc and ?Metals in acid

Page 20 Here is a suitable experiment. Yours is probably similar.Put equal volumes (the same amount) of vinegar into each jar. Add the piece ofcopper to one jar and, at the same time, add the pinkish orange solid to the other.

The independent variable is the kind of substance. (You are testing twodifferent substances – copper and the pinkish orange solid.)The dependent variable is the way that the metal reacts with the acid.(You are observing to see if this is different.)Some variables you would control are the amount of vinegar, its temperatureand how long the substances are in the acid. It would be a better experimentif you could control the sizes of the pieces of each substance.Variables that you control are kept the same, or constant.

Lesson 5 Black and blueWhat happened?

Page 25 1. Some, or maybe all, of the black solid has disappeared.The solution has turned blue.

2. Some, or maybe all, of the black solid has disappeared from this jar.The solution has also turned blue.

3. The black substance was probably copper oxide since it behaves in thesame way as copper oxide.

Page 27 Organising the results

Activity on Chemicals combined What formed?

page 2 solidcopper sulfate and water copper sulfate solution

page 2 copper sulfate solution and zinc

mixture ofthree solids and

colourlesssolution

page 12 copper sulfate solution and

ammoniasolution dark blue solution

page 12 filtrate and ammonia solution no change

page 20 copper and acid no change

page 21 zinc and acid bubbles of gas(hydrogen) and

colourless solution

page 25 copper oxide and acid pale blue solution

page 26 copper oxide and acid and

ammonia solution dark blue solution


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Lesson 5 continued

Steps

Page 29 1. Max’s statements are matched down the side of the flow chart.

filter

stir

leave to stand

physical separation

conductor?

add acid add acidadd acid

conductor? conductor?

black silvery pinkish orange

pinkish orangemetal

copperzinc

blacknot a metal

copper oxide

water copper sulfate

clear, blue coppersulfate solution

zinc

clear, colourless solutionwith a mixture of solids

clear, colourless solution mixture of solids

silverymetal

E

B

C

D

A

2. Here is a description of each step.

Step 1: E – make copper sulfate solution

Step 2: B – put zinc into copper sulfate solution

Step 3: C – filter experiment

Step 4: D – test electrical conductivity of residue

Step 5: A – test residue with acid

Page 30 3. On the flow diagram, the words used to identify:

the filtrate? are clear, colourless solution

the residue? are mixture of solids.


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Send-in page Name ______________________________

Lesson 1: A chemical investigation

Exercise 1

Here is a description of some chemicals.

Cobalt is a silvery metal with the symbol Co.Cobalt chemically combines with chlorineto form cobalt chloride, CoCl2.

When cobalt chloride is dissolved in water,the mixture forms a pink solution.

In the far left column below, there is a list of terms that were definedin Lesson 1. In the middle column are the definitions of these termsbut the definitions are not in the correct order. In the third column,there are some examples that come from the description above.

Add lines to the diagram to match each term with its correct definitionthen each definition with the correct example. Notice that two examplescan be used twice.

Terms Definitions Examples

element a substance (usually solid) thatdissolves in another substance cobalt chloride

compound a pure substance made ofone type of atom only

mixture ofcobalt chlorideand water

solutiona substance (usually liquid)in which another substancecan be dissolved

cobalt

solute a pure substance containingmore than one type of atom pure water

solventan impure substanceoften consisting of a soliddissolved in a liquid


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Send-in page Name ______________________________

Lesson 4: Copper, zinc and ?

Exercise 4.1

1. Describe a suitable experiment to compare the reaction with acidand zinc and the silvery substance that you suspect to be zinc.

2. What is the independent variable?

3. What is the dependent variable?

4. What are two variables that you will control in your experiment?

Exercise 4.2

1. Name the indicator that you used this lesson. _____________________________

2. What can you use this indicator to do?(What is the role, or job, of the indicator?)


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Exercise 4.3

In this set, you have been investigating scientifically.You are being creative, curious, objective and logical as youtest and observe chemicals.

Read your 'first impression' about the chemicals on page 7.Then read another idea you had about the reaction at the bottomof page 12.

Explain how being creative, curious, objective and logicalhave helped you in this investigation.(If you can’t think of an example for each word, come back to this send-in exercise when you have finished Set 1. You may have thought of an example to use.)

creative _____________________________________________________________________________________

curious _____________________________________________________________________________________

objective _____________________________________________________________________________________

logical _____________________________________________________________________________________

Your teacher may organise a teleconference so that you can discussyour answers with other students.


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Send-in page Name ______________________________

Lesson 5: Black and blue

Exercise 5.1

1. Here are the steps from the experiments you have performedin this set. However, they are still out of order.

Sequence the steps by writing 1 in the box beside the first stepand so on.

❒ Copper sulfate was dissolved in water to make a blue solution.

❒ The mixture of solids was separated from the colourless solutionby filtration.

❒ The three solids were tested with acid.

❒ The three solids were tested for electrical conductivityto determine if they were metals.

❒ Zinc was put into copper sulfate solution and left to stand.

2. Describe how you performed the step that you numbered 3.

3. On which page or pages did you follow the directions to performthe step that you numbered 4?


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Exercise 5.2

In Set 1, you have worked scientifically to find out about the substancesin a chemical reaction between copper sulfate solution and zinc.

Use examples from this investigation to answer the questions below.

1. Scientists isolate sets of observations in investigations.(This means that they choose particular things that happen as important. They do not pay attention to everything.)

What is a set of observations that you isolated in your investigation?

2. Scientists identify trends and patterns in their resultsand observations.

What is a trend or pattern that you noticed during your investigation?

3. Scientists use these patterns to suggest hypotheses and models.(This means that they suggest an explanation of what happened. If they can, they try to explain why it happened.)

What is a suggestion that you made to explain part of yourinvestigation?

Documents

Chemical combinations - Login Department of Educationlrr.cli.det.nsw.edu.au/legacy/Science/31701_cc_set1.pdfChemical combinations Set 1 i Chemical combinations Here are the names of