qld prelims hqsp8 si - hi.com.au · pdf filescience laboratory is located it is essential that...

Working safely1.21.2

A science laboratory is a place where you can carry out investigations and conduct experiments. You have already learned that everybody can be a scientist and science is used all around us every day. So there are many places that can be called science laboratories, not just your school laboratory or a research laboratory at a university, hospital or factory.

A laboratory can be a source of accidents. So wherever your science laboratory is located it is essential that there are rules for your safety. Always ensure that you think before you act so that you don’t endanger yourself or others.

Science 8: A Contextual Approach6

ssciciffileileExperiments are carefully planned step-by-step practical activities, which can be recorded and reported in many different ways.

questions 1. 1

1. List ten ways that you have used science today.

2. List ten things that you could not have done without scientists creating or making discoveries.

3. Which of the following are observations and which are inferences? Present your answers in a table.

Aaron is 168 cm tall. The bushfi re was caused by lightning. Steven is stronger than David. The population of Darktown is 1.2 million. Lanah’s cat weighs 2 kg. Jaimie is a faster runner than Soula.

4. Every branch of science has a special name. Can you match the names below with what they study?

acarology fungi oology fruit

anemology snakes ophiology mountains

bryology clouds orology reptiles and amphibians

dendrochronology wind palynology ants

herpetology mouth disorders pomology rivers

mycology fossil pollen potamology age of trees by rings

myrmecology birds’ eggs pteridology mosses

nephology fermentation stomatology dreams

nosology ferns trichology classifi cation of diseases

oneirology hair zymology mites and ticks

5. Make a cartoon strip or poster about one of the things you listed in question 1.

6. In a small group create a play or write a song about using scientifi c skills in your everyday life. Perform this for the class.

7. Look through a newspaper or magazine or browse the Internet to fi nd an article that discusses scientifi c methods. Cut out or print out the article and paste it into your workbook. Explain to your class what the article is about and what will be its benefi ts or problems.

8. Find some examples of how scientists use models. Explain what the model is for and how it helps our understanding.

01_HQSP8_SI.indd 601_HQSP8_SI.indd 6 12/5/06 3:48:25 PM12/5/06 3:48:25 PM

Figure 1.7

How does the Bunsen burner work?


The Bunsen burnerIn a laboratory many experiments require heat. A Bunsen burner is often used to provide heat, and it is important that you are able to use it safely.

Steps for using a Bunsen burner: 1. Always use a heatproof mat. 2. Connect the gas tube to the gas outlet. 3. Close the air hole before lighting. 4. Hold a lit match beside the mouth of the barrel. Turn on the gas and

move the match over the barrel to light the gas. 5. Open the air hole slowly. Set the air hole and gas for the fl ame required.

At the top of the Bunsenburner this mixture ofgas and air can beignited to produce aflame, which is used toheat substances.

The amount of heatproduced by the burnercan be controlled byturning the metal ring orcollar at the bottom ofthe barrel.

The base of the Bunsenburner can get very hotso the burner should always be used on a heatproof mat.

barrel

collar

gas supply

rubber tubing

base

Opening and closing the air hole changes the amount of air mixing with the gas and so allows you to control the amount of heat produced by the Bunsen burner.

As gas moves into the Bunsen burner from the gas tap, air moves into the barrel of the burner through the air hole and mixes with the gas.

ssciciffileileRobert Wilhelm Bunsen did not actually invent the Bunsen burner—he just improved it. He made much greater contributions to areas of chemistry such as organic chemistry, arsenic compounds, gas measurements and analysis, the galvanic battery, elemental spectroscopy and geology.

S C I E N C E work

Recognising some science equipment

What you need

• Bunsen burner • test-tube brush • spatula• gauze mat • boss head and clamp • evaporating dish• test-tube • test-tube rack • watch-glass • fi lter funnel • test-tube holder • heatproof mat • measuring cylinder • tripod • pipe clay triangle • dropping pipette • tongs • stirring rod• retort stand • beaker • conical fl ask

What to do

1. Divide the class into groups of two or three students.

2. Your teacher will give each group three pieces of equipment plus nine blank cards or pieces of paper.

3. The task for each group is to prepare a set of three cards for their equipment—‘equipment name’, ‘scientifi c drawing’, and ‘what it is used for’.

4. Each group presents their cards to the class and answers any questions about their equipment.

5. Cards can then be swapped between groups and used for matching activities.

Activity 1 .4


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S C I E N C E work

Using a Bunsen burner

Aim

To learn to use a Bunsen burner safely.

Materials

• Bunsen burner • platinum or nichrome wire • matches • test-tube • heatproof mat • test-tube holder

Method: Lighting the Bunsen burner

1. Your teacher will demonstrate how to use a Bunsen burner. You may need to write some notes or draw some diagrams.

2. Connect your Bunsen burner to the gas tap. 3. Close the air hole by turning the collar. 4. Hold a lighted match at the top of the barrel towards the side of the opening. 5. Turn the gas tap to the fully open position and move the match over the barrel to light the gas. 6. Note the appearance of the fl ame. This fl ame is called a safety fl ame.7. Using the test-tube holder, hold the test-tube near the top and place the bottom of the

test-tube into the fl ame. Observe the deposit that forms on the test-tube. Record your observations in your book.

8. Place the test-tube into the test-tube rack so that your bench is not damaged. Remember, it will be hot!

9. Slowly turn the collar of the Bunsen burner until the air hole is fully open. As you do so, observe and report the changes in:

(a) the amount of light and heat given off (b) the colour of the fl ame (c) the size of the fl ame.

Results and discussion

Draw a fl ow chart showing the steps involved in lighting and using a Bunsen burner. Include any safety rules.

EXPERIMENT 1 .5

questions 1.2

1. Think about two laboratory safety rules you consider important. (a) Share your rules with a partner and make

up a list of fi ve rules.

(b) With your partner, decide on how you will share your rules with the rest of the class. Some ways to present your rules are as a rhyme, song, rap or role play.

(c) Swap your list with another pair and evaluate their rules.

2. Many chemicals can stain, irritate or burn the skin and some are poisonous. Many chemicals are only safe if used correctly. What should you do in each of the situations listed below?(a) You spill a solid powder.

(b) You spill a liquid.

(c) You break some glassware.

(d) Your experiment is fi nished.



Microscopes and magnification

1.31.3

There are many things in our environment that we cannot see without help. We use telescopes to help us see things that are far away such as the planets and details of the surface of the Moon. We use microscopes to see objects that are very small. Light microscopes and electron microscopes provide the images that you will see most commonly.

Microscopes and other magnifi ers contain lenses that allow light to pass through them, but bend the light rays so that we can see things more clearly.

3. Why is it important that you let your teacher know if there has been an accident or breakage in the science laboratory?

4. Some chemical bottles have warning labels on them. So do some household substances. At home try to fi nd some of these warning labels and sketch what they look like, or design your own warning label for the following:

(a) a poisonous substance

(b) a fl ammable substance

(c) a corrosive substance.

5. Name the item(s) of science equipment that can be used to:

(a) mix large amounts of liquids together

(b) heat small amounts of liquid

(c) measure small volumes of liquid

(d) hold test-tubes

(e) support equipment

(f) heat small amounts of solids.

6. There are two different fl ames on the Bunsen burner. Draw them both and explain when you would use each one.

7. Can you fi nd the ten pieces of science equipment in the puzzle in fi gure 1.8? Draw each piece separately into your book and label it.

8. Why should you never point the mouth of a test-tube towards yourself or others when heating it?

9. Describe one piece of science equipment as carefully and accurately as you can without naming it. See if your partner can identify it.

10. Write your own ‘dangerous laboratory drama’. Perform your play and ask the other students to list any dangers shown in your play. Watch the dramas by other students and make a list of their dangers.

11. Create a multimedia presentation or movie to explain how different pieces of science equipment can be used in a laboratory.

Figure 1.8

How many pieces of scienceequipment can you fi nd?


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Light microscopesThere are many different types of light microscope. Some have only one eyepiece for you to look through. These are called monocular microscopes. Others with two eyepieces are called binocular microscopes.

For the microscope to work properly, light must be able to pass through the object (or specimen) you are looking at and then through a selection of lenses. The lenses magnify the specimen being studied. The microscope is focused by changing the distance between the lenses and the specimen. The specimen must be very thin. Special cutting tools are used to cut these thin sections. Sometimes specimens are stained with a dye to make certain features easier to see. You will probably use a microscope like the one in fi gure 1.10.

Figure 1 .9

Human eyesight is limited. We need instruments to help us see the detail of structures that are far away or very small. We use different types of lenses to carry out different functions.

Figure 1 .10

The diagram shows how the parts of a microscope are organised.

Game



S C I E N C E work

Getting to know your microscopeOptical microscopes come in a variety of shapes and sizes; however, all of them have the same basic parts.

What to do

1. Collect a microscope. Make sure you carry it with two hands, one around the arm and the other under the base; your teacher will show you how. Place your microscope on the bench away from the edge.

2. Look closely at your microscope and use fi gure 1.11 to fi nd each of the labelled parts. With a partner, try to decide what each part is used for.

3. If you can’t work out what some parts are for, write some questions about them as labels on the drawing.

4. Join up with another pair to see whether they have the answers to any of your questions.

5. Table 1.2 contains a description and a function for each part of the microscope but they are all mixed up. Unscramble the information and write the corrected table into your book.

6. Compare your table with another group and discuss any differences.

Activity 1 . 6

Figure 1 .11

A standard light microscope. Microscopes that are used in schools may look a little different from those used in labratories, but essentially they work the same way.

Table 1 .2 Parts of a microscope

Name of part

Description Function

eyepiece(ocular) lens

fl at bottom surface holds the slide in place, letting light pass through it

objective lens fl at surface to sit slides on, has hole in its centre, may have clips

adjusts the position of the lenses so that the object can be seen clearly; can be coarse or fi ne

focus knob iris-like aperture that can be adjusted to allow light through

light travels through it to the eyepiece lens

base knob that can be turned to move the lenses

controls the amount of light passing through the object

mirror the adjustable tube between the eyepiece and objective lenses

supports the microscope

stage lenses of different focal lengths that can be positioned above the slide

refl ects light up through the slide into the lenses

diaphragm round with a shiny surface used to get different magnifi cations

microscope tube

single lens closest to the eye bends the light to make the object look bigger


Using microscopesMicroscopes are very expensive and delicate instruments. They should be used with care at all times. Here are the fi ve important rules to remember when using your microscope.• When carrying your microscope, always use both hands.• Keep your microscope well away from the edge of your

workbench.• To prevent damage to your eyes, make sure that sunlight is not

shining directly up the tube of your microscope. Use a lamp with a fi lter whenever possible.

• Look from the side of the microscope and move the tube down so that it is as close to the microscope slide as possible. You can then focus your microscope by looking through the eyepiece or objective lens and moving the tube slowly upwards.

• If your microscope lenses are dirty, use lens tissues to clean them. Never wipe them with paper towel or your fi ngers.

Microscopes and magnifi cationThe magnifi cation of the microscope tells you how much bigger the image is than the real object. If the microscope has a magnifi cation of ×400, then the image you are looking at is 400 times bigger than the actual object. (The symbol × stands for ‘magnifi ed by’.)

To work out the magnifi cation, look at both the eyepiece lens and the objective lens of the microscope. Each has a number on it, such as ×10 or ×20. Multiplying these numbers together gives you the total magnifi cation of the microscope.

Fields of view of the light microscopeHow big is it really?When looking at specimens using a microscope, we have to remember how big they really are. First let’s look at a measurement that makes sense to us—our height. We usually measure this in centimetres or metres. You may be 160 cm tall, or you may prefer to say 1.60 m. If you had to measure the width of your foot, you would probably use centimetres or millimetres. For the width of a coin you would probably use millimetres. The small objects that you see under the microscope are usually measured in micrometres (µm). A micrometre is one thousandth of a millimetre, or one millionth of a metre.

How much do we see?When you look down your microscope you see only part of the specimen. The circle of light that you see is called the fi eld of view. The area covered by the fi eld of view varies between microscopes and according to the magnifi cation you are using. For example, if you use a magnifi cation of ×40, a typical microscope would have a fi eld of view around 4 mm in diameter. Table 1.3 lists the most common fi eld of view sizes. Note that as the magnifi cation increases the fi eld of view decreases.

Figure 1.12Calculating the total magnifi cation.

Opticalmicroscope

Magnifi cation10 × 40 = ×400

Ocular lens×10

Objective lens×40

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Cells vary in size from the smallest bacterium (1 µm across) to nerve cells that can be over a metre in length. Human skin cells are about 50 µm across.

ssciciffileile


Imagine that a specimen observed at low power occupies about half of the fi eld of view. We know from table 1.3 that the fi eld of view has a diameter of 4 mm (4000 µm), therefore an object that occupies half of the fi eld of view would be about 2000 µm long.

Figure 1 .13The fi eld of view gets smaller as the magnifi cation gets higher.


Table 1 .3 Common magnifi cations and their fi elds of view

PowerObjective lens magnification

Ocular lens magnification

Total magnification

Field diameter (mm)

low (LP) 4 10 40 4.0

medium (MP) 10 10 100 1.6

high (HP) 40 10 400 0.4

S C I E N C E work

EXPERIMENT 1 . 7Using a microscope

Aim

To become familiar with the use of a microscope.

Materials

• light microscope • tissue • mini grid (optional)• microscope lamp with fi lter • newspaper • slides and cover slips• tweezers • cotton wool • hair• clear plastic ruler • fabric

Part A: How big is it really?

Method

1. Collect a microscope and carry it with both hands to the workbench, placing it well away from the edge.

2. Work out the magnifi cation of your microscope when using the low and high power lenses.3. Adjust your mirror so that an appropriate amount of light passes through the hole in the stage.4. Place a clear plastic ruler on the stage of your microscope so that you can focus on the

millimetre scale. Once you have focused your microscope, the area that you can see is called the ‘fi eld of view’. It should appear as a round circle of light.

5. Using your low power objective lens, measure the width of your fi eld of view. Note this down in your book.

6. Using your high power objective lens, measure the width of your fi eld of view. Note this down in your book. How does it compare with your fi eld of view using the low power objective lens?


Figure 1 .14A microscope from 1716 —an expensive toy for the inquisitive rich.

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Extension

Your teacher may have a ‘mini grid’ that you can use to estimate the size of what you see under the microscope. Learn how to use the mini grid and then estimate the width of a strand of your hair. If you don’t have a mini grid, remember the width of your fi eld of view measured above and use this to estimate the width of the hair. Compare your hair with other people’s hair—is it thicker or thinner? Is blond, red or dark hair thinnest? Compare curly and straight hair—is there a difference in the thickness?

Part B: Upside down and back-to-front

Method

1. Cut out a piece of newsprint 1 cm square. Make certain that it contains the letter ‘e’. 2. Place the print onto a microscope slide. Place a cover slip over the top of this.3. Use the low power objective lens. While watching from the side, use the coarse

adjustment to lower the objective lens until it is just above the stage. Pressing it down too far may shatter the slide.

4. While looking through the eyepiece, carefully turn the coarse adjustment until the specimen can be seen clearly.

5. Carefully use the fi ne adjustment so that you can see the details of your specimen as clearly as possible.

6. Carefully move the slide until you have an ‘e’ in focus. 7. Pencil a sketch of what you see. Is it right side up, upside down or back-to-front?

How much of the fi eld of view is covered by the ‘e’ at this magnifi cation?8. In which direction did the paper under the microscope move when you moved the slide to

the left? What about when you moved it towards you? 9. Record the magnifi cation that you are using.

Evaluation

What diffi culties did you encounter while using the microscope?How could you improve your microscope technique?

Extension

Look at some other specimens, such as tissue, cotton wool, coloured paper and frayed edges of fabric. Sketch what you see and label the diagrams clearly. Remember to write down the magnifi cation that you are using.

ssciciffileileDuring the seventeenth and eighteenth centuries people could not think of any ways that microscopes could be useful. They regarded them as just a toy. They would be amazed to know that of all the tools used by scientists today, the microscope is among the most useful. Microscopes allow scientists to ‘look into’ living things in a very detailed way.


ssciciffileileThe fi rst electron microscope was built by the German physicist Ernst Ruska. Electron microscopes are more powerful than optical microscopes because magnifi cation is increased with shorter wavelengths and electron waves are much shorter than ordinary light waves.

Figure 1 .16A simplifi ed explanation of how we see things with a scanning electron microscope.

Figure 1 .15An electron microscope enables us to see things like this fl ea in amazing detail.


electron source

electromagnetsnarrow the electron beam

specimencovered with electron-densematerial

stage

emittedelectrons

detector

image on screen

Electron microscopesElectron microscopes use beams of tiny particles called electrons rather than a light source, and can magnify up to a million times! All images are seen in black and white. They cannot be used for viewing live specimens.

The fi rst type of electron microscope to be developed was the transmission electron microscope (TEM). The TEM sends a beam of electrons through an ultra-thin section of a specimen that has been stained with an electron-dense stain such as lead or uranium. The beam of electrons is affected by the structure of the specimen and a picture is created.

The scanning electron microscope (SEM) was developed later and it has many uses. A simplifi ed version of how an SEM works is shown in fi gure 1.16.


Let's experiment1.41.4

Fair testsWhen you plan an experiment, you should be sure that it is a fair test. A fair test changes only one variable at a time and repeats each test at least three times to reduce errors. Other people should be able to carry out the same experiment and get similar results.

FAIR TEST

CONTROLAll variables should be kept the same,

except the one being tested.

TitleDecide on a name for your test.

AimWrite your question.

HypothesisMake a

prediction.

VariablesList all the things that can change.

MethodHow will you carry out the experiment?

ResultsHow will yourecord your

results?

EvaluationHow good is your

method? Can you improve the accuracy of your

results?

Figure 1 .20

There are many steps to follow when planning a fair test.

ssciciffileileA variable is a factor that can change the outcome of an experiment, e.g. temperature, amount of light, brand of tyre.

Interactive


questions 1.3

1. Name the two main types of microscope and list the main similarities and differences between them.

2. If you wanted a very detailed image of a cell, which microscope would you use?

3. List the ways that an image seen under a light microscope can differ from the original specimen placed on the stage.

4. Outline the steps you would follow to obtain a clear focus using a light microscope on low power and then on high power.

5. Explain why it is important for a specimen viewed using a light microscope to be very thin.

6. (a) If our eyes can see things as small as 0.1 mm, and one cell is one-tenth of this size, what is the size of the cell in micrometres?

(b) How many micrometres are there in one millimetre? If a cell is 50 µm in diameter, how big is it in millimetres? Would we be able to see this cell without a microscope?

7. What is the greatest magnifi cation you can gain with the microscope you used in your laboratory? Explain how you calculated your answer.

8. Create a rhyme that would help you remember how to use a microscope.

9. Design a poster for use in the classroom demonstrating for students the correct way to:

(a) carry and set up a microscope. (b) focus the microscope on low, medium

and high power.


01 Chapter review

34

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Science 8: A Contextual Approach

aimBunsen burnerconclusioncontroldataequipmentexperimentevaluationfair testhypothesisinferenceinvestigationlaboratorymassmeasurementmeniscusmethodobservationsresultssafetyscientisttemperaturetitlevariablevolumeweight

key ideasideasey ieekey ideaskey ideaskeyTrue or False? Which of the statements below are true? If you think any are false, rewrite them as correct statements.

1. The science laboratory has rules that need to be followed for your own and other people’s safety.

2. Scientifi c drawings are done in colour.

3. When using a Bunsen burner, the blue fl ame is the safety fl ame and the yellow fl ame is used for heating.

4. An observation is an educated guess.

5. Graphs allow trends and patterns to be observed easily.

6. Weight and mass are the same thing.

7. Distance is measured in grams.

8. Inferences are suggested explanations for our observations.

9. A science laboratory is any place where experiments and investigations are carried out.

10. A light microscope gives a greater magnifi cation than an electron microscope.

1. Explain why a hypothesis is sometimes described as being an ‘educated guess’.

2. List possible points to include when writing a practical report.

3. Imagine that you need to describe a Bunsen burner to someone who hasn’t seen one before. Explain, without using a diagram, what the parts of a Bunsen burner look like, how they fi t together, and how they work.

4. Unscramble the names of laboratory equipment in the following table, then match each item with its correct use.

Equipment Used to

snuben errbun hold test-tubes while heating

zuega tam spread heat when heating a fl ask or a beaker

gnots heat things

smearguni inderlcy pick up small amounts of solids

poringateva hids accurately measure the volume of a liquid

laptusa evaporate a small amount of solution

5. A microscope has a ×5 eyepiece and three objective lenses: ×4, ×10 and ×40. Draw up a table that shows the magnifications that could be achieved using this microscope and how each magnification could be produced.

6. What is the difference between an observation and an inference? Make up your own table of three matching observations and inferences.

review questions


35

reflection science

7. For each of the following statements correct the units used so that the sentence makes sense.

(a) A baby weighs 3975 cm.

(b) I drank 1.0 m of water.

(c) In 1 hour, Friedrich ran 4 kg.

(d) Mary has a height of 163 s.

8. Why should you never shake a test-tube with your thumb over the top of it?

9. Design a cartoon illustrating one dangerous situation in your science laboratory.

10. The following is a list of ways to reduce the risk of fi re: (a) Clear away fallen leaves, long grass and

dead undergrowth from within 30 m of your home.

(b) Remove wood piles, heavy mulch and other fl ammable materials.

(c) Check that hoses reach all sides of the house.

(d) Check that electrical leads are not worn or frayed.

Explain how each of these preventative measures reduces the risk of fi re.

11. Create a booklet that tells the story of a famous scientist. The booklet is to be used by primary schools for their Year 4 level and should include the birthplace of the person, what the person is famous for, and in what ways they have contributed to our scientifi c knowledge. Make sure it is interesting, well illustrated and suitable for Year 4 students.

Some suggestions are: Alfred Nobel, Marie Curie, Sir Frank Macfarlane Burnet, Albert Einstein, Suzanne Cory, Don Metcalfe, Peter Doherty, Isaac Newton, Gustav Nossal, Barry Marshall, Robin Warren.

12. A trip to the supermarket will never be the same. Murray Laidlaw of the UK has been awarded a $75 000 grant to build a better shopping trolley. His hi-tech plans include a sophisticated Global Positioning System (GPS) so shoppers don’t get lost, a touch screen display where previous shopping lists can be stored, and an in-built price scanner to minimise check-out delays. The trolley will even ask shoppers if they’ve forgotten any important ingredients!

Design and draw or build a model of your own Robotrolley.

In this chapter you have learnt many new skills and discovered how we use science every day at home, at school and at work. Now is the time to complete the third and fourth columns in your KWLH chart. Your teacher may want to see a copy of your chart.

Present your laboratory safety policy to your School Council. Make sure that you have fi rst trialled your report with another group of students or teachers.

You should ask the trial audience for feedback on how you can improve your report.

1. T 2. F 3. F 4. F 5. T 6. F 7. F 8. T 9. T 10. F

complete

Figure 1.35

Robotrolley.


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