TABLE OF CONTENTS - 香港布廠商會朱石麟中學sci_e/ENG NOTES/Teacher Note_(eng...Integrated Science Sample SBA Task Teacher Notes – C2 6 Area B (Maximum 10 marks): Marks

TABLE OF CONTENTS

Task Title

C1

Osmosis in Living Tissue

C2

Catalytic Activity of Enzyme

C4

Passing Electricity through Everyday Substances

C5

Do All Conductors Obey Ohm’s Law?

C6

Composting Bioreactor

C7

Ultraviolet (UV) Radiation Protection of Sunglasses

C8

Extracting DNA from Fruits

E3

How Cross-linking Changes the Properties of a Polymer

Integrated Science Sample SBA Task

Module C1: Water for Living

Osmosis in living tissues Teacher Notes

Osmosis is the movement of water through a selectively permeable membrane, from a solution of higher water potential to a solution of lower water potential. It provides the primary means by which water is transported into and out of cells. In this experiment, students will put samples of potato tissues in sucrose solutions of various concentrations and observe their behaviour. They have to find in which sucrose concentration the sample of potato tissue shows neither an increase nor a decrease in length and hence to deduce the water potential of the potato tissue. Curriculum Link C1: Water for Living 1.2 Movement of water in and out of cells by osmosis Pre-laboratory Preparation 1. Ask students to find out from textbooks or other reference sources the meaning of

osmosis and its importance in biological systems. 2. Ask students to devise plans to investigate how the potato tissue behaves in sucrose

solutions of various concentrations and hence to find the water potential of the potato tissue in terms of the concentration of sucrose solution.

Pre-laboratory Talk 1. Conduct a brief revision on osmosis. 2. Demonstrate how to prepare a potato cylinder using the cork borer. 3. Draw students’ attention to the safe handling of cork borer and razor blade. 4. Ask students to suggest ways to present the results and to determine the water potential

of the potato tissue. Time Required Pre-laboratory talk: 10 minutes Experiment and report writing: 65 minutes Grouping Students may work individually or in groups of two to three.

Teacher Notes – C1 1


Technician Notes 1.0 M sucrose solution can be prepared by dissolving 342 g of sucrose in water and making up to 1 L. Laboratory Report If students are asked to write a detailed report, the report should include the following items: 1. Title 2. Aims 3. Theory/Background (optional) 4. Apparatus and materials 5. Design of the experiment 6. Procedure 7. Precautions 8. Results (including data and observations) 9. Discussion (including sources of error and improvements to be made) 10. Conclusion 11. Questions for further thought (optional) Remarks Depending on the ability of the students, there may be variations for this investigation, such as:

1. for high-achieving students, inform them of the purpose of this investigation and provide them with a list of apparatus; ask them to devise the set-up and procedure for the investigation (Version 1 of Student Handout);

2. for students of average ability, a detailed worksheet can be provided to guide them step by step (Version 2 of Student Handout).

Suggested Solutions to Questions for Further Thought 1. Besides measuring the length of the potato cylinders, what other parameter can you

measure in order to determine the water potential of the potato tissue?

Measuring the weight of the potato cylinders can be used to determine the water potential of the potato tissue. When the potato cells lose water in a solution of lower water potential, the whole potato cylinder becomes lighter. Likewise, the potato cylinder gets heavier when it is placed in a solution with higher water potential because water will move into the cells.



Suggested Mark Allocation Area A (Maximum 10 marks):

Marks

Abilities to be assessed 0 1 2

Competence in handling pipette

leveling of the liquid to the graduation mark of

the pipette

proper draining out of the ‘last drop’ from the

pipette

Measuring the length of potato cylinders

blot-drying the potato cylinder before

measuring its length

taking measurements with a precision within

that of the ruler

Carrying out the experiment safely

handling cork borer safely

handling razor blade safely

Performing the experiment in an organised and

efficient way

proper labeling of boiling tubes and pipettes

keeping a record of the data in an appropriate

way

Keeping work area neat and tidy

TOTAL:




Area B (Maximum 10 marks):

Marks


Experimental design

independent and dependent variables

assumptions made in the investigation

Experimental plan

using sucrose solutions of various

concentrations

immersing potato cylinders of the same length

in the sucrose solution for a suitable length of

time

Presentation of results

making appropriate use of table and graph to

present data

recording readings accurately (in appropriate

units)

Interpretation of results

accounting for the changes in length of potato

cylinders in terms of osmosis

determining the water potential of potato tissue,

and expressing it in terms of the concentration

of sucrose solution

Evaluation of experimental procedure

discussion of the sources of experimental error

suggestions for improvement

TOTAL:


Module C2: Balance within Our Body

Catalytic activity of enzyme Teacher Notes

Starch acts on iodine to give the characteristic blue-black colour of the standard iodine test. In the presence of an enzyme, amylase, starch is hydrolysed to give predominantly maltose, some glucose as well as other simple sugars. These products do not react with iodine to give the blue-black colour. In this experiment, students are required to study the effect of temperature on amylase activity. A small amount of amylase is used to act on a given quantity of starch at different temperatures. When the starch is almost completely hydrolysed, the reaction mixture will give a negative result to the iodine test (absence of blue-black colour). The reciprocal of the time for the first instant of the absence of the blue-black colour gives an indication of the rate of the enzymatic reaction. From the experimental findings, students should be able to deduce the optimum temperature for amylase activity on starch. They should also recognise the importance of optimum temperature for metabolic reactions within the body. Curriculum Link C2: Balance within Our Body 2.2 The role of enzymes in metabolism; the effect of temperature on enzyme

activity Pre-laboratory Preparation 1. Ask students to devise plans to study the effect of temperature on enzyme activity. 2. Ask students to carry out an information search on chemical structure and specificity of

enzymes. Pre-laboratory Talk 1. Conduct a brief revision on enzyme properties and factors affecting enzymatic

reactions. 2. Discuss with students how to monitor the rate of a chemical reaction. 3. Ask students to suggest the operating temperatures for the investigation. 4. Remind students that keeping the amylase and starch solutions in a water bath for

sufficient time are to ensure the solutions attain the desired temperature. 5. Remind students of safety issues related to the use of hot plate and hot water bath. 6. Remind students NOT to spill iodine solution onto clothes.



Time Required Pre-laboratory talk: 10 minutes Experiment and report writing: 60 minutes Grouping Put students in groups of three. Each student in a group will be required to work on two given temperatures. All data collected from the three students will be pooled together and used in writing the laboratory report. Technician Notes A stock iodine solution is prepared by dissolving 1 g iodine and 2 g potassium iodide in 1 L of distilled water. In carrying out the iodine test for starch, it is advisable to use a very dilute iodine solution. Prepare the dilute iodine solution by adding 0.5 ml of the stock iodine solution to 10 ml of distilled water. A spot colour made up by mixing 0.01% of starch solution and iodine solution may be used as an arbitrary standard for the absence of starch. Amylase solution should be freshly prepared. Laboratory Report If students are asked to write a detailed report, the report should include the following items: 1. Title 2. Aims 3. Theory/Background (optional) 4. Apparatus and materials 5. Design of the experiment 6. Procedure 7. Precautions 8. Results (including data and observations) 9. Discussion (including sources of error and improvements to be made) 10. Conclusion 11. Questions for further thought (optional)



Remarks Depending on the ability of the students, there may be variations for this investigation, such as:

1. for high-achieving students, inform them of the purpose of this investigation and provide them with a list of apparatus; ask them to devise the set-up and procedure for the investigation;

2. for students of average ability, a detailed worksheet can be provided to guide them step by step.

If time allows, students should be encouraged to repeat the experiment at other temperatures so as to find out the optimum temperature for amylase activity. Suggested Solutions to Questions for Further Thought 1. Why does the dark-blue colour of the iodine mixture not appear as mentioned in Step 3?

When the starch is completely hydrolysed, no starch is left to react with iodine solution to give the dark-blue colour.

2. What is the implication of the experimental findings on biochemical (metabolic)

reactions within the body?

Most of the metabolic reactions taking place in the body are catalysed by enzymes. The activity of enzymes plays a very important role in regulating metabolism, thus maintaining balance within the body. An enzyme works best at an optimum temperature and the rate of the enzymatic reaction is the highest under this condition. Most of the enzymes found in the body work best at about 37 oC which is the normal body temperature.

3. Account for the temperature dependency of the catalytic activity of enzymes in terms of

chemical bonding and structure.

Enzymes are protein in nature. When the temperature rises, the substrate and the enzyme molecules have greater kinetic energy. This increases the chance of colliding with each other to form an enzyme-substrate complex and hence the rate of reaction increases. The reaction rate reaches the highest at the optimum temperature. However, further increase in temperature beyond the optimum temperature breaks the hydrogen bonds and other intramolecular attractions which maintain the specific 3-D structure of the enzyme molecule. In this way, the enzyme is denatured and becomes mal-functional. Thus, the enzyme activity drops dramatically when the temperature exceeds the optimum temperature (Fig.1).



Heat energy causes more collisions between enzyme and substrate

Optimum temperature

Rat

e of

rea

ctio

n Enzymes denature at high temperatures so rate falls rapidly

30 40 50 6010 20 0

Temperature / oC

Fig. 1 Effect of temperature on enzyme activity

References 1. http://www.rsc.org/education/teachers/learnnet/cfb/enzymes.htm 2. http://en.wikipedia.org/wiki/Enzyme




Marks


Competence in handling pipette

leveling of the liquid to the graduation mark of

the pipette

proper draining out of the ‘last drop’ from the

pipette

Measuring the time for the disappearance of starch

in the reaction mixture

carrying out the test for starch quickly at

2-minute intervals

appropriate use of the stopwatch

Carrying out the experiment safely

Handling hot water bath safely

No spilling of iodine solution onto clothes

Performing the experiment in an organised and

efficient way

proper labeling of test tubes and pipettes


way

Keeping work area neat and tidy

TOTAL:





Marks


Experimental design


control set-up and precautions



present data


units)


the temperature and amylase activity

relationship

Making inferences and conclusions

reaching overall conclusion on the effect of

temperature on enzyme activity

relating the optimum temperature of enzyme

activity to metabolic reactions within the body


discussion of the sources of error


TOTAL:


Module C4: Chemical Patterns

Passing electricity through everyday substances Teacher Notes

In this experiment, students will pass electricity through everyday substances, and classify them as good or poor electrical conductors. They will then conduct an experiment on the electrolysis of an aqueous sodium chloride solution, and will be asked to provide an explanation for the reactions that occur during the electrolysis. Students will acquire the skills of handling multimeters and setting up circuits for electrolysis, and the ability to make deductions on reactions occurring during electrolysis.

Curriculum Link C4: Chemical Patterns 4.5 Electrolysis and the ionic theory C5: Electrical Enlightenment 5.2 Application of electrolysis: decomposition of substances E3: Chemistry for World Needs 3.2 Production of chlorine by electrolysis of brine

Pre-laboratory Preparation 1. Ask students to find from reference books possible ways for measuring electrical

conductivity of substances. (Remind students NOT to conduct the experiments at home using the a.c. mains.)

2. Ask students to carry out an information search on electrolytes.

Pre-laboratory Talk 1. Carry out a demonstration of how to use a multimeter and a power supply unit. Discuss

how to select the appropriate scale on the multimeter. Remind students of safety issues relating to the use of electricity.

2. Ask students to state the relationship between resistance and conductance of a substance.

3. Ask students to propose ways of measuring the resistance of liquids and solutions. 4. Explain to students the meaning of 5% aqueous solution. 5. For more able students, ask them to measure the resistance of other substances

commonly encountered in daily life. 6. Remind students about the particles of matters they have come across, including atoms

(eg metal atoms) and molecules (eg water molecules and glucose molecules). Through this experiment, student will be introduced to some charged particles in matters – ions, and they will experience the process through which scientists discovered ions.

7. Draw students’ attention to the proper way of smelling gases. 8. Tell students that chemical changes can be described concisely using chemical/word

equations.


9. Suggest possible ways of recording experimental results and presenting experimental findings, e.g. taking photographs of the observations, presenting findings using posters.


Time Required Pre-laboratory talk: 15 minutes Experiment: 25 minutes for Part I 25 minutes for Part II Discussion/debriefing: 10 minutes Grouping Put two to four students in a group (depending on the availability of multimeters, power supply units and electrolysis cells). Technician Notes In Part I, students may need help in preparing the powder samples (using a pestle and mortar set) and in preparing the aqueous solutions (weighing solid substances and dissolving them in water). A 9V battery pack can be used if the number of power supply units is insufficient. In Part II, chlorine gas will be liberated in the electrolysis. Ensure that the laboratory is well ventilated or the experiment is conducted in a fume cupboard. Laboratory Report If students are asked to write a detailed report, the report should include the following items: 1. Title 2. Aims 3. Theory/Background (optional) 4. Apparatus and materials 5. Design of the experiment 6. Procedure 7. Precautions 8. Results (including data and observations) 9. Discussion (including sources of error and improvements to be made) 10. Conclusion 11. Questions for further thought (optional) Students can also be asked to present their findings using posters and/or PowerPoint slides.



Remarks For Part I, students may notice that the measured resistance of a substance depends on factors such as the distance between the two carbon rods, the concentration of the solution used, the contact areas between the carbon rods and liquid/solution used. Students can suggest possible ways of controlling the variables in the experiment. For Part II, students may notice that electrolysis will not take place unless a certain voltage is applied. This is due to over-voltage for the liberation of gaseous products in electrolysis. Students are not required to have this knowledge. The chlorine liberated in the experiment is irritating and causes choking. Students should avoid smelling it directly. Suggested Answers to the Questions Part I: 1. What is the relationship between the resistance and conductance of a substance?

The higher the resistance the lower the conductance of a substance and vice versa. So a good electrical conductor has a low resistance.

2. Which substances in Table 1 are electrical conductors?

Stainless steel ruler, sodium chloride solution (5%) and water (very poor electrical conductor).

3. Which of these substances is/are electrolyte(s)? Explain briefly.

Sodium chloride. It cannot conduct electricity in solid state but conducts electricity in aqueous solution.

4. Find in your textbook or in any other reference material, the explanations for (i) the electrical conducting properties of substances, and (ii) the different behaviour of electrolytes and non-electrolytes with electric current.

(i) Some substances have mobile charged particles (electrons or ions). These charged particles make it easy for electricity to flow through the substances.

(ii) The electrolytes contain mobile ions when in molten state or aqueous state while the non-electrolytes do not contain mobile ions for the conduction of electricity.



Part II: 1. Based on the experimental results, deduce the gases liberated at the positive and

negative electrodes.

Positive electrode: chlorine (It is greenish yellow in colour, bleaches the pH paper and has a choking smell.)

Negative electrode: hydrogen (It is colourless and burns with a ‘pop’ sound.)

2. Write chemical (word) equations for the reactions occurring at the positive and negative

electrodes.

Positive electrode: 2Cl(aq) → Cl2(g) + 2e

chloride ions → chlorine gas + electrons Negative electrode: 2H+(aq) + 2e → H2(g) hydrogen ions + electrons → hydrogen gas 3. What are the ions present in sodium chloride solution? Why is sodium metal not formed

at the negative electrode in the electrolysis?

Na+, Cl H+ and OH ions Sodium is a very reactive metal. Sodium ions cannot be easily discharged if the

electrolysis is conducted in aqueous solutions. Suggestions for Further Investigation Teachers may ask students to further explore the action of electricity on substances by working on the following variations of the experiment: 1. Compare the electrical resistance of:

aqueous solutions of sodium chloride of different concentrations aqueous solutions of salts of the same concentration aqueous solutions of salts with singly-charged and multiple-charged ions

2. Investigate how the results of the electrolysis would be affected by varying:

the concentration of the sodium chloride solution the voltage applied to the electrolysis cell the pH of the sodium chloride solution




Marks


Handling and using a multimeter

selecting the appropriate range of the scale

connecting wires correctly

Measuring the resistance

cleaning the surface of the substances where

appropriate

cleaning the carbon rods

Preparing the aqueous solutions for resistance

measurements and for electrolysis

weighing solid correctly

using appropriate apparatus to make solutions

Conducting the electrolysis experiment

setting up the apparatus properly

having correct circuit wiring and applying an

appropriate voltage

Conducting the tests on the gases collected

taking correct steps in testing the gases

TOTAL:





Marks


Devising an appropriate experimental procedure for

measuring electrical properties (resistance) of liquids

and solutions

Presentation of results for Part I

recording the multimeter readings correctly

presenting the data appropriately

Interpretation of results for Part I

making logical and correct inferences about the

electrical conducting properties of electrolytes

Presentation of results for Part II

recording the observations on electrolysis

properly

recording the observations for the tests of gases

properly

Interpretation of results for Part II

giving the correct/logical inferences about the

gaseous products from results of the tests

deducing the ions that may be present in the

sodium chloride solution

TOTAL:


Module C5: Electrical Enlightenment

Do all conductors obey Ohm’s law? Teacher Notes

This experiment consists of two parts. The first part is a simple standard set-up to repeat Ohm’s experiment to investigate the relationship between the voltage across a conductor and the current flowing through it. The second part is a modified version to show that some conductors do not follow Ohm’s law if certain conditions (e.g. temperature) are not kept constant. Students should be able to verify Ohm’s law in the first part, and discover discrepancies in the second part and provide an explanation for the discrepancies. In this experiment students will practise the skills needed to connect circuits according to circuit diagrams given and take readings at suitable intervals. Students should also develop the skills to plot graphs to a suitable scale and to interpret the results. They should be aware that not all mathematical relationships in science are linear. Curriculum Link C5: Electrical Enlightenment 5.4 Ohm’s contribution to current electricity Pre-laboratory Talk 1. Remind students of the common errors in connecting a circuit - wrong connection of the

positive and negative terminals, and incorrect series or parallel connection of voltmeters and ammeters.

2. Remind students to check their circuits before connecting to the power supply. 3. Remind students to use the d.c. supply of the power pack in Part B because a d.c.

ammeter and voltmeter are used. 4. Remind students NOT to touch the nichrome wire and the light bulb during the

experiment as they might get very hot. 5. Remind students to take readings at suitable intervals. If the current is adjusted at 0.1 A

interval, there is not much change of voltage; if the adjustment of current is at a large interval, some important features of the relationship might be missed.

6. Remind students to plot graphs to a suitable scale. Time Required Pre-laboratory talk: 10 minutes Experiment and report writing: 65 minutes Grouping Put two to four students in a group (depending on the availability of power packs, nichrome wires, light bulbs, rheostats, ammeters and voltmeters).

Teacher Notes – C5

1


Laboratory Report If students are asked to write a detailed report, the report should include the following items: 1. Title 2. Aims 3. Theory/Background (optional) 4. Apparatus and materials 5. Design of the experiment 6. Procedure 7. Precautions 8. Results (including data and calculations) 9. Discussion (including sources of error and improvements to be made) 10. Conclusion 11. Questions for further thought (optional) Remarks Depending on the ability of the students, there may be variations for this investigation, such as:

1. for high-achieving students, inform them of the purpose of this investigation and provide them with a list of apparatus (but circuit diagrams are NOT provided); ask them to suggest the set-up and procedure for the investigation;

2. for students of average ability, a detailed worksheet can be provided to guide them step by step. If students find it difficult to connect circuits according to the circuit diagrams given, teachers can provide photographs of the set-ups to help them complete the task.

Suggested Solutions to Questions for Further Thought 1. You are advised NOT to allow a large current to flow through the nichrome wire when

performing the Part A experiment. Explain why.

A conductor no longer follows Ohm’s law when its temperature becomes high due to a large current flow. Using a large current in Part A will heat up the nichrome wire and the wire will not obey Ohm’s law.

2. Explain the results obtained in Part B using the particle theory.

The atoms in a conductor vibrate more vigorously when the temperature of the conductor becomes higher and this hinders the flow of electrons. Therefore, the resistance becomes greater as the temperature increases.

3. Find out if there are any other conductors that do not follow Ohm’s law.

Graphite and semiconductors are examples of non-ohmic conductors.



References 1. http://en.wikipedia.org/wiki/Electrical_conductor 2. http://en.wikipedia.org/wiki/Nichrome 3. http://en.wikipedia.org/wiki/Light_bulb




Marks


Competence in connecting circuits

correct wiring of positive and negative

terminals of ammeter and voltmeter

correct series or parallel connections of

ammeter and voltmeter

Measurement techniques

current is gradually increased at suitable

intervals

measurements are taken with a precision within

that of the ammeter and voltmeter

Data collecting and recording

collecting adequate number of ammeter and

voltmeter readings


way

Safety measures taken

small current (for Part A) / small voltage (for

Part B) is used at the start of the experiment

a large current is NOT used throughout the

experiment

Working efficiently and neatly

TOTAL:





Marks




present data


units)

Plotting of graphs

voltage (as the y-axis) against current (as the

x-axis) and suitable scale for the graphs

correct shape of graphs


comparing the graphs

explanations for the different shapes of graphs

Drawing meaningful conclusions




TOTAL:


Module C6: Balance in Nature

Composting bioreactor Teacher Notes

Composting is the aerobic decomposition of organic matter such as leaves, grass and food scraps by various organisms. The compost that results is a valuable product that can be used to enrich the soil for plant growth. Quality compost can be obtained from a proper mix of ‘carbon-rich’ and ‘nitrogen-rich’ waste with adequate amounts of moisture, oxygen and time. Contrary to large scale compost piles, bioreactors built from soda bottles are small and inexpensive systems. This small system allows students to design and carry out individualised investigation, to compare the effect of different types of compost materials, particle size and moisture content of the materials on compost temperature. In this activity, students are required to design experiments using soda bottle bioreactors, change factors in the bioreactor and track the temperature changes. They are expected to develop skills in making close observations and measurements, careful recording and analysing data, constructing data tables and graphs, and in presenting results. After the activity, students should have a better understanding of the composting process and the benefits of composting. Curriculum Link C6: Balance in Nature 6.3 The important role of decomposers in the cycling of materials Pre-laboratory Preparation 1. Ask students to search for information on composting. 2. Ask students to devise plans to compare the effect of factors on compost temperature

using home-made soda bottle bioreactors, and review the design of their plans before proceeding.

Pre-laboratory Talk 1. Conduct a brief revision on composting. 2. Lead a class discussion about the factors that affect the success of a composting system. 3. Show the soda bottle bioreactor and explain briefly how it can be built. 4. Draw students’ attention to the safe handling of cutter, scissors and nail. 5. Remind students of health and safety issues related to the handling of compost

materials.



Time Required Pre-laboratory talk: 15 minutes Experiment: 50 minutes for Parts A and B 3 weeks for Parts C and D Grouping Put two to three students in a group. Each group is required to work on one factor and follow the progress of the compost for three weeks. Data collected from different groups will be pooled together and used in writing the laboratory report. Technician Notes Holes in the side of the bottle can be made by carefully heating a nail and using it to melt through the plastic. Dial / digital thermometer with stem long enough to reach down into the centre of the compost should be employed. If possible, a datalogging interface should be provided for students to monitor the temperature change of the bioreactor. To prevent any possibility of odour problems, students may be asked to vent the bioreactor through a window using flexible tubing. Meat, fish, dairy and cooked food should not be composted as they can attract pests (e.g. flies and rats). On the completion of the experiment, students should be asked to transfer all materials from the bioreactors to another composting container for curing for at least six months before use. Laboratory Report If students are asked to write a detailed report, the report should include the following items: 1. Title 2. Aims 3. Theory/Background (optional) 4. Apparatus and materials 5. Design of the experiment (To avoid complicated sketch, students can use digital camera

to take a photo of their set-up and include it in the report with clear labeling) 6. Procedure 7. Precautions 8. Results (including data and observations) 9. Discussion (including sources of error and improvements to be made) 10. Conclusion



11. Questions for further thought (optional) Remarks Students are not advised to conduct an investigation on the factor of aeration, as it may incur offensive odour. In small systems such as soda bottle bioreactors, it is possible that the compost temperature will reach its peak in less than 24 hours. To avoid missing a possible early peak, use a continuously recording temperature sensor, or ask the students to measure the temperature more frequently during the first few days. Soda bottle bioreactors generally reach temperatures of 40-50 C, somewhat lower than temperatures achieved in larger composting systems. With the soda bottle bioreactor, the product may not look like the finished compost from larger composting systems. With enough time, it is likely that the volume of compost in the bottle will shrink by 1/2 to 2/3 and that the original materials will no longer be recognisable. Suggested Solutions to Questions for Further Thought 1. What are the factors that affect the success of a composting system?

These factors include a right mix of nitrogen-rich materials (e.g. food scraps) and carbon-rich materials (e.g. autumn leaves and sawdust), moisture content, particle size of the materials, aeration, and the presence of microorganisms.

2. How can you tell when the composting process is completed?

The compost will no longer heat up even after stirring and mixing well, and the initial ingredients are no longer recognisable.

3. What are the benefits of composting food scraps and garden waste?

It can reduce waste sent to landfill/ reduce pollution from landfill or incinerator/ recycle nutrients back to the soil.

4. What are the problems and social issues associated with the development of large

community composting projects?

Problems: collection of food scraps and garden waste; odour problems created by the compost piles

Issues: choosing appropriate sites for composting facilities; support from local community/government; making the programme mandatory or voluntary



References 1. http://compost.css.cornell.edu/why.html 2. http://compost.css.cornell.edu/soda.html 3. http://www.lcsd.gov.hk/green/en/organic.php




Marks


Competence in handling apparatus such as

thermometer/ datalogging interface

Building a bioreactor

correct set-up

proper filling of compost materials


proper location in the bioreactor for

temperature measurement

taking adequate number of temperature

readings


handling cutter, scissors and nail safely

wearing gloves when handling compost

materials

Performing experiment in an organised and efficient

way

TOTAL:





Marks


Experimental design




making appropriate use of table to present data

recording observation and temperature readings

(in appropriate units) accurately

Plotting of graph

showing compost temperature and ambient

temperature on the same graph

giving appropriate title and labels

Interpretation of results and drawing conclusions

the temperature and decomposition relationship

relevant conclusions of the effect of factors on

composting




TOTAL:


Module C7: Radiation and Us

Ultraviolet (UV) protection of sunglasses Teacher Notes

This experiment illustrates how science can be applied to check whether the claims made by manufacturers regarding their sunglasses’ providing protection from ultraviolet radiation are valid. The investigation can be conducted either inside a laboratory or outdoors under direct sunlight. Students should be able to distinguish among independent variables, dependent variables and control variables while planning the experiment. They can also develop skills in using a datalogger to collect data instantly. It is anticipated that students will apply the concepts/principles learnt to make informed decisions should they need to buy a pair of sunglasses. Curriculum Link C7: Radiation and Us 7.2 EM radiation as a carrier of energy Pre-laboratory Preparation 1. Ask students to browse the websites provided on the handout for background

information and to read the manuals of the UV sensor and UV lamp before the experiment.

2. Ask students to collect different types of sunglasses for conducting the experiment. Pre-laboratory Talk 1. Remind students that there is no standard set-up for the investigation. They can design

an experiment that is conducted either outdoors or inside the laboratory. 2. Ask students to sketch the set-up of their design to help illustrate the experimental

procedure. 3. Remind students NOT to look directly at the UV lamp or the sun. 4. Remind students that several readings are required for each trial. 5. Tell students that they may need to convert the raw data in a suitable way to enable

meaningful interpretation. Time Required Pre-laboratory talk: 10 minutes Experimental design: 20 minutes Conducting experiment: 50 minutes



Grouping Put two to four students in a group (depending on the availability of UV sensors, UV lamps and datalogging interfaces). Technician Notes Not all UV sensors measure the intensity of both UVA and UVB bands. The manual of the UV sensors should be consulted. Laboratory Report If students are asked to write a detailed report, the report should include the following items: 1. Title 2. Aims 3. Theory/Background (optional) 4. Apparatus and materials 5. Design of the experiment (Students can use digital camera to take a photo of their set-up

and include it in the report with clear labeling.) 6. Procedure 7. Precautions 8. Results (including data and calculations) 9. Discussion (including sources of error and improvements to be made) 10. Conclusion 11. Questions for further thought (optional) Remarks Students should be able to identify:

1. the independent variable – different types of sunglasses (e.g. different coatings, different colours of lenses, etc.);

2. the dependent variable – intensity of UV radiation to be measured; and 3. the control variables –

distance between UV sensor and UV lamp; background UV radiation.

While planning the experiment, students should be able to suggest the necessary precautions such as:

1. the lenses of sunglasses should be clean and dry; 2. the front side of the lenses (i.e. the side with coating) should face the UV lamp; 3. the UV sensor and UV lamp should be kept at a fixed distance; 4. the UV sensor and UV lamp should be aligned directly at the same level; 5. the set-up should be free from background UV radiation if the experiment is to be

conducted inside the laboratory.



Suggested Solutions to Questions for Further Thought 1. Is it better to carry out this experiment outdoors under direct sunlight?

It is more authentic to carry out this experiment under direct sunlight. However, there are factors that affect the measurement such as the position of the sun and the presence of moving clouds. These factors cannot be controlled easily.

2. Is it more desirable to carry out this experiment inside the laboratory with sunlight

being blocked by blinds or black curtains?

It is easier to carry out the experiment in a controlled environment inside the laboratory. However, one should note that the UV radiation (frequency and intensity) emitted by the UV lamp may not be comparable to those of sunlight.

3. Is it dangerous to wear sunglasses with coloured lenses which do not block UV

radiation effectively? Explain.

The pupil of the eye will dilate in the shade. If one wears sunglasses with coloured lenses, one’s pupils will dilate and more light rays will enter the eyes. If the coloured lenses do not block UV radiation effectively, the increased UV radiation entering the eyes will damage them.

4. What are the chemicals commonly used in photochromic sunglasses to block UV

radiation?

Silver halides (usually silver chloride). 5. Is there any relationship between the colour of lenses and their effectiveness at blocking

UV radiation?

There is no relationship between the colour of the lenses of sunglasses and the effectiveness of blocking UV radiation. It is the coating on the lenses that matters. Sunglasses with reflective lenses (which look like a silver mirror) are more effective in blocking UV radiation than sunglasses with dark coloured lenses.

6. Will you choose sunglasses with glass lenses or plastic lenses if your primary concern is

blocking of UV radiation?

Plastic lenses usually provide better protection as some plastic materials, such as polycarbonate, can block most UV radiation.

7. Can you think of any situation, other than being out in strong sunlight that requires

wearing of protective eyewear to protect from UV radiation?

During welding of metals, strong UV radiation of short wavelength will be emitted. Welders should use a mask/wear goggles that can effectively block UV radiation.



8. How would you modify the experiment to verify the claim made by some manufacturers that their umbrellas have UV protection?

The set-up is basically the same except that an umbrella is used instead of a pair of sunglasses. More stands and clamps are needed to fix the umbrella.

References 1. http://www.weather.gov.hk/publica/gen_pub/uv_e.htm 2. http://en.wikipedia.org/wiki/Uv 3. http://en.wikipedia.org/wiki/Sunglasses 4. http://www.allaboutvision.com/sunglasses/




Marks


Competence in handling UV sensor and datalogging

interface


keeping the UV lamp and UV sensor at a fixed

distance

measuring background UV radiation

Data collecting and recording

obtaining adequate number of readings for each

trial


way


NOT looking directly at the UV lamp or the sun

switching off the UV lamp after each

measurement

Self-reliance and working efficiently

TOTAL:





Marks


Experimental design

independent, dependent and control variables


Experimental plan

clear and logical procedure

necessary precautions taken


making appropriate use of tables to present data


units)

Treatment and interpretation of data

converting the raw data into a percentage of the

UV radiation measured without sunglasses

interpreting the results in terms of absorbance

Discussion of findings and drawing conclusions

TOTAL:


Module C8: From Genes to Life

Extracting DNA from fruits Teacher Notes

DNA is the genetic material of living organisms and is found in the chromosomes of every cell. To obtain DNA from living tissues, the cell and nuclear membranes must be disrupted to release the DNA. In this experiment, students will apply cell disruption and separation techniques to extract DNA from plant tissues, and then examine the isolated DNA under the microscope. They will work on strawberry and on one other fruit sample like kiwifruit, banana or mango. After the activity, students should develop an appreciation of the importance of DNA extraction and its applications. Curriculum Link C8: From Genes to Life 8.1 Genetic information flow that controls life phenomena 8.2 DNA as the genetic material 8.4 Applications of DNA technology Pre-laboratory Preparation 1. Ask students to carry out an information search on the roles of DNA in living

organisms and the basic techniques for extracting DNA. 2. Ask students to carry out an information search on the applications of DNA technology. Pre-laboratory Talk 1. Conduct a brief revision on the importance of DNA to life. 2. Lead a class discussion on how to extract DNA from plant tissues. 3. Remind students of the proper way of handling a microscope. 4. Draw students’ attention to the safe handling of knifes. 5. Remind students of the safety issue related to the use of methylene blue stain. 6. Emphasise that the procedures should be followed closely since the temperature and

timing are crucial to the experiment. Time Required Pre-laboratory talk: 10 minutes Experiment: 60 minutes



Grouping Put two students in a group. Technician Notes The ethanol used should be ice-cold. Place it in a plastic bottle in a freezer about a day before the experiment. If a freezer is unavailable, put some ice in an insulated container and then stand the bottle of ethanol in it for several hours before use. Filter papers with fast flow rate and coarse porosity should be provided so that the time for filtering in Step A8 can be shortened. Putting two pieces of gauze on a folded filter paper can make the filtration faster. Laboratory Report If students are asked to write a detailed report, the report should include the following items: 1. Title 2. Aims 3. Theory/Background (optional) 4. Apparatus and materials 5. Procedure 6. Precautions 7. Results (including data and observations) 8. Discussion (including sources of error and improvements to be made) 9. Conclusion 10. Questions for further thought (optional) Remarks Fruits that have multiple sets of chromosomes are more suitable for DNA extraction. Strawberries are octoploid (i.e. they have 8 copies of each chromosome), thus they can provide remarkable quantities of DNA for extraction. The four key steps in extracting DNA from fruits are:

1. Breaking apart of the tissue and cell wall by physical means such as squeezing, smashing or grinding the fruit sample.

2. Disrupting the cell and nuclear membranes by detergent present in extraction solution to release the DNA. (Detergent and the salt solution also help strip away proteins that are associated with the DNA molecules.)

3. Filtering the extraction mixture to remove the insoluble cellular fragments.

4. Separating DNA from other cellular materials by precipitation in a suitable solvent. (By adding alcohol, DNA precipitates out and collects at the interface of the alcohol and filtrate layers. The colder the alcohol, the less soluble the DNA will be in it, and the more DNA will be collected.)



The spooled DNA will appear as a transparent, slimy, clotted mass adhering to the bamboo stick.

If the DNA appears fluffy, most likely it has sheared in the extraction process. The appearance of the spooled DNA under the microscope:

Low power (50X) High power (200X)

Suggested Solutions to Questions for Further Thought 1. Why is it necessary to squeeze and smash the fruit sample in Step A 4?

This is to provide a mechanical breakdown of the cell wall and structure. 2. The extraction solution used in Step A5 contains detergent. What is the function of the

detergent?

This is to break open the cell and nuclear membranes to release the DNA. The detergent causes the membranes to break down by dissolving the lipids and proteins of the cell, and disrupting the bonds that hold the membranes together.

3. Why should ice-cold ethanol be used in Step A9?

The colder the ethanol, the less soluble the DNA will be in it, thus yielding more visible clumping of DNA.

4. Is the DNA extracted in Step A11 pure? What substance(s) might be attached to the

DNA? No. The white, stringy stuff is a mix of DNA, RNA and proteins



5. Why is DNA extraction important to scientists? State some of its applications.

The extraction of DNA from a cell is often the first step for scientists in studying a gene. The study can provide information about the genomic DNA. Applications of DNA extraction include DNA fingerprinting to solve crimes, and genetic engineering to give an organism specific traits and to produce medicines.

References 1. http://learn.genetics.utah.edu/content/labs/extraction/ 2. http://www.imb.uq.edu.au/index.html?id=66795




Marks


Preparing the extraction solution


using appropriate apparatus to make solution

Filtration techniques

setting up of filtration apparatus correctly

using folded filter paper

Competence in handling microscope

handling observed sample properly

using correct procedure for viewing sample

under low-power and high-power


handling knife safely

handling methylene blue stain safely

Performing experiment in an organised and efficient

way

TOTAL:





Marks


Presentation of results for Part A

good recording of the appearance of thread-like

substance in the ethanol layer

good recording of the appearance of the spooled

DNA

Presentation of results for Part B

good recording of the observation of the

residual DNA being stained by methylene blue

appropriate use of drawings to show the

appearance of the stained DNA under

microscope


correct inference for the thread-like substance

appeared in the ethanol layer

correct explanation for the spooled DNA

Drawing meaningful conclusions


discussion of the sources of errors


TOTAL:


Module E3: Chemistry for World Needs

How cross-linking changes the properties of a polymer? Teacher Notes

The properties of a polymer can be manipulated by varying its microscopic structures. A polymer can be made soft and flexible by adding plasticisers. On the other hand, cross-linking agents can add strength to a polymer and make it more elastic. In this experiment, students will be adding a cross-linking agent, borax solution, to strengthen a polymer, polyvinyl alcohol (PVA). In Part I of the experiment, students will prepare several slime samples by mixing PVA solution with varied amounts of borax solution which acts as a cross-linking agent. They will compare the viscosity of the slime samples and find out how the amount of cross-linking agent affects the properties of a polymer. In Part II, students will study the characteristic mechanical properties of a slime sample by observing how it behaves when subject to different external forces. Curriculum Link E3 Chemistry for World Needs 3.4 Man-made polymers fit for different purposes Pre-laboratory Preparation 1. Ask students to devise a method to compare the viscosity of some viscous materials. 2. Ask students to carry out an information search on cross-linking. 3. Ask students to carry out an information search on the characteristic properties of a

slime material. Pre-laboratory Talk 1. Explain to students the principles of cross-linking in polymer chemistry, and give

examples of cross-linked polymers used in daily life. 2. Show students the chemical structure of PVA, and how cross-links are formed in the

presence of borax. 3. Discuss the applications of PVA in daily life. 4. Ask students to propose ways of comparing the viscosity of some viscous materials. 5. Suggest possible ways of recording experimental results and presenting experimental

findings, e.g. keeping a log of the results, taking photographs of the observations, presenting findings using posters, etc.

6. Draw students’ attention to the safe handling of borax – students should wash their hands thoroughly after the experiment.

7. Remind students to handle the hammer (or mallet) carefully to avoid injury.

Teacher Notes – E3 1


Time Required Pre-laboratory talk: 15 minutes Experiment: 30 minutes for Part I 15 minutes for Part II Discussion/debriefing: 10 minutes Grouping Put two to three students in a group (depending on the availability of apparatus). Technician Notes In preparing the 4% PVA solution, slowly add 4 g of PVA to 100 ml of distilled water, which has been heated to about 80 oC. Keep stirring until the PVA dissolves. Allow the solution to cool. Students may need help in preparing the stock solution of borax. It is advisable to cover the laboratory benches with a disposable plastic table-cloth to facilitate cleaning up after the session. Dispose of any slime in the rubbish bin. Do not put it down the drain as it will clog the drain. Laboratory Report If students are asked to write a detailed report, the report should include the following items: 1. Title 2. Aims 3. Theory/Background (optional) 4. Apparatus and materials 5. Design of the experiment 6. Procedure 7. Precautions 8. Results (including data and observations) 9. Discussion (including sources of error and improvements to be made) 10. Conclusion 11. Questions for further thought (optional) Students can also be asked to present their findings using posters and/or PowerPoint slides.



Remarks In Part I, students should be able to realise that the viscosity of a slime is proportional to the amount of cross-linking agent added to it. They may also realise that carrying out tests with samples of the same size and shape is crucial to the comparability of the tests. In Part II, students carry out tests to study the characteristic mechanical properties of a slime. They would observe that the slime resists a gentle blow, but breaks apart into small pieces when hit with a sharp blow. When the slime is pulled quickly, it breaks into two halves immediately. However, the slime can be stretched into a thin film without breaking if it is pulled gently and slowly. Suggested Answers to the Questions Part I: 1. What happens to the mixture of PVA solution and the borax solution when it is stirred

vigorously? 2. Which slime sample is the most viscous and which one is the least viscous? 3. Why is it necessary to remove excess water and air bubbles from the slimes before

performing the tests? 4. Why is it necessary to have the slime samples for testing made into the same size and

shape? 5. Should we perform the test on a piece of paper instead of the plastic sheet? Explain

briefly. 6. How can we get a better measure of the diameter of the slime? 7. Does the degree of cross-linking of PVA slime increase or decrease with the

concentration of the borax solution added? Explain briefly. 8. Apart from varying the proportion of borax in PVA slime, what other experiments can be

done on the slime to study its viscosity? 1. What happens to the mixture of PVA solution and the borax solution when it is stirred

vigorously?

The slime sample becomes more viscous. / The viscosity of the mixture increases.

2. Which slime sample is the most viscous and which one is the least viscous?

The slime sample prepared with 5% borax solution is the most viscous. The one with 1% borax solution is the least viscous.

3. Why is it necessary to remove excess water and air bubbles from the slimes before performing the tests?

To ensure comparability among the tests. Squeezing the excess water out from the samples is to make sure all the samples have similar water content. Removing the air bubbles is to make sure the samples are uniform throughout.

4. Why is it necessary to have the slime samples for testing made into the same size and

shape?



To ensure comparability among the tests. 5. Should we perform the test on a piece of paper instead of the plastic sheet? Explain

briefly.

Plastic sheet is superior to paper for carrying out the viscosity test because plastic sheet does not absorb water and hence will not change the properties of the slime samples during the test.

6. How can we get a better measure of the diameter of the slime?

Place a graph paper below the plastic sheet; read the diameter from the grids of the graph paper. Read the diameters at 2 perpendicular directions and take the average.

7. Does the degree of cross-linking of PVA slime increase or decrease with the

concentration of the borax solution added? Explain briefly.

The degree of cross-linking increases as the concentration of borax solution increases. Borax is a cross-linking agent. More cross-links can be formed with an increased amount of borax added to the sample.

8. Apart from varying the proportion of borax in PVA slime, what other experiments can be

done on the slime to study its viscosity?

Compare the viscosity of a slime sample at different temperatures. Suggestions for Further Investigation Teachers may ask students to further explore the properties of cross-linked polymers by carrying out the following activities:

Comparing the viscosity of slime samples prepared from PVA of different concentrations

Comparing the viscosity of a slime sample at different temperatures

Comparing the properties of other cross-linked polymers such as those prepared by mixing ‘white glue’ with the appropriate amount of borax

Investigating the mechanical properties of commercial available slimes such as ‘Slime’ toys




Marks


Preparing the stock borax solution


using appropriate techniques in making solution

Preparing the borax solutions of varied

concentrations

adding the correct amount of water

using appropriate apparatus to make solutions

Conducting fair tests to measure the viscosity of the

slime samples

making samples of same size and shape

using same measuring time

Testing the slime sample with an external force

using appropriate set-up for the test

handling hammer (or mallet) when hitting the

sample safely

Working efficiently and neatly

TOTAL:





Marks


Presentation of results for Part I

recording accurately the amount of distilled

water used for dilution

recording accurately the diameter of the slime

Plotting a graph of the diameter of the slime against

the concentration of borax solution

giving appropriate title and labels

drawing an appropriate graph through the data

points

Interpretation of results for Part I

giving the correct/logical inference from the

graph

Presentation of results for Part II

making a good recording of the observations for

hitting the slime sample with a hammer (or

mallet)

making a good recording of the observations for

pulling the slime sample with both hands

Conclusions and suggestions for further

investigations

TOTAL:

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