science activity two: improving glue delivery · science activity two: improving glue what you will...

© STEMNET 2012 | pagE 1 of 11Endorsed by the Society of Biology

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Sponsored by AstraZeneca Science Teaching Trust.

SciENcE acTiviTy Two: iMproviNg gluEcaN you MaKE a STroNgEr gluE?

01 introduction 5-15 minutes02 practical activity ~40 minutes03 plenary 10-15 minutesIt would be useful to give the school some information about yourself in advance of the session. You may be able to bring photographs, equipment or other means to illustrate your work. The session should help students to recognise that the science they do in school relates to science in the real world, scientists are real people, and that they could be scientists too.Throughout the session, try to refer to your own personal experience as a scientist as much as possible.It takes around 15 minutes to make a glue using the procedure in the student instructions. With the apparatus set up and the method practised, more glues can be made more rapidly. Each group should have time to make glue using the procedure and at least one modification, and then try out a strength test using pre-glued lolly sticks. If time is short, students could compare their glued sticks with the pre-glued ones in a later lesson. The school will need to set aside a second lesson to carry out the strength tests for the glues made by the students. It is possible to quickly demonstrate the strength testing procedure for later use.During the practical work you will be able to walk round and talk to students to gain an idea of what level you will need to adopt for the discussion and plenary.

dElivEry

Students make glues using milk. They make a glue following a given procedure and then alter the method to see if they can make a stronger glue. Different milks and bases are provided, though some students may decide to make the glue acidic or basic or add less water when making the glue.The students can also try out a method for testing the strength of the glues.

© STEMNET 2012 | pagE 2 of 11

SciENcE acTiviTy Two: iMproviNg gluE

Introduce yourself as a professional scientist.Explain, using examples from your own experience, that:

Scientists collect data and make sense of it. ●

They learn how things work through observation and experiment. They try to explain ●observations and test their explanations through experiments. When they have a good explanation they can use it to solve problems.

The taskBackground infoYou could use the following information, or you may have your own ideas that relate more directly to your own work and expertise.Why milk? The Ancient Chinese used milk to make glue thousands of years ago. In the 1800s, Swiss gluemakers developed milk glues. Milk glue can be very strong. It was used in making huge wooden arches in the Central Station in Stockholm and in building World War 2 aircraft. In the second half of the 20th century, glues using methanal (also called formaldehyde) took over. But methanal is now known to be a dangerous chemical which is poisonous and can cause allergies and even cancer.Milk glue is not only safer than methanal glues, it can also be manufactured much more cheaply.

Getting startedHow can we use science to improve something to make it work better?In this activity you are going to work as scientists to try to discover how you can improve the bonding power of glue made by using milk.Can you discover a method for making a really good milk glue? Can you work as scientists to find out?You will collect data – working accurately and recording your observations as precisely as you can.Explain to the students that they will be working in pairs and briefly run through the procedure, emphasising any safety precautions and pointing out any other important information. For example, they need to make two glues - one following the method provided and one by modifying the method in some way. Also, the glue needs time to set, so the students will need to wait at least until the next day before they can test how strong their glues are. However, they can try the strength test on some lolly sticks that have already been stuck together with glue made using the original procedure.You will need to make sense of your data - using your scientific knowledge to try to explain what has happened.

iNTroducTioN01



what you will needCheck this with the teacher and/or technician at the school. Make sure that everything will be available on the day.Some glue will need to be made in advance (by you or by the school) to glue together lolly sticks to be used to try out the strength testing method (see To test glue, below).For each student

Eye protection ●

Student Instruction Sheet (may be printed separately, or you may wish to modify this ●to suit your own circumstances)

For class useVarious types of milk for comparison (high fat, skimmed, and at least one or two others ●such as semi-skimmed, raw, pasteurised, UHT, sterilised, made up from milk powder)Distilled white vinegar (available from supermarkets) or ethanoic acid ●

Bases such as sodium hydrogencarbonate, magnesium carbonate, calcium carbonate, ●magnesium hydroxide (milk of magnesia) – choose one for everyone to use first

For each pair of studentsTo make glue:

Whole milk (enough to measure out 100 cm ● 3)A base from those made available (same for pre-glued sticks and all pairs first time) ●

Spatulas ●

Stirring rods ●

Measuring cylinders (25 cm ● 3 and 100 cm3)Beakers (100 cm ● 3 and 250 cm3)Bunsen burner, tripod, gauze, heat resistant mat ●

Filter funnel and filter paper ●

Lolly sticks (available from craft shops) ●

Universal indicator paper ●

To test glue:Pre-glued lolly sticks (make and use whole milk* glue at least the day before) ●

Weight hanger and 100 g weights ●

Thread, twist tie or similar (to attach weight hanger hook to lolly sticks) ●

Sand tray or box of screwed up newspaper (to catch falling weights) ●

*If whole milk is used, this will give students the opportunity to make stronger glues by using skimmed or low fat milk (see PLENARY: Explanations).

pracTical acTiviTy02



Health and safetyAll activities have been trialled and tested by 4science (www.4science.org.uk) and every reasonable effort made to ensure that the activities are safe when conducted as instructed.However, a full risk assessment should be carried out before any practical work is undertaken. The supervising teacher should be able to advise on this and any local requirements, such as procedures recommended by Local Authorities or safety advisers used by the institution.4science assume no responsibility for any damage or injury caused or sustained while carrying out these activities to the full extent permitted by law.For this practical you may wish to discuss with the teacher issues such as the safe handling of glassware and safe use of Bunsen burners. KS3 students may need more guidance or a more thorough reminding of safe working procedures when heating using a Bunsen burner, tripod and gauze. As this procedure involves heating milk which may froth over or burn if heated too fiercely, students should have experience of heating liquids gently with a Bunsen burner. Eye protection should be worn. Students must be supervised at all times during practical work by a teacher (and/or responsible adult).

Vinegar (Low hazard) CLEAPSS Hazcard 38A ●

Sodium hydrogen carbonate (Low hazard) CLEAPSS Hazcard 95C ●

Magnesium carbonate (Low hazard) CLEAPSS Hazcard 59A ●

Calcium carbonate (Low hazard) CLEAPSS Hazcard 19B ●

Milk of magnesia (Low hazard) CLEAPSS Hazcard 59B ●

what you will needInternet connected computer/data projector or interactive whiteboard ●

Popper beads to demonstrate polymerisation (optional) ●

observationsWhat do scientists know about what happens when you make milk glue? Can the students work out anything about what is happening using their observations and scientific knowledge? Discuss what has happened. (What do you think the curds (lumps) were? What do you think the curds were formed from?)Some pupils may have heard of casein and some may know that protein is present in milk. They should be aware that milk is a highly nutritious food. If necessary, try to prompt them to obtain the idea that protein is present in milk. (Why is milk good for you? What is in milk that makes it a good food?)

plENary03



Why do you think vinegar was added to the milk? (Answer: To precipitate the casein / convert it to an insoluble form / curds.)You can explain that cheese is made from casein which is precipitated using the enzyme rennin, and that cottage cheese has curds like those they have formed. The liquid part is “whey” - as in “little Miss Muffet sat on a tuffet, eating her curds and whey”.Why is a base added? (Answer: To remove excess acid.)How could you tell when the acid had been neutralised without using an indicator? (Answer: The foaming stops – no more carbon dioxide is liberated.)Why change only one thing at a time when you make a new glue? (Answer: You know what has caused any change in the strength of the glue. If you change more than one thing you don’t know what effect either has had.)What weight could the glue made using the original method support? Was this consistent?Check and compare the class results. What might affect the reliability of the results? Discuss what value should be beaten if a stronger glue has been made using a new method.Find out what changes students made to the method for making the glue. Discuss why they chose to make the changes. Ask students to suggest explanations of what is happening. (Can you explain what is happening? Why is this happening? What is causing this effect?)

ExplanationsThe level of explanation that you can give to the students will depend on their ability and background. You will need to discuss this with their teacher, but you should also be able to get an idea of the students’ level if you talk to them and ask questions while they are conducting the activity.

Simple explanationShort protein molecules in milk can keep coming together to form very long chains. ●These can tangle up so that they ‘stick’ to each other.Possible demonstration: use popper bead necklaces to show how short chains can be ●made longer and how long chains can tangle up.

More complex explanationExplain the concept of polymerisation. Some students may know that proteins are ●made from amino acids. You can explain that amino acids have an acid and a base which allows them to combine to form long chains. So it is possible for protein molecules to polymerise in the right conditions (-NH2 and -COOH at the ends of the chains can continuously combine to give peptide bonds).Proteins are large molecules which can fold up to hide parts that will not dissolve in ●water while keeping water soluble parts on the outside. So despite being very large, many proteins can dissolve in water.



Some useful informationCasein is the predominant protein found in milk, where it exists as a soluble calcium salt.Casein is precipitated by acids. Insoluble casein cannot change structure and stays insoluble in water.Insoluble casein has little secondary or tertiary structure and is relatively hydrophobic – so it is fairly insoluble in water.Casein is not only a valuable food, but as well as being used in glues it is used for protective coatings, plastics such as knife handles and knitting needles, fabrics and other products.Polymerisation of the protein molecules forms the glue – the casein molecules join together in long chains.Changing the base used for neutralising acid has little effect, but the strongest glues tend to be made from skimmed milk. This is because the fat molecules in milk can get in the way and prevent the polymer chains from forming – so they stick together less well.Possible approaches to strength testingYou could do one of the following:

Explain what is happening when the glue forms and ask students if they can predict ●which milk would give the strongest glue.Explain your prediction for the students to test. ●

Let students attempt an explanation when they have completed their tests. ●

A second lesson will be needed for students to test the strength of their glues. You could ask them to report their findings back to you.Students could use the Biuret test for protein on the curds and whey.A more systematic project could be undertaken, with a competition to find the formulation for the strongest glue.Students could be asked to research and report on casein and its uses.

follow up



There is an opportunity for curriculum links to be made. You may like to discuss with the supervising teacher whether they would like specific examples to be used or any issues to be raised.

Science: programme of Study for Key Stage 3ks3

Key concepts

1.1 Scientific thinkinga. using scientific ideas and models to explain phenomena and developing them creatively to generate and test theories.b. critically analysing and evaluating evidence from observations and experiments.

1.2 Applications and implications of sciencea. exploring how the creative application of scientific ideas can bring about technological developments and consequent changes in the way people think and behave.

Key processes

2.1 Practical and enquiry skillsa. use a range of scientific methods and techniques to develop and test ideas and explanations.b. assess risk and work safely in the laboratory, field and workplace.c. plan and carry out practical and investigative activities, both individually and in groups.

2.2 Critical understanding of evidencea. obtain, record and analyse data from a wide range of primary and secondary sources, including ICT sources, and use their findings to provide evidence for scientific explanations.b. evaluate scientific evidence and working methods.

2.3 Communicationa. use appropriate methods, including ICT, to communicate scientific information and contribute to presentations and discussions about scientific issues.

range and content

3.2 Chemical and material behavioura. the particle model provides explanations for the different physical properties and behaviour of matter.b. elements consist of atoms that combine together in chemical reactions to form compounds.c. elements and compounds show characteristic chemical properties and patterns in their behaviour.

3.3 Organisms, behaviour and healtha. life processes are supported by the organisation of cells into tissues, organs and body systems.

curriculum opportunitiesa. research, experiment, discuss and develop arguments.b. pursue an independent enquiry into an aspect of science of personal interest.c. use real-life examples as a basis for finding out about science.e. experience science outside the school environment, including in the workplace, where possible.f. use creativity and innovation in science, and appreciate their importance in enterprise.i. prepare to specialise in a range of science subjects at key stage 4 and consider career opportunities both within science and in other areas that are provided by science qualifications.k. make links between science and other subjects and areas of the curriculum.

curriculuM liNKS>>



You will need to liaise closely with the teacher.Have you checked:

that all the necessary materials and resources, including worksheets, will be available? ●

the meeting arrangements at the school (for example: time, place, people’s names, ●contact numbers, parking)?the length of the session? ●

that risk assessments have been made and any appropriate safety measures are in place? ●

how your experiences as a working scientist can be related to the activity? ●

if and how any curriculum links should be made to the activity (this might also be ●related to your experience if you have provided the school with information about your work and interests)?what kind of follow up (if any) would be useful? ●

cHEcKliST>>



improving gluecan you make a stronger glue?

STudENT SHEET pagE 1 of 3

what you need to do

making glue

Measure 100 cm3 of milk and 20 cm3 vinegar or ethanoic acid into a 250 cm3 beaker. Heat using the Bunsen burner with a gentle blue flame, using the tripod and gauze on the heat resistant mat. Stir constantly until small lumps (these are curds) form, then turn off the burner and stir until no more curds form.Safety: Heat the mixture gently and do not allow it to froth up or boil over. Move the Bunsen burner from under the gauze and close the air hole to give a visible yellow flame when not in use. Remember the tripod will remain very hot for some time. Allow it to cool before handling.What do you think the curds may be formed from?

Allow the curds to settle and then decant off as much liquid as you can (pour off liquid to leave lumps of solid at the bottom of the beaker).

Add about half a spatula full of a base to the paste. Mix thoroughly with a stirring rod and wait for any foaming to stop.

Gently squeeze the warm curds in the filter paper to remove excess liquid (take care that they are not hot). Place them in the beaker and add 15 cm3 of water. Stir until you have a smooth paste.

Filter the curds, collecting the liquid (called whey) in a 100 cm3 beaker. Allow them to cool. Rinse the beaker.

Work with a partner to follow a procedure to make glue from milk. ●

Modify the method to try to make a stronger glue. ●

Try out a method for testing the strength of glue. ●

Safety: Wear eye protection.


SciENcE acTiviTy Two: iMproviNg gluE STudENT SHEET pagE 2 of 3

Test the paste with universal indicator paper. Transfer a spot of paste to the paper. If it is not yet neutral or slightly alkaline, add more base. Mix and test again when any foaming has stopped. Repeat until the mixture is no longer acid. You have now made your glue.

Use a pencil to mark a line 2 cm from one end of each of two lolly sticks. Label one stick with your names and the type of milk and base used.

What could you change in the procedure that might alter the strength of the glue? Choose one thing and record the reason for your choice.

Spread a thin layer of glue over the marked area at the end of one stick and stick it to the marked end of the other stick. Overlap by 2 cm so that the ends meet the pencil lines.

Make other glues changing the method (record the changes you make to the procedure) and use them to stick other lolly sticks together. Label them clearly and leave overnight before testing.

teSting glue

Arrange two stools so that the tops are 10 cm apart. Lay two glued lolly sticks across to form a bridge between the stools.Safety: Place a sand tray or box of twisted newspaper immediately below the lolly sticks. This is to catch falling weights.

who made the StrongeSt glue? uSe the teSting glue method to find out ...

Tie some thread or a twist tie around the lower stick right next to the glued end. Hang a weights hanger onto the thread or tie.

Add weights of 100 g at a time until the glue joint breaks. Record the highest weight supported by the glue (weight just before the joint breaks).


SciENcE acTiviTy Two: iMproviNg gluE STudENT SHEET pagE 3 of 3

reSultS and queStionS

Who made the strongest glue?

What change did they make to the procedure? Can you suggest why this method gave stronger glue?

Use this space (and over the page) to record (i) your changes to the procedure for making the glue; (ii) the reasons for your choice for any change; and (iii) the largest weight supported by the glued lolly sticks ...

science activity two: improving glue delivery · science activity two: improving glue what you will...

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