Secondary Chemistry - Superstuffs: Cellulose (part 2)

The nineteenth century dominance of cotton persuaded many chemists to explore the properties of cellulose.  In 1846, Christian Schonbein reacted cotton with a mixture of nitric acid and sulfuric acid.  His product, nitrocellulose, was six times more explosive than gun powder.  Schonbein’s gun-cotton was used for blasting in mines and quarries, as well as in cannon.  Jules Verne imagined it being used to launch a space craft to the Moon.

Alexander Parkes experimented with cellulose reacted with a slightly less violent mixture of nitric acid to make a form of nitrocellulose that was not explosive though still rather flammable.  Parkes mixed his nitrocellulose with camphor to make a hard substance.  In 1872, John Hyatt developed Parkes’ discovery into artificial ivory for snooker and pool balls.  The material was called celluloid.   Celluloid replaced ivory in many products such as combs, handles of cutlery, and accordion keys.    The properties of celluloid could be modified to turn it into a flexible transparent film.  In 1889, the Eastman Kodak Company, among others, started to use it to make photographic film.  It was this development that paved the way for motion picture films.  Celluloid film is unfortunately very flammable and cinema fires were unfortunately a frequent occurrence in the early twentieth century.  Also many early films have been lost because celluloid decomposes after just a few years.

Copyright of Marcel Oosterwijk

It was the 1930s when one solution was found using another derivative of cellulose – cellulose acetate.

Cellulose acetate was first made in 1865 by Paul Schutzenburger by reacting cellulose with acetic anhydride (a pungent, corrosive liquid).  The product was dissolved in acetone.  One of the first uses was in “dope”.  Early aircraft which were made of cloth stretched over a wooden frame.  When the dope was painted over the cloth the acetone evaporated leaving a film of cellulose acetate that made the cloth rigid and airtight.  It took until 1934 before cellulose acetate “safety” film was used in the cinema.  It was less flammable and therefore safer but in the 1980s was replaced by synthetic polyester film.   Cellulose acetate could also be extruded through tiny holes called spinnerets to make a fibre.

In the late nineteenth century the textile industry had two problems.  The supply of cotton could not keep up with demand and people wanted a fibre that looked and felt like silk but was cheap.  Rayon was the answer to both problems.   Cellulose, from wood pulp, was reacted with carbon disulfide (a toxic liquid) in an alkali to produce a solution called “viscose”.  When viscose reacted with dilute sulfuric acid and sodium sulfate the cellulose was reformed and could be extruded to form fibres.  The Courtaulds company began manufacture of rayon in 1905.  It was marketed as artificial silk because the fibres in rayon are smoother than the natural cellulose fibres.   Rayon is still widely used in clothing and soft furnishings (such as curtains).

Viscose can also be mixed with glycerine to make a flexible film.  This product was called cellophane and was first used in 1912 for sweet wrappers.  Later it was used in sticky tape (sellotape) and as a transparent wrapping material.

In the last sixty years, materials derived from cellulose have been replaced by synthetic polymers for many uses but the story of cellulose is not over yet.  Paper has yet to be replaced despite computers and e-books and cotton is still the most popular textile because it absorbs moisture and feels comfortable against the skin.  Cotton is still being improved upon.  In 1987 Courtaulds introduced a new cellulose fibre called Tencel.  It was made by dissolving cellulose in a special solvent then extruding it through spinnerets.  Tencel is softer, stronger and more hardwearing than natural cotton and is used in many clothes today.

The story of cellulose is not over.  It is a renewable resource and biodegradable.  In a future of declining stocks of crude oil for fuel and synthetic polymers, cellulose will continue to be in demand both as a source of energy and as a versatile material.  Surely cellulose deserves the accolade of “superstuff”.

Activities

1              Check your clothes – what items are made of cotton or cellulose derivatives such as rayon (or viscose) or Tencel (also known as lyocell)?

2              Find out what things are made of cellulose derivatives such as celluloid, cellophane or cellulose acetate.

3              Explain why newspapers are sometimes referred to as the “old rags”.

4             Discover how cellulose fibres from flax, hemp, sisal, coir and bamboo are used today.

5              Examine the cultivation of elephant grass, willow or poplar as energy crops.  How do they compare with using mature trees as a source of wood for fuel?

6              Find out how to make your own paper from plant material or old clothes (made from cellulose fibres not synthetic polymer fibres).

7              What is the future of cellulose?  Compare the properties and uses of cellulose fibres and derivatives with those of synthetic polymers.

8 (A level) (a) Find out the structure of glucose and cellulose

(b)          Write an equation for the formation of tri-nitrocellulose (gun cotton).

(c)           Explain why guncotton can explode even in the absence of oxygen.

Peter Ellis

Peter Ellis taught science (mainly chemistry) in secondary schools to GCSE and A level for 35 years and was a head of department for twenty years.  He is now a freelance writer of educational materials in science and dabbles in writing fiction.  

Secondary Chemistry - Superstuffs: Cellulose (Part 1)

Since pre-historic times one substance has provided mankind with fuel, shelter, clothing and many other useful materials.  That substance is cellulose.

Cellulose is a carbohydrate like sugar and starch.  Plants make cellulose for their cell walls.  It gives them rigidity and the strength to support their roots, stems and leaves.  The first stage in producing cellulose is photosynthesis.  Light energy is used to react carbon dioxide with water to make glucose (C₆H₁₂O₆) and release oxygen as waste by-product.  As well as using glucose as a source of energy, plant cells use glucose to make fats and proteins and other carbohydrates.  Cellulose is manufactured in cell membranes where special enzymes link glucose molecules together to form a polymer chain.

n C₆H₁₂O₆   ->   (C₆H₁₀O₅)_n  + nH₂O

glucose                 cellulose

The length of the polymer chain varies with n being 300 to 1700 in woody plants to up to 10,000 in cotton.

Each glucose link in the cellulose chain has a flat, hexagonal ring.  This means that the molecules can lie close to each other, held by forces called hydrogen bonds.  This makes the polymer strong as well as flexible.

Plant cell walls act like a strong but floppy bag unless the cell is full of water.  That is why plants wilt without water.   Woody plants have an extra substance called lignin which acts like a glue and makes the cellulose chains stiffer.  Wood will keep its shape even when it has dried out.

Cellulose is flammable and burns to release the energy, carbon dioxide and water that were originally bound together by photosynthesis.  Until the Industrial Revolution wood was the main fuel available.  It is still the most used fuel in developing countries and as a renewable source of energy it promises to be an important fuel for the future.   Wood also has been used as a building material from simple wooden huts to the timber framed buildings of today.  Strong, flexible, relatively light and easily shaped it is an ideal material.  It is still the most commonly used material for furniture.

Copyright of William G Woodward

Plant cells link together combining the cellulose in their cell walls to make fibres.  Across the world the fibres of many plants have been used for weaving cloth for clothes, sheets, carpets, sails and ropes.   Hemp provided strong fibres for weaving canvas used in sails and tents.  Some varieties of hemp also produce the drug cannabis.  Flax or linseed, makes a smooth, cool, fabric called linen used for bed sheets and clothing.  Flax also produces an edible oil. In the nineteenth century, one plant fibre came to dominate the market - cotton.  The cotton mills of Lancashire and elsewhere were as much a sign of Britain’s industrial development as the coal mines, ironworks and engineering projects such as ships and railways.   Cotton replaced other plant fibres for most uses.  Today linen is made from cotton although hemp and flax are making a comeback.

Two thousand years ago the Chinese discovered that cellulose could be turned into a flat sheet instead of a fibre.  They had invented paper.  Hemp was the first material used but just about any plant cellulose can be turned into paper – even grass after it has been chewed and egested by  sheep (sheep poo paper).   Old rags were an important source of cellulose for paper in the nineteenth century.  However the growth in the number of books, magazines and newspapers meant that paper manufacturers looked for another source.   Wood was the obvious choice but separating the cellulose from the lignin was a problem.  A solution was found by German, Carl Dahl in 1879.  His process mixed wood chips with sodium hydroxide and sodium sulfide to make wood pulp that could be turned into paper.  Unfortunately the process produces a lot of waste and the paper is acidic and less durable than that made from other sources of cellulose.

Click here for part two of the history of cellulose + class activity! 

Peter Ellis

Peter Ellis taught science (mainly chemistry) in secondary schools to GCSE and A level for 35 years and was a head of department for twenty years.  He is now a freelance writer of educational materials in science and dabbles in writing fiction.  

Architecture and Primary Maths

Architecture to the artist is all about design and beauty but through part of those aspects; symmetry, we link into mathematics.  Whilst no one wants an ugly building, the practicality is that without maths and science, we’d never know whether the design of beautiful buildings would work until it was too late.

Activity One - House of Cards

LO:  Understand how different shapes have different properties relating to strength and stability
       Be able to state how a shape can be strengthened by introducing triangles into it

This activity helps children to understand the strength of shapes and how they can be used in buildings
Divide the children into groups of four and give them a pack of playing cards. Ask them to build a structure as tall as they can using the cards. Don’t give them any clues as to how they should do it. Some will begin with standard square shapes but find that they are unstable whilst others will use a triangle shape which they’ll find more stable.

Ask the children to tape four cards together to make a square and another three to make a triangle. Place each on the desk and get them to press gently on the top of each, what do they notice happening?
Talking Point: If they have completed a science module on forces ask them to describe what is happening at the places where the cards join and to the cards themselves. They should notice that the square simply collapses as the angles change from 90 degrees at each adjoining edge. With a lot of force placed centrally, the top will bend inwards causing the sides to fold in also. With the triangle they should feel more resistance and whilst the sides may flex inwards, the shape should remain more stable. Ask them how they could stabilise the square shape and they may suggest adding a brace so it forms a triangle.

Extension: Get a tray of 36 eggs and ask the children what they think would happen if they stood on them. Tell the children that one of them is going to try. Place a piece of board on top of the eggs and ask a child to slowly and carefully stand on the centre of the board. The eggs will not break. Now show the children the cross section of the eggs, the tray and the board and ask them to say why they think the eggs supported their weight.

At Home: Find pictures of objects which are strengthened using triangles e.g. cranes, bridges, greenhouses etc.

Activity Two: Density and Weight
LO: Understand how the force exerted by an object is determined by the weight of the object and the area of the base where the force is being applied
Understand that the force can be reduced by increasing the surface area of its point of contact or by reducing its mass    

Ask the children to research why New York has many skyscrapers and why London has so few. They should discover that it’s because of the type of ground the building is constructed on. London is mainly built on soft soil whilst New York has a rock base. If London had the same size buildings as New York, they would sink into the soil. Demonstrate this to children with a tray of wet soil and a block of wood. Stood on its end, it sinks into the wet soil. Placed on its side, it sinks in much less.

Talking Point: Why does the horizontal building sink less than the vertical one? This is a difficult question but many children answer it by saying there’s more of the building touching the soil without going on to explain why this helps.

You can demonstrate why it works by getting two or more bathroom scales and a plank of wood. Place the plank of wood on one of the scales and ask a child to stand on it, noting their weight. Now try the same with the wood placed across two scales and again across three if you have another. The children will find that the two scales each show half the weight whilst three will show a third of the weight.
Explain to them that it’s forces at work again and that the building presses down over its base area and that the force is calculated by the weight divided by the base area in each case so with the horizontal building having a bigger base, the force is less.

Talking Point: Ask the children if they can think of another way in which the force could be reduced. Remind them that the key elements are the surface area of the point of contact, the mass and gravity. They should suggest reducing the mass by using lighter materials.

At Home: Ask the children to investigate pressure around the home. With parents’ help, move some of the furniture and see the marks left by it in carpet or lino. Which has the deepest marks? What can be done to reduce damage to the floor coverings?

Activity Three: Plans and Scale Drawings
LO: Understand how scales are used to represent buildings or locations in real life
Use scales to calculate actual sizes or to reduce actual size to be able to represent an object on a piece of paper

Architects and builders work from plans drawn to scale to ensure that the finished building is as the architect designed it. It would be very difficult to work from a full size drawing so the plans are reduced in size and drawn to scale.

Show the children various maps and plans drawn to scale. Ask them to identify how they would know what size it represents. They should notice two kinds of scale; one where it simply gives a ratio so 1: 100,000 where 1cm on the plan or map represents a kilometre or it may have the scale as a bar with the relevant distance marked off on it.

This activity needs a big space such as the school hall or playground if the weather is good.

Put the children in groups of four and ask them to bring in up to ten cardboard boxes of the same size if possible. Ask them to construct a ‘building’ from them and then draw it to scale from various aspects. They will need to think very carefully which scale to use so that it fits on a sheet of A3 paper. Remind them that they need to mark the scale on their plan.

Extension: Once everyone has completed their plan, place all the boxes in the middle of the hall or playground, jumbled up, and pass the plans to different groups. Ask them to decide what size the ‘building’ is in real life using the scale and get them to find the correct size boxes to build it.

At Home: Ask the children to draw the floor plan of their home to scale so it fits on a piece of A3 paper.

Dave Lewis
Primary Teacher

For even more inspiring activities based on architecture take a look at Projects Inspired by Architecture, a brand new addition to the Belair On Display series.

Exploring Calendars in Primary Maths

Happy New Year!

The start of a new year sees the annual taking down and putting up one of the most frequently referred to data handling charts – the calendar.

Exploring calendars with your children provides lots of opportunities to link maths with other areas of the curriculum, particularly science, history and geography. Make use of this valuable opportunity by asking children to investigate some of the following.

Key Stage 1
- What patterns do you notice in the month of January? Are these patterns the same for February? What patterns are similar in these two months? What patterns are different?
- What similarities are there between the 2012 calendar and the 2013 calendar? What differences are there?
- Choose any two by two square of dates from a month on a calendar. Add together the two pairs of numbers that are diagonally opposite, for example 7 + 15 and 8 + 14. What do you notice about the two answers? Repeat for other sets of four numbers. Try a different month. What do you notice? Explain why this happens.

Lower Key Stage 2

- In 2013, the Chinese New Year begins on February 10th.  According to the Chinese calendar, 2013 is the Year of the Snake. Investigate how the Chinese calendar works. Find a Chinese calendar and use it to work out which Chinese year you were born in. What about other members of your family? 

- Choose any two by two square of dates from a month on a calendar. Add the four numbers together. Multiply the smallest number by 4 and add 16 to the product. What do you notice about the two answers? Repeat for other sets of four numbers. Try a different month. What do you notice? Explain why this happens.

- Choose any three by three square of dates from a month on a calendar. Add together the two pairs of numbers that are diagonally opposite, for example 15 + 31 and 17 + 29. What do you notice about the two answers? Compare these answers with the number in the centre of the square, i.e. 23. What do you notice? Repeat for other sets of nine numbers. Try a different month. What do you notice? Explain why this happens.

Upper Key Stage 2

Ask the children to investigate one or more of the following:

- January 1st marks the start of our Gregorian calendar. Investigate the history of the Gregorian calendar.

- Other calendars operate on a different cyclical pattern. Investigate other calendars such as Islamic, Jewish, Chinese or Hindu calendars. 

- Investigate different historical calendars, for example, the Mayan, Egyptian, Sumerian, Athenian or Julian calendars.

- Our calendar year runs from January 1st until December 31st. Investigate other “years” such as the academic or fiscal years. How do these differ between countries?

- Choose any two by two square of dates from a month on a calendar. Multiply together the two pairs of numbers that are diagonally opposite, for example 9 x 17 and 10 x 16. What do you notice about the two answers? Repeat for other sets of four numbers. Try a different month. What do you notice? Explain why this happens.

- Choose any three by three square of dates from a month on a calendar. Add together the numbers in the four corners, for example 13 + 15 + 27 + 29. Compare the sum with the number in the centre of the square, i.e. 21. What do you notice about the two numbers? Repeat for other sets of nine numbers. Try a different month. What do you notice? Explain why this happens. 

- Choose any column of five dates from a month on a calendar. Add the five numbers together, for example 3 + 10 + 17 + 24 + 31. Compare the sum with the number in the middle of the column, i.e. 17. What do you notice about the two numbers? Repeat for other columns of five numbers. Try a different month. What do you notice? Explain why this happens. 

- What other amazing patterns can you discover from a month on a calendar? Investigate dates in rectangles rather than squares, for example, 3 x 2 (or 2 x 3), 3 x 4 (or 4 x 3) and 4 x 2 (or 2 x 4) rectangles.

Peter Clarke

Series editor, Collins New Primary Maths

Sociology - Class activities to beat the New Year slump

The start of the spring term is always tricky- the sixth form tend to be a combination of stressed about UCAS and sluggish from the holidays, with the view that the exam ‘isn’t for months yet’. This lacklustre attitude seems to really come to the fore when we hit some of the ‘drier’ elements of the A-Level course, or in fact at any given point based on their mood that day - we are dealing with teenagers after all! As such, this year we have been really trying to focus on how to keep the students engaged in their studies.

Here are a few ideas for activities to beat the post-holidays slump:

Putting method into action– I find ‘practical’ trials of the methods work well here. For example, we head into the local town to conduct surveys; watch Youtube clips of interviews (e.g Alan Carr or similar, contrasted with Andrew Marr); carry out participant observation in classrooms; and hold group interviews with other students. This seems to help them engage with this section of the unit, and aids their evaluation of each method.

Pass the Parcel – This can be done two ways, either an actual parcel with each layer having a question and sweet inside for a revision game (I haven’t tried this, but colleagues used it for A2 History recently); or the ‘parcels’ are in fact just excerpts from articles or text books which are then passed around and students have some form of sheet to complete. For example, recently with yet more ‘internal factors’ influencing education, I copied sections from the textbook and students had 4 boxes to fill in – their task was to condense each ‘parcel’ into 3 bullet points before the timer ran out. A sand-timer on the board and chart music via Youtube helped keep the pace.

Word and time-limit presentations – Each student or pairs can be assigned a section of a topic and asked to give a presentation. But, in order to keep focus and to ensure the presentation isn't simply chunks of Wikipedia pasted onto slides, give a strict word and time limit. For example: no more than 10 words on a slide, a maximum of 20 seconds per slide and 10 slides in total to deliver the content. This forces the students to prepare and actually know what they are saying, but also adds an element of competition as other ‘teams’ can be timers and word counters.

Mr Men cartoons – Divide class into pairs and assign each a Mr Men character based on New Religious Movements – they need to produce a comic strip to be compiled into a booklet for the class to illustrate their life in the movement, reasons why they joined etc. (E.g. Little Miss Scientologist, Mr Summum, Mr Hare Krishna, Little Miss People’s Temple etc). This could also be used for theorists for any unit, or be substituted for Sociologist Top Trumps which would work in a similar way!

Online research – The Texas Department of Criminal Justice website is a great resource for looking at capital punishment. An interesting angle is to get the students to tally up ethnic backgrounds as a link to the Ethnicity and Crime section of the A2 unit.

Esther Zarifi

Esther Zarifi teaches Sociology at Prudhoe High School, Northumberland.

Childcare - 'Tis the Season

As the end of the year approaches, our thoughts turn towards the seasonal festivities in schools and nurseries across the country. Many of your learners will be in their placements helping out with end of term parties, nativity plays, Christmas concerts and other celebrations and it is always a good time to remind ourselves of the many different religious festivals and celebrations that are recognised across the UK.

Equality and diversity in the early years is a very important part of both the Level 2 Certificate and Level 3 Diploma for the Children and Young People’s Workforce, particularly:

L2:       Unit SHC 23 Introduction to equality and inclusion in health, social care or children’s and young people’s settings

L3:       Unit SHC 33 Promote equality and inclusion in health, social care or children’s and young people’s settings

Unit CYP 3.7 Understand how to support positive outcomes for children and young people

In addition, Diversity, Equality and Inclusion in the Early Years also form a whole unit (Unit 10) of the new Edexcel BTEC Level 3 National Diploma in Children’s Play, Learning and Development (supported by the forthcoming Collins student textbook). This unit also includes strategies for inclusive practice and planning to meet children’s individual needs.

Copyright Vicky Brock

In order to really appreciate diversity and discrimination, learners need to be aware of their own attitudes, values and beliefs. I have frequently used an “Attitude Poll” as a starter exercise in class, which provides a forum for learners to explore their own beliefs as well as reflect on how they might deal with ideas that challenge their own views. Divide your learners into small groups and provide each group with a set of statements, including several controversial ones (Some examples are attached). Invite the learners to discuss each statement in turn and decide if they agree or disagree with the statement. Each group should then select one statement (perhaps the one they had the most discussion about or the most controversial) to share with the whole group. You will need to act as facilitator, adjudicator (and sometimes referee!), but it can give rise to some extremely interesting and thought-provoking discussion. This has an important message for learners who will someday be working with a wide variety of people, holding a mixture of different views, which will very often be in opposition to their own. How will they handle that? Learners can sometimes be very critical of parents and families, but it is important for them to think about how they will maintain a professional attitude, which encompasses diversity and is non-judgemental.

Many of your learners will have studied different religions in school, but their knowledge and understanding is often varied. One way to consolidate what your learners already know is to use the blank chart on world religions (Attached) and ask your learners to work in groups to complete as much of the chart as they can. Explain that it is not a test and stress that they are not being assessed on how much they know. Provide the completed chart (Attached, and adapted from http://www.bbc.co.uk) for your learners to fill in the gaps.

The significance of this relates to the implications for early years practice, particularly in areas like festivals and celebrations, dress, diet and dealing with death. Your learners may already have some understanding of different religious practices from their own lives or their placement experience. Invite learners to share their experiences and create a collage about the different ways that early years settings embrace religious diversity in practice, (for example by celebrating different religious festivals, having a range of resources or involving parents or community leaders in the setting).

One activity I have found very thought provoking for learners is a role-playing exercise around answering children’s questions, (Attached). This can be extremely challenging, but can also give rise to some very useful discussion and practical advice. If learners are reluctant to engage in role-play, then encourage them to think about how they would respond and then share their ideas in the group. With issues involving different religious beliefs, stress the importance of putting the question back to the child, or checking in with what the child already knows i.e. “Where do you think people go when they die?” or “What has you mum told you about that?”

Amidst the hectic whirl of the end of term and preparing for the holidays, we can always count on young children to bring us all back down to earth.

Janet Stearns, Lecturer in Early Childhood Studies, former Lead Examiner for CACHE

Changes to the Primary Maths Curriculum

When and how is the curriculum changing?
In June 2012, the Education Secretary set out the draft Primary National Curriculum Programmes of Study for English, Maths and Science. The next draft is expected for consultation in early 2013, including details about how current levels of achievement will be replaced with the expectation that children master age-related concepts and skills in the new curriculum. The final version is due in schools by September 2013, with statutory implementation beginning in September 2014. The new Programmes of Study are clearly more demanding than the existing National Curriculum, so schools need to be aware of the changes.

What are the aims of the Programme of Study for Maths?
The draft National Curriculum for mathematics aims to ensure that all pupils:
• become fluent in the fundamentals of mathematics
• can solve problems by applying their mathematics
• can reason mathematically by following a line of enquiry.

How will the curriculum be organised?
The Attainment Targets of the current National Curriculum (2000) and the strands of the Primary National Strategy Mathematics Framework (2006) will be replaced and the 2014 Programme of Study for Mathematics will be structured and sequenced under the following domains, with content arranged into yearly blocks which children will be expected to master.

What are the key differences?
Overall, the levels of expectations have been raised, especially in relation to number and recall of addition, subtraction, multiplication and division number facts. A strong emphasis has been placed on mental and written calculation of whole numbers, decimals and fractions. Many mathematics topics are now introduced at an earlier stage and taught at an accelerated pace. This is especially the case in Key Stage 1 where, at the end of Year 1, children will be expected to recall and use number bonds and related subtraction facts within 20. Some new topics have also been introduced, such as Roman numerals, identifying parts of a circle, recognising binary numerals and a more formal introduction to algebra in Year 6.

How can schools get ready for 2013–2014?
In preparation for 2013–2014, I would strongly advise schools to:
• become familiar with the draft Programme of Study for Maths and updates to follow
• begin to look at any differences between current levels/standards and expected levels/standards
• identify two or three priorities for your school and begin to implement these
• refocus teachers, support staff, children and parents on the importance of memorizing key mathematical facts and, in particular, knowing by heart the:
- addition and subtraction number facts to 5, 10 and 20
- times-tables and related division facts up to 12 x 12
- product of a multiple of 10 and 100 and a 1-digit number, e.g. 40 x 7, 600 x 9.


Where can schools find more information?

Keep up to date with the new Primary National Curriculum:
www.education.gov.uk/nationalcurriculum

Download reports related to this article:
• DFE–00135–2011 (report of the Expert Panel)
• DFE–RR178 (analysis of curricula of high-performing jurisdictions worldwide)
• DFE–00136–2011 (responses to the call for evidence)
www.education.gov.uk/publications/Search/Search

Peter Clarke
Series editor, Collins New Primary Maths