Case Study 1:

Characterising a concept by the process of measurement – the concept of temperature.

Initial thinking about temperature measurement, related to particle modelling

Overview
Temperature was a rather elusive concept until it was measured. The development of instruments for quantitative measurement was vital for characterising the concept, for explaining human sensations of hot and cold, for providing ways of exploring a range of temperatures greater than that of direct human experience, and for exploring the nature of the measuring instruments themselves.
Temperature is a basic concept in junior high school (lower secondary school) science. Through practical activities, it provides a tool for learners to start to distinguish between temperature and heat, largely through the effects on different phases of water at different temperatures. In many countries, including the UK, learners explore particle explanations for change in junior high school, and this activity is intended to build on that experience, and to consolidate it.
Traditionally, learners would be presented with traditional liquid-in-glass thermometers with very little idea of how it worked but an instrumental. The approach in this Case Study is to start from the construction of a particular thermometer, one of the first types in history, a gas thermometer. It is also important to give learners personal practical experience, so here the choice of equipment is made to ensure that most schools will have the relevant equipment. It differs from a more common approach based on making a thermometer based on expansion of liquids for more fundamental reasons. The first is that liquid expansion with increasing gas temperature is much more difficult to explain using particle models than increasing gas pressure alone. There are serious conflicts with the notion of with a model of liquid particles moving faster and a model of their motion being curtailed by being in a condensed phase and this does not apply to a gas. Secondly, it is easy to experience directly increased pressure by its effect on the skin as a finger is placed over the end of the tube leading from the gas container.
In terms of the history of thermometry it is difficult to extract from the literature which came first, gas thermometers or liquid thermometers. However, gas pressure was easier to measure historically using relatively crude glass tubing since only the height difference in a manometer is being measured. Using liquid expansion requires much more uniform bore glass tubing, demonstrating the effect of precision glass making on temperature measurement.This activity focuses more on pressure measurement, being easier pedagogically.
Philosophical considerations include the impact of measurement in establishing scientific concepts; determining cause and effect, and the nature of a scientific explanation.
Target learners: 11-14 years old, all abilities

Description
The activity can be divided into parts:
Part 1

The starter activity is a traditional one to show how ineffective skin is a thermometer: Weber's 3 bowl experiment. Place one hand in a bowl of cold water, and the other in a bowl of warm water. Now put both hands in the same bowl of room temperature water. Do you think using the hand is a sound way of assessing temperature? If not, then perhaps we need a more reliable way. Discussion here is a valuable way of both engaging learners and of finding out their ideas, but avoiding spending too much time on this section. We could use a calibrated thermometer (dictionary: An instrument used to measure temperature. There are many types of thermometers; the most common consist of a closed, graduated glass tube in which a liquid expands or contracts as the temperature increases or decreases. Other types of thermometers work by detecting changes in the volume or pressure of an enclosed gas or by registering thermoelectric changes in a conductor (such as a thermistor or thermocouple).)
Learners set up boiling water, preferably in a wide test tube. Using some string to hold a thermometer, they lower the thermometer slowly into the test tube, noting the reading at points above the boiling water and into the thermometer. This parallels the historical search for a fixed boiling point for water, for calibration purposes. The purpose of this section is to mimic the problems of finding a truly fixed point for all thermometers. The issue of pressure differences is avoided by carrying out the experiement on the same day.
Part 2
Take a syringe or flask attached to a flexible tube. Put your finger over the end of the tube. Now put the container into warm water and feel the extra pressure as the air pushes against your finger. What happens to the air particles when the flask/syringe is in the warm water?
Part 3
This next activity focuses on the measurement of pressure and its change with temperature. There are two instruments we use here that early scientists used. Your teacher may use a metal pressure gauge called a Bourdon Gauge.This Wikipedia page on pressure measurement will also give you some background information. Do not worry if you do not understand all of it! Another instrument you may use is called a U-tube manometer. Your teacher will explain how to take pressure measurements. Home made manometer instructions and photographs. U-tube manometer explanation of how it works (lots of maths)

Obstacles to teaching and learning
Harries (1981) highlighted confusion about meanings of heat, heat flow and heat capacity, referring to the underlying notion of heat as a substance. Hewson and Hamlyn (1984) pointed out the embedded ideas of heat as a substance in our terminology. Ericksen (1977) also noted this point. Engel Clough & Driver (1985) mention that pupils also think of ‘cold’ as a substance. They say that pupils think of cold and hot as different substances, rather than as apart of a continuum.
Watts & Gilbert (1985) found 7 alternative children’s ideas:
· Conspicuous heat where heat is there only when obvious
· Dynamic heat, associated with movement
· Motile heat, which spreads out
· Normal heat, for body temperature
· Product heat, manufactured by a process
· Standard heat, heat is above freezing and cold is below freezing
· Regional heat, where heat is in one area
Engel Clough and Driver (1985) see pupils as able to describe heat (it rises, hot things expand) but unable to offer what they see as causal explanation. Tiberghien (1983) reported that heat is hot, temperature is heat, and temperature is a way of measuring heat. Driver & Russell (1982) found confusion about what might happen if two samples of water at different temperatures were mixed. And this was elaborated by Strauss and Stavy (1982). Stavy and Berkovitz (1980) found similar results. Driver and Russell (1982) discovered that their pupils (between 8 and 14 years old) confused about what might happen to the temperature of an ice water mixture if more ice was added. Appleton (1985) studied 25 Australian children aged 8 – 11 years old who did not recognise a mercury-in-glass thermometer and did not know what it might be used for. They were also poor at estimating temperatures jus above freezing or just below the boiling point of water.
Review: Confusion in this topic is heavily influenced by everyday use of scientific words, and by the lack of explicit teaching of scientific meanings of words, i.e. simply assuming that it is obvious that the pupils will know. A more insidious issue is the holding of the idea that heat is a substance. There is plenty of evidence that practising scientists at all levels have this problem, for example, including heat as a substance in chemical equations. Clearly, the idea is not easy to overcome, and much of our language concerned with heat and heat conduction has implications that heat is a substance. Much of the discussion about heat capacity uses the notion that heat is a substance as its premise. With temperature, we are so used to using the skin as a thermometer (e.g. for testing baby’s bath water) that we are oblivious to its inaccuracy, and to it limitations to temperatures not too different to room temperature. Proposals for dealing with these issues are:
· Increase teacher awareness of issues concerning language
· Explicit teaching of terminology, especially where words in common everyday use are encountered
· Devise practical/ experiential activities that focus on one concept only
· Ask learners to explain given incorrect or incomplete explanations
· Ask learners to create explanations and use group critiques
· Devise practical work that challenges one incorrect explanation directly
· Include teacher included discussion of phenomena
References
Appleton K (1985) Children’s ideas about temperature Research in Science Education 15 122-6
Brook A, Briggs H, Bell B & Driver R (1984) aspects of secondary students’ understanding of heat Centre for Studies in Science and Mathematics Education, University of Leeds
Driver R & Russell T (1982) An investigation of the ideas of heat temperature and change of state of children aged between 8 and 14 years, Centre for Studies in Science and Mathematics Education, University of Leeds
Engel MET (1982) The development of understanding of selected aspects of pressure, heat and evolution in pupils aged 12 to 16 years. Unpublished PhD thesis, University of Leeds
Engel Clough E & Driver R (1985) Secondary students’ conceptions of the conduction of heat: bringing together scientific and personal views Physics Education 20 176-82
Ericksen G (1977) Children’s conceptions of heat and temperature phenomena Paper presented as part of a symposium on ‘Patterns of student beliefs – implications for science teaching’ at the CCSE convention, June, Fredericton
Harries WF (1981) Heat in undergraduate education, or isn’t it time we abandoned the theory of caloric? International Journal of Mechanical Engineering Education 9 317-21
Hewson MG & Hamlyn D (1984) The influence of intellectual environment on conceptions of conceptions of heat. European Journal of Science Education 6(3) 245-62
Stavy R & Berkovitz B (1980) Cognitive conflict as a basis for teaching quantitative aspects of the concept of temperature Science Education 64(5) 679-92
Strauss S & Stavy R (1982) U-shaped behavioural growth: implications for theories of development in Hartup W (ed) Review of child development research 6 University of Chicago Press
Tiberghien A (1983) Critical review on the research aimed at elucidating the sense that notions of temperature and heat have for students aged 10 to 16 years Research in Physics Education, Proceedings of the first international workshop, 26 June – 13 July, La Ronde les Maures, France, Editions du Centre National de la Rechereche Scientifique, Paris 1984 pp 75-90
Watts DM & Gilbert JK (1985) Appraising the understanding of science concepts: heat Department of Educational Studies, University of Surrey, Guildford

Historical and philosophical background, including the nature of science
Scientific historical bacground in Europe
In 1592 Galileo develops the thermoscope and in 1593 he invents a water thermometer. In 1630 Descartes develops the concept of inertial motion where all motion resulted from collision with particles called corpuscles, opening up explanations at the sub-microscopic level (cause and effect). Over the rest of the 17th century, technologists and engineers were designing and building machines that worked from steam. In science, this engineering approach took the form of making more and more precise scientific instruments, such as the telescope, the microscope, In 1699 Amontons published early idea of absolute zero, which is the basis for this activity. In other sciences, this was an era in which empirical research (based on data, rather than thought) became the dominant way that science progressed. In the early part of the 18th century, scientists saw the need for absolute calibrations, leading to a number of different temperature scales (e.g Fahrenheit, Celsius). Elsewhere in science, the early part of the 18th century gave birth to classifications and broad theories, such as Linnaeus' classification of living things, and classification of chemical substances based on chemical behaviour, classification of rocks in terms of age. Ideas about colour (theory of three primary colours) underpinned work on accurate colour printing, while printing also produced an increasing number of periodicals, which may have led to scientific journals. In the second half of the 18th century, possibly based on ideas of heat as a substance, latent heat and heat capacity concepts were characterised by Black, while later Gay-Lussac and Charles provided evidence of regularities in the effect of temperature on the volumes and pressures of gases, which is used in this Case Study (Wikipedia reference) Technology was beginning to have a major effect on industrial and agricultural production, the start of the industrial revolution.

Links to other sites on historical background
Early thermometry historyfrom Wikipedia
Biographies: Guillaume and Amontons
Amontons used approximate thermometers but came up with the idea of an absolute zero.
Galileo gas thermometerGalileo used a gas thermometer
Wikipedia on gas thermometers
Timeline of temperature and pressure measurement technology
Explanation of principles of Galileo thermoscope
Inventors of thermometers
Cultural background in Europe
University libraries were established during the 17th century, as printed stores of human thinking, alongside the first newspapers. No doubt that this development was promoted by the availability of printing presses. In politics, the 17th century was a time of extended major civil and national wars as kings and politicians sought to achieve power across larger populations. Many ordinary people were caught up in these wars as soldiers and refugees, or by being killed or possessions taken away by force. In the latter part of the 18th century, the French Revolution happened, and many significant scientists were involved on both sides.
Philosophical background
A central notion of measurement is one of objectivity. This characterises measurement as being the same whoever makes the measurement, if they measure in the same way. In this activity, this search for objectivity is played out in the simple activity of measuring the boiling point of water using a thermometer. To say this was problematic for scientists is to make an understatement - it took a very long time to establish the upper fixed point of the boiling point of water with any certainty, even when allowing for pressure variations.

The activity simplifies the historical process into a form suitable for 11-12 year old pupils. After discovering that determining the boiling point of water is far from simple, we introduce them to scientists' best methods for doing just that, mixing steam and water. We avoid the notion of whether providing a uniform scale makes the expansion of the liquid linear. There is just so much they can take at this young age. We leave them with the thought that the best scientists in the world grappled with the practicality of measurement. Finally, we finish off with a theoretical notion of absolute zero, when there is no pressure and all the particles are 'perfectly still' in the gas. The notion of being 'perfectly still' fits with what these learners understand about particles in a gas.