Keeping Track Of Heat (Lehrerversion)

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2. It's getting cold here...

4. Physics for your Eyes: see, shine and flow

6. Chemistry and Environment

Chemistry Vocabulary List

It is not just interesting wether or not a reaction releases or absorbs energy, but also how to effectively isolate things and how to dissipate¹ heat. An important issue is the thermal conductivity² of elements and compounds³. When heating something in a test tube⁴, you can comfortably hold the test tube in your hand for quite some time - because glass is a poor heat conductor. By contrast, metal conducts heat very well: you will quickly feel your fingers getting hotter, when stirring your tea with a metal spoon. The following experiment will visualise how heat 'travels' through different metals: Experiment Material: Styrodur-structure with samples of Ag, Pb, Cu, Zn, and Fe Preparation: Boil some water and pour it into a thermos. Set up the thermal imaging camera and focus on the experiment. Procedure: Start a video recording and pour hot water from the thermos into the box (leave approx. 3mm of space to the brim). Put the cover with the samples on top and make sure that the front is covered by the Styrodur-structure.

• 6.11 Log your observations by a thermal imaging camera. • 6.12 Using literature values, try to match the samples with their corresponding element.

Element Ag Pb Cu Fe Zn

heat conductivity [W/(m•K)] 429 35 380 80 110

¹ to dissipate - auflösen, abführen ² thermal conductivity - Wärmeleitfähigkeit ³ compound - Verbindung

⁴ test tube - Reagenzglas

Experiment (to be carried out in a dark room) Material: black box, 3 beakers (100ml), 1 spatula, potassium ferricyanide, water Preparations: Make two solutions: Pour 50 mL of solution A (0,1g luminol, 16ml 10% NaOH solution in 1L H₂O) into one beaker. Pour 50 mL of solution B (4g K₃[Fe(CN)₆], 8ml 30% H₂O₂ solution in 1L H₂O) into a second beaker. Add a spatula tip's full of&nbsp;potassium ferricyanide into a third beaker. Prepare the thermal imaging camera. Make sure, the third beaker is in focus. Procedure: In the dark, pour solutions A and B into the third beaker simultaneously. • 5.7 Carry out the experiment and record it using both a regular camera and the thermal imaging camera. Use the dual mode in 'Seek Thermal' to do so. • 5.8 The followig simplified reaction equation shows the chemical process leading to the emission of light: Luminol is oxidised by hydrogen peroxide and forms a dianion in an excited state¹. Excited&nbsp;states are marked with an asterisk (*). Molecules in an excited state will emit light, when going back to their ground state². Use the following words to describe the process in the luminol reaction:

• 5.9 In the luminol reaction you can see the emission of 'cold light'. Explain this term using your observations with your own senses and with the thermal imaging camera. Relate your answer to LEDs and tungsten light bulbs and fireflies.

5.7) 5.8) Most chemical reactions involving chemiluminescence create unstable peroxides (oxidation). Due to their electron configuration, peroxides can degrade to products in an excited state. When these products degrade, light is emitted and the molecules go back to their ground state. When working with luminol, the reaction is catalysed by&nbsp;potassium ferricyanide - without, the reaction would be so slow, you would probably not see any light. 5.9) The processes involved in chemiluminescence do not generate heat, as opposed to most other light emitting phenomena in our everyday life, hence the name 'cold light'. Tungsten light bulbs produce an enormous amount of heat compared to LEDs, however LEDs still do produce some heat. Fireflies also emit cold light and no heat, so the name might be misleading. In biological systems, this is called bioluminescence.

chemical reaction, oxidation, emission of light, luminol, catalysed by potassium ferricyanide, ground state, excited state

¹ excited state - angeregter Zustand ² ground state - Grundzustand

Now that we know there is thermal radiation that interacts with matter in a similar way, we want to investigate further. Warm objects can either exclusively radiate thermal radiation or radiate visible light and thermal radiation, as you might know from fires. What we are looking for is how both types of radiation are related to each other. Can we predict what type of radiation is emitted by different objects? To find an answer for that question, we have to work with a radiation source that can emit light and heat. A good example would be a lightbulb, however we will work with "simplified light bulb" in the next experiment. Experiment Material: constantan wire, power supply, 2 cables , 2 crocodile clips Preparation: First of all, switch off the power supply and set all controls to 0! A small piece of wire (~1cm) is fixed between the crocodile clips. The crocodile clips are then connected to the power supply. Procedure: Switch on the power supply and slowly increase voltage¹ and current². Observe the wire with a regular camera and the thermal imaging camera set to IR range. Make sure the camera is in Hi/Lo-mode to show the hottest areas. • 4.3. Make a table and write down your observations at the following temperatures: 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, and &gt;300°C.

• 4.4. What do you call the phenomenon that can be observed at about 80°C? • 4.5. Using your table, deduce how light and thermal radiation correlate. How does that change for temperatures above 80°C? Your deduced rule should explain colour and intensity of this visible phenomenom.

4.4) Glowing 4.5) The hotter the object gets, the more intense it glows. The colour changes from a dark glowing red to a bright white.

¹ voltage - Spannung ² current - Stromstärke

Chemistry and Environment

You will find the term 'heat energy' in science as well as in your everyday life. In this chapter, we will have a closer look at the term and how heat energy affects us. There are many processes around us that release heat energy (exothermic reactions). A fire will burn and emit a noticeable amount of heat, just as the nuclear fusion¹ reaction in the sun. These reactions are self-sustained². Protein, on the other hand, will not denaturate on its own: In order to get a white solid egg, one has to spend energy, usually by boiling it. This might lead to the conclusion that heat emitting processes react spontaneously and others don't. The next experiment is a good example for a rather rare type of reaction: There are reactions that will absorb heat energy (endothermic reaction) from their surroundings and are still self-sustained. Experiment Material: watch glass, spatula, citric acid C₆H₈O₇, sodium carbonate pentahydrate Na₂CO₃ • 5H₂O Preparation: Put small separate piles (one or two spatulas) of citric acid and sodium carbonate pentahydrate on a watch glass. Procedure: Turn on the thermal imaging camera and focus on the watch glass. Using your spatula, coarsely mix the two substances. Keep an eye on the watch glass and observe it with the camera. After that, thoroughly mix the rest.

Disposal: Mix the reactants with water and pour the solution down the drain. • 6.1 Briefly, write down your observations. • 6.2 Citric acid C₆H₈O₇ and sodium carbonate pentahydrate Na₂CO₃ • 5H₂O react to form carbon dioxide CO₂, water H₂O and sodium citrate C₆H₅O₇Na₃. Write a reaction equation.

6.2) 2 C₆H₈O₇ (s) + 3 Na₂CO₃ • 5H₂O (s) → 3 CO₂ (g) + 18 H₂O (l) + 2 C₆H₅O₇Na₃ (aq)

¹ nuclear fusion - Kernfusion ² self-sustained reaction - selbstständig ablaufende Reaktion

Thieves and Spies

In this chapter, we will discuss thermal imaging cameras and night vision cameras. • 3.1. Switch on the night vison camera and familiarise¹ yourself with its image. How does it depict its surroundings? Make some recordings by filming the display of the camera with the tablet. • 3.2. Compare the pictures of a thermal imaging camera, a night vision camera, and a regular camera. For this purpose, examine the torches² provided. If possible, work in a darkened room. In which situations are night vision cameras useful (compared to thermal imaging cameras)? Relate to your observations and the displayed newspaper article.

3.1.) The night vison camera displays all colours to be slightly off colour and with a strong rose tint.

3.2) Looking at the light of a multi-colour torch, one can see that the night vison camera cannot properly distinguish between red and green.

¹ to familiarise- sich mit etwas beschäftigen, vertraut machen ² torch - Taschenlampe, auch: Fackel

Having explored, why tungsten light bulbs have been banned, we have to mention that there are also situations where, instead of emitting light, generating heat is the primarily desired¹ effect. A good example is the 'red light' emitted by heat lamps: • 5.5. Inspect the heat lamp and compare it with the regular tungsten light bulbs you worked with earlier. Consider the specifications as well as your own measurements (your own senses, thermal imaging camera and 'LightMeter'). • 5.6. Make a bullet point list of possible uses for heat lamps. In 1880, Thomas Alva Edison reinvented the light bulb. He made major improvements to William Robert Gove's design of a platinum-filament² light bulb from 1840. Edison's lightbulb was groundbreaking³ and greatly influenced the life of the European society. However, long before Edison and Gove came up with their ideas, nature already had a variety of possibilities to generate light. Fireflies⁴ are just one of many examples for this phenomenom. Looking at these insects, the question arises how they manage to generate this impressively bright light, as there seem to be neither electricity nor any kind of combustion⁵. We want to investigate, why fireflies glow consistently without burning themself.

5.6) - providing heat and warmth to pet animals - pain relief - skin problems

¹ desired - gewünscht, erwünscht ² filament - Glühfaden ³ groundbreaking - bahnbrechend

⁴ firefly - Glühwürmchen ⁵ combustion - Verbrennung

2.5) Clothes insulate the body, so body heat does not migrate into the environment, see pictures below:

This lovely summer day is coming to an end and at sunset, it is starting to become noticeably chilly¹, so you put on your sweater. • 2.5. Using the thermal imaging camera, examine the effects of clothes. • 2.6. Develop a theory, why people in particularly² hot climates often wear long clothes. Despite your sweater, you are still feeling cold. In your bag you find the pocket warmer, you got as a freebie³ last winter. Luckily, it is still 'charged' and you activate it by clicking⁴ the small metal disc inside. • 2.7 Watch closely what happens with the pocket warmer, after activating it. Use the thermal imaging camera and the regular camera side by side. In order to do this, open the 'Seek Thermal' app and switch on the dual recording mode.

2.6) For isolation against high ambient temperature, which is greater than body temperature.

¹ chilly- kühl ² particularly- besonders, vor allem ³ freebie - Werbegeschenk, Gratisartikel

⁴ clicking - knacken, klicken, hier: drücken

A: to absorb acid acidic alkaline amplifier analogy B: base beaker to bypass C: catalyst chemiluminescence citric acid combustion compound conclusion conversion correlation current D: to degrade to denaturate disposal to dissipate E: to emit endothermic energy/reaction coordinate diagram entropy

absorbieren Säure sauer alkalisch Verstärker Analogie, Ähnlichkeit Base Becherglas etwas umgehen Katalysator Chemielumineszenz Zitronensäure Verbrennung Verbindung Schlussfolgerung Umwandlung Zusammenhang Stromstärke zerfallen denaturieren Entsorgung auflösen, abführen emittieren, abgeben endotherm Energie/Reaktionskoordinate-Diagramm Entropie (Maß für Unordnung in Systemen)

evaporation excited state exothermic F filament firefly fire-resistant G: ground state H: hydration shell hydrochloric acid hypothermia I: infrared insulation to interact L: lattice (tungsten) light bulb M: matter motion detector N: night vision camera nuclear fusion O: observation oxidation

Verdunstung angeregter Zustand exotherm Glühdraht Glühwürmchen feuerfest Grundzustand Hydrat-Hülle Salzsäure Unterkühlung infrarot Isolierung interagieren Gitter Glühbirne (Tungsten = Worlfram) Materie Bewegungsmelder Nachtsichtkamera Kernfusion Beobachtung Oxidation

Night vision cameras can help demystifying¹ other technical secrets from your everyday life. In the newspaper article, it was reported that the museum gate was opened with a stolen remote control². These remote controls work just like the regular ones you know from your TV. Interestingly, when pressing any button on your remote, you normally won't see a thing, right? • 3.5. Investigate this by looking at the LED of the remote control with your eyes and with the night vison camera. Record your findings with pictures or videos and compare the infrared lamp with the remote control.

¹ to demystify - entmystifizieren, etwas Verborgenes aufdecken ² remote control - Fernbedienung

In the last section we discussed what happens when we mix a salt and water. Now we will look at a different type of reaction and mix two solutions: an acidic¹ and an alkaline² solution. When they are mixed, a neutralisation can take place. Experiment Material: Petri dish, pipette, sodium hydroxide solution NaOH(aq), c = 0,1 mol/L, hydrochloric acid HCl(aq), c = 0,1 mol/L Preparation: Set up the thermal imaging camera and focus on the empty Petri dish. Fill the Petri dish about 3-5 mm high with sodium hydroxide solution. Procedure: Carefully add a few drops of hydrochloric acid solution into the Petri dish. Record in dual mode. Disposal: Neutralise the solutions and pour everything down the drain. • 6.8 Write down your observations. • 6.9 Develop a reaction equation. • 6.10 Name the phenomenom you just witnessed in the experiment. Try to guess where the heat energy is coming from.

6.9) NaOH (aq) + HCl (aq) → H₂O (l) + NaCl (aq) [exothermic]

¹ acidic - sauer ² alkaline - alkalisch

P: Petri dish physical quantity potassium procedure property R: radiation reaction equation to reflect S: sample to scale down something self-sustained reaction sodium hydroxide solution spatula spot plate T: test tube texture&nbsp; thermal blanket thermal conductivity&nbsp; thermal imaging camera&nbsp; thermogram transmission V: voltage W: watch glass wavelength

Petrischale physikalische Größe Kalium Durchführung Eigenschaft Strahlung Reaktionsgleichung reflektieren Probe etwas verkleinern selbstständig ablaufende Reaktion Natriumhydroxid Lösung Spatel Tüpfelplatte Reagenzglas Beschaffenheit Wärmedecke Wärmeleitfähigkeit Wärmebildkamera Thermogramm (Aufnahme einer Wärmebildkamera) Transmission, "Hindurchtreten" Spannung Uhrglas Wellenlänge

• 6.13 Make a guess: How does heat 'travel' through matter? Do you know other ways heat can flow? • 6.14 If you touch a piece of metal with clammy hands in winter at temperatures way below 0°C, you will almost immediately freeze to the piece of metal. Explain this phenomenom.

6.13) There are three ways heat can travel: conduction, convection and radiation. Conduction: The warmer matter gets, the faster move its molecules. When two objects with different temperature touch, the molecules inside them collide and transfer energy (heat) between the objects. Convection: All matter is affected and pulled down by gravity, however flowing substances (gases and liquids) can, if heated, become less dense in the heated area, making these 'hot' gas portions rise. Radiation: Heat can move as energy waves (infrared radiation). A good example is our sun: There is almost no matter between the sun and our earth, yet we can still feel the heat. The infrared radiation can travel without medium and stimulates faster molecule movement. 6.14) If you put your hand on a very cold piece of plastic or rubber it is very unlikely to stick, so it has something to do with a substance property. The one in question is called thermal conductivity. Metals have a high thermal conductivity and plastics/rubber have much lower thermal conductivity, meaning that metal can absorb the heat from your body faster than it can supply heat.

5.2) See pictures (left: tungsten light bulb, right: LED light bulb).

• 5.2 Turn on both lamps and compare them. Use your own senses and a tablet wit the app 'LightMeter'. • 5.3 Take a picture of both lamps... a) with a normal camera. b) with a thermal imaging camera. • 5.4. Looking at the data from your results from 5.2 and 5.3, estimate¹ the amount of energy the tungsten light bulb converts to heat, compared to LED light bulbs.

¹ to estimate - (ab)schätzen

5.4) Tungsten light bulbs convert most of the electric energy to thermal energy (about 90-95%) and get really hot, while LED light bulbs are comparably more efficient and get barely warm.

In school and in the last chapters you have been dealing with the term 'energy'. In our everyday life, we encounter various different forms of energy and over the past couple of years, discussions about 'saving energy' and 'energy consumption' became more and more important. Due to the raised awareness, the EU banned the tungsten light bulbs¹ and replaced them by energy-saving halogen or LED technology, expecting massive energy savings. We will have a closer look at this aspect. Examine an energy saving LED light bulb and an outdated tungsten light bulb, using your own senses as well as the tablet with the apps 'LightMeter' and the thermal imaging camera. • 5.1 What parameters differ between the types of light bulbs?

5.1.) They differ in brightness and power consumption

¹ tungsten light bulb - Glühbirne (tungsten - Wolfram)

3.6) The motion detector cannot trigger in bright surroundings. Also, if the sensor is covered with a piece of plastic, glas or wood, it won't trigger either. 3.7) The motion detector actually detects heat, instead of motion.

Apparently, the motion detectors¹ on the museum grounds² did not trigger an alarm. You can find out how a motion detector works by placing it in complete darkness (a black box or completely darkened room). It won't work outside of the black box due to daylight. • 3.6. Try to work out how motion detectors work. Place a motion detector in complete darkness and test if it can detect motions of different materials (e.g. a piece of wood, metal, glass or cardboard) or a humand hand. Can you find a way to bypass³ detection from it? • 3.7. Relating to your experimental results, comment on the term "motion" detector.

¹ motion detector - Bewegungsmelder ² grounds - Gelände, Anlage ³ to bypass - etwas umgehen

Author, videos and pictures: Simon Kleefeldt Illustrations, editing and translation: Max Schall

No part of this e-book may be reproduced or transmitted in any form or by any means, without permission from the publisher.

Front cover illustration: Nico Meuter

It's getting cold here...

Imagine you are at the pool in the blazing¹ sun. It's 30 degrees in the shade and you are drenched² in sweat. Interestingly, your neighbour's dog doesn't sweat • 2.1. Why do people sweat? Develop a theory and try to verify it with a suitable experiment. Climbing out of the pool, still wet, you decide to stay there and enjoy the sun. After some time, you even start to feel cold. • 2.2. Why are you starting to feel cold on a bright sunny day like this? Try to explain briefly. • 2.3. What would happen if human beings could sweat nail polish remover (acetone)? Test this on a small spot on you hand and write down your perceived results. • 2.4. Dogs pant³ instead of sweating. Imitate the panting of a dog and make a video using the thermal imaging camera.

2.1) People sweat in order to reduce their body temperature: The sweat evaporates, a process that takes heat. As an example, you can try to 'paint' with a wet finger on your skin and watch the evaporation process (video).

2.2) See 2.1. This process is accelerated due to constant air flow.

2.3) Nail polish remover (acetone) has a lower boiling point and a higher vapor pressure. The cooling would be more effective and humans would have to perspire less.

2.4) Panting will simulate the heat regulation of dogs (round lips, no tongue).

¹ blazing - brennend, lodernd ² drenched - durchnässt, klitschnass ³ to pant - hecheln

1.1) Thermal imaging cameras give information about the surface temperature of objects and depict this with various shades of colour.

Research, building restoration, hunting, military and firefighting are just a few of the areas that rely on thermal imaging camera¹. The thermograms ² also play a vital role in scientific experiments, as they give new insight to aspects of processes humans can not observe with their eyes. Go try it yourself! • 1.1 What physical quantity³ can be depicted with a thermal imaging camera? How is this physical quantity visualised? • 1.2 Identify which objects the thermal imaging camera can register and explain why some things can or can not be registered. To show this, insert pictures of objects taken by a thermal imaging camera and a normal camera. • 1.3 Experiment with the thermal imaging camera and examine the colour in the thermogram. Explain the meaning of the colours depicted. After having carried out your first experiments with the thermal imaging camera, you want to take a look at the created thermogramms (the images taken by the thermal imaging camera). You want to know what influences the objects' colouring in the thermogramm.

1.2) A thermogram will show objects with a surface temperature that is higher or lower than the ambient temperature. Objects at ambient temperature are hardly visible in thermograms, as depicted in the two pictures below (left: normal picture; right: thermogram).

1.3) An easy experiment showing that the various colours can be performed with water at different temperatures. Fill three (plastic) cups with water, each at a different temperature and look at them with your thermal imaging camera. With the right measuring range, the cup filled with cold water should be displayed to be blue, while the hot one should be displayed to be red. Using a thermometer, one can also measure the temperature&nbsp;quantitatively, and thus verify the results.

¹ thermal imaging camera - Wärmebildkamera ² thermogram - Thermogramm (Aufnahme einer Wärmebildkamera) ³ physical quantity - physikalische Größe

One week after the incident, the police finds some suspicious paintings. Even though these paintings look different from the stolen ones, it seems like they might have been painted over. The paintings are brought to the lab for further investigations with infra-red light. 

Experiment Material: IR lamp, painting, night vision camera, tripod Preparations: The painting is placed in front of the IR lamp, so that it is shined on from behind. Procedure: Examine the front of the painting, using the night vision camera.

• 3.11. What is hidden under your painting? Carry out the experiment and decide if the painting has been painted over. Insert pictures of what you have seen with the night vision camera.

3.11) The IR lamp shined on the back of the painting. The colours absorb heat differently. The colours of the 'original' painting absorb heat to a greater extent than those of the front 'fake' painting. The areas that are painted on the original appear darker when looked at with a night vision camera, if the motives of both paintings differ.

3.3) The visible light is not detectable, however, the infrared light is.

Having made your first experiences with night vison cameras, you want to investigate how things are at actual nighttime. Night vision cameras always have a low-light amplifier¹, that will increase the sensitivity of the camera. In total darkness even the amplifier will be of no use - that's why people use infrared light. • 3.3. Test the night vision camera in complete darkness. Can it still detect objects? Use the infrared lamp and test the night vision camera again. For comparison, take pictures using the tablet. • 3.4. Examine the torches and the infrared lamp with the thermal imaging camera. What are your observations? Looking at the wavelength² chart below, what are the ranges of wavelengths that regular cameras, night vision cameras, and thermal imaging cameras use?

3.4) Regular cameras can capture the visible light, night vision cameras can amplify visible light and capture infrared light, and thermal imaging cameras can exclusively capture infrared light.

¹ amplifier- Verstärker ² wavelength- Wellenlänge

The article mentions, that the unknown suspects used a targeted¹&nbsp;detonation to gain access to the museum grounds. The term 'targeted', immediately suggests&nbsp;that explosions are reactions, which can be started in a controlled manner. In the following experiment, we will scale that down² and have a closer look at it: Experiment: Material: thermal imaging camera, tablet, thunder caps³, hammer, fire-resistant surface Preparations: Take a thunder cap and put it on a fire-resistant surface. Angle the thermal imaging camera at the thunder cap and set it to thermogramm-video. Procedure: Detonate the thunder cap with a light blow⁴ of the hammer. • 3.8. Carry out the experiment with the thunder cap and make a thermal and a regular video of the explosion. • 3.9. What does the blow of the hammer do? Why didn't the thunder cap explode just by itself? • 3.10. Make an energy/reaction coordinate diagram⁵ and label it.

3.8) See video 3.9) The blow of the hammer gives the required activation energy. 3.10)

¹ targeted- zielgerichtet ² to scale down sth. - etwas verkleinern ³ thunder cap - Knallerbse

⁴ blow- Schlag, Hieb ⁵ energy/reaction coordinate diagram - Energie/Reaktionskoordinate-Diagramm

Experiment Material: thermal imaging camera, water (hot, cold and room-temperature), thermos, cups (3 different colours and three transparent ones) Preparations: Set up the camera and line up the cups. Procedure: Develop experiments that will help you answer the questions below.

The only relevant factor is the surface temperature (three transparent cups filled with water of different temperatures).

• 1.4 Are there factors or properties¹ of the objects influencing the colouring in the thermogram? For example, consider factors like surface texture². • 1.5 Is there a correlation³ between the object's visible colour and its colouring in the thermogram? Take pictures with a normal camera and a thermal camera to support your answer. • 1.6 Open the thermal imaging camera's app and search for other colour ranges in the bottom menu bar. The settings will influence the colouring of the objects, test them.

Pictures of cups of various colours, filled with water of the same temperature show that an object's colour has no impact on the colouring of the thermogram.

Also a coating of gold or silver paint has some impact on the thermogram, as the coatings have an insulating effect.

1.5) The object's real colour has no impact on the colours of the thermogram, just like size and form. For pictures and explanations, see next page.

1.4) Size and form of the object have no impact on the colours of the thermogram. Material and surface texture might distort the results. It can be quite hard to properly measure the surface temperature of metals and other objects with a reflective surface.

1.6) The colour range settings will influence the colouring of the objects in the thermogram:

¹ property - Eigenschaft ² texture - Beschaffenheit ³ correlation - Zusammenhang

• 6.3 Using the reaction equation, give reason why this reaction happens spontaneously, even though it is endothermic. Refer to the term 'entropy¹' in your answer.

6.3) The reaction is endothermic, but the entropy increases, meaning the reaction is entropy-driven and reacts spontaneously. 

• 6.5 Can you think of practical applications for endothermic and exothermic solution processes? Write them down. • 6.6 Where does the energy come from in exothermic solution processes? Write down your assumptions. • 6.7 Exlain why KCl and NH₄NO₃ spontaneously dissolve in water, even though it is an endothermic process.

There are other examples for spontaneous endothermic reactions: while some salts dissolve they cool their environment. On the other hand, there are salts that dissolve in an exothermic way. Both phenomena can be found in everyday applications².

Experiment Material: KCl, NaOH, NH₄NO₃, spot plate, water, 4 pipettes Preparation: Put a spatula tip full of each salt in the dents of the spot plate. Use the thermal imaging camera and focus on the spot plate. Procedure: Using the pipettes, add water to all three dents simultaneously and fill an additional dent as reference. Disposal: Dilute the solutions and pour everything down the drain.

6.5) Applications for endo- and exothermic dissolution processes: disposable cooling/warming pads used for injuries in sport

6.6) Salts are made up of ions in a regular lattice. When dissolving salts in water, the electrostatic attraction between the ions has to be broken down. A hydration shell is formed around the ions. The lattice energy is smaller than the hydration energy.

• 6.4 Write down the observations you made with the thermal imaging camera.

6.7) In the ionic crystal every ion has a precise position, while the ions in the solution are almost free in their movement. The dissolution process is driven by entropy and the free enthalpy ΔG is negative because the entropy S compensates the enthalpy H.

¹ entropy - Entopie (vereinfacht: Maß für Unordnung in einem System) ² application - Anwendung

A couple of minutes ago, a kid tripped and strained¹ his foot pretty badly. While waiting for the ambulance, the staff wraps him in a thermal blanket² to avoid hypothermia³. You have a closer look at the thermal blanket: it's a thin foil, one side is silver-coloured, the other side is gold-coloured - you might remember it from a first aid course. Considering that clothes are way thicker, it seems weird, that a thin foil like this will keep him warm. Experiment Material: thermal blanket, thermal imaging camera, small candle Preparations: Set up the camera and open out the thermal blanket. Procedure: Using the thermal imaging camera, record how the thermal blanket works, when exposed to a heat source (your hand or a small candle). Develop experiments that will help you answer the questions below. • 2.8 Figure out, if and how a thermal blanket will help keeping your body warm. Is there a difference between the silver-coloured and the gold-coloured side? Which side should point to the patient in this situation? In what situations should one use the other side?

2.8) Thermal blankets help keeping you warm by reflecting heat from your body. The silver-coloured side reflects more than the gold-coloured side. That's why the silver one is used for low ambient temperatures and the gold one is used for high ambient temperatures. .

¹ to strain sth. - sich etwas zerren ² thermal blanket- Wärmedecke ³ hypothermia - Unterkühlung

Physics for you Eyes: see, shine and flow

Having worked with the thermal imaging camera, you wonder how these cameras actually work. You examine the thermal imaging camera thorougly. On the front of the camera, there is a lens, as you would expect from a regular camera. Also, there is a focus setting wheel, that you used during the last couple of experiments. All the information about the object and its surface temperature passes through the lens - again, pretty much like a regular camera. Also, the name thermal imaging CAMERA implies, that there is at least some degree of analogy¹ to your everyday camera. Of course, there are some differences as well: In order to understand them you have to deal with electromagnetic radiation or "different kinds of light". • 4.1. Name three phenomena which can occur when light interacts with matter². • 4.2. Looking at the following pictures, are there similar processes if you think of thermal radiation³ or heat?

4.1) Light can be reflected, absorbed and it can pass through suitable (transparent) materials.

4.2) Yes, the examples show reflection of thermal radiation using a reflective surface (mirror) and the transmission of different materials.

¹ analogy - Analogie, Ähnlichkeit ² matter - Materie ³ radiation - Strahlung

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