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Thermal expansion of solids

Source: licencja: CC 0.

Link to the lesson

Before you start you should know

  • we distinguish three states of matter;

  • that molecules move faster as the temperature increases.

You will learn

  • to explain what thermal expansion of solids is;

  • to carry out an experiment demonstrating thermal expansion of solids;

  • provide examples how thermal expansion can be used in the construction industry.

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Nagranie dźwiękowe abstraktu

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As you already know, solids have a definite shape and a definite volume. A solid does not easily change its shape or its volume. Does this mean that they are not subject to thermal expansionthermal expansionthermal expansion? Let’s find out by performing an experiment.

Rozszerzalność cieplna ciał stałych1
Experiment 1

Examining the effect of temperature on the volume of solids.

You will need

  • a board,

  • two nails,

  • pliers,

  • candle,

  • coin.

Instruction

  1. Ask an adult to hammer the nails into the board at a distance equal to the width of the coin. It should be possible to move the coin between the nails.

  2. Take the pliers and grasp the coin with them. Hold it over the flame of the candle for a minute. Do not touch the coin – it is very hot!

  3. Still holding the coin in the pliers, try to move it between the nails. What is happening?

Summary

If the coin does not fit between the nails, it means that it must have increased its volume under the influence of heat.

Task 1

Before you watch the film “Thermal expansion of solids”, write down a research question and a hypothesis. Watching the film, write down your observations and, finally, your conclusions.

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Polecenie sformułuj pytania i hipotezy przed zapoznaniem się z poniższym filmem “Thermal expansion of solids”. Po zapoznaniu się wypowiedz wnioski.
Analysis of the experiment
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Nagranie filmowe doświadczenia przeprowadzonego w laboratorium. W doświadczeniu wykorzystano: małą deskę z  dwoma, lekko wbitymi blisko siebie gwoźdźmi, monetę pięciozłotową, zapaloną świeczkę, szczypce laboratoryjne. W szczypce wzięto monetę i wielokrotnie wsadzano w przerwę między gwoźdźmi. Podpisano: The coin freely goes between nails driven at a distance equal to its thickness. Następnie ponownie wzięto monetę w szczypce i podgrzano nad rozpaloną ogniem świeczkę. Próba wsadzenia rozgrzanej monety między gwoździe nie powiodła się. Podpisano: What happens when we heat a coin? A warmed-up coin can not squeeze between the nails although the gap between them has not changed. This means that the volume has increased due to the heat.
Thermal expansion of solids
Source: licencja: CC BY-SA 3.0.

Film dostępny na portalu epodreczniki.pl

Thermal expansion of solids
Source: licencja: CC BY-SA 3.0.

Nagranie filmowe doświadczenia przeprowadzonego w laboratorium. W doświadczeniu wykorzystano: małą deskę z  dwoma, lekko wbitymi blisko siebie gwoźdźmi, monetę pięciozłotową, zapaloną świeczkę, szczypce laboratoryjne. W szczypce wzięto monetę i wielokrotnie wsadzano w przerwę między gwoźdźmi. Podpisano: The coin freely goes between nails driven at a distance equal to its thickness. Następnie ponownie wzięto monetę w szczypce i podgrzano nad rozpaloną ogniem świeczkę. Próba wsadzenia rozgrzanej monety między gwoździe nie powiodła się. Podpisano: What happens when we heat a coin? A warmed-up coin can not squeeze between the nails although the gap between them has not changed. This means that the volume has increased due to the heat.

Solids change their volume due to changes in their temperature. This phenomenon is much more visible in the case of metals. In the table below you will find some examples, if the length of the objects, which measure 1 m, are changed and are made of different materials, if we raise the temperature by 50°C.

Substance (length of 1 m)

Change in the length (mm) after increasing the temperature by 50°C

A rail made of steel

0.6

A tube made of lead

6.0

An optical fibre made of quartz glass

0.02

The phenomenon of thermal expansion has a huge impact on our lives. Engineers have to take it into account when designing buildings and all metal structures: bridges, railway tracks or high‑voltage cables, as well as metal constructions of some buildings.

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Ilustracja interaktywna przedstawia budowę pięciu wieżowców w mieście przy estakadzie. Thermal expansion in our surroundins. Na ilustracji są opisy i poszczególne fotografie: 1-High voltage grid in the summer- In the summer, high-voltage wires hang loosely, because their length increases due to high temperature- Ilustracja przedstawia sieć wysokiego napięcia latem - widać, że przewody elektryczne luźno zwisają pomiędzy kolejnymi słupami. 2-High voltage grid in the winter- In the winter, the wires are tight, because their length decreases due to low temperature- Ilustracja przedstawia sieć wysokiego napięcia zimą - widać, że przewody są napięte. 3- An expansion gap in a railway track in summer and in winter- Railway tracks are provided with sites where two sections of rails overlap. In winter, when rails decrease their length under the influence of low temperature, rails do not break and, at the same time, no gaps appear in the track- Fotografia przedstawia przerwy dylatacyjne w szynach kolejowych latem i zimą. 4- An expansion gap in a bridge in summer and in winter- In sections of bridges, there are special expansion joints. When the length of the bridge decreases in winter, expansion joints prevent the formation of gaps in the bridge- Fotografia przedstawia przerwy dylatacyjne w moście latem i zimą. 5- Reinforced concrete slab- Houses should be built from materials with similar thermal expansion characteristics. Otherwise, the volume of one of materials may change too much, causing the walls and floors to break or even leading to the collapse of the house - Fotografia przedstawia blok budowany z płyty żelbetonowej.
Thermal expansion in our surroundings
Source: Concrete Forms, Federico Cantoni (Jollyroger), Juhana Leinonen, Malikbakt, Michael Gil, Tomorrow Sp. z o.o., d5e, licencja: CC BY-SA 3.0.
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Exercise 1
Omów rozszerzalność cieplną ciał stałych latem i zimą.
Source: Federico Cantoni (Jollyroger), Juhana Leinonen, Tomorrow Sp. z o.o, licencja: CC BY-SA 2.0.
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Exercise 2
Ćwiczenie ocen prawdziwość stwierdzeń. Decide whether the following statements are true or false. A change in the temperature of a solid body leads to a change in its volume. Możliwe odpowiedzi: True, False. All solid bodies are made of molecules being at rest. Możliwe odpowiedzi: True, False. The average distances between molecules change when the temperature changes. Możliwe odpowiedzi: True, False

Decide whether the following statements are true or false.

True False
A change in the temperature of a solid body leads to a change in its volume. □ □
All solid bodies are made of molecules being at rest. □ □
The average distances between molecules change when the temperature changes. □ □
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Exercise 3
Ćwiczenie dokończ poprawnie zdanie. Choose the correct ending for the sentence. A glass filled with hot water breaks, because Możliwe odpowiedzi: 1. the whole glass expands too quickly., 2. the outer part of the glass expands more that its inner part., 3. the outer part of the glass expands less than its internal part which comes into contact with the hot liquid., 4. hot water expands and breaks the glass.

Choose the correct ending for the sentence. A glass filled with hot water breaks, because

  • the whole glass expands too quickly.
  • the outer part of the glass expands more that its inner part.
  • the outer part of the glass expands less than its internal part which comes into contact with the hot liquid.
  • hot water expands and breaks the glass.
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Exercise 4
Ćwiczenie wybierz właściwą odpowiedź. Choose the right sentence describing the relationship between the temperature of a body and its volume. Możliwe odpowiedzi: 1. The higher the temperature, the smaller are changes in the length of the body., 2. The higher the temperature, the larger the volume of the body, 3. Changes in the length of bodies under the influence of temperature do not depend on the type of substance from which bodies are made.

Choose the right sentence describing the relationship between the temperature of a body and its volume.

  • The higher the temperature, the smaller are changes in the length of the body.
  • The higher the temperature, the larger the volume of the body
  • Changes in the length of bodies under the influence of temperature do not depend on the type of substance from which bodies are made.

Summary

  • Thermal (temperature‑induced) expansion is a change in the volume of bodies due to a change in their temperature.

  • Thermal expansion of bodies is associated with an increased velocity of molecules and a rise in temperature.

  • Gases expand the most while being heated, but the phenomenon of thermal expansion occurs in liquids and solids too.

  • The phenomenon of thermal expansion must be taken into account when designing buildings and equipment.

Keywords

thermal expansion, thermal expansion of solids, expansion gapexpansion gapexpansion gap

Glossary

thermal expansion
thermal expansion
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Nagranie dźwiękowe słówka.

Nagranie dostępne na portalu epodreczniki.pl

Nagranie dźwiękowe słówka.

rozszerzalność cieplna – zmiana objętości ciała na skutek zmiany jego temperatury

expansion gap
expansion gap
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Nagranie dźwiękowe słówka.

Nagranie dostępne na portalu epodreczniki.pl

Nagranie dźwiękowe słówka.

przerwa dylatacyjna – szczelina celowo utworzona w konstrukcji budynku lub budowli

Lesson plan (Polish)