Physical phenomenon and chemical transformation

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Link to the lesson

Before you start you should know

that the substances have specific physical properties;
we divide substances into simple (elements) and complex (chemical compounds);
substances can be mixed together to form homogeneous and heterogeneous mixtures;
mixtures can be separated into components.

You will learn

to describe the differences between physical phenomenon and chemical transformation;
to give examples of physical phenomena and chemical transformations taking place in the human environment;
to design and perform a simple experiment illustrating physical phenomena and chemical reactions;

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What transformation is associated with a change in the physical properties of a substance?

In our environment we can observe many tranformations in which the physical properties of matter change, but not itself. An example of this is freezing of water. The ice that is produced as a result of this process is not a new material but still water. As a result of the temperature decrease, only physical state (physical property) of the substance changes. Such process, as a result of which matter only changes its physical properties, we call physical transformationphysical transformation or physical phenomenonphysical phenomenon.

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Grafika przedstawia trzy ilustracje, pokazujące kolejno: zgiętą na pół kartkę A4, obcinanie kartki oraz sposób j jej złożenia. — Cutting the piece of paper into parts does not change the type of material - it is still paper, only in smaller pieces

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Ilustracja przedstawia trzy mniejsze fotografie, pokazujące kolejno: cukier w miseczce i szklankę z wodą, wsypywanie cukru z miseczki łyżeczką do szklanki wody oraz mieszanie szklanki wody łyżeczką, po wsypaniu cukru. — After throwing in sugar (sucrose) into the water, a homogeneous mixture of sugar in water is formed

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Ilustracja przedstawia trzy fotografie pokazujące kolejno: kostki lodu znajdujące się na talerzu, topniejące kostki lodu znajdujące się na talerzu oraz talerz z wodą. — When melting the ice cube, the water changes state

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Ilustracja przedstawia trzy fotografie, pokazujące kolejno: cukier w szklanym pojemniku, przesypywanie cukru ze szklanego pojemnika do blendera oraz cukier znajdujący się w blenderze. — During grinding, food sugar (sucrose) changes its state of fragmentation

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Ilustracja przedstawia trzy fotografie pokazujące kolejno: deskę, młotek i gwóźdź; następnie ktoś wbija gwóźdź w deskę, ostatnie zdjęcie przedstawia wbity w deskę gwóźdź. — Failed punching the nail does not change the material it is made from, but only its shape

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Ilustracja przedstawia trzy fotografie, które pokazują kolejno: krojenie białej świecy, proces topnienia świecy znajdującej się na palniku w rondelku oraz przelewanie stopionego materiału z rondelka do szklanego pojemnika — Melting and re-solidifying the material from which the candle is made makes it take on a different shape

Task 1

Before watching the movie “Obtaining plastic sulfur”, formulate a research question and hypothesis. Write down your observations and concluding remarks.

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Analysis of the experiment: ‘Obtaining plastic sulfur‘

Research question

Hypothesis

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Obtaining plastic sulfur

Experiment 1

Research problem

What transformation (physical or chemical) occurs when heating and then cooling down sulfur?

Hypothesis

Sulfur subjected first to high and then low temperature undergoes physical transformation.

You will need

heat‑resistant test tube,
burner,
wooden clamp for test tubes,
a teaspoon,
beaker,
sulfur.

Instruction

Fill the tube with a sulfur of $\frac{1}{4}$ its height.
The contents of the tube should be gently warmed in the flame of the burner until the sulfur for the second time obtains a smooth consistency.
With vigorous movement pour over liquid sulfur into a beaker filled halfway with cold water.
When the sulfur has cooled down, take it out using a glass rod and put it on a watch glass. Using glass rod examine the plasticity of sulfur – try to stretch it, bend it, etc.

Summary

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Observations

Conclusions

What transformations make one substance transform into another?

In our environment, many transformations can be observed, during which substances undergo constant changes and transform into other substances.

Transformations presented in above photographs take place under the influence of various factors: high temperature action, microorganisms, interaction of various substances. They have one thing in common – they result in new substances with different properties. Such processes are said to be chemical transformationschemical transformations or chemical reactionschemical reactions.

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Ilustracja przedstawia zapalanie białej, długiej świecy zapalniczką, a następnie tą samą świecę prawie w całości wypaloną w świeczniku. — The candle burns with carbon dioxide

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Ilustracja przedstawia dwie prawie identyczne fotografie - talerze w owocami (banan, jabłko, śliwka, kiwi, pomarańcza). Jest jedna różnica - pierwsza fotografia przedstawia świeże owoce, druga zaś bardzo dojrzałe i zasuszone. — The fruits under the influence of microorganisms are spoiled and unfit for consumption. New substances created in them are harmful to human health

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Ilustracja przedstawia dwie fotografie: dwie formy z ciastem w piekarniku oraz dwa wypieczone bochenki chleba położone na desce do krojenia. — Under the influence of high temperature, the raw dough is transformed into usable bread

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Ilustracja przedstawia trzy fotografie, pokazujące kolejno: wlewanie mleka z plastikowej butelki do dzbanka, mleko w dzbanku i efekt przekształcenia się mleka w kwas mlekowy. — Fresh milk undergoes lactic fermentation thanks to the bacteria that naturally occur in it. During this process, other lactose is transformed (milk sugar), transformed into another substance - lactic acid

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Ilustracja przedstawia trzy fotografie pokazujące kolejno: wsypywanie cukru na patelnię, zmianę postaci cukru mieszanego na paleni drewnianą łyżką oraz karmelizację cukru. — Under the influence of high temperature sugar (sucrose) is transformed into various chemical compounds that give the aroma and taste of the resulting caramel

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Ilustracja przedstawia dwie fotografie, pokazujące kolejno: palenie kartki - listu nad białym talerzem oraz popiół na talerzu pozostały po spalonej kartce. — As a result of the burning of the paper, ash is formed, which is a different material than paper

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Ilustracja przedstawia trzy fotografie pokazujące proces robienia jajecznicy: rozbijanie jajek, mieszanie jajek na patelni drewnianą łyżką oraz efekt końcowy - jajecznicę. — Under the influence of high temperature substances contained in egg white break up, transforming into others

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Ilustracja przedstawia dwie fotografie: gwóźdź i ten sam zardzewiały gwóźdź. — The iron contained in steel as a result of interaction with oxygen and water contained in the air will rust. Other substances are formed from iron

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Ilustracja przedstawia trzy fotografie, pokazujące kolejno: cążki z magnezem, reakcje z tlenem oraz rezultat - powstanie tlenku magnezu. — As a result of magnesium combustion (reaction with oxygen) a new substance (magnesium oxide) is formed

Task 2

Consider and answer the following questions:

Are hair cutting and dyeing the same type of transformation? Specify these processes.
Are carving in wood and firing patterns in it transformations of the same type? Name them.

Sulfur combustion1

Experiment 2

Research problem

What transformation sulfur undergo during combustion?

Hypothesis

Burning sulfur undergoes chemical transformation.

You will need

combustion spoon,
burner,
combustion cylinder,
sulfur.

Instruction

Apply a small amount of sulfur to the combustion spoon.
Place the spoon in the flame of the burner and wait for the sulfur on it will ignite.
Place the combustion spoon with burning sulfur in a high cylinder.
Observe the sulfur combustion process, the flame color and other effects that accompany it.

Summary

Sulfur placed in the flame of the burner first melts and then ignites. Burns with a blue flame.
The combustion of sulfur produces a colorless substance with a gaseous state – sulfur dioxide. This transformation is an example of chemical reaction (transformation).

What is the difference between physical and chemical reaction?

Physical phenomenaPhysical phenomena and chemical transformations accompany us every day. It is not always easy to assess their type. In many cases, just process observation is not enough to determine whether a new substance was created as a result of it, or only the physical properties (e.g. state of aggregation) of the substance undergoing this transformation have changed. The factors used also do not determine the type of transformation. As a result of heating, the substance may either change physically or take part in a chemical reaction.

As a result of mixing two different substances, their mixture may be formed (physical phenomenon) or a chemical reaction may occur. This depends on properties of substances themselves and on conditions in which they are placed. In predicting the type of transformations under influence of various factors, knowledge about properties of substances is very useful.

Mixing sulfur with iron and heating the resulting mixture1

Experiment 3

Research problem

What transformations occur when mixing with one another and then heating up sulfur and iron?

Hypothesis

Mixing sulfur with iron is a physical transformation and as a result of their heating a chemical reaction takes place.

You will need

sulfur,
iron in the form of dust (so‑called iron powder),
mortar,
spatulas,
ceramic tile,
gas burner.

Instruction

Weigh 2 g of sulfur and 3.5 g of iron.
Transfer the weighed amount of elements to the mortar and mix thoroughly.
Check if the iron is still in the mixture – place the magnet close to it.
Transfer the mixture of sulfur and iron to the ceramic tile.
Place the plate on the tripod and heat it from the bottom using burner.
Keep heating until the mixture is glowing.
After the end of any transformations check presence of iron in resulting mass using the magnet.

Summary

Sulfur mixed with iron forms a gray mixture. The magnet close to its surface attracts iron powder. After heating to a high temperature, the mixture ignites. The heat covers the entire mixture. After finishing glowing, a black‑colored mass is formed. The magnet does not attract any of its components.
Iron powder can be extracted from its mixture with sulfur using a magnet. During the heating, a chemical reaction occurs in the mixture – sulfur reacts with iron. A new substance is created which, in contrast to iron – does not exhibit magnetic properties.

How can we describe chemical reactions?

Chemists have found a universal way of describing chemical transformations, during which one substance is transformed into another. With the help of arrow they indicate the direction of the transformation – from substances that took part in the chemical reaction to substances that were created:

$substances that participated in the reaction → substances that were formed as a result of reaction$

Substances that undergo chemical transformation are called substratessubstratessubstrates, and substances resulting from it are called productsproductsproducts. The record, in which using arrows and molecular formulas transition from substrates to products is shown, is called chemical reaction equationchemical reaction equationchemical reaction equation. The general scheme is as follows:

$substrates → products$

In the chemical reaction equation, substrates are always on the left side of the arrow, and the products – are on the right. The arrow is directed from the substrates to the products.

In experiment 2 from sulfur and oxygen we obtained sulfur dioxide. Sulfur has reacted with the oxygen presented in the air. This reaction can be described by the following equation:

$sulfur + oxygen → sulfur dioxide$

Experiment 3, based on heating of sulfur with iron, led to the formation of iron(II) sulfide. This chemical transformation can be presented by the following equation:

$sulfur + iron → iron(II) sulfide$

Another chemical reaction, in which magnesium oxide is formed as a result of magnesium, can be described by the equation:

$magnesium + oxygen → magnesium oxide$

Chemical reaction equation	Substrates	Products
$sulfur + iron → iron(II) sulfide$	sulfur, iron	iron(II) sulfide
$sulfur + oxygen → sulfur dioxide$	sulfur, oxygen	sulfur dioxide
$magnesium + oxygen → magnesium oxide$	magnesium, oxygen	magnesium oxide
$hydrogen + oxygen → water$	hydrogen, oxygen	water
$sodium + chlorine → sodium chloride$	sodium, chlorine	sodium chloride
$carbon + oxygen → carbon dioxide$	carbon, oxygen	carbon dioxide
$calcium + oxygen → calcium oxide$	calcium, oxygen	calcium oxide
$hydrogen + chlorine → hydrochloride$	hydrogen, chlorine	hydrogen chloride

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Exercise 1

Which of the above-mentioned activities do you attribute to physical phenomena, and which to chemical reactions (transformations)?

Salting potatoes, Dissolving juice in water, Cooling water, Dissolving sugar, Heat up the oil, Rinsing potatoes, Fryed meat, Peeling potatoes, Gas ignition, Acidification of cream with citric acid, Boiled potatoes, Boiling water, Burning butter, Dissolving butter, A burning match

Physical phenomena
Chemical transformation

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Create a multiple-choice test based on today's lesson. Then exchange your questions with a friend or classmate.

Question: ...

Summary

Physical phenomena are based on changing the physical properties of a substance. During these processes new elements and new chemical compounds are not created.
Chemical transformation is a process during which one substance is transformed into another.
Substances that undergo transformations in chemical reaction are substrates, and those that result from them are products;
The chemical reaction equation is a symbolic record of chemical reaction course. Substrates are written on the left side of the reaction equation, on the right – products. The arrow indicates the direction of the reaction from substrates to products.

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Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

Key words

products, chemical reaction equation, substrates

Glossary

products

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nagranie dźwiękowe słówka

produkty – substancje, które powstają w wyniku reakcji chemicznej

chemical reaction (chemical transformation)

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nagranie dźwiękowe słówka

reakcja chemiczna (przemiana chemiczna) – proces, w którym z jednej substancji lub większej ich liczby powstaje jedna lub więcej nowych substancji o odmiennych właściwościach

chemical reaction equation

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nagranie dźwiękowe słówka

równanie reakcji chemicznej – zapis przebiegu reakcji chemicznej za pomocą symboli i wzorów chemicznych; przedstawia substraty i produkty reakcji oraz często warunki zachodzenia danej reakcji

substrates

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nagranie dźwiękowe słówka

substraty – substancje, które biorą udział w przemianie chemicznej

physical phenomenon (physical transformation)

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Nagranie dźwiękowe słówka

zjawisko fizyczne (przemiana fizyczna) – proces, w wyniku którego zmieniają się właściwości fizyczne substancji

Lesson plan (Polish)

What transformation is associated with a change in the physical properties of a substance?

What transformations make one substance transform into another?

What is the difference between physical and chemical reaction?

How can we describe chemical reactions?

Summary

Key words

Glossary