Is the heating of water a chemical change?

Fire / combustion / oxygen

 

 

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It's not always easy to tell if one is chemical reaction has taken place. They often occur during an experiment physical property changes such as changing a physical state. For example, if liquid water freezes, ice is still water. So there was no change of substance into a new substance. Consequently, no chemical reaction has taken place in this example either. Sometimes changes occur that we in the everyday life also know as property changes (e.g. shape or size). But these are not typical material propertiesthat change there. So it is important that you have typical fabric properties describe and distinguish can.

Let's watch one Change of a typical material property, so we can assume that a chemical reaction has taken place, so a new substance originated. However, you have to make sure that you include the starting material and the reaction product same conditions (Temperature, pressure) compares. A release from energy in the form of light, heat or an explosion is also an indication of a chemical reaction. But this is only an indication, not a certainty: For example, when water freezes, heat is released even though no reaction takes place here, only the state of aggregation changes (physical change).

In most reactions, activation energy has to be added first. For a candle to burn, for example, you have to light it first. If more energy is released afterwards than I added through the activation energy, then it is a so-called exothermic reaction.

 

The following experiment shows you what you really have to pay attention to in order to be sure whether a chemical reaction has taken place, i.e. whether a new substance has been created.

 

Does a chemical reaction take place when the yellow salt (potassium chromate) is heated?

 

 

 Teacher demonstration attempt only with special precautionary measures!

 

No chemical reaction has taken place. The color has only changed temporarily, no new fabric with new properties has emerged!

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Recipe: caramel candies

You take
125 grams of sugar
1 cup of cream (200ml)
1 packet of vanilla sugar
20 grams of margarine
1 teaspoon honey


Bring the sugar and cream to the boil - preferably in a pan. Then stir, stir, stir (at high temperature) until the mass becomes thick. Not surprised; this could take a good 10 minutes.

 

 

Then the vanilla sugar, margarine and honey are added. Let simmer - stir, stir until the mixture comes off the bottom.

Then put this "porridge" on a large piece of baking paper, cut into bite-sized pieces and let cool down.

(If you prefer soft caramel candies, add 15-20g powdered sugar just before the boil ends)

Hmm ... KAh! Candy!

Due to the high temperatures when the sugar is heated, chemical reactions take place, most of which have not yet been clarified. What is certain, however, is that at these temperatures some of the sugar molecules break down into smaller molecules, which then combine to form new compounds.

 

Didactic forum on this topic

 

How can you get a
recognize chemical reaction?
Brief test: How can you
recognize a chemical reaction?