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There are FOUR changes which can indicate that a chemical reaction has taken place are:
· A colour change
· A solid being produced / a precipitate forming
· An energy change
· A gas given off / effervescence.
Definitions
Definitions
Precipitate - Is an insoluble solid which forms when two solutions react together.
Precipitation - A chemical reaction where a precipitate forms.
Effervescence - When a reaction produces a gas and you see fizzing /bubbles.
Endothermic reaction - A reaction which gives out energy.
Exothermic reaction - A reaction which takes in energy.
Decomposes - When a chemical breaks down to form other chemicals.
The videos below illustrate some of the changes that can occur when a chemical reaction takes place.
This short video clip shows the production of a precipitate when cobalt chloride solution reacts with a solution of sodium carbonate (the mixture on the left in this video).
The precipitate (insoluble solid) formed in this reaction is called cobalt carbonate.
This video shows the colour change that occurs after copper carbonate undergoes decomposition by heating.
This video shows the effervescence produced when hydrochloric acid reacts with chalk.
This video shows the decrease in temperature when ammonium nitrate is dissolved in water. This is an endothermic process.
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