Question

Define a chemicals reaction. State four observation which help us to determine that a chemical reactions has taken place. Write one example of each observation with a chemical equation

Answer 1

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What are 4 possible clues that a chemical reaction has taken place?

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EXPERT ANSWERS

JEEW-M | CERTIFIED EDUCATOR

There are several observations that we can identify some chemical reaction have taken place with in a system.

Change in temperature
-usually when a reaction takes place heat will be absorbed or released which result in a temperature change.
-eg: put a piece of sodium in water. you will feel or observe that the temperature is increased

 

Change in colour
-Some times we see a colour change in the media when a reaction takes place.
-eg:put NaOH and solution to a river water sample.you will see the color will change to brown

 

Emission of gas
-sometime when a reaction took place a gas can be removed from the system
-eg:put a piece of sodium in water. you will observe that a gas is emitting by the forming of bubbles

 

smell or odor
-When some reactions take place the formation of some substances can give us a smell or odor.
-eg: Add HCl to a FeS solution. You will taste the strong odor of 

 

Other than this there are several clues we can identify that a chemical reaction had taken place.

Change in PH

Dissolving of reactants

Forming of precipitates

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