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Water
Water on Earth
Changes of state in the nature: the water cycle
Water in human body
Test for water
Properties of water in different states
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Boiling water
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Changes of state: mass and volume
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Mixtures and solutions
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Distillation
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Dissolving a solid in water
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Miscibility in water

Mass and volume
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Mass of a liter of water

Air and atmosphere
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The electrical neutrality of the atom

Combustions
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How to distinguish metals ?

Corrosion of metals

Electrical conductivity of solid materials

Electrons and free electrons

Electric current in metals
Ions
The conductivity of aqueous solutions
Aqueous solutions and ions
The direction of movement of ions
Formation of ions
Tests for ions
Acidic and basic solutions
pH of aqueous solutions
Ions in acidic and basic solutions
Dilution of acids and bases
Composition of hydrochloric acid
Chemical reaction between iron and hydrochloric acid

Electrochemical cells and chemical energy
Chemical reaction beteween a copper sulphate solution and zinc
Copper sulfate and zinc battery
Basics of electrochemical cell



















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Electrochemical cells and chemical energy

Chemical reaction beteween a copper sulphate solution and zinc

       
The purpose is to study the chemical transformation between metallic zinc and a solution of copper sulphate.

Realization: zinc powder is placed in a test tube. The tube is stirred and then the result is observed.

Chemical reaction between zinc and a copper sulphate solution


observations:
- Touching the test tube we can feel that it is abnormally hot. A temperature measurement with a thermometer can be used to confirm that the temperature of the solution is significantly higher after mixing than before.

- The solution of copper sulphate that is initially blue becomes almost colorless.
- Zinc powder changes color: it takes an orange color which recalls that of copper
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Additional test:
A test is performed to identify ions in solution.
Sodium hydroxide is added and a precipitate is obtained which is not blue but white.
This test suggests that copper ions have disappeared from the aqueous solution and have been replaced with zinc ions which form a white precipitate with sodium hydroxide


Test for zinc ion

Interpretation and synthesis:
The disappearance of the blue color and the absence of blue precipitate during the test indicates that the copper ions have been consumed. These ions have formed metallic copper on the remaining zinc powder.
The test also indicates that zinc ions have formed from zinc atoms.

Sulphate ions don't undergo any particular modification and remain in solution after the chemical transformation where they form, with zinc ions, a solution of zinc sulfate.

These transformations can be summarized by the following chemical reaction:

Zinc + copper sulphate copper + zinc sulphate

This chemical transformation is also accompanied by heat release.
The chemical energy present in the reactants is partly released as heat energy.


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