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Mechanics lessons
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
States of matter
States of matter and its changes
Boiling water
Water: freezing and melting
Changes of state: mass and volume
Molecules in different states of matter

Mixtures and solutions
Heterogeneous mixtures
Homogeneous mixtures
Vaporization of water
Dissolving a solid in water
Conservation of mass on dissolving
Miscibility in water

Mass and volume
Volume and its units
Measuring volume with a graduated cylinder
Mass and its units
Measuring the mass of a liquid
Mass of a liter of water

Air and atmosphere
Earth's atmosphere protect us
Threats to the Earth's atmosphere
Composition of air
Air and life
Atoms and molecules
Molecules in mixtures and pure substances
Molecules and states of matter
Composition of molecules
Constituents of the atoms
The electrical neutrality of the atom

Basics of combustion
The combustion of carbon
The combustion of butane
Atoms and chemical reactions
Chemical reactions
Chemical equations
Law of conservation of mass
Chemical synthesis

Most common metals

How to distinguish metals ?

Corrosion of metals

Electrical conductivity of solid materials

Electrons and free electrons

Electric current in metals
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


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

- 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


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.