Learning physics and chemistry easily and freely - Science for elementary school, middle school and high school

Free online chemistry lesson for elementary school, middle school and high school.


Mixtures and solutions


1) Vaporization of mineral water

After the vaporization of a mineral water, some whitish compounds form in the container: these are minerals
During vaporization water changes of state but minerals keep their solid state and they form crystals

2) In which cases can a vaporization be useful ?

The vaporization can be used to recover the solid compounds dissolved in water since they are not vaporized but they return to their original solid appearance.
Example: In the salt marshes, vaporization is used to recover the salt contained in seawater.

We can therefore use the vaporization in order to get solid compounds dissolved in water like salt, minerals, sugar etc.

3) What is pure water ?

Given that the vaporisation reveals the presence of minerals, it means that water is not pure.
In chemistry we say that a substance is pure if hasn't been mixed with other substances.
If water is mixed with mineral salts it is therefore no longer pure.

It should not be confused pure water with potable water. A potable water is a water which consumption does not represent a health risk and this does not preclude the presence of minerals that are even essential to human body.

Science class

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
Volumetric mass density

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


©2021 Physics and chemistry