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.


Air and atmosphere

Threats to the Earth's atmosphere

The atmosphere is polluted by gases that humans produce (cars, industries etc).

- The fumes produced during combustions consist of microparticles that are dispersed into the air. These fumes are responsible for the blackening of the facades of buildings and their degradation.

- Acid rains form after releases to air of nitrogen oxides and sulfur oxides. These rains are harmful to vegetation and can destroy entire forests. They can also damage some building materials (marble, iron, aluminum, zinc). The limitation of emissions of sulfur oxides and nitrogen oxides has helped reduce this phenomenon.

- Destruction of the ozone layer is caused by chlorinated compounds released into the air. The ozone layer has regularly regressed: its thickness decreases and even tends to disappear completely at the poles.

- The amplification of greenhouse effect leads to a general increase in temperatures.
The greenhouse effect is a natural phenomenon necessary to maintain temperatures favorable for life on Earth but the rejection of some gases (mainly carbon dioxide and methane) amplifies it.
 If this rise of temperatures continues it will be responsible for dramatic changes. This change may:
- favors the expansion of arid areas
- multiplies extreme weather events such as cyclones
- changes vegetation
- causes a rise in sea level making disappear many coastal areas and islands,
- rises acidity of oceans and make disappear many marine species.

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