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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



Water in human body

The essential about water in human body

Percentage of water in human body
Like all living tissues, our body contains water in various amounts:
- 75% for a baby
- 70% for one child
- 60% for an adult
Percentage of water in a human body
( diagram: percentage of water in human body )

How much water in human body ?
Previous percentages can be used to calculate the amount of water in a human body.
For instance:
- A baby whose mass is 3 kg:
 3 x 75 : 100 = 2,25 kg
This baby has 2,25 kg of water in its body ( it corresponds to 2,25 L )
- A child whose mass is 40 kg:
 40 x 70 : 100 = 28 kg
This child has 28 kg of water in its body ( it corresponds to 28 L )
- An adult whose mass is 70 kg:
 70 x 60 : 100 = 42 kg
This adult has 42 kg of water in its body ( it corresponds to 42 L )



How human body loses water ?
The water in our body is eliminated in three ways:
- By the urine (approximately 1 L per day)
- By sweating (about 0.5 L per day)
- By breathing which rejects water vapor (about 0.5 L per day)

Water balance in the body

To maintain a stable percentage of water in the body and avoid dehydration, lost water must be replaced:
Therefore in total 2L of water must be consumed per day: 1.5 from drinks and the balance being provided by food.


Learn more about water in human body

The water in you: more detail about percentage of water in various parts of human body and factors that may affect it.

The healt benefit if water: how water may affect healt in various ways

Drinking too much can kill: article from scientific american that explain water should not be consummed with excess.

Water losses of the human body and how to compensate for them: Various factors that may cause losses of water and how to balance them