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

Chemistry

Electricity

Optics

Mechanics
Mechanics lessons
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
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
Decantation
Centrifugation
Filtration
Vaporization of water
Distillation
Chromatography
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
Atmosphere
Earth's atmosphere protect us
Threats to the Earth's atmosphere
Composition of air
Air and life
Pressure
Atoms and molecules
Molecules
Molecules in mixtures and pure substances
Molecules and states of matter
Atoms
Composition of molecules
Constituents of the atoms
The electrical neutrality of the atom

Combustions
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
Metals

Most common metals

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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Water

Properties of water in different sates

   

The essential about water and its different states

The free surface of water


What is a free surface?
A liquid is in contact with its receptacle but also with air. The liquid surface in contact with air is also called " free surface ".

Diagram: free surface of water:

Free surface of water in a beaker


In a stationary vessel, the free surface of water is always flat and horizontal whatever the inclination of the vessel.

Diagram: free surface of water in an inclined beaker
Horizontal free surface of water in inclinated beakers


Properties of the liquids

Diagram: water in a beaker, an erlenmeyer and a measuring cylinder
Volume of water in a beaker, an erlenmeyer and a measuring cylinder

If liquid water is transferred into graduated containers of different shapes, it can be observed that water takes the same shape as its container but keeps the same volume.
Liquid water has its own volume but no own shape.

Properties of solids

If an ice cube is poured from one container to another it keeps its shape and its volume
Solid water has its own volume and its own shape.

Properties of gases

A gas enclosed in a container occupies all available space: it thus has no own shape.

If some air is enclosed in a plugged syringe its piston can be moved to reduce or to increase the volume of the air: air therefore has no own volume.

To sum up:
Own shape Own volume
Solid Yes Yes
Liquid No Yes
Gaz No No

Comment:
The sand (like other substances composed of powder or grains) has properties that are close to those of liquids.
Each grain has a own shape and a own volume but the sand takes the shape its receptacle: it therefore has no own form (like a liquid).
However unlike liquids, its free surface isn't necessarily flat and horizontal.

Learn more about water and its properties

Basic properties of fluids and definition:
http://www.brighthub.com/engineering/civil/articles/42883.aspx

Properties of gases:
http://www.chemtutor.com/gases.htm

Properties of liquids, solids and gases explained for grade 4:
http://www.nyu.edu/pages/mathmol/textbook/statesofmatter.html




 


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