Water

Wikipedia  water http://en.wikipedia.org/wiki/Water

water molecule http://en.wikipedia.org/wiki/Water_(molecule)

water vapor http://en.wikipedia.org/wiki/Water_vapor

The composition of the atmosphere is usually given as the composition of dry air.  78% Nitrogen, 21% Oxygen, 1 % Argon plus trace gasses adds to 100%

However, water can make up a variable part of the composition of air depending on the humidity, up to 4%.

Here is an activity that explores the composition of air. http://www.exo.net/~pauld/workshops/weather/earthatmcompositionrice.htm

Water is a polar molecule. It is an electric dipole with a negative charge on its oxygen and a positive charge on its hydrogens.

This means that water can be attracted by electrostatically charged objects. http://www.exo.net/~pauld/activities/sweden/electrostaticwaterattract.html

There is a classic activity where a falling thin stream of water is attracted to an electrically charged object. http://www.chem.umn.edu/outreach/Card-BendWater.html

Water has a surface tension, light metal coins can be floated on water http://www.exo.net/~pauld/activities/patterns/FloatingCoins.html

Dry ice bits can also be floted on water. http://www.exo.net/~pauld/activities/astronomy/icybodies.html

The surface tension of water can be used to drive convection http://www.exo.net/~pauld/activities/fluids/soapconvectionmilk.html

Solid Liquid Gas  a thought experiment http://www.exo.net/~pauld/workshops/weather/solidliquidgas.html

Water will boil at 100 °C at atmospheric pressure. It will boil at lower temperatures at lower pressures. It will boil at 0°C at 6 millibars pressure.

Boil water at room temperature in a syringe. http://www.exo.net/~pauld/activities/boylingwater/boylingwater.html

This can also be done with a vacuum pump http://www.exo.net/~pauld/activities/astronomy/mars/martianwater.html

The celcius scale of temperature is defined in relation to the kelvin scale, the triple point of water where solid liquid and gas water can exist in equilibrium is defined as 273.16 K, and 6.1173 millibars.

Super cooled water http://www.exo.net/~pauld/workshops/weather/supercooledwaterballoon.htm

Temperature  Have people line up by hand temperature. http://www.exo.net/~pauld/activities/thermodynamics/feeltemperature.htm

Pressure  Feel the presure versus depth of water http://www.exo.net/~pauld/workshops/fluids/feelpressure.htm

Water can be melted by the application of salt, ice balloons. http://www.exo.net/~pauld/activities/patterns/iceballoonmeanders.html

A syphon http://www.exo.net/~pauld/physics/syphon/syphonphysics.htm

Water Cycle Video http://www.exo.net/~pauld/activities/watercyclevideo.html

Just for fun make a lava lamp with water oil and salt http://www.exo.net/~pauld/activities/fluids/lavalampoilsalt.htm