QUOTE FOR THE DAY

Our lives are not determined by what happens to us but by how we react to what happens, not by what life brings to us, but by the attitude we bring to life. A positive attitude causes a chain reaction of positive thoughts, events, and outcomes. It is a catalyst, a spark that creates extraordinary results.

- ANON-.

WATER

THE MAGIC MOLECULE

Many important chemical reactions occur in solution.

A solution is a homogeneous mixture. It occurs when one substance (solute) is dispersed through another substance (solvent) – the solute is dissolved in the solvent.

If we sample any part of a solution, we will find the concentration of the solute to be the same.

A good example would be sugar dissolved in water. We can change the concentration by adding more sugar, so it is a homogeneous mixture.

We can have solid, liquid, and gaseous solutions.

An example of a solid solution would be an alloy. If we mix nickel, chromium, and iron in the liquid state and allow the mixture to solidify, we have an alloy, an example of a solid solution.

An example of a gaseous solution would be air.

We will be concerned first with water solutions, because most of the chemical reactions that are important to life take place in water.

The human body is from 55 to 78% water.

In addition to life being carbon based, it is also water based.

IN A TRUE SOLUTION, THE SOLUTE IS DISTRIBUTED IN THE SOLVENT IN THE FORM OF ATOMS, IONS, OR MOLECULES.

IF THE PARTICLES ARE LARGER, BUT NOT LARGE ENOUGH TO SETTLE OUT, YOU HAVE A COLLOID.

IF THE PARTICLES ARE LARGE ENOUGH TO SETTLE OUT OVER TIME, YOU HAVE A SUSPENSION.

A COLLOID OR A SUSPENSION WILL SCATTER LIGHT. THIS IS CALLED THE TYNDALL EFFECT.

WATER IS FORMED WHEN HYDROGEN AND OXYGEN SHARE ELECTRONS.

WATER IS A POLAR MOLECULE.THIS MEANS THAT THE ELECTRONS ARE NOT SHARED THE SAME WAY.

OXYGEN GETS A BIGGER SHARE, SO IT HAS A SLIGHT NEGATIVE CHARGE.

THE HYDROGENS HAVE A SMALLER SHARE, SO THEY HAVE A SLIGHT POSITIVE CHARGE.

WHAT THIS MEANS IS THAT WHEN YOU PUT A BUNCH OF WATER MOLECULES TOGETHER, THE POSITIVE ENDS OF ONE WILL BE ATTRACTED TO THE NEGATIVE ENDS OF OTHERS.

THIS IS LIKE A GLUE THAT HOLDS THE MOLECULES CLOSER TOGETHER THAN WOULD BE THE CASE IF THEY DID NOT HAVE THE CHARGES.

THIS “STICKEYNESS” GIVES WATER SOME UNUSUAL PROPERTIES.

WE CALL MOLECULES THAT HAVE NEGATIVE ENDS AND POSITIVE ENDS POLAR MOLECULES.

COMPOUNDS THAT ARE BUILT OF POLAR MOLECULES HAVE ADDITIONAL ATTRACTIONS BETWEEN THE MOLECULES THAT OTHER COMPOUNDS DON’T.

WATER HAS A VERY LOW MASS, BUT IT HAS A VERY HIGH FREEZING POINT AND BOILING POING FOR SUCH A LIGHT MOLECULE.

Melting Point Boiling Point

Water, H2O Oo C 100o C

Methane, CH4 -184o C -162o C

Water molecules

OTHER UNUSUAL PROPERTIES OF WATER:

1. HIGH HEAT OF FUSION (heat to melt)

2. HIGH HEAT OF VAPORIZATION (heat to boil)

3. HIGH SURFACE TENSION

4. SOLID IS LESS DENSE (ICE FLOATS)

5. WATER DISSOLVES OTHER POLAR MOLECULES AND SALTS

SURFACE TENSION IS DUE TO UNEQUAL FORCES AT THE SURFACE OF WATER.

THERE ARE NO MOLECULES ABOVE THE SURFACE, SO ALL OF THE FORCES ARE DIRECTED TO THE SIDES AND DOWN.

IT IS THIS UNBALANCE OF FORCES AT THE SURFACE THAT MAKES WATER DROPLETS SPHERICAL.

BECAUSE OF THIS UNBALANCE OF FORCES AT THE SURFACE, YOU ALSO HAVE TO USE ENERGY TO EXPAND THE SURFACE OF WATER.

THIS MAKES IT POSSIBLE FOR WATER STRIDERS TO WALK ON WATER.

THIS UNBALANCE OF FORCES AT THE SURFACE ALSO MEANS THAT WATER WILL RISE IN A CAPILLARY TUBE.

THIS SAME EFFECT IS WHAT CAUSES WATER TO RISE IF YOU DIP THE END OF A PAPER TOWEL IN WATER.

ARRANGEMENT OF WATER MOLECULES IN ICE

Water molecules in ice

WATER EXISTS IN ALL THREE PHYSICAL STATES IN NATURE:

1. SOLID

2. LIQUID

3. VAPOR (GAS)

IF YOU HEAT ICE, THE TEMPERATURE WILL RISE TO THE MELTING POINT.

AT THAT POINT, THE MOLECULES GET ENOUGH ENERGY TO BREAK SOME OF THE POLAR BONDS BETWEEN THEM.

THE WATER BECOMES MORE FLUID, AND MELTING OCCURS.

AS YOU CONTINUE TO ADD ENERGY, THE MOLECULES GAIN ENERGY AND MOVE FASTER RELATIVE TO EACH OTHER.

EVENTUALLY, YOU REACH THE BOILING POINT, AND THE MOLECULES HAVE ENOUGH ENERGY TO COMPLETELY SEPARATE AND BECOME GAS.

BOILING OCCURS.

http://wine1.sb.fsu.edu/chm1045/notes/Forces/State/Forces04.htm

http://wine1.sb.fsu.edu/chm1045/notes/Forces/State/Forces04.htm

iceberg

SOLID AND LIQUID WATER

ICEBERG ABOVE AND BELOW WATER