LESSON PLAN

 

Name: Chad Springer

 

Title of lesson: Oil and Water Properties

                                                                                                                       

Length of lesson: 1 hours

 

Description of the class:

                     Name of course: Chemistry                                                          

                     Grade level: 10-12

                     Honors or regular: Regular

 

Source of the lesson:                                                                               

http://www.lenntech.com/water-chemistry-FAQ.htm 

 

I.       Overview
This lesson covers the basic physical and chemical properties water.  This lesson also gives a very basic introduction to chemical properties of oil.  
 
II.  Performance or learner outcomes

            Students will be able to

Composition

Mass

Phases

Hydrogen bonding and its role

Water’s role as a solvent

                        Composition

                        Non-solubility in water

                       

 

 

 

 

Important Vocabulary Terms

            Boiling Point

            Melting Point

            Hydrophobic

            Hydrophilic

            Soluble

 

 

 

 

 

Part I

Properties of Water

What is water?  What is Oil?

Water is a very important substance, as it makes up the larger part of an organism's body. But what exactly is water? Inside the body of a human being there is a skeleton, which makes your body solid and makes sure you can stand up without falling apart. Water is also a kind of skeleton. It consists of tiny particles, the atoms, just like every other substance on earth. One of these atoms is called hydrogen and the other is called oxygen. As you probably know the air that we breathe also contains oxygen. One particle of water is called a molecule. When lots of water molecules melt together we can see the water and drink it or use it, for instance to flush a toilet. 

          Crude oil is a mixture of many different chemicals.  These chemicals are of similar chemical compositions.  The components of oil have long carbon chains that form when carbon bonds to itself.  Components of oil such as propane and butane are very small and evaporate quickly from oil when exposed to air (this is because they have low boiling points).  Other components can be huge in comparison and have high molecular weights, such as waxy substances.  When oil is refined at refineries such as the ones in Corpus Christi, the different components of crude oil are separated and refined for use by us.  Some of the components become gasoline, wax, lighter fluid, etc….

How is a water molecule built up?

A water molecule consists of three atoms; an oxygen atom and two hydrogen atoms, which are bond together like little magnets. The atoms consist of matter that has a nucleus in the centre.

Briefly show what a carbon chain looks like to the students. 

How much does a mole of water or oil weigh?

Hydrogen has a relative atomic mass of 1 g/ mol and oxygen has a relative atomic mass of 16 g/ mol. Water consists of one oxygen atom and two hydrogen atoms. This means that the mass of a water molecule is 1g + 1g + 16g = 18 g/ mol.
When the number of moles of water is known, one can calculate how many grams of weight this is, by using the molar weight of water.

We can calculate the molecular weight of the components of crude oil, such as methane CH4.  It has a molecular weight of 16g/mol.  We do not calculate the molecular weight of crude oil because it is not a molecule.  Crude oil is a mixture of differing molecules/chemicals. 

 

 

 

 

In what states (phases) can water/oil be found?

Water exists in three states: solid, liquid and gaseous. At a normal temperature of about 25oC it is liquid, but below 0oC it will freeze and turn to ice. Water can be found in the gaseous state above 100oC, this is called the boiling point of water, at which water starts to evaporate. The water turns to gas and is then odourless and colourless.
How fast water evaporates depends on the temperature; if the temperature is high, water will evaporate sooner. 

Crude oil has components in different phases.  The very large components may be solid, while the very small components may be in liquid phase.  Some of the components are very volatile, meaning they have very low boiling points so they evaporate extremely quickly.  Remember the anchor video; on the tanker there was a no smoking sign; this was due to these volatile chemicals evaporating off the crude oil.  Just to put things in perspective, gasoline is less volatile than chemicals such as methane and propane. 

Why does ice float on water?

When substances freeze, usually the molecules come closer together. Water has an abnormality there: it freezes below 0oC, but when temperatures fall to 4oC, water starts to expand and as a result the density is lower. Density of a substance means the weight in kilograms of a cubic meter of a substance. When two substances are mixed but do not dissolve in one another, the substance with the lowest density floats on the other substance. In this case that substance is ice, due to the increased density of water.

How come not all substances are water-soluble?

Polarity determines if a substance is water-soluble. A polar substance is a substance that has two kinds of 'poles', as in a magnet. When another substance is also polar the poles of the substances attract each other and as a result the substances mix. A substance then dissolves in water.  An example would be dissolving salt in water. 
Substances that contain no 'poles' are called nonpolar substances. Oil for instance is a nonpolar substance, which is why oil does not dissolve in water. In fact it floats on water, just like ice, due to its smaller density.

 

How are water molecules bond together?

Hydrogen atoms are attracted to other atoms such as oxygen atoms, because the electrons are pulled closer to the oxygen atom, due to its greater attraction for electrons. As a result the oxygen atom has a slightly negative partial charge and the hydrogen atoms have a slightly positive partial charge. The slightly positively charged hydrogen atoms are then attracted to the slightly negatively charged oxygen atoms of other water molecules. These forces of attraction are called hydrogen bonds. The forces holding two molecules together in a hydrogen bond are much stronger than those between molecules and hydrocarbons. The attraction between hydrogen and oxygen atoms results in a much higher boiling point of water than anticipated for a different molecule with the same mass.
Hydrogen bonds can also be formed between atoms of hydrogen and sulphur or nitrogen, typically SH- and NH2- groups.

In this picture you can see what hydrogen bonds in water look like: