Humboldt State University ® Department of Chemistry

Richard A. Paselk

Science 331
Fall 2004 Lecture/Activity Office: SA560a
Notes: 25 August Phone: x 5719
Home: 822-1116
e-mail: rap1

Safety

Safety Lecture and Quiz

Elements Exercise

HSU has one of the few display collections of "large" samples of all of the elements with non-radioctive forms (isotopes). Using this display determine the following at "room temperature and pressure":

What is Chemistry?

Why Chemistry is often considered the "central science." Examples.

Chemistry is the study of matter and its transformations.

More specifically, chemistry is the scientific study of matter. So what do we mean by science? Two common "definitions":

Let's look at a couple of chemical problems:

Matter

What is matter? Stuff. Has mass and occupies space.

Mass: The measure of quantity for matter. Mass is the property of matter resulting in its inertia and and attraction via gravity.

What is matter? Stuff. Has mass and occupies space.

Mass: The measure of quantity for matter. Mass is the property of matter resulting in its inertia and and attraction via gravity.

Matter has both physical properties and chemical properties. These are properties which do not depend on the quantity of substance and therefore they can be used to identify a substance (sometimes referred to as intensive properties).

States of Matter. Matter can exist in three states under earth-surface conditions:

A fourth state of matter commonly occurs under special conditions: a plasma. A plasma is an ionized fluid - can be contained by magnetic fields.

 

Conservation Laws

Law of Conservation of Mass: Mass is neither created nor destroyed during a chemical change. (Strictly speaking there is no measurable change.) For example, if we burn gasoline (octane) in air we will get carbon dioxide and water:

C8H18 + 12 1/5 O2Æ 8 CO2 + 9 H2O

If we were to weigh (determine the mass) of the carbon and oxygen vs. the carbon dioxide and water we would find them to be identical - the masses are the same on both sides of the equation (that's why its called a chemical equation, the two sides indicate are equal). Looked at another way, if you count the atoms, the numbers of each kind of atom on each side are identical - so we can also say that atoms are conserved in chemical processes.

Law of Conservation of Energy: Energy is neither created nor destroyed in chemical processes.

Problem here of course is- What is energy? Energy is the capacity to do work. So what's work? Work occurs when an object (mass) is moved against a force. Some common forms of energy important to our study include:

Another form of energy we need to be familiar with is:

Note that these forms of energy are readily interconverted.


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© R A Paselk

Last modified 25 August 2004