| Chem 107 |
Fundamentals of Chemistry |
Fall 2008 |
| Lecture Notes: 25 August |
© R. Paselk 2005 |
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What is Chemistry?
Why Chemistry is often considered the "central
science." Examples.
Chemistry is the study of matter and its transformations.
- "Classical" chemistry involves mostly electron
transfers and/or interactions of charges (electron and nuclear).
As we'll see only some electrons in atoms are involved - the
outer or valence electrons of atoms.
- Nuclear chemistry is an extension of chemistry where nuclei
are transformed changing one kind of atom (element or isotope)
to another. This is a completely separate realm of phenomena,
largely unimportant in everyday life (unless you work at a nuclear
power plant!).
More specifically, chemistry is the scientific study
of matter. So what do we mean by science? Two common "definitions":
- The body of knowledge and rules/laws/theories we have discovered
regarding the natural world.
- The method of discovery and confirmation used by scientists.
Classically we describe this process as the "Scientific
Method" summarized in the steps below:
- Identify a problem based on initial observations
- Collect data via planned Observations and/or Experiments
("asking nature a question")
- "Clean" simple experiments vs. statistical inference
- Controls - everything the same except the variable of interest.
- Analyze and Evaluate results
- Hypothesis
- Theory (model)
Let's look at a couple of chemical systems:
- Candle flame
- H2 balloons.
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.
- Do not confuse mass and weight. Weight is the force acting on an object due to gravity. We often interchange these terms in conversation, but they are quite different - you have the same mass whether you are weightless in space on here on Earth (taking a shuttle flight is no substitute for a diet!). To confuse us further we call the determination of mass "weighing"!
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).
- Physical properties of substances can be observed without, in principle, changing their compositions. Physical properties include mass, color (the interaction with light), density etc. Note that physical changes such as melting, cutting, etc. do not change composition.
States of Matter. Matter can exist in three states under earth-surface conditions:
- Solid: definite shape and volume (Crystals vs. super-cooled liquids or glasses)
- Liquid: definite volume, but no defined shape - will fit to container etc.
- Gas: no definite shape or volume - will fill whatever container they are in.
- both liquids and gases are fluids.
A fourth state of matter commonly occurs under special conditions: a plasma. A plasma is an ionized fluid - can be contained by magnetic fields.
© R A Paselk
Last modified 28 August 2008
