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Science 331 |
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| Fall 2004 |
Lecture/Activity |
Office: SA560a |
| Notes: 13 October |
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Phone: x 5719
Home: 822-1116 |
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e-mail: rap1 |
Safety
Safety Lecture and Quiz
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!) and we will not cover it.
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 problems:
- H2 balloons
- Candle flame.
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"!
What is matter? Stuff. Has mass and occupies space.
Elements Exercise
Elements are substances which cannot be broken down
further into simpler substances.
Atoms are the smallest constituents of elements.
Some important terms which you must know are:
- Atomic number (Z) - the number of protons in the nucleus.
This number is characteristic of a given element.
- Atomic mass number (A) - the sum of the protons and
neutrons in a given atom (p + n).
- Atomic mass - the actual mass of an average
atom in a sample. The characteristic atomic masses for Earth
are shown on periodic tables.
- Atomic Mass Unit: the atomic mass unit = amu is a
unit of mass for atoms. It is defined as 1/12 the mass of one
atom of 12C, where the mass of 12C is defined
as 12 exactly.
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":
- How many elements are gaseous? (symbols & numbers)
- How many elements are liquid? (symbols & numbers)
- How many elements are colored? (For this exercise consider
white, silver, grey and black to have no color.)
- List (symbols & numbers) the colored elements and their
colors.
- What is the highest number for a non-radioactive element?
- How many elements are non-radioactive?
- How many elements would you guess are metals? Why?
- Look up the term element in your text and/or a dictionary
and define it:
- What determines what element an atom is?
- What is an isotope? What distinguishes the isotopes of a
single element?
© R A Paselk
Last modified 13 October 2004
