CH110A

Chapter 1 Notes

Why are we here?

Legislation is passed, judgements are made, about what to make, what to eat, how to produce food and materials, etc, etc, without any knowlege of the science behind the emotion.

Chemistry

The study of the COMPOSITION, STRUCTURE, and PROPERTIES of matter and the CHANGES that occur in matter.

THE BIG SECRET

Treat chemistry as a second language. IF YOU EVER DON'T UNDERSTAND A WORD YOU READ OR A WORD I SAY IN CLASS LOOK IT UP/ASK FOR CLARIFICATION.

Matter

Everything in the physical world....everything we see, touch, taste, etc.

Macroscopic

Able to be seen with the naked eye. Normally, we are dealing with things too small to be seen (MICROSCOPIC) so we "scale up" our discussion to numbers and sizes we can "put our hands on".

Atom

Smallest DISTINCTIVE unit of matter (composed of protons (positively charged), electrons (negatively charged), and neutrons (no charge)). An atom is the smallest unit of matter which retains the same properties of the bulk element. There are other subatomic particles (generally studied in advanced Physical Chemistry or Particle Physics) which we do not cover.

Molecule

A fixed combination of atoms

Composition

Type and number of atoms in a COMPOUND. (See your Chem CDX CD for a demonstration)
All samples of a compound have the same composition; all samples have the same proportions by mass of the elements present according to Proust's Law of Definite Proportions. (see chapter 2, page 37)

Physical change

Occurs with no change in composition

Chemical change

The formation and breaking of bonds. The former releases energy, and the latter requires energy. Composition changes.

Nuclear change

A change in the number of protons/neutrons in the nucleus of the atom. The atom becomes a different atom.

Mixtures

Can be homogeneous (uniform) or heterogeneous (nonuniform). Nonfixed composition.

Measurements

UNITS, UNITS, UNITS!!!! If your units are correct, the answer will be correct. Use dimensional analysis, factor labelling, whatever you want to call it, to convert what you are given into what you are asked for.

Precision

How close to each other a series of measurements are.

Accuracy

How close to an accepted value a measurement is.

Significant figures.

All nonzero digits are significant
Trailing digits AFTER a decimal point are significant
Trailing digits WITHOUT a decimal point are NOT significant
When performing calculations, do NOT limit the number of significant digits in your answer because of a conversion factor.
In an addition or subtraction, the answer has as many digits past the decimal point as the number with the least number of digits past the decimal point in the question.
In a multiplication or division, the answer has as many significant digits as the number with the least number of significant digits in the question.