WHAT IS CHEMISTRY?
- Chemistry is the science that deals with the materials of the universe, and the changes they undergo.
- Materials of the universe can be of several forms:
Gas: air, oxygen
Liquid: water, gasoline, vinegar, orange juice,
Solid: rocks, charcoal, table salt, sugar, wood, baking soda
Liquid: water, gasoline, vinegar, orange juice,
Solid: rocks, charcoal, table salt, sugar, wood, baking soda
- Some examples of changes:
Burning of charcoal
charcoal + oxygen ??? carbon dioxide
Burning of gasoline
gasoline + oxygen ??? carbon dioxide + water vapor
Fermentation of grape juice
glucose ??? ethyl alcohol + carbon dioxide
(in water) (in water)
(in water) (in water)
Souring of wine
ethyl alcohol + oxygen ??? acetic acid
(in water) (from air) (in water)
(in water) (from air) (in water)
THE SCIENTIFIC METHOD
- The scientific method is a process of creative thinking and testing aimed at objective and verifiable discoveries. It is generally composed of the following steps:
Examples:
Identify each of the following as an observation, a hypothesis, an experiment or a conclusion:
- Drinking coffee at night keeps me awake.
- I will try drinking coffee only in the morning.
- If I stop drinking coffee in the afternoon, I will
be able to sleep at night. - When I drink decaffeinated coffee, I sleep better
at night. - I am going to drink only decaffeinated coffee.
- If I stop drinking coffee in the afternoon, I will
- I sleep better at night because I stopped drinking caffeinated drinks.
- I sleep better at night because I stopped drinking
caffeinated drinks.
KEY MATH SKILLS & CONCEPTS
- Knowledge of the skills and concepts listed below are essential in your success in this course. Use the resources available at the college to brush up your knowledge of these skills and concepts at the start of the semester in order to be more successful in this course.
Calculating Percentages:
To determine a percentage, divide the parts by the total (whole) and multiply by 100. For example, if an aspirin tablet with a mass of 545 mg has 325 mg of active ingredient, the percentage of aspirin (active ingredient) in the table can be calculated as shown below:
Solving Equations:
In chemistry, we use equations that express the relationship between certain variables. Solving for the variable in these equations are important, as they represent the information desired. As an example, the steps below shown how to solve for x in the equation
combine like terms:
combine like terms:
isolate the variable
Examples:
- A bag of gumdrops contains 16 orange gumdrops, 8 yellow gumdrops and 16 black gumdrops. What is the percentage of each color of gumdrops in a bag?
- Solve each equation below for m :
a)
b)
SCIENTIFIC NOTATION
- Scientific Notation is a convenient way to express very large or very small quantities.
General form:
- Converting between decimal and scientific notation:
- Move the decimal point in the original number so that it is located after the first nonzero digit.
- Follow the new number by a multiplication sign and 10 with an exponent (power).
- The exponent is equal to the number of places that the decimal point was shifted.
- For numbers smaller than 1 , the decimal moves to the right and the power becomes negative.
Examples:
- Write 6419 in scientific notation:
- Write 0.000654 in scientific notation:
- Addition and subtraction (NOT COVERED)
- Multiplication and division :
- Change numbers to exponential form.
- Multiply or divide coefficients.
- Add exponents if multiplying, or subtract exponents if dividing.
- If needed, reconstruct answer in standard exponential notation.
Examples:
- Multiply
- Divide 30,000 by 0.006