1. Introduction to Chemistry

2.  No eating or drinking!  Wear goggles at all times!  Use common sense!

3.  All of the “stuff” in the universe is made of MATTER  Chemistry is the study of matter and the changes it undergoes.  “Why is chemistry important to me?”

4.  Matter, all the “Stuff” in the universe, has many different forms.  All matter has mass  This is different than weight.  On earth a person with a mass of 70 kg weights 154 lbs  On the moon the same 70 kg person only weights 25.5 lbs.

5.  Scientific Methods: ◦ Any systematic approach used in scientific study. ◦ An organized process used by scientists to do research.  The most important part of any scientific method is making observations.  Qualitative data: Descriptive  Quantitative data: Measurements  After making observations scientists then come up with a hypothesis.  A hypothesis is a proposed explanation for what is being observed.

6.  Experimentation  An experiment is a set of controlled observations that test the hypothesis.  scientists must carefully plan experiments in order to test their hypothesis.  In any experiment there are many different variables.

7.  Variables are quantities or conditions that can be changed.  A control is used by scientists as a basis for comparison.

8.  A Theory is an explanation of a natural phenomenon based on many observations and investigations over time.  A Law is based on scientific facts.  Law of Gravity.

10.  All scientists around the world us the SI system.  This ensures that all scientific findings are reported in the same way.  An SI base unit is a defined unit in the SI system that is based on an object or event in the physical world.

11.  There are seven SI base units.  Time: ◦ Seconds (s)  Length: ◦ Meter (m)  Mass: ◦ Kilogram (kg)  Temperature: ◦ Kelvin (K) ◦ The formula to convert from Celsius to kelvin is ◦ K = o C + 273

12.  Amount of a substance: ◦ mole (mol)  Electric current: ◦ Ampere (A)  Luminous intensity: ◦ Candela (cd)

14.  Not all things can be measured directly using SI base units.  For example to SI unit for speed is m/s. We need to measure both time and length at the same time to get speed.  Volume: The derived SI unit for volume is the Liter.

15.  Density is also a derived unit of measurement.  Density = Mass/Volume

16.  To record very small or very big numbers scientists use SCIENTIFIC NOTATION.

17.  The diameter of the sun is 1,392,00 km

18.  In order to add and subtract numbers in scientific notation, the exponents must be the same.  2.840 x 1018 J  3.146 x 1018 J  3.60 x 1017 J  1.50 x 1017 J  6.9 x 1016 J  6.565 x 1018 J

19.  For multiplication, multiply the numbers and then add the exponents.  (2 x 10 3 ) x (3 x 10 2 )  2 x 3 = 6  3 + 2 = 5  6 x 10 5  For division, divided the numbers and then subtract the exponent of the divisor from the exponent of the dividend.  (9 x 10 8 ) ÷ (3 x 10 -4 )  9 ÷ 3 = 3  8 – (-4) = 8 +4 = 12  3 x 10 12

20.  Dimensional Analysis is a systematic approach to problem solving that uses conversion factors to move, or convert, from one unit to another.  How many pizzas do you need to order if 32 people will attend a party, each person eats 3 slices of pizza, and each pizza has 8 slices?

21.  We can do the same types of conversions with SI units.  We just need to know the relationship between the units we want to convert.  Examples:  We know that there are 1000 m in 1 km.  We can rewrite this as:  1000m/1km or 1km/1000m  Then if we are given and number of meters or kilometers we can convert.  Convert 48 km into meters.

22.  All measurements contain uncertainties that affect how a calculated or measured result is presented.  Each teaspoon you measure in the kitchen contains some error.  Accuracy refers to how close a measured value is to an accepted value.  Precision refers to how close a series of measurements are to one another.

24.  When we make a measurement we always measure to the last known marking on our tool and then we make one guess.  The significant figures in these measurements are all of the known digits plus our one guess.

25.  When there is liquid in a graduated cylinder we can only know the exact measurement for sure up to a certain value.  This picture shows us definitely 50mL, definitely 51mL, and definitely 52mL.  The actual volume is somewhere between 52 and 53.  We are allowed and MUST make our best estimation of the actual volume.

28.  1. Zeros between nonzero digits are always significant. ◦ 1005 kg – Has 4 significant figures  2. Zeros at the beginning of a number are never significant. ◦ 0.02 g – Has one sig. fig. ◦ 0.0025 - Has two sig. figs.  3. Zeros at the end of a number are significant only if there is a decimal in the number. ◦ 0.0200 g – Has three sig. figs. ◦ 3.0 cm – Has two sig. figs. ◦ 100 cm – Has only one sig. fig.

29.  When we use measured quantities to do calculations, the least certain measurement limits the certainty of our calculation.  Therefore the number of significant figures in our answer is determined by the number of sig figs in the least certain number.  Rules: ◦ For addition and subtraction: The answer has the same number of decimal places as the number with the least amount of decimal places. ◦ 20.42 + 1.322 + 83.1 = 104.842, we round to 104.8 ◦ For multiplication and division: The answer has the same number of sig figs as the number with the smallest number of sig figs. ◦ 6.221 x 5.2 = 32.3492, we round to 32