1. Introduction to Chemistry
CHEMISTRY = the study of the composition of matter, its chemical and physical changes, and the changes that accompany these changes.

2. DEMO
The Think Tube
Chemistry is all about trying to figure out things you can’t necessarily see.

3. The Nature of Science Scientific law versus theory:
Scientific law: a summary of an observed natural event.
Scientific theory: a well tested, possible explanation of a natural event.

4. The Way Science Works…
Science involves critical thinking, or applying logic and reason to observations and conclusions.
Observation vs. Inference
Observation: descriptive of what you see, hear, taste, feel, smell
Inference: an assumption made as a result of an observation (not always correct!!)

5. Variables and Controls
A variable is anything that can change in an experiment.
Independent variable: The variable being changed or controlled by the scientist.
Dependent variable: The variable being measured or observed by the scientist.
A controlled experiment tests only one variable at a time.

6. DEMO
On the Level
The Unknown Bubble

7. The Scientific Method: A series of logical steps to follow in order to solve problems.
OBSERVE
FORMULATE A QUESTION
FORM A HYPOTHESIS
DESIGN AND CONDUCT AN EXPERIMENT
MAKE OBSERVATIONS
RECORD AND ANALYZE DATA
DRAW CONCLUSIONS
FORMULATE NEW QUESTIONS and CONTINUE CYCLE

8. Making Measurements
Measurements are made in this class using SI units.
LENGTH (m): distance between 2 points
VOLUME (L): space occupied.
MASS (kg): the amount of matter in an object.
WEIGHT (N): the force with which gravity pulls on a quantity of matter.

9. Precision vs. Accuracy
Accuracy: the extent to which a measurement approaches the true value.
Precision: the degree of exactness of a measurement.
A scale may be precise to the nearest 100th of a gram, or +/- 0.01g

10. Precision vs. Accuracy
increasing precision
increasing accuracy

11. Density = mass/volume Example: M D V
What is the mass of 10 mL of a liquid that has a density of 3.76 g/mL?
d = m / v
m = dv
m = (3.76 g/mL)(10 mL)
m = 37.6 g
m = 40 g (correct # of sig. figs.) M D V

12. Coke vs. Diet Coke
Which is less dense? Meaning which will float in water?
Coke or Diet Coke?

13. WHY is Diet Coke less dense?
There is less mass in the same volume (355 mL)
Coke has 39 grams of sugar in it to sweeten it ( = 394 g)
Diet Coke only needs 0.1 g of Nutra Sweet to make is just as sweet as Coke ( = g)

14. Temperature Conversions
Temperature is a measure of the average kinetic energy in a system.
K = Kelvin
oF = degree Fahrenheit
oC = degree Celsius
R=Rankin (we won’t use this one in this class)

15. Temperature Conversions
K = oC + 273
oF = (1.8 x oC) + 32
oC = (oF – 32) / 1.8

16. Percentage Error
Calculate this value in labs where the accepted value is given.

17. Organizing Data Data is organized and presented in tables, charts, and graphs.
GRAPHING...
Graph - visual representation of data
1) title
2) x and y axis labeled
3) units for both the x and y axis
4) scale is evenly and correctly spaced for data
5) legend when appropriate

18. LINE GRAPH LINE GRAPH: best for displaying data that change.
Independent Variable: x-axis
Dependent variable: y-axis

19. BAR GRAPHS
BAR GRAPH: useful when you want to compare data for several individual items

20. PIE CHARTS
PIE CHART: ideal for displaying data that are parts of a whole.