Chemistry UNIT 1

1. Chemistry UNIT 1

2. Susie SmithAugust, 2010 Chemistry is the study of matter.

3. Scientific Method • A logical method of problem solving.

4. Steps of the Scientific Method • Making observations that lead to a question. • Forming a hypothesis to answer the question. • Testing the hypothesis by experimentation. • Making a conclusion based on the results.

5. Definitions • Observation- use of senses and devices in the lab to obtain information. • Conclusion- a statement based on observations and prior knowledge.

6. Types of observations • Quantitative- includes numbers and units. • Qualitative- does not include numbers and units. • Examples-

7. Hypothesis- an educated guess • Explains an observation. • Can be tested. • Will predict an outcome. • Must be written as a statement.

8. Experiment • Designed to test an hypothesis. • Involves variables • Is performed under controlled conditions.

9. Variables • Variables are factors that can be changed. • Control variable is a variable that is held constant. • Manipulated or independent variable is changed by the scientist. • Responding or dependent variable changes as a result of the experiment.

10. International System (SI) • Measuring system used in science (also called the MKS)

11. Length • Distance between two points • Base Unit- Meter (m) • Instrument- meter stick or metric ruler

12. Mass • Amount of matter in a substance • Base Unit- gram • SI Unit – kilogram • Instrument- triple-beam balance

13. Volume • Amount of space an object occupies • Base Unit- liter (L) • Instrument- metric ruler or graduated cylinder

14. Time • Interval between two occurances • Base Unit- second (s) • Instrument- stop watch

15. Temperature • Average kinetic energy • Base Unit- Celsius (oC) or Kelvin (K) • Instrument- thermometer.

16. Scientific Notation • Numbers are expressed in this form: • M X 10n • M is a number between 1 and less than 10. • And n is equal to an exponent.

17. How to take numbers out of scientific notation • 1 X 103 = 1000 • Positive exponents move the decimal place to the right n spaces. • 1 X 10-3 = .001 • Negative exponents move the decimal place to the left n spaces.

18. Scientific Notation • 6.2 X 104 • 1.5 X 10-2 • 2.4 X 10-5 • 7.06 X 106 • 6.0 X 106

19. How to put numbers into Scientific Notation • 6,011,000 • 0.058 • 24 • 0.009009 • 6.734114

20. Conversion Factors • One large unit = how many smaller units. • One dozen = 12 units.

21. Common Conversions • “

22. Conversions • Start every problem with the original amount. • Then use a conversion fact to convert the units of measurement to what you need. • Set up every problem as a fraction with the unit you are looking for on top and the unit you started with on bottom.

23. Practice Problems • 1 kg = ________ g • 1s = _________ ds • ________ = 1 L • ______ dollars = 100 centidollars • 100 dg = _____ g

24. How to work your calculator? • Look for EE, X10, or ^ keys on your calculator • Every calculator is different. • Make notes about how to use your calculator.

25. Practice • Convert 152 cm to m. • Use the conversion fact 1m = 100cm • 152 cm X 1m = 1.52 m 100 cm

26. Conversion Practice • Convert 62 kg to _________ g. • Convert 1700 mm to _______ m • Convert 0.0056 mm to ______km.

27. Conversions with Derived Units • Convert 570 g/L= __________ g/mL • 16 m/min = ______________ m/s • Convert 65 km/h =____________ m/s

28. Order of operations • Please Excuse My Dear Aunt Sally. • Parenthesis • Exponents • Multiply or Divide • Addition or Subtraction

29. Definitions • Accuracy- closeness of a measurement to the accepted value • Precision- the reproducibility of a measurement

30. Significant Digits • All measured digits plus 1 estimated digit • Read the smallest division on the instrument and then estimate one more digit • 3.21 cm, _____ significant digits, ____ measured and ___ is estimated.

31. Zeros and significant digits • Zeros are placeholders. • They are only significant if they are in between two non zero numbers. 906 • They are significant if they follow a non zero number and are after a decimal. 15.00 • They are not significant if they are before a decimal and before a non zero number. 0.0015 • They are significant if a bar is placed on top of the 0.

32. Rules for rounding • After multiplying or dividing • Round to the least number of significant digits • Round to the weakest link. • Ex. 420 X 100 = _________

33. Rounding • After adding and subtracting, • Round answer to 1st column containing an estimated digit • Round to the weakest column 12.001 4.02 + 3 19.021 19

34. Rule of 5’s • When a number is exactly half way between two numbers, always round to the even number. • 12.5 rounds to 12 • 11.5 rounds to 12 • 12.5001 rounds to 13

35. Scientific Method • Variable- a physical quantity which can change in the experiment • In a good experiment, only one variable is allowed to change.

36. Parts of an Experiment • Manipulated (independent) variable- is changed by the experimentor • Responding (dependent) variable- depends on the results of the experiment • Control variables- are variables that are held constant on each group.

37. Weight verses Mass • On the moon, your mass would not change, and your weight would change. • Mass- is the amount of matter an object has • kilograms • Weight- is the affect of gravity pulling on an object • Newtons

38. Scientific Method • Question • Hypothesis • Research • Experimentation • Conclusion • Retest

39. Graphing scientific data • X axis- independent variable • Y axis- dependent variable • a means “is directly proportional to”

40. Straight Line Graph y a x • y = kx , where k is a constant • Slope is y/x or rise/run

41. Inverse proportion y a 1/x • y = k/x • Graph is a hyperbola

42. Equations • When the variables of an equation are on the same side of the equal sign, the variables are inversely proportional. • When the variables of an equation are on opposite sides of the equal sign, the variables are directly proportional. • P A = F