1. Scientific Method
A logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypothesis, and formulating theories that are supported by data.

2. Observation and Collecting Data
Starts with observation- noting and recording facts by using senses.
Often involves collecting data
Either qualitative (quality) or quantitative (quantity)
Ex/ a heavy car vs kg car
Cold room vs. the room is 21.0 degrees Celsius
Which form of data is more “measurable”?

3. Formulating Hypotheses
Hypothesis - a testable statement
Serves as a basis for carrying out further experiments.
Often drafted as “if-then” statements
Ex/ If I don’t do my homework, then I will still get a good grade on the test.

4. Testing Hypotheses Requires experimentation
Controls - remain constant throughout experiment
Variables - any condition that changes
If testing reveals predictions not correct, hypothesis must be modified

5. Theorizing When data suggests hypothesis is correct.
Scientists may explain by constructing a model.
Ex. Bohr’s atomic model
Models are usually part of a theory
Theories are broad generalizations that explain a body of facts or phenomena.

6. Observations Hypothesis Experiment Cycle repeats many times.
The hypothesis gets more and more certain.
Becomes a theory
A thoroughly tested model that explains why things behave a certain way.
Observations
Hypothesis
Experiment

7. Theory can never be proven.
Useful because they predict behavior
Help us form mental pictures of processes (models)
Observations
Hypothesis
Experiment

8. Observations Hypothesis Experiment
Another outcome is that certain behavior is repeated many times
Scientific Law is developed
Description of how things behave
Law - how (mathematical)
Theory- why
Observations
Hypothesis
Experiment

9. Example Getting a date :
Observation : A lot of athletes have girlfriends

10. Hypothesis: If I play sports, I will get a date.

11. Test: Join the golf team.

12. Data either supports or does not support
If it does not support the hypothesis, the hypothesis must be modified or rejected.
If it supports the hypothesis, we have a theory and scientists publish result

13. Types of measurement Quantitative- use numbers to describe
Qualitative- use description without numbers

14. Scientists prefer Quantitative- easy check
Easy to agree upon, no personal bias
The measuring instrument limits how good the measurement is

15. The Metric System
An easy way to measure

16. The Metric System Easier to use because it is a decimal system
Every conversion is by some power of 10.
A metric unit has two parts
A prefix and a base unit.
prefix tells you how many times to divide or multiply by 10.

17. Base Units Length - meter more than a yard - m
Mass - grams - a bout a raisin - g
Time - second - s
Temperature - Kelvin or ºCelsius K or ˚C
Energy - Joules- J
Volume - Liter - half f a two liter bottle- L
Amount of substance - mole - mol

18. Prefixes (Larger) tera T 1000 000 000 000 times larger
giga G times larger
kilo k 1000 times larger
hecto h 100 times larger
deka da 10 times larger

19. Prefixes (smaller) deci d 1/10 centi c 1/100 milli m 1/1000
micro  1/
nano n 1/
pico p 1/
femto f 1/
atto a 1/

20. Frame of references kilometer - about 0.6 miles
centimeter -about the width of a paper clip
millimeter - the width of a paper clip wire

21. Volume calculated by multiplying L x W x H
Liter is equivalent to one cubic decimeter
so 1 L = 10 cm x 10 cm x 10 cm
1 L = 1000 cm3
1/1000 L = 1 cm3
1 mL = 1 cm3

22. Volume 1 L about 1/4 of a gallon - a quart
1 mL is about 20 drops of water or 1 sugar cube

23. Mass weight is a force, Mass is the amount of matter.
1gram is defined as the mass of 1 cm3 of water at 4 ºC.
1000 g = 1000 cm3 of water
1 kg = 1 L of water

24. Mass 1 kg = 2.5 lbs 1 g = 1 paper clip
1 mg = 10 grains of salt or 2 drops of water.

25. Which is heavier: A pound of feathers or a pound of lead?
They both weigh the same.
Which is more dense?
What is density?
How does it occur?

26. Density how heavy something is for its size
the ratio of mass to volume for a substance
D = M / V
Independent of how much of it you have
gold - high density
air low density.

27. Calculating units will be g/mL or g/cm3
A piece of wood has a mass of 11.2 g and a volume of 23 mL what is the density?
A piece of wood has a density of 0.93 g/mL and a volume of 23 mL what is the mass?

28. Calculating
A piece of wood has a density of 0.93 g/mL and a mass of 23 g what is the volume?

29. Floating Lower density floats on higher density.
Ice is less dense than water.
Most wood is less dense than water
Helium is less dense than Oxygen, Nitrogen, and Carbon Dioxide
A ship is less dense than water.
What gases are found in Earth’s upper atmosphere?

30. Density of water 1 g of water is 1 mL of water @ 4 ˚C
density of water is .997 room temperature (~25˚C)

31. Measuring Temperature
0ºC
Measuring Temperature
Celsius scale.
water freezes at 0ºC
water boils at 100ºC
body temperature 37ºC
room temperature ºC

32. Measuring Temperature
273 K
Measuring Temperature
Kelvin starts at absolute zero (-273 º C)
degrees are the same size
C = K -273
K = C + 273
Kelvin is always bigger.
Kelvin can never be negative.

33. Temperature is different than heat.
Temperature is a measure of how hot (or cold) something is; specifically, a measure of the average kinetic energy of the particles in an object.
Heat is the energy transferred between objects that are at different temperatures

34. Units of heat are calories or Joules
1 calorie is the amount of heat needed to raise the temperature of 1 gram of water by 1ºC
a food Calorie is really a kilocalorie
1 calorie = 4.18 J

35. Specific heat c Some things heat up easily
some take a great deal of energy to change their temperature.
The Specific Heat Capacity amount of heat to change the temperature of 1 g of a substance by 1ºC
specific heat SH

36. Converting Convert using conversion factors and dimensional analysis.
A conversion factor is a ratio derived from the equality between two different units that can be used to convert from one unit to the other
Ex/ 1 m/10 dm
Dimensional analysis is a mathematical technique that allows you to use units to solve problems involving measurements.
Ex/ convert 1.54 kg to g
Convert 3.78 cm to inches
Figure out how old you are in minutes

37. Conversions Change 5.6 meters to millimeters
5.6 meters X 1000 millimeters/1 meter
Meters cancel out
Answer is left in millimeters

38. Conversions convert 25 mg to grams convert 0.45 km to mm
convert 35 mL to liters

39. How good are the measurements?
Scientists use two word to describe how good the measurements are
Accuracy- how close the measurement is to the actual value
Precision- how well can the measurement be repeated

40. Differences
Accuracy can be true of an individual measurement or the average of several
Precision requires several measurements before anything can be said about it
examples

41. Let’s use a golf analogy

42. Accurate? No
Precise?
Yes

43. Accurate?
Yes
Precise?
Yes

44. Precise? No
Accurate?
Maybe?

45. Accurate?
Yes
Precise?
We cant say!

46. In terms of measurement
Three students measure the room to be m, 10.3 m and 10.4 m across.
Were they precise?
Were they accurate?

47. Significant figures (sig figs)
When we measure something, we can (and do) always estimate between the smallest marks. 2 1 3 4 5

48. Significant figures (sig figs)
The better marks the better we can estimate.
Scientist always understand that the last number measured is actually an estimate 1 2 3 4 5

49. Sig Figs
What is the smallest mark on the ruler that measures cm?
142 cm?
140 cm?
Here there’s a problem does the zero count or not?
They needed a set of rules to decide which zeros count.
All other numbers do count

50. Which zeros count?
Those at the end of a number before the decimal point don’t count
12400
If the number is smaller than one, zeros before the first number don’t count
0.045

51. Which zeros count? Zeros between other sig figs do. 1002
zeros at the end of a number after the decimal point do count
If they are holding places, they don’t.
If they are measured (or estimated) they do

52. Sig Figs Only measurements have sig figs. Counted numbers are exact
A dozen is exactly 12
There are 28 people in this class
If it is exact the number has infinite accuracy, so it is considered to have infinite sig figs

53. Sig figs. How many sig figs in the following measurements? 458 g

54. Sig Figs.
405.0 g
4050 g
0.450 g g g

55. Problems 50 is only 1 significant figure
if it really has two, how can I write it?
A zero at the end only counts after the decimal place
Scientific notation
5.0 x 101
now the zero counts.

56. Rules for Calculations
We use sig fig rules in calculations because we can only be as precise as our least precise measurement.

57. Adding and subtracting with sig figs
The last sig fig in a measurement is an estimate.
Your answer when you add or subtract can not be better than your worst estimate.
have to round it to the least place of the measurement in the problem

58. For example
27.93
6.4 +
First line up the decimal places
27.93
6.4 +
27.93
6.4
Then do the adding
Find the estimated numbers in the problem
34.33
This answer must be rounded to the tenths place

59. Rounding rules look at the number behind the one you’re rounding.
If it is 0 to 4 don’t change it
If it is 5 to 9 make it one bigger
round to four sig figs
to three sig figs
to two sig figs
to one sig fig

60. Practice
6.0 x x 103
6.0 x x 10-3

61. Multiplication and Division
Rule is simpler
Same number of sig figs in the answer as the least in the question
3.6 x 653
2350.8
3.6 has 2 s.f. 653 has 3 s.f.
answer can only have 2 s.f.
2400

62. Multiplication and Division
Same rules for division
practice
4.5 / 6.245
4.5 x 6.245
x .043
3.876 / 1983
16547 / 714