Chap 2: Measurements Chap 2: Measurements and Calculationsand Calculations

Notes #1: Scientific Method Notes #1: Scientific Method

Today’s Date

Discussion

1. What steps might a detective take to solve a case?

2. How would you determine the best way to get to school?

3. How would the two above processes be similar to how a scientist would make discoveries?

How are scientific discoveries made?

A. serendipity- discovery made by accident while looking for something else*Ex: -finding a dollar, while looking for a sock

-discovery of Teflon-coating on windshields

B. trial and error

Movie

movie-discovery by trial and error or accident.asf

C. scientific method- logical approach to solving problems-exact steps may vary– its NOT a fixed process*HO: Sci. Method

Activity: Observation1. The scientific method deals with making

good observations and collecting good data—being observant is a mark of a good scientist!!

2. In your notebook under the title “Observations”, write down as many observations of the object as you can in 1 minute. Use your senses (smell, hearing, seeing). Also, try to estimate some data (such as height, width, etc…).

3. Make sure you observe w/o prejudges. Do not make inferences or interpretations. Make observations!!

Discussion Look at your observations of the potato

“candle”.1. Give me some qualitative observations you made.2. What could have been some you could have made, if you were allowed to observe it closer?3. Give me some quantitative observations you made.4. What could have been some you could have made, if you were allowed to observe it closer?

Discussion Atomic Theory- explains ideas about the

atom. It has changed many times thru history.

Law of Gravitation- describes gravity, but as of right now there is NO explanation for it.

movie-Scientific Method.asf*What is wrong with 1 of the statements from

the movie?

Chap 2: Measurements Chap 2: Measurements and Calculationsand Calculations

Notes #2: Measurements Notes #2: Measurements (Quantitative Data)(Quantitative Data)

Today’s Date

Discussion

1. Who in here wants 100?

2. What does the number 100 mean in the above question?

Measurement basics

A. Measurements without units are MEANINGLESS!!

Activity

1. Measure the length of your desk using your palms and fingers. Write down your measurements.

2. Compare your results to 2 people you are sitting near.

3. What did you notice about your measurements?

B. Must have standard measuring devices!!

*Read pg 33, 5th paragraph1. Who keeps track of our standards and

styles for measuring?2. Why do we not use commas in

numbers in science class?

*Look at pg 34, Table 1– look at the standards

Movie movie-History of Measurement.asf

Le Systeme International d’Unites (SI)

A. based on metric system

B. US is only major country NOT using SI*Metric Conversion Act passed in 1975– US agreed to convert to SI on voluntary basis

*HO: Metric System Base Units, …-look at pg 35, Cross-Disciplinary box-look at pg 36, Table 3 (Derived Units)

Movie movie-Metric System.asf

C. SI symbols and names:1. write symbols:

a. nanonseconds- b. gigagram-

c. dekaliter- d. micrometer-

2. write names:a. mm- b. Mm-

c. m- d. dL-

Temperature Scales Used in Science

A. Celsius (◦C)-increments equivalent in size to Kelvins, but represented by different numbers

B. Kelvin (K)1. standard SI unit of temp2. Absolute zero (0 K)- coldest temp. possible; temp. at which everything would be frozen

*no movement of atoms

Discussion: Temp. Transparency

Compare 3 temp. scales for water:1. Boiling temp

2. Freezing temp

3. Coldest temp possible

Chap 2: Measurements Chap 2: Measurements and Calculationsand Calculations

Notes #3: ConversionsNotes #3: Conversions

Today’s Date

Activity

1. Using a ruler, measure the front cover of your Chem I book from top to bottom in inches than in centimeters.-Compare inch value to centimeter value-Compare 1 inch to 1 cm on ruler.

2. Explain why the numbers are different even though they are measuring the same dimension.

Discussion

1. We can relate measurements made in English system to unit in the SI system:

length: 1.0936 yard = 1 m

2. We can relate measurements made in an SI unit to another SI unit:

length: 1 m = 1000 mm

3. We can do this mathematically using….

Dimensional Analysis

A. Def- method to convert from one unit to another using conversion factors

B. conversion factors- equivalents between differing units written as a ratio

C. HO: SI Units and Conversion Factors*highlight the SI standard units listed under each dimension

Discussion1. When you multiply by 1 do you change

the number?Ex: 2 m x 1 = 2 m

2. When you use conversion factors you are multiplying by 1, thus we are NOT changing the measurement only the value to which it is being compared:

Ex: 1 m = 1000 mm 1 = 1 m

1000 mm4000 mm x 1m = 4 m

1000 mm

Discussion

1. However, not all conversions are done using dimensional analysis.

2. Temperature conversions are done using equations….

Temperature conversions◦F to ◦C (large # to small #)

◦C to ◦F (small # to large #)

◦ C to K K to ◦C

Chap 2: Measurements Chap 2: Measurements and Calculationsand Calculations

Notes #6: Reliability of Notes #6: Reliability of MeasurementsMeasurements

Today’s Date

Activity

1. Measure your book from top to bottom (just as you did previously) cover in centimeters only.

2. Compare your measurement with at least 2 people around you and write down what you found.

3. Can measurements be exact? Why or Why not?

No Measurement is Perfect

A. accuracy- values close to most accepted answer1. errors cause inaccuracies

*most of time, can be improved by being more careful

2. judge accuracy using: percent error

Activity

1. 2 pair of students measure width of book (from left to right– NOT from top to bottom) with the 3 differently calibrated rulers using as many decimal places for their values as the ruler will allow. Have each pair compare their measured values.

2. What can be said about each measurement?

3. Which would be the best measurement and why?

B. precision- values close to one another1. describes limitations of measuring instrument

*Ex: meterstick divided into cm is not as precise as one divided into mm

*thus, precision can only be improved if a more precise measuring device is available

2. keep track of precision using: significant figures (sig. figs.)

3. thus, may need to: round or use scientific notation (sci. not.)

C. accuracy vs precision: Dartboard (bull’s eye is most accepted

position)