Question of the Day Day List and briefly define 3 “vocabulary” words from unit # 2 (this unit). 2. Why do we use scientific notation? 3. Solve: (3.0 * 10 3 ) ÷ (6 * )

FRIDAY 11-9!!! Day

Question of the Day Day List and briefly define 2 “vocabulary” words from unit # 2 (must be different than yesterday’s). 2. Solve: (3.0 * 10 3 ) + (6 * 10 2 )

FRIDAY 11-9!!! Day

Accuracy vs. Precision Precision – repetition – if you do the same exp. or measurement over and over how close are the values. If something is precise it is repeatable

Accuracy vs. Precision Accuracy – accepted – measures how close your value is to the accepted or literature value

Accuracy vs. Precision You measure the density of 10 pennies and every time you get between and g/ml. You look up the density of a penny and find that it is 8.2 g/ml. What can you say about precision? Accuracy? What does this imply? Are you doing something wrong?

Accuracy vs. Precision Precision: An analysis = average deviation Accuracy: An analysis = percent error

Accuracy vs. Precision An analysis = average deviation Precision: X – X X = MEAN DEVIATION The absolute value of the difference between a measurement and the average (mean)

Accuracy vs. Precision If your average deviation is small relative to your measurements it indicates that your measurements were all close together or… Precise

Accuracy vs. Precision Calculating average deviation: Measurements: run # 1 – 7.51 cm run # 2 – 7.55 cm run # 3 – 7.49 cm run # 4 – 7.58 cm 1. Calculate average7.53 cm 2. Calc. deviations for each run

run # 1 → 7.51 cm – 7.53 cm = run # 2 → 7.55 cm – 7.53 cm = run # 3 → 7.49 cm – 7.53 cm = run # 4 → 7.58 cm – 7.53 cm = Accuracy vs. Precision 2. Calc. deviations for each run X – X run # 1 → 0.02 cm run # 2 → 0.02 cm run # 3 → 0.04 cm run # 4 → 0.05 cm 3. Calc. average deviation

Accuracy vs. Precision run # 1 → 0.02 cm run # 2 → 0.02 cm run # 3 → 0.04 cm run # 4 → 0.05 cm 3. Calc. average deviation 0.03 cm = 3 * cm

Accuracy vs. Precision Calculate the average deviation for the shoe sizes of the 4 people sitting closest to you in your notes (SHOW ALL WORK!). How could you have gotten a lower average deviation?

Accuracy vs. Precision Accuracy: An analysis = percent error % error = Measured – accepted accepted X 100 Period 7 left off Monday 11-5

Accuracy vs. Precision If your % error is small compared to your measurement that indicates that the measurement was close to the accepted value or… Accurate

Accuracy vs. Precision Calculating % error: Measurement: 7.51 cm Accepted value: 7.33 cm % error = Measured – accepted accepted X 100

Accuracy vs. Precision Calculating % error: % error = 7.51 cm – 7.33 cm 7.33 cm % error = Measured – accepted accepted X %

Question of the Day Day Joey measures the density of water in lab and calculates a 1% percent error. What can you say about his accuracy? What can you say about his precision?

Review Homework

Tic-Tac-Toe  Battle of the Sexes The branch of chemistry that seeks to identify unknowns = ? Define density without using the words mass or volume. Explain why we use scientific notation. (4.0*10 4 )*(5.0*10 -1 ) The branch of chemistry associated with carbon = ? What is the density in g/ml if the mass is kg and the volume is 30 dL? If a test tube contains a pink liquid over a green liquid over a yellow liquid, how do the densities of the liquids compare? 8.5 / 2.0 Convert: 5.50 mg = __ µg Absolute zero = _____ K _____ °C You saw me drop ice in alcohol, put the following in order of INCREASING density: water, alcohol, ice cube A scientist studies the digestion of diabetics - what branch of chemistry? Is air matter? How do you know? (3.0*10 4 ) / (4*10 -1 ) (4.00*10 4 )-(3*10 2 ) How does the arrangement of particles determine density? If a measurement is accurate that means …? FREE SPOT 5.00 * 2.0 Take out of sci. not.: 4.00 * 10 6 Take out of sci. not.: 4.00 * The branch of chemistry associated with laws, models, and equations ? The discipline that seeks to explore and explain = ? Explain why we use sig. figs.

Tic-Tac-Toe  Battle of the Sexes The branch of chemistry that seeks to identify unknowns = ? Define density without using the words mass or volume. Explain why we use scientific notation. (4.0*10 4 )*(5.0*10 -1 ) The branch of chemistry associated with carbon = ? What is the density in g/ml if the mass is kg and the volume is 30 dL? If a test tube contains a pink liquid over a green liquid over a yellow liquid, how do the densities of the liquids compare? 8.5 / 2.0 Convert: 5.50 mg = __ µg Absolute zero = _____ K _____ °C You saw me drop ice in alcohol, put the following in order of INCREASING density: water, alcohol, ice cube A scientist studies the digestion of diabetics - what branch of chemistry? Is air matter? How do you know? (3.0*10 4 ) / (4*10 -1 ) (4.00*10 4 )-(3*10 2 ) How does the arrangement of particles determine density? If a measurement is accurate that means …? FREE SPOT 5.00 * 2.0 Take out of sci. not.: 4.00 * 10 6 Take out of sci. not.: 4.00 * The branch of chemistry associated with laws, models, and equations ? The discipline that seeks to explore and explain = ? Explain why we use sig. figs.

Measure me % error = Measured – accepted accepted X 100

What test version did you take yesterday? Day Prelab

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