Unit 1: Measurements, Accuracy, and Precision Notes

Key Concept 1–Qualitative data: deals with descriptions. –Quantitative data: deals with numbers– Examples

Room Number: 169429–What was an example from our Mass and Change Lab of quantitative data?

–T/F Did the Mass and Change Lab have any qualitative data?

Qual vs. Quant

Units

• Significant Figures: Crash Course Stop at 3:45

• Système Internationale d'Unités (SI) is an internationally agreed upon system of measurements.

• A base unit is a defined unit in a system of measurement that is based on an object or event in the physical world, and is independent of other units.

Units (cont.)

Key Concept 2

Comparing Units of Volume

• Key Concept 3: Volume measures the amount of space an object takes up, and is a derived SI unit.

Key Concept 4: The volume of a cube is V=length x width x height

Comparing Units of Volume

• Key Concept 6: Volume can be measured in cubic centimeters (cm3) using a ruler or in milliliters (mL) by using a graduated cylinder.

Key Concept 5: The volume of a cylinder is V= πr2 x height

Quick Activity

Goal: Compare the volume that are calculated using a rule with those measured using a graduated cylinder.

mL and cm3

How can you minimize error?

Class Data Cube

cubic centimeters (cm3) Milliliter (mL)

Cylinder cubic centimeters (cm3) Milliliter (mL)

Quick Activity

Goal: Compare the volume that are calculated using a rule with those measured using a graduated cylinder.

How are mL and cm3related?

Closure Type: Socrative Exit Poll

Volume is not concerned an SI unit. How did scientist choose to define volume?

Yesterday

• Measurements can be:– Qualitative– Quantitative

• SI Units

Today

1. SI Units2. Important of Units3. Sig Figs4. Review Scientific Notation5. Accuracy vs. Precision

• 1792: French established a new system of weights and measures

1 m = distance from N. pole to equator ten-million

• Then, in the 1870s: 1 m = distance between fine lines on Pt-Ir bar– Accurate copies sent around the worldTime and length linked

SI Units- Length

• The SI base unit for length is the meter (m).• A meter is equal to the length of the path

travelled by light in a vacuum during a time interval of 1⁄299,792,458 of a second.

SI- Length

• The SI base unit of mass is the kilogram (kg), about 2.2 pounds

SI- Mass

SI- Temperature

• The SI base unit of temperature is the kelvin (K).

• Zero kelvin is the point where there is virtually no particle motion or kinetic energy, also known as absolute zero.

• Two other temperature scales are Celsius and Fahrenheit.

• In 1999 the United States lost the Mars Climate Orbiter as it approached Mars.

• The loss of the $125 million spacecraft was due to scientists confusing English units and metric units.

Importance of Units

• The spacecraft team in Colorado used English units of pounds of force to describe small forces needed to adjust the spacecraft’s orbit. The data was shipped via computer, without units, to the NASA’s Jet Propulsion Lab (JPL) , where the navigation team was expecting the to receive the data in metric measure.

Importance of Units

• A train of length 2, weighing 200, travels from Denver to Santa Fe at 15. How long did the trip take?

Importance of Units

• This brings up the issue of units. In your math class, numbers by themselves are fine to work with, but in science a number without units is pretty useless.

• NO NAKED NUMBERS“NO STREAKING”

Importance of Units

“We can only be as accurate as our weakest measurements”.

Importance of Units

Today

1. SI Units2. Important of Units3. Sig Figs4. Review Scientific Notation5. Accuracy vs. Precision

Significant Figures

• Often, precision is limited by the tools available.

• Key Concept 7: The significant figures of a number are those digits that carry meaning contributing to its precision. When measuring significant figures include all known digits plus one estimated digit.

Learning Check

What is the length of the wooden stick?

Learning Check• Record the measurement using significant

figures.

Significant Figures (cont.)

• Rules for significant figures

– Rule 1: Nonzero numbers are always significant.– Rule 2: Zeros between nonzero numbers are

always significant.– Rule 3: All final zeros to the right of the decimal

are significant.– Rule 4: Placeholder zeros are not significant. To

remove placeholder zeros, rewrite the number in scientific notation.

– Rule 5: Counting numbers and defined constants have an infinite number of significant figures.

Shoulder Partner Practice SF’s

1. 3 6. 42. 2 7. 43. 3 8. 24. 4 9. 35. 4 10. 5

Meter Stick

Quick Demo

I need two groups of three volunteers that can measure using a meter stick (cm).

Number of trails

Length of tape in cm

Length of tape in cm

123

Scientific Notation

5.67 x 105 coefficient base exponent

In order for a number to be in correct scientific notation, the following conditions must be true:

1. The coefficient must be greater than or equal to 1 and less than 10.

2. The base must be 10.3. The exponent must show the number of decimal

places that the decimal needs to be moved to change the number to standard notation.

Scientific Notation (cont.)

800 = 8 102

0.00003430 = 3.430 10–5

• The number of places moved equals the value of the exponent.

• The exponent is positive when the decimal moves to the left and negative when the decimal moves to the right.

Today

1. SI Units2. Important of Units3. Sig Figs4. Scientific Notation5. Accuracy vs. Precision

Accuracy and Precision

• Key Concept 8: Accuracy refers to how close a measured value is to an accepted value.

• Key Concept 9: Precision refers to how close a series of measurements are to one another.

• Pin the mitten on the kitten

Today

1. SI Units2. Important of Units3. Sig Figs4. Scientific Notation5. Accuracy vs. Precision

You have Unit 1A and Unit 1B Practice Problem.

Unit 1 Prove It Quiz is 26th or 27th