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Name: _____________________ Date: _____9/6____Period: ___________

Unit 1Making and Recording Measurements

Essential Questions:

I it ibl t b 100% fid t b t t?• Is it possible to be 100% confident about any measurement?

• Do “accurate” and “precise” have the same meaning?

Do Now

1

102

10

1

1005 1

100 20

Need to know to successfully read

measurement scales!

103

104

105 1

10 2

100 20

7

1008

100

9

Slide 2

8

109

10

100

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Review: Why is measurement important in science?

• Reason 1: Measurement is a way to • Assign numbers to ideas (concepts)

• Communicate information in a way others can understand

• Reason 2 (new info): Numbers help us to see patterns• Patterns help us to discover scientific laws and to make

predictions R 2 ill b d i

Slide 3

predictions Reason 2 will be covered in a future lesson

Any questions from last class?

Vocabulary word you want to go over?

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Objectives

• Explain the difference between analog and digital scales.

• Explain what it means to calibrate an instrument (if needed).

• Measure length and temperature to correct precisionMeasure length and temperature to correct precision.

• Label measurements with the quantity being measured.

• Correctly record measurements, including thevalue (or number) and units.

• Explain the difference between measurement accuracy, precision, and uncertainty (“error”).

Slide 5

y ( )

• Identify possible sources of error in a measurement.

Measuring instruments can have an analog scale“analog” = smooth or continuous; you must guess values between marks

• Scale: Marks on an object used to assign a number to a quantity during measurement.

“riders”

Slide 6

• Division on a scale: Distance between marks.

• Smallest division on a scale: Smallest distance between marks.

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Measuring instruments have a digital display“digital” = values increase/decrease in steps; you don’t have to guess

• Digital instruments display the measured value as specific numbers on a screen

Slide 7

Individual Activity

1. Measure the length and width of the given card 3 times using the top ruler in your notes.

2. Repeat the measurements in step 1 using the other 2 rulers, 3 measurements each.

3. Record your measurements neatly and in an organized way. (Hint: Use a table!)

Slide 8

• Question: Which of the 3 measurements is the• Least/Most accurate?

• Least/Most precise?

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In your notes: Rulers for measurement activity

1

2

3

Slide 9

Measurement Skills Review

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Steps for making and recording measurements

1. “Zero” or Calibrate Instruments

2. Check the value of the smallest division on the scale

3. Read scale to 1/10th of the smallest division

4. Record quantity label, value, and units

Slide 11

What is happening in this animation?

Slide 12

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Step 1: “Zero” or Calibrate Instruments

• Before you measure, adjust the instrument to read “zero.”

Wh i t t d t d “ ” b f t t• When instruments do not read “zero” before you start, the measurement will not be accurate.

Calibrating an instrument means 2 things:

• Making a scale that matches standard units

Slide 13

Making a scale that matches standard unitsExample: Make a metric ruler with marks that match the standard ruler. All metric rulers should be the same.

• Adjusting an instrument to read zero before measuring

Calibrating different instruments

Ruler or Meter Stick1 Align one edge of the object with “0”1. Align one edge of the object with 02. If “0” mark is worn off, start at the next

number.Remember to subtract that number from your final measurement.

Can you “zero” a thermometer?

Slide 14

Triple-Beam Balance1. Slide back all the

weights on the beams.2. If the pointer is not at

the zero line, turn the zero adjustment knob to get the pointer at zero.

Digital Balance1. Turn scale “On.”2. Check that scale reads correct

units (usually “grams”).3. Press “Tare” button to zero

scale.

Pointer

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Step 2. Check the value of the smallest division on the scale

Smallest division: _______________

Slide 15

Smallest division: _______________

________ ⁰C

Smallest division

________ ⁰C

3. Read scale to 1/10th of the smallest division

cm

Object

For example:

• Smallest division on Ruler A is “1 cm”

• Object length is more than “4 cm + more”“4 ” k f !

Length of object = 4.8 cm

Object

Slide 16

“4 cm” you know for sure!

• Imagine dividing the smallest division into 10 equal parts

• Guess (or estimate) that the rest of the length – e.g., 8/10th or 0.8 cm

• Record length as 4.8 cm – the last digit is always a guess!

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3. Read scale to 1/10th of the smallest division

cm

Object

For example:

• Smallest division on Ruler B is 1/10th cm, or “0.1 cm”

• Object length is “4 cm + 8/10th cm + more” = “4.8 cm + more”“4.8 cm” you know for sure!

P t d t di id th ll t di i i i t 10 l t

Length of object = 4.85cm

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• Pretend to divide the smallest division into 10 equal parts, each is 0.01 cm

• Guess (or estimate) that the rest of the length, e.g., ½ of 0.1 cm = 5/100 cm = 0.05 cm

• Record length as 4.85 cm – the last digit is always a guess!

4.8

0.05

4.85

4. Record quantity, value, and units

• For single measurements:• Example: “Length = 4.85 cm”

• For multiple measurements, organize in a table.Use column headers to state units.

Quantity Value Units

Trial # Length (cm)R l 1

Length (cm)R l 2

Length (cm)R l 3

Slide 18

Ruler 1 Ruler 2 Ruler 3

Trial 1

Trial 2

Trial 3

Trial Average

Like this….

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What’s the difference between these?

Trial # Length (cm)Ruler 1

Length (cm)Ruler 2

Length (cm)Ruler 3

Trial 1

T i l 2 Lik thiTrial 2

Trial 3

Trial Average

Length (cm)

Trial # Ruler 1 Ruler 2 Ruler 3

Like this….

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Trial # Ruler 1 Ruler 2 Ruler 3

Trial 1

Trial 2

Trial 3

Trial Average

Or like this….

Make your own table below and re-record your measurements from the Individual Assignment based on what you just learned

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Crowd-sourcing data: What did you notice about the measurements collected from the class?

Length (cm)

Trial Average Ruler 1 Ruler 2 Ruler 3Trial Average Ruler 1 Ruler 2 Ruler 3

1

2

3

4

5

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• Were all the trial average measurements the same for each ruler?

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Vocabulary

• Accurate (adjective)When a measuring instrument agrees with the standardand is used correctly.

“The meter stick in our classroom matches the standard1 meter and I used it correctly.”

• Precise (adjective)Not a definition: How many numbers you have in a

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Not a definition: How many numbers you have in a measurement. More numbers → More precise

We will learn the true definition by practicing in a future class!

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In the Individual Activity, which ruler gave the most….

• Precise measurement? Explain.

• Accurate measurement? Explain.How would you test for accuracy?

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y y

Sources of uncertainty or error

• You can’t know any measured value exactlybecause no measurement has an infinite numbers or digits!

• “Uncertain” or “error” means a measurement is not known exactly, with 100% precision. (Here, error is not a mistake.)

• Some sources of uncertainty or error:1. Instruments cannot have scales with infinite divisions

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OR Instruments have “limited precision.”

2. Instrument is not properly calibrated (or “zeroed”).

3. Experiment can be set up incorrectly and all measurements will be “off”.

NEVER say “Human Error”! Be more specific.

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Fraction and decimal equivalents:Useful for reading metric measurement scales

10.1

102

0 2

cm cm

0.2103

0.3104

0.4105 1

0.510 2

10.01

1005 1

0.05100 20

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10 2

80.8

109

0.910

7

0.07100

80.08

1009

0.09100

What do you record when the measurement is

on the scale line?

Practice: Reading Length Scales 1

cm

Record Measurement

Length = 3.3 cm

cm

Slide 26

cm

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Practice: Reading Length Scales 2Record

Measurement

Length = 3.24cm

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Practice: Reading Temperature Scales 1

Record Measurement

_____ C

_____ F

Slide 28

Record values to correct precision!

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Practice: Reading Temperature Scales 2

Record Measurement

24 C

_____ F

What is the freezing and boiling

Slide 29

What is the freezing and boiling temperature of water in both units?

_____ C _____ F

Celsius OR

Practice: Reading Digital Mass Pounds (lb or lbs) measure weight,

not mass! They are different!

Slide 30

Record Measurement

Record Measurement

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Essential Questions

• Is it possible to be 100% confident about any measurement?

Why or why not? (Consider sources of uncertainty )

Wrap Up

Why or why not? (Consider sources of uncertainty.)

• Do “accurate” and “precise” have the same meaning?

Slide 31

Do accurate and precise have the same meaning?

If not, how are they different?