Measurements and significant figures

​Objectives

• ​To recall conversions

• To calculate the density of an object

• To apply the rules of significant figures

• To differentiate between accuracy and precision

• ​To calculate the percentage of error

​A master piece( Noora Mohammad)

​Demo

​Solve conversion questions on Classkick

​Denisty Demo:

• ​D= m/V

• Units g/ml or Kg/L

• 1 g/ml= 1 Kg /L​

• Density of water= 1g/ml or 1000Kg/m³

  (m³= 1000 L​)

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​Density- experimentally- Volume displacement method Demo:

Group work

​Use classkick code(WZK 2FUWZK 2FU) to show your work and present

​Use classkick code(WZK 2FUWZK 2FU) to show your work and present

Multiple Choice

Which of the following choices best represents the volume reading from the graduated cylinder pictured?

• 61 mL

• 61.5 mL

• 61. 52mL

• 61.8 mL

​The Reliability of a Measurement

• ​Scientific measurements are reported so that every digit is certain except the last, which is estimated.

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​The Reliability of a Measurement- Demo

Open Ended

What is the volume reading by the cylinder?

​Master pieces

​Master pieces

​Master pieces

​Master pieces

​Significant figures rules

​Significant figures- Why do we need to know the number of significant figures in measurements?

• ​They are the measured digits in a reported measurement and they do not include placeholders.

• Significant figures deal with writing numbers to reflect precision.(The precision of a measurement depends on the instrument used to make the measurement)

• The preservation of this precision during calculations can be accomplished by using significant figures.

• The greater the number of significant figures, the greater the certainty of the measurement.

​Significant figures rules- Important notes

1. ​Decimal points are placed after one or more trailing zeroes if the zeroes are to be considered significant.

2. ​Exact numbers/ constants never limit the number of significant figures in a calculation​. This we don't use to specify the significant figures

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​Significant figures rules- operations

1. ​For multiplication and division: Consider the measurement the least number of significant figures

2. For addition and subtraction: Consider the measurement the least number of Decimal place

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Multiple Choice

How many significant figures does the following number have: 0.002040

• 6
• 4
• 3
• 2

Multiple Choice

How many significant figures does the following number have: 100.00210

• 7
• 5
• 10
• 8

Multiple Choice

How many Significant Figures in the number below?
4.56 x 10³

• 5
• 4
• 6
• 3

Multiple Choice

How many significant figures does the following number have: 1740200

• 2
• 1
• 3
• 5

Multiple Choice

Calculate 5.50 cm + 5.5 cm and give your answer with the correct number of significant figures.

• 11 cm
• 11.0 cm
• 11.00 cm
• 11.000 cm

Multiple Choice

Which of the following measurements contains two significant figures?

• 0.00400 L
• 0.00404 L
• 0.00044 L
• 0.00440 L

Multiple Choice

Solve and give your answer with the correct number of significant figures
(12.470)(271)

• 3366.9
• 3.37x10³
• 3400
• 3370

Multiple Choice

Solve and give your answer with the correct number of significant figures
24.28 + 12.5

• 3.687 x 10¹
• 36.8
• 37
• 3.70x10¹

Multiple Choice

Give the answer to the correct number of significant figures to

145.63 - 28.9

• 116.73

• 116.7

• 116.70

• 117