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# Chapter 1 Measurements PowerPoint PPT Presentation

Chapter 1 Measurements. Measured Numbers and Significant Figures. Measured Numbers. When you use a measuring tool to determine a quantity such as your height or weight, the numbers you obtain are called measured numbers . Reading a Meterstick.

Chapter 1 Measurements

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### Chapter 1Measurements

Measured Numbers and Significant Figures

### Measured Numbers

When you use a measuring tool to determine a quantity such as your height or weight, the numbers you obtain are called measured numbers.

. l2. . . . I . . . . I3 . . . .I . . . . I4. . cm

First digit (known)= 2 2.?? cm

Second digit (known)= 0.7 2.7?cm

Third digit (estimated)between 0.05- 0.07

Length reported=2.75 cm

or2.76 cm

or2.77 cm

### Known + Estimated Digits

• Known digits 2 and 7 are 100% certain

• The third digit 6 is estimated (uncertain)

• In the reported length, all three digits

(2.76 cm) are significant including the estimated one

### Learning Check

. l8. . . . I . . . . I9. . . .I . . . . I10. . cm

What is the length of the line?

1) 9.2 cm

2) 9.22 cm

3) 9.23 cm

### Solution

. l8. . . . I . . . . I9. . . .I . . . . I10. . cm

Estimate to the hundreth’s place (0.01 cm)

2) 9.22 cm

3) 9.23 cm

The estimated digit may be slightly different. Both readings are acceptable.

### Learning Check

l5. . . . I . . . . I6. . . .I . . . . I7. . cm

What is the length of the line?

1) 6.0 cm

2) 6.06 cm

3) 6.60 cm

### Solution

l5. . . . I . . . . I6. . . .I . . . . I7. . cm

Estimate to the hundreth’s place (0.01 cm). The reading is between 6.0 and 6.1. You may have estimated 6.07 cm as well.

2) 6.06 cm

### Zero as a Measured Number

. l3. . . . I . . . . I4 . . . . I . . . . I5. . cm

What is the length of the line?

First digit 4.?? cm

Second digit 4.5? cm

Last (estimated) digit is 4.50 cm

(not to the left or right of .5)

### Exact Numbers

• Obtained when you count objects

2 soccer balls

1 watch

4 pizzas

• Obtained from a defined relationship

1 foot = 12 inches

1 meters = 100 cm

• Not obtained with measuring tools

### Learning Check

A. Exact numbers are obtained by

1. measuring

2. counting

3. definition

B. Measured numbers are obtained by

1. measuring

2. counting

3. definition

### Solution

A. Exact numbers are obtained by

2. counting

3. definition

B. Measured numbers are obtained by

1. Using a measuring tool

### Learning Check

Classify each of the following as an exact (1)

or a measured (2) number.

A.___Gold melts at 1064°C

B.___1 yard = 3 feet

C.___A red blood cell with diameter 6 x 10-4 cm

D.___There were 6 hats on the shelf

E.___A can of soda contains 355 mL of soda

### Solution

Classify each of the following as an exact (1) or a measured(2) number. Give reason.

A. 2 Requires a thermometer(measuring tool)

B. 1 From a definition in U.S. system

C. 2 Need measuring tool to determine

D. 1 Counted the hats

E. 2 Measured