Ch 2 Wks #1-Rounding and Significant Figs



Ch 2 Wks #1-Rounding and Significant Figs Name___________________

Rules for significant figures

Non-zero digits are always significant.

Examples: 657 has ______ significant figures

1435 has _____ significant figures

Leading zeroes are not significant.

Examples: 0.00682 has _____ significant figures

0.035 has _____ significant figures

Imbedded zeroes are always significant.

Examples: 1.072 has _____ significant figures

0.0108 has _____ significant figures

Trailing zeroes are significant if there is a decimal point.

Examples: 300 has _____ significant figures

300. has _____significant figures

300.0 has _____ significant figures

0.0030 has _____ significant figures

Practice: How many significant figures do the following numbers have?

A. 678.0 ______ C. 0.0678 ______

B. 6780 ______ D 6708 ______

Rounding –

Round 0.06507 to the indicated number of significant figures.

A. 3 _______ C. 2 ______

B. 1 _______

Round 8083.05 to the indicated number of significant digits.

A. 1 _______ B. 3 _______ C. 4 _______

Operations

Addition or Subtraction: The last digit retained is set by the first doubtful digit.

Examples: 4.7832 1.0236

1.234 − 0.97268

+ 2.02

Multiplication and Division: The answer contains no more significant figures than the least accurately known number.

Examples: 2.8723 × 1.6 = ________

45.2 ÷ 6.3578 = ________

Practice:

1. How many significant figures are contained in each of the following measurements?

a. 37.4 g b. 6070. dm

c. 0.009 03 km d. 605.03 g

e. 350.0 K

2. Round off each of the following measurements to the indicated number of significant figures.

a. 35.27 g to 3 significant figures

b. 0.414 kL to 2 significant figures

c. 87.257 dm to 3 significant figures

d. 135 K to 2 significant figures

e. 6250 cm to 2 significant figures

3. Round off 359.78 to the indicated number of significant figures.

a. 2

b. 3

c. 4

d. 1

4. Perform the following calculations and express the answers with the correct number of significant figures.

a. 6.43 mL + 2.016 mL

b. 2.50 g / 0.04 cm3

c. 6.821 m + 2.0 m + 0.45 m

d. 107.38 L - 65 L

e. 26.50 dm × 0.062 dm

f. 1.30 g / 0.02 cm3

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