Download presentation

1
**Counting Significant Figures:**

1) All non-zero digits are significant. 1.5 has 2 significant figures. 2) Interior (sandwich) zeros (between two digits) are significant. 1.05 has 3 significant figures. 3) Trailing zeros after a decimal point are significant. 1.050 has 4 significant figures. Tro's "Introductory Chemistry", Chapter 2

2
**Counting Significant Figures, Continued**

4) Leading zeros (on the left of a number) are NOT significant. has 4 significant figures. 5) Zeros that do nothing but set the decimal point (to the right of a number) are NOT significant: So 150 has 2 significant figures. 542,000, has 3 significant figures. Tro's "Introductory Chemistry", Chapter 2

3
**Tro's "Introductory Chemistry", Chapter 2**

Practice: How many significant figures are in each of the following numbers? a) b) c) d) 2.97 × e) 100,000--- 2 sig. fig. (leading zeros are not significant).(Rule #4). 4 sig. fig. (zeros after the decimal & interior zeros are significant). (Rules #2 & 3). 4 sig. fig. (all non zeros digits are significant).(Rule #1). 3 sig. fig. (all non zeros digits are significant) (Rule #1). 1 sig. fig. (zeros to the right of a # with out decimal point are not significant) (Rule #5). Tro's "Introductory Chemistry", Chapter 2

4
**Rules for rounding numbers:**

If the digit immediate right of the last significant figure is: a) greater than 5 – Round up the last sig. figure: 2.54 b) lesser than 5 – Do NOT round up: 2.53 c) equal to 5:

5
c) equal to 5: 1) followed by a non-zero –ROUND UP: 2.54 2) followed by zero: If the last significant figure: - is an odd digit – ROUND UP: - is an even digit– Do NOT round up: 2.52

6
**Tro's "Introductory Chemistry", Chapter 2**

Rounding to 2 significant figures: 2.34 rounds to: 2.3 2.37 rounds to: 2.4 rounds to: rounds to: or × 10-2 rounds to: or × 10-2 Tro's "Introductory Chemistry", Chapter 2

7
**Rounding Rules in Addition & Subtraction:**

The result must be rounded up to the same number of digits after the decimal point than the measurement with the fewest number of digits after the decimal point: cm cm cm cm ≈

8
**Rounding Rules in Addition & Subtraction:**

The result must be rounded up to the same number of digits after the decimal point than the measurement with the fewest number of digits after the decimal point: cm cm cm cm ≈ 77.2 cm

9
**Tro's "Introductory Chemistry", Chapter 2**

Practice: 1) = 2) = 9.214 = 9.21 2 decimal places 3 decimal places 3 decimal places 0.835 = 0.8 1 decimal place 3 decimal places Tro's "Introductory Chemistry", Chapter 2

10
**Rounding Rules in Multiplication & Division:**

The answer must have the same number of significant figures as the measurement with the fewest number of significant figures: 24 x 3.28 = 23.5 x 1.2 = 60.2 ÷ 20.1 = 78.72 ≈ 79 28.2 ≈ 28 2.995 ≈ 3.00

11
**Tro's "Introductory Chemistry", Chapter 2**

Practice: 1) 5.02 × × 0.10 = 2) ÷ 6.10 = 3) 1.01 × 0.12 × ÷ 96 = 4) × ÷ = = 45 3 sig. figs. 5 sig. figs. 2 sig. figs. = 0.966 4 sig. figs. 3 sig. figs. = 0.068 3 sig. figs. 4 sig. figs. 2 sig. figs. 2 sig. figs. = 1.52 4 sig. figs. 3 sig. figs. 6 sig. figs. Tro's "Introductory Chemistry", Chapter 2

Similar presentations

© 2021 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google