1.1a Significant Digits

Question 1

Significant digits are necessary because…

Answer 1

measurements have inherent precision in them (decimal place) that needs to be reported

Question 2

All digits in a number are divided into 2 types:

Answer 2

significant digits and placeholders

Question 3

Significant digits are…

Answer 3

digits derived directly from the measurement taken

Question 4

placeholder digits are

Answer 4

0s that are in place to secure the size of the measurement. They disappear when the number is written in scientific notation.

Question 5

In the number 6.022x10²³, 6.022 is called the…

Answer 5

significand

coefficient

mantissa

Question 6

The digits in the significand are…

Answer 6

always significant and never contain placeholders

Question 7

0.0023 has ____ sig digs?

Answer 7

2

0.0023 significant

0.0023 placeholders

2.3x10^-3 when written in scientific notation. Placeholders disappear.

Question 8

0.02030 has ___ sig digs?

Answer 8

4

0.02030 significant 0s at the right in a decimal are ALWAYS significant

0.02030 placeholders

2.030x10^-2 when written in scientific notation. Placeholders disappear. 0 at right is the scientist estimating that it’s exactly “on the line” instead of anywhere “between the lines”

Question 9

20300. The meaning of the decimal point is

Answer 9

that the zeros to the left are significant

Question 10

20300. the # of sig digs is

Answer 10

5

Question 11

20300 the # of sig digs is

Answer 11

3

The 2 zeros at the right are place holders. If written in scientific notation:

2.03x10⁴

Question 12

Significant Figures (math on sig digs) rule for multiplication and division

Answer 12

the answer will have the # of sig digs of the number used with the least sig digs e.g.

2. 3 (2 sig digs)
3. 34567 (6 sig digs)

when multiplied or divided, the answer can only have 2 sig digs

Question 13

Significant Figures (math on sig digs) The rule for addition and subtraction is

Answer 13

the answer must be reported to the decimal of the least precise number e.g.

1234.1 (tenths)

+ 22 (ones)

1256

(ones is least precise)

Question 14

In a scientific number, the right most digit is always

Answer 14

uncertain

Question 15

Some numbers have an infinite number of significant digits, such as …

Answer 15

• things that are counted (14 persons)
• some constants in formulae A=1/2b•h (1/2 has infinite precision)
• when quantities are doubled, tripled, halved, etc.