chapter 3 - scientific measurement

What are Significant Figures (sigdigs)

all digits that are known and the last digit that is estimated. Is used when a number is very exaggerated or isn’t exact.

Rules for determining correct number of sigdigs

1. all non-zero digits in a measurement are significant

   • ex) 535 = 3 sigdigs

2. sandwich rule: any zero between non-zero digits is significant

   • ex) 5001 = 4 sigdigs

3. zeros to the right of the decimal point (trailing) are significant

   • 15.0 = 3 sigdigs

4. placeholders are not significant (they only show the magnitude of the value

   • ex) 0.0510 = 3 sigdigs

Components of measurnment

a quantity with a unit and number

Density calculation

density = mass(g) / volume(mL or cm³)

Precision

how close measurements are to eachother

Accuracy

how close you are to the true value

accepted value

accepted value is the correct value for a measurement based upon reliable references

experimental value

the value of a measurement that is obtained during the lab

percent error equation

% error = [error / accepted value] x 100

• error being [ experimental value - accepted value ]

temperature

measure of how hot or cold something is

equation for Celsius to kelvin conversion

K=°C+273.15

How to round sigdigs

determine how many sig digs your answer should have, look at the next number after that amount of sig digs and if it is less than 5 keep the number before the same, 5 or greater you want to round the last sig dig up to the next number.

• ex) 8.477 = 8.48

Addition and subtraction rule for sigdigs

report answer using the least amount of decimal places in the problem

• ex) 45.0 - 0.0478 = 44.9522

  • final answer = 45.0

sigdig multiplication and division rule

report the answer using the least amount of sigdigs in the problem

• ex) 52.0 × 0.70 = 36.4

  • final answer = 36

metric prefixes

Prefix	Symbol	Meaning	Factor
giga	G	1billion times larger than the unit it precedes	109
mega	M	1million times larger than the unit it precedes	106
kilo	k	1000 times larger than the unit it precedes	103
deci	d	10 times smaller than the unit it precedes	10-1
centi	c	100 times smaller than the unit it precedes	10-2
milli	m	1000 times smaller than the unit it precedes	10-3
micro	μ	1million times smaller than the unit it precedes	10-6
nano	n	1billion times smaller than the unit it precedes	10-9
pico	p	1trillion times smaller than the unit it precedes	10-12