chem 1 unit test

The metric system and metric conversion use what mnemonic

KHDudcm

K

Kilo

H

Hecto

D

Deca

u

unit (base) m, L, g, j, s

d

deci

c

centimeters

mm

millimeters

Accuracy

how close a measurement is it true or accept accepted value: Like hitting the center bullseye on our target

Precision

how close a set of measurements are to each other: Hitting the exact same corner of target repeatedly

High Accuracy + High Precision:

clustered tightly in the center bullseye

Low Accuracy + High Precision:

Clustered tightly but far off in one corner

High Accuracy + Low Precision:

Scattered far apart but their average hits the center

Low Accuracy + Low Precision :

randomly scattered all over the target

significant figures rules

1) all non zero numbers are significant

ex: 1,2,3,4

2) zeros in front of other numbers (leading zeros ) are not significant place holders

ex: 0.000002

3) zeros behind other numbers ( trailing zeros ) are significant if the number has a decimal written

ex: 2000.

4) zeros between non zero numbers are significant

ex: 808

Calculations with sig figs

rule 1: addition and subtraction

round answer to the fewest number of decimal places in the problem

Calculations with sig figs

rule 2: multiplication and division

round answer to the fewest total significant figures in the problem

Dimensional Analysis of converting units

formula

given X ( desired unit / given unit) = converted answer

Percent Error

formula

Percent error = ( experimental value - accepted value ) / accepted value X 100

experimental value :

what you measured in lab

Accepted value :

the true , official , or standard in the lab

Temperature conversions

celsius to kelvin formula :

c + 273.

Temperature conversions

kelvin to celsius formula:

k- 273.

Temperature conversions

fahrenheit to celsius formula:

(f - 32 ) / 1.8

Temperature conversions

celsius to fahrenheit formula

(c x 1.8) +32

Regular notation to scientific notation

If the decimal moved to the left, the exponent will be positive

If the decimal was moved to the right, the exponent will be negative

Scientific notation to regular notation

if exponent is negative, you move the decimal to the left and add zeros were needed

And if the exponent is positive move the decimal to the right and add zeros were needed

3 triple beam scale

add the marked numbers together and put a .5 decimal or .1 decimal