MEASUREMENTS

EXACT NUMBERS! Numbers determined by counting or by definition Ex: 6 apples, 1 teacher 1 inch=2.54 cm

IN SCIENCE… Numbers are based on MEASUREMENTS made in the lab. Our data is only as good as the measurements we make and the instruments we use.

UNITS OF MEASUREMENT There is one system for all scientists around the world. We must have a standard for comparison length – meter (m) mass – gram (g) time – second (s) volume – liter (L)

Accuracy: how close a measured value is to the actual (true) value. Precision: how close the measured values are to each other.

ACCURACY VS. PRECISION

SIGNIFICANT FIGURES Shows how PRECISE a measurement is Indicates the QUALITY of the instrument you use (how sensitive or exact) EX. Graduated cylinder vs. beaker When recording measurements, always estimate one place value more than the instrument provides.

SIG FIG RULES!

COUNTING SIGNIFICANT FIGURES sig figs 2 sig figs 4 sig figs 6 sig figs

SCIENTIFIC NOTATION Used to write really LARGE or really small #’s Why? To save space & time

SCIENTIFIC NOTATION RULES! Written in the form of m x 10 n m: ≥ 1 AND <10 indicates the number of sig figs

STEPS OF THE SCIENTIFIC NOTATION Step 1) Determine the sig figs  106,000,000 = Step 2) Determine the value of “m” using the sig figs  1.06 (remember this must be between 1 and 10) Step 3) Add the 10’s multiplier  1.06 x 10 n 3 sig figs

Step 4) Determine the value of “n” by counting the number of times you move the decimal in the original number to get the value for “m” Step 5) Determine the sign of “n” by looking at the direction that you moved the decimal  Move decimal to left =  Move decimal to right = “n” is positive “n” is negative

Ex. 1) 7, 801 Ex. 2) x x 10 -4

Ex. 3) 3.1 x 10 4 Ex. 4) 4.08 x , NOW GO THE OTHER WAY!!