Measurements

MEASUREMENTS

Scientific Notation

■ Chemistry often deals with very large and very small

numbers

–

There are 602,000,000,000,000,000,000,000 molecules of water in 18 mL!

–
one electron has a mass of 0.000000000000000000000000000911 g!

■ Scientific Notation expresses a value by using a number

between 1 and 10 (the coefficient) and a power of 10

■ This makes very large or very small numbers easier to work

with

■ Example: 5000 🡪 5x103

0.0000783🡪 7.83x10-5

Putting a Number into Scientific
Notation

Putting a Number into Scientific
Notation

SI Units

■ SI units are the international system of units used

by scientists to measure
– Derived units are made by multiplying or dividing two or

more other units

SI Units

SI Units

Match the unit with the measurement.

1.

_____ 13 cm

a. time

2.

_____ 157 mg

b. volume

3.

_____ 27o C

c. Length

4.

_____ .05 ms

d. quantity of matter

5.

_____ 3.5 mL

e. temperature

6.

_____ .035 mol

f. Mass

7.

_____ 26 K

8.

_____ 5 km

9.

_____ 30 cm3

10.

_____ 15.5 g

9

Limits of Measurements

❖

Measurements are performed with instruments and no instrument can read to
an infinite number of decimal places

Which of these balances has the greatest
uncertainty in measurement?

Neither

accurate nor

precise

Precise but not

accurate

Precise AND

accurate

■

Scientists use two word to describe how good the
measurements are-

■

Accuracy- how close the measurement is to the actual value

■

Precision- how well can the measurement be repeated

Limits of Measurements

What do you think? Should the United
States switch over to the metric
system?

At the bottom of your notes, give me your
answer and tell me WHY in at least 5
sentences! When you’re done…..

Scavenger Hunt!

Show me something measured in metric
units! Think volume :)