8/2. why do we need this? scientists need standard units of measurement so that their work can be...

MEASUREMENT/SI UNITS

8/2

SI Units

Why do we need this? Scientists need standard units of

measurement so that their work can be reproduced by other scientists. (previously known as the metric system)

Base Units

There are seven base units in SI.

A base unit –has no prefix (what is a prefix) Exception –mass (kg)

So what is expressed in base units? Time Length Mass Temperature

How Do I Remember It?

King Henry Died By Drinking Chocolate Milk

Kilo, Hecto, Deca, BASE, Deci, Centi, Milli

B = Base Unit (No Prefix)

Let’s Practice Converting Between Units

1 mL KL 45 g cg 0.26 decaseconds deciseconds 410 Km cm

All you are doing is moving the decimal!!!

How do I measure things in chemistry?

To measure mass you will use a triple beam balance. Your METRIC units will be in grams.

To measure liquids or volume, you will use a

graduated cylinder. Your METRIC units will be in

milliliters (mL) . To measure the length, width, or height of

an object, you will use a ruler. Your metric units will be

in millimeters, centimeters, or meters. What is the difference between these units?

The metric unit for temperature is Kelvin (K) What would I use? C + 273

Triple Beam Balance

http://www.wisc-online.com/objects/index_tj.asp?objID=GCH202

What are the units?

Ruler

http://www.funbrain.com/measure/

What are the units?

Graduated Cylinder

http://www.uwplatt.edu/chemep/chem/chemscape/labdocs/catofp/measurea/volume/gradcyl/gradcyl.htm

What are the units?

Rounding

What does it mean to round to the nearest tenth?

Hundredth?

Thousandth?