Name ____________

10^th Grade Chemistry

Measurement

Old systems:

Cubit: Distance from end of your fingers to the elbow

Inch: width of thumb

Foot: length of foot

Your group should select one person and make the following measurements. You can always estimate one more decimal place than the unit. For example you can have 1.2 or 1.3 ft. Also be sure to include a unit behind your number.

Measure the width of your lab table using your thumb ___________________
Measure the length of your lab table using your shoe _____________________

Measure the length of the table using “cubits” ______________________

PLACE YOUR ANSWERS ON THE BOARD

1.)    What do you notice about these numbers? Explain.

2.)    If we would re-measure using a ruler do you think your results might change? Why or why not.

Through the years standards were developed for measurement. In 1960 Most countries agreed to the Systeme International d’Unites (SI) system.

Some examples of Base units of SI

Derived units are combination of base units. Some examples are

Estimating with metric units

 Choosing the Right Unit

First choose which METRIC unit would you use to measure the following then estimate how many you would have. ex 20 mL

a.) volume of a coffee cup ____             b.) Volume of a swimming pool____  c.) mass of a ladybug ______

d.) height of empire state building ____   e.) distance to Yankton ______         f.) length of this room _____

g.) mass of a person ______                  h.) length of your pencil _______        i.) diameter of pencil lead ___

 Converting within the metric system.

Method 1: Use the factor label method.

The scientific notation always goes with the unit (ie. L, m, g, etc)

1.) Convert 25,000 meters to kilometers.

25,000 meters X (1 km/10³m) = 25 m

2.) Convert 450 milliliters to liters.

450 milliliters x (10^-3L/mL) = 0.450 L Remember that 10^-3 = 1/10³  (reciprocal) so it could also look like

450 milliliters x (L/10³mL) = 0.450 L Notice the difference in the placement of the exponent.

3.) Convert 35 Mg to grams

35 Mg x (10⁶ g/Mg) = 35 x 10⁶ g

Sample problems: Show the factor label method

1.)    35 kg = _______g

2.)    35 mm = __________m

3.)    23,560 kg ____________g

4.)    345 L= ___________ mL (You can do this as a two step or one step)

5.)    45 mg ____________g

6.)    45 m _________________mm

7.)    50 gigawatts ___________watts

You many think that you will never run across some of these prefixes but here are some common examples. (giga watt You tube video)

      8.)  An old computer floppy disk could hold about 1.44 MB (megabytes) of information. A typical CD- R’s can hold about 650 MB. About how many floppies can fit on a CD-R?

      9.) I just bought a 2 GB USB flash drive to store pictures, word documents, etc. How many floppies can fit on my flash drive?

      10.) If you lost your electricity a 4500 watt generator would probably be big enough to power most of your house. How many kw is this?

      11.) Recently a wind turbine was put up in Chamberlein, SD that is capable of producing 1.3 Mw. Assuming a typical home needs 4500 watts, how many homes is this one windmill capable of providing power for?

      12.) In the back to future clip how many homes could be powered by 1.2 Gw?

Method 2: Use the Stair step diagram (see handout)

Sample Problems:

a.)  25 km _________m     b.) 3.4 m _____________cm          c.) 25 mL ___________L

d.) 2.3 mm _________cm   e.) 45 dL ___________mL            f.) 75 g ____________mg

g.) 23.5 kg ____________mg   h.) 12.5 daL _________kL          i.) 52 hm __________m