Experiment 1 – METRIC SYSTEM MEASUREMENTS AND CONVERSIONS

25 Jun Experiment 1 – METRIC SYSTEM MEASUREMENTS AND CONVERSIONS

Question
Experiment 1 – METRIC SYSTEM MEASUREMENTS AND CONVERSIONS

BACKGROUND:

In order to enhance commerce and science throughout the world, it is vital that there be a standardized system of measurements and units. Actually, there are two widely used systems.

In the U.S., we use the English system of units; common units for length, mass, and volume are feet, slugs, and gallons. Mass is a quantity of matter, and is a measure of inertia. The pound, a unit in the English system that we use for weight, is actually a force due to gravity.

In most of the rest of the world, the metric system, known now as the International System (S.I.), is used. The standard S. I. metric units for length and mass are the meter (m) and kilogram (kg); the “unofficial” standard unit of volume is the liter (L). Non-standard units are commonly used in the S.I. system (and English system), and conversions to standard units, or vice versa, often are done. Common conversion prefixes are: mega- = 1,000,000, kilo- = 1000,

centi- = 1/100, and milli- = 1/1000. A further list of conversion factors is seen in the Appendix.

One milliliter is 1/1000 of a liter and it equals one cubic centimeter (1 mL = 1 cm3). By definition, one gram of water occupies one cubic centimeter of volume (at 4oC (39oF)).

Some units are represented as ratios, e.g., for density, which is defined as mass per unit of volume. A non-standard, but commonly used S.I. unit for density is grams per cubic centimeter, g/cm3. A common English unit for density is pounds per cubic foot, lb/ft3. (For example, the density of water is 62.4 lb/ft3).

OBJECTIVES:

– To learn and use the proper S. I. metric units.

– To learn how to make simple measurements and to understand accuracy .

– To learn how to convert a measurement or quantity from one unit to another

PROCEDURE:

The following equipment will be needed: meter sticks (2), bathroom scale, wood block, balance, graduated cylinder (100 mL), graduated cylinder (25 mL), beaker (250 mL), iron nails (3).

A. Measurements of Length

Where applicable, show all calculations.

1. Bench (or table) dimensions:

a. Predict the length of your table top, in units of meters. Then use the meter stick (or a tape measure) to verify your prediction. Measure to the nearest centimeter, and convert to meter units (to two decimal places (e.g., 384 cm converts to 3.84 m)).

Prediction m Table Length cm; __________ m

b. Measure the width of the Table top: Width cm; __________ m

c. Calculate the area of the Table top, using the formula: area = length x width (A = LW)

A = _________ m2.

2. Heights of student scientists:

a. Height Measurements. Have your height measured by someone, to the nearest centimeter, using two meter sticks and sliding one on the other. Record your height (in centimeters).

Your height in centimeters cm

Convert your height to inches (1 in = 2.54 cm) in

B. Measurements of Mass, Volume, and Density

1. Mass:

a. Weigh yourself on a bathroom scale. lb

b. Convert the pounds to kilograms (1 kg = 2.2 lb) kg

{Each student should do this calculation individually; show the setup}

2. Density of solids:

This procedure is useful for measurement of the density of materials and objects that have a regular shape, e.g., a rectangular solid, or a sphere, or a cylinder.

a. Measure the dimensions (length, width, height) of a block of wood.

b. Calculate the volume (V) in cubic centimeters (cm3), using the formula:

volume = length x width x height [V = L W H]

c. Using a balance, determine the mass to the nearest 0.1 g

d. Density is the mass per unit of volume. Using the formula for density, p = m/V, calculate the densities of the blocks.

mass (g) length (cm) width (cm) height (cm) Volume (cm3) density (g/cm3)

Wood ____ ______ _______ _____ _______ _______

e. The accepted values for density of the various materials, in units of g/ cm3, are:

wood, 0.4-0.5; aluminum, 2.7; lead, 11.4; brass, 8.6; and iron, 7.9. How does your experimental value (EV) for the metal compare with the accepted value (AV)? That is, is it exact, or close (slightly off), or not close (way off)?

___________________

3. Density Of Water:

a. Using the balance, weigh a 100 mL graduated cylinder to the nearest 0.1 g.

________ g

b. Then carefully pour water from a 250 mL beaker into the graduated cylinder,

so that the volume is close or equal to 100.0 mL.

Recordthis volume, to the nearest 0.1 mL ________ mL

c. Weighthe cylinder plus water. ________g

d. Calculate the mass of the water (c. minus a.) ________g

e. Calculate the volume of water, in units of cm3 ________ cm3

(Remember: 1 mL = 1 cm3).

f. Calculatethe density of water, using the equation: p = m/V. _________ g/cm3

(Record this value to two decimal places)

g. The accepted value (AV) for the density of water is 1.00 g/cm3.

Calculate the accuracy, as represented by the experimental error, for your experimental measurement (EV) of this density, using the equation:

Experimental Error = 100(EV –AV)/AV = _______ %

4. Density Of Iron:

This procedure is useful for measurement of the density of solid materials and objects that have an irregular shape.

a. Determine the mass of three nails, to the nearest 0.1 g. Recordthe mass in the table below.

b. Add water into a 25 mL graduated cylinder to about the 18-20 mL mark. Recordthe volume of water, to the nearest 0.1 mL.

c. Place the three iron nails in the water. Record the new volume. The rise in water level is equal to the volume of the nails. Calculatethis volume.

d. Now calculate the density of iron, using the equation: p = m/V.

Mass of iron nails __________ g

Volume of water plus iron nails ________ mL

Volume of water ________ mL

Volume of iron nails _________mL = cm3

(remember – – 1 mL = 1 cm3)

Density of iron (p = m/V) ___________ g/cm3

The accepted density of iron is 7.9 g/cm3. Calculate the experimental error for your measurement of this density, using the equation:

Experimental Error = 100(EV –AV)/AV = _______ %

C. Additional Questions:

1. Why is it important to establish standard units of measurement?

2. What are the standard units of length and mass in the S.I. metric system?

A] length B] mass

3. What is the difference between mass and weight?

4. What are two methods measuring the volume of solids?

A] B]