Measurements in Science

                 

The Capital Gate, a 2-billion dollar worth skyscraper built in Abu Dhabi, is the building to hold the Guinness Book of World Records’ “World’s Furthest Leaning Man-made Tower” that features a gravity-defying 18-degree incline to the west, leaning 5 times more than the Leaning Tower of Pisa in Italy. Careful planning and measurement is needed to build this record-breaking building to prevent it from collapsing due to gravity or earthquakes.

INTRODUCTION

               The African Elephant is the largest land animal on earth. An average male elephant weighs 4990 kg. If an average Third Year High School student weighs 120 lbs., how many students is equivalent to one African Elephant?

Measurement is part of our everyday lives. Whenever we prepare our breakfast, take a bath, or go to school, we have to measure things around us to avoid waste of precious resources. In chemistry, careful measurement is needed to avoid wasting expensive chemicals and to prevent possible chemical spills or accident. In some instances, we simply take measurements through rough estimation of the amount, but when dealing with chemicals, accuracy and precision implemented to get the correct data in an experiment.

2.2 QUALITATIVE DATA VS. QUANTITATIVE DATA

Part of the scientific method is gathering information. This information that you can gather in a research or experiment may boa both qualitative and quantitative.

ÿ        Qualitative Data - consisting of general observations about the system (color, shape, odor, appearance, etc.,)

ÿ        Quantitative Data -  comprising numbers obtained by various measurements of the system (mass, length, time, density, etc.,)

Looking at the picture to the right, here are examples of qualitative and quantitative data:

Qualitative data:

1. Ginger bread men are brown in color;

2. White lining was used for drawing the details;

3. Some parts of the Ginger Bread men were missing.

Quantitative data:

1. There are six ginger bread men;

2. Two ginger bread men got damaged or cut off head;

3. Three ginger bread men lost its left leg.

                Qualitative data gathering normally uses the five senses while quantitative data gathering requires the use of measuring tools and devices. Measuring tools and devices are used to get exact values and these measuring tools should follow international standards when comparing our measurement with other people.

2.3 QUANTITATIVE MEASUREMENT

                 Quantitative measurements are usually written as a number with an appropriate unit. A number like 123 would be meaningless if it does not have a unit to describe the number. But if we say 123 hours or 123 meters; then the number would have more sense to it. Different countries make use of different units of measurement.

                Israel use Shekel as a unit for mass while US use pounds, and Russia pud. The scientific community in the 1800’s used the metric system, which was conceived by an assembly formed by Louis XVI of France. Later in 1960, the 11^th General Conference on Weights and Measures revised the Metric System (with five basic units) into the International System of Units (Système Internationale d’Unites) or SI Units (with seven base units). These units are not used as the international standard for measurement.

Table 2.1 SI Base Units

Base Units	Name of Unit	Unit Symbol
Length Mass Time Electrical Current Temperature Amount of Substance Luminous Intensity	Meter Kilogram Second Ampere Kelvin Mole Candela	M Kg s A K mol cd

Quantities can either be base or derived:

Base Quantity – are conventionally accepted as functionally independent of one another (see table above)

Derived Quantity – quantity defined in a system of quantities as a function of base quantities of that system (density, volume, area, pressure, coulomb, etc.,)

All basic and derived units would use a set of prefixes. Prefixes are use to multiply or divide the measure by a factor of 10.

Table 2.2 Prefixes used for SI Units

Prefix	Symbol	Equivalent	Factor
Yotta- Zetta- Exa- Peta- Tera- Giga- Mega- Kilo- Deca- Deci- Centi- Milli- Micro- Nano- Pico- Femto- Atto- Zepto- Yocto-	Y- Z- E- P- T- G- M- K- da- d- c m µ n p f a z y	1 000 000 000 000 000 000 000 000 1 000 000 000 000 000 000 000 1 000 000 000 000 000 000 1 000 000 000 000 000 1 000 000 000 000   1 000 000 000   1 000 000   1 000   10 0.1 0.01   0.001   0.000 001   0.000 000 001   0.000 000 000 001   0.000 000 000 000 001   0.000 000 000 000 000 001   0.000 000 000 000 000 000 001   0.000 000 000 000 000 000 000 001	1024 1021 1018 1015 1012 109 106 103 101 10-1 10-2 10-3 10-6 10-9 10-12 10-15 10-18 10-21 10-24

Mass vs. Weight

                The terms “mass” and “weight” are two terms that are commonly mistaken as synonymous.

ÿ        Mass – the amount of matter in an object

ÿ        Weight – the force on an object due to gravity (mass times acceleration due to gravity)

Your mass here on earth as well as in Jupiter is the same while your weight in Jupiter is 2.5 times than that of your weight here on earth.

Volume

                Volume is a unit of length that refers to the space occupied by matter. The Si unit for volume of cubic meter (m³0 but since it is a large quantity, chemists use smaller units of volume like liter or milliliter.

1 cubic meter (m³) = 1000 dm³ or 1000 L

                                    = 100 000 cm³ or 100 000mL

Density

Density is the ratio of mass and volume.

 The SI derived unit for density is kg/m³, but since kg and m³ are large quantities, a smaller unit like g/cm³ is used for laboratory applications. The units used for measuring densities are:

o   g/cm³ for solid substances

o   g/ml for liquid substances

The device used for measuring the density of a substance is called pycnometer. You can compute for the mass or volume of a given substance using density. By transposing a variable, you can derive two formulas:

                                                                             

Table 2.3 Densities of Some Common Substances at 20oC
Substance	Density (g/cm3)
Hydrogen Gas Oxygen Gas Water Ice Table Salt Ethyl Alcohol Milk Lead Silver Gold Diamond	0.0000899 0.00133 1.00 0.917 2.16 0.791 1.03 11.34 10.50 19.32 3.51

“The Archimedes Principle”

In the first century BC, a Roman architect named Vitruvius related the story on how Archimedes solved the problem on whether the golden wreath crown of King Hiero II of Syracuse was made up of pure gold or not. During those times, goldsmiths mix silver with gold. Because the crown was meant to be placed on the statue of a god or goddess, Archimedes could not disturb the wreath in any way (non-destructive testing).

Archimedes was really problematic on how he could solve the problem. To relax himself, he took a bath in his bathtub that is brimming with water. When he stepped into the tub, the water overflowed. Upon seeing what happened, he shouted, “Eureka!”, which means, “I’ve found it!”. Archimedes found a way to determine whether the wreath crown was pure or not.

His idea was to place a weight of pure gold that is equal to the wreath crown into a bowl brimming with water. The pure gold would be removed and the King’s crown in its place. If the wreath crown was made up of pure gold, it would have the same volume as that of the pure gold initially placed in the bowl and the water would not overflow and just reach the brim. But since light silver-gold alloys are bulkier, it would cause the water in the bowl to overflow.