PHYSICAL SCIENCE Chapter 1 The Nature of Science

PHYSICAL SCIENCE Chapter 1 The Nature of Science 1. 2 Standards of Measurement

1. 2 Standards of Measurement Objectives • Name the prefixes used in SI and indicate what multiple of ten each one represents. • Identify SI units and symbols for length, volume, mass, density, time, and temperature. • Convert related SI units.

Units and Standards • A standard is an exact quantity that people agree to use to compare measurements. • Cubits (forearm tip from tip of middle finger to bottom of elbow) and spans (distance from end of little finger to end of thumb of a spread hand) were used in ancient times as units of measurement. • What problems do you expect with these units?

Measurement Systems • Both a number and a unit must be used for a measurement to make sense. • English system of measurement commonly used in US. • Most countries use the metric system. • In 1960, an improved metric system was developed – SI (International System of Units – Le Systeme Internationale d’Unites) • SI standards are universally understood and accepted by scientists globally.

Measurement Systems • Every type of SI measurement has a base unit. • SI is based on multiples of ten. • Prefixes are used with the base unit name to indicate the multiple of ten to be used.

Measurement Systems Quantity Measured Unit Symbol Length meter m Mass kilogram kg Time second s Electric Current ampere Symbol Multiplying Factor Kilo- k 1, 000 Deci- d 0. 1 Centi- c 0. 01 Milli- m 0. 001 Micro- μ 0. 000001 Nano- n 0. 00001 A Temperature kelvin K Amount of Substance mol candela cd Intensity of Light Prefix

Measurement Systems • A conversion factor is a ratio that is equal to one, and is used to change one unit to another unit. • See “Applying Math” pg. 16. http: //www. wonderwhizkids. com/conceptmaps/ conversion_factor_units. html

Measuring Distance • Length is the distance between two points. • SI basic unit of length is the meter. • Rulers and metersticks are used to measure distances. • Choose appropriate unit of length to avoid multiple zeros.

Measuring Volume • The amount of space occupied by an object is its volume. • The formula for a block is length x width x height. • The most common units for liquid volume are liters and milliliters. • One milliliter is equivalent to one cubic centimeter.

Measuring Matter • Mass is the measurement of a quantity of matter in an object. • Density is the mass per unit volume of a material. • Density may be found by dividing an objects mass by its volume. • A unit of measurement that can only be found by combining other units is called a derived unit.

Measuring Time and Temperature • SI unit for time is the second. • In science, temperature is often measured on the Celsius scale. • On Celsius scale, water freezes at 0°C and boils at 100°C. • Average human body temperature is 37°C Typical room temperature is between 21 - 24°C. • Kelvin is SI unit of temperature. • On Kelvin scale, water freezes at 273 K, and boils at 373 K.