Chapter 2, Section 1

Measurement – A Common Language

Chapter 2, Section 1 – The Nature of Science and Technology

A Standard Measurement System

The Metric System› A system of measurement based on the

number 10

The International System of Units (SI)› Using SI allows scientists to compare data

and communicate with each other about their results

LENGTH The basic unit of length in

the SI system is the meter To measure objects smaller

than a meter scientists use units called the centimeter (cm) or the millimeter (mm)

Large distances are measured using kilometers (km)

To measure length we use a metric ruler

MASS The basic unit of mass in the SI system

is the kilogram (kg) To measure the mass of smaller objects

we use the gram (g) Even smaller masses are measured in

milligrams (mg) To measure mass we use a balance

MASS VS. WEIGHT…

Weight is the force of gravity acting on an object. This CAN change

Mass is the measure of the amount of matter an object contains. This ALWAYS stays the same!!

VOLUME

The amount of space an object takes up

To measure the volume of liquid scientists use the liter (L)

Smaller volumes are measured using milliliters (mL)

Volume of Liquids

To measure the volume of liquid just pour it into a container with markings that show the volume

Be sure you read the volume at the BOTTOM of the meniscus (the curved upper surface of a liquid in a column of liquid)

Volume of Rectangular Solids

To measure the volume of solid we use the cubic centimeter (cm3)

Larger volumes can be measured using the cubic meter (m3)

Calculate the volume using the formula: Volume=Length X Width X Height (or V=LWH)

Volume of Irregular Solids

To measure the volume of solid such as rock we can immerse the object in water and measure how much the water rises

Density

Density is the measure of how much mass is contained in a given volume

To calculate density divide the mass of the object by it’s volume (D=M/V)

Density is always expressed using TWO units such as grams per cubic centimeter (g/cm3), or grams per milliliter (g/mL)

Time

The SI unit of time is the second

The second can be divided, just as other units can (example, millisecond=one-thousandth of a second

Longer times are measured in minutes or hours

Temperature

Scientist commonly use the Celsius scale

On this scale water freezes at 0oC and boils at 100oC

Scientist may also use the OFFICIAL SI unit, Kelvin (K)

On Kelvin water freezes at 273oK and boils at 373oK

Measure temperature using a thermometer