1.3 Measurement

Chapter 1, Section 3

Page 16

Section 3:Measurement

Why do scientists use a standard measurement system?

What are the SI units of measurement for length, mass, volume, density, time, and temperature?

A Standard Measurement System • The SI (or Systeme International d’Unites) is the

international standard system of measurement.

• Why is it important to have a single standard system for measurement?

• The SI allows scientists to compare data and communicate with each other about their results.

A Standard Measurement System SI units are based on multiples of 10.

A Standard Measurement System

SI units are based on multiples of 10.

kilo-

1,000

k

hecto-

100

h

deka-

10

da

Base

1

deci-

0.1

d

centi-

.01

c

milli-

.001

m

King Henry died by drinking chocolate milk.

A Standard Measurement System

SI units are based on multiples of 10.

kilo-

km

King

hecto-

hm

Henry

deka-

dam

Died

Base

m

meter

By

deci-

dm

Drinking

centi-

cm

Chocolate

milli-

mm

Milk

A Standard Measurement System

SI units are based on multiples of 10.

kilo-

kg

King

hecto-

hg

Henry

deka-

dag

Died

Base

g

gram

By

deci-

dg

Drinking

centi-

cg

Chocolate

milli-

mg

Milk

A Standard Measurement System

SI units are based on multiples of 10.

kilo-

kL

King

hecto-

hL

Henry

deka-

daL

Died

Base

L

liter

By

deci-

dL

Drinking

centi-

cL

Chocolate

milli-

mL

Milk

Length

The basic unit of length in SI is the meter (m).

It was defined as one-ten millionth of the distance from the equator to the north pole.

Weight vs. Mass

Mass has to do with the amount of matter an object contains. An object’s mass is the same regardless of where it is.

Weight has to do with the measure of the pull of gravity on the object. This pull of gravity differs with location. So, an object‘s weight differs with its location.

Weight vs. Mass• Joe, who weighs 140

pounds on Earth, would weigh 23 pounds on the Moon. His body mass would stay the same. But his weight changes due to a lesser pull of gravity on the Moon.

Mass

The SI unit of mass is the kilogram (kg).

Volume

The SI unit of volume is the cubic meter (m3).

Common units of volume are the liter (L), the milliliter (mL) cubic centimeter (cm3 or cc).

When determining the volume of a fluid using a graduated cylinder …

Density

Density refers to the amount of matter that is contained in a certain amount of volume or space. It is better known as mass per unit volume.

It is determined by first finding the mass and the volume of an object.

Then, density is the mass of an object divided by its volume. Or:

Density = __Mass__ Volume

Calculating Density • Suppose that a metal object has a mass of

57 g and a volume of 21 cm3. Calculate its density.

• Read and Understand• What information are you given?• Mass of metal object = 57 g• Volume of metal object = 21 cm3

Calculating Density • Suppose that a metal object has a mass of

57 g and a volume of 21 cm3. Calculate its density.

• Plan and Solve• What quantity are you trying to calculate?• The density of the metal object = __• What formula contains the given quantities and the

unknown quantity?• Density = Mass/Volume• Perform the calculation.• Density = Mass/Volume = 57 g/21 cm3 = 2.7 g/cm3

Calculating Density •Suppose that a metal object has a mass of 57 g and a volume of 21 cm3. Calculate its density.

•Look Back and Check

•Does your answer make sense?•The answer tells you that the metal object has a density of 2.7 g/cm3. The answer makes sense because it is the same as the density of a known metal–aluminum.

Calculating Density• Practice Problem

• What is the density of a wood block with a mass of 57 g and a volume of 125 cm3?

• 0.46 g/cm3

Calculating Density• Practice Problem

• What is the density of a liquid with a mass of 45 g and a volume of 48 mL?

• 0.94 g/mL

Density

• Because density is actually made up of two other measurements–mass and volume–an object’s density is expressed as a combination of two units. The density of a substance stays the same no matter how large or small a sample of the substance is.

Time

The second (s) is the SI unit of time.

Temperature

Scientists use the Celsius and Kelvin scales to measure temperature. The kelvin (K) is the SI unit of temperature.

Celsius (Co)

Celsius (Co)

More on Measurement

• Click the PHSchool.com button for an activity about

measurement.

End of Section:Measurement