C HAPTER 4: S CIENTIFIC M EASURES Ms. Johnson Foundations.

CHAPTER 4: SCIENTIFIC MEASURESMs. Johnson

Foundations

OBJECTIVES Mass is a measure of the amount of material in an

object. Mass may be measures in grams (g) or kilograms (kg) with a balance.

Volume is the amount of space an object occupies. Volume may be measure in milliliters (mL) with a graduated cylinder.

Length is the distance between two points. Length may be measured in meters (m) or centimeters (cm) with a ruler or tape measure.

OBJECTIVES

Temperate measures how hot or cold something is. Temperature is measured in degrees Celsius (°C) with a thermometer.

In the metric system, a prefix is used to change the value of a unit: kilo=1000 milli= centi=

Density= An object floats if it is less dense than the

liquid in which it is placed.

VOCABULARY

Metric system Meter Mass Weight

Volume Graduated cylinder Meniscus Density Temperature

MAKING MEASUREMENTS

Quantity Unit Abbreviation

Length Meter m

Mass Kilogram kg

Volume Liter L

Time Second s

Temperature Degree Celsius °C

Energy Joule J

Power Watt W

Force Newton N

Scientists make many different kinds of measurements and use the same types of units to express them. This system is called the metric system.

This table lists some of the quantities that scientists measure and the units they are expressed in.

MAKING MEASUREMENTS

Prefixes Used in the Metric System

0.000001 micro-

0.001 milli-

0.01 centi-

0.1 deci-

1,000 - Kilo

1,000,000 - Mega

1,000,000,000 - Giga

Ex. 1 A kilogram is ____________ grams.Ex. 2 A millisecond is ______________ of a second.

100011000

TOOLS OF MEASUREMENT

Length: the distance between two points. Standard unit: meter (slightly longer than a

yard) Smaller measurements: centimeter, millimeter Long distances: kilometer


Mass: quantity that measures the amount of a material in an object. Measured in: grams or kilograms A kilogram is equal to a quart of milk, and a

gram is about equal to a large paperclip Mass is measured with a balance


Weight: a measure of the pull of gravity on an object.

Depends on the mass of an object and the strength of gravity.

Weight is measured with a scale The metric unit for weight is the Newton

TOOLS OF MEASUREMENT Since weight depends

on gravity, an objects weight can change, but the mass stays the same. For example, on the

moon there is less gravity than Earth; your mass would not change, but you weigh significantly less.

Since weight can changed based on gravity, scientists usually use Mass.


Volume: the amount of space an object occupies. For solids, the unit is the cubic centimeter () To solve for volume you take an objects

length x width x height For liquids, the unit is the liter (L)

1 liter= 1000 To measure volume, scientists use a graduated

cylinder


Once liquid has been poured, the graduated cylinder is placed on a level surface

You read the measurement from the bottom of the meniscus Meniscus: a curve

at the surface


Density: the mass of an object divided by its volume.

Expressed in g/cm3

The mass and volume of a piece of metal depends on the size of the piece of metal, its density depends on the general nature of the metal.

For example, airplanes are made out of aluminum while fishing sinkers are made of lead.

Lead has a density of 11.3 g/cm3 and aluminum has a density of 2.7g/cm3

USING DENSITY TO IDENTIFY A METAL

Tin foil and aluminum foil look alike.

• Aluminum: 2.7 g/cm3

• Tin: 7.3 g/cm3

If you are handed a 5.0 cm3 piece, and you weigh it and its mass is 36.5 g, which type of foil do you have?

1. Start with the original formula for density.

2. Plug in the numbers you do have.

3. Solve.

The sample you have is Tin foil, based on the answer you got for density.

WHY DO OBJECTS FLOAT?

The reasons why thing float and sink lies in the densities they have. A material will float

if it is less dense than the liquid it is placed in A wooden log floats

on water An iron nail sinks

Water has a density of 1 g/cm3

When comparing densities in this column, you can see that Honey is at the bottom while vegetable oil is towards the top, so you can conclude that honey is denser.

WHAT ABOUT HOT AIR BALLOONS? Helium balloons float in the

air, so helium must less dense than air.

Hot air balloons use hot air instead of helium, and they also float. From this we can conclude

that hot air must be less dense than cold air.

When most materials are heated they expand, so their volumes increase, which causes a decrease in density.

An increase in temperature causes a decrease in density.


Temperature: a measure of how hot or cold something is. Measured with a thermometer

Consists of a liquid (usually mercury or alcohol) which expands when heated

As the liquid expands, it moves up the column Temperature is either measured in Fahrenheit

(°F) or Celsius (°C)


Two important temperatures to remember are the freezing and boiling points of water Freezing: 0 °C or 32 °F Boiling: 100 °C or 212 °F

Two other temperatures are room temperature and body temperature Room: 20 °C or 68 °F Body: 37 °C or 98.6 °F

YOU HAVE A ROCK WITH A VOLUME OF 15CM3 AND A MASS OF 45 G. WHAT IS ITS DENSITY?

YOU HAVE A DIFFERENT ROCK WITH A VOLUME OF 30CM3 AND A MASS OF 60G. WHAT IS ITS DENSITY?

IN THE ABOVE TWO EXAMPLES WHICH ROCK IS HEAVIER? WHICH IS LIGHTER? IN THE ABOVE TWO EXAMPLES WHICH ROCK IS MORE DENSE? WHICH IS LESS DENSE?

Rock 1 d: Rock 2 d:

Rock 2 is heavier with a mass of 60 g. Rock 1 is lighter with a mass of 45 g.

Rock 1 is more dense, and rock 2 is less dense.

QUESTIONS?

C HAPTER 4: S CIENTIFIC M EASURES Ms. Johnson Foundations.

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