Making Measurements & Using the METRIC SYSTEM

Physical Science 200

p.204-205

Types of OBSERVATIONS

Quantitative: Tells us how many. Describes “Quantity” Describes observations with numbers.

Qualitative: Tells us about it. Describes “Quality” Describes observations with words.

Qualitative Vs. Quantitative

His shirt is red. There are 2 apples left. The table is 5 meters long. A blue crystal formed on the bottom of our

100mL beaker. Her shirt is 100% cotton.

What are units?

Steve has 10. There are 43.6 of salt.

Numbers do not make sense if there is no unit. A unit tells us what the number measures.

In science class there are NO NAKED NUMBERS- make them appropriate with a unit!

Precision Vs. Accuracy

Precision is how closely repeated measurements match each other. If you can measure something 1000

times and every time you get the same measurement, you are precise.

Accuracy is how closely a measurement matches the correct or expected value. If you measure something very

closely to the measurement that it is supposed to be, you are accurate.

A ball player's height can be measured precisely, but still not be accurate.

How tall is that horse?

In the past it was common to measure the height of a horse in hands.

Measure the height of your desk in hands and write it below:

Is this a good system for measuring?

The International System of Units

ALL SCIENTISTS us the International System of Units.

We abbreviate it as SI. Some good things about measuring in SI:

It is based on multiples of 10. There are no fractions- we use decimals in the

metric system. All scientists use the International System of

Units.

Who uses the SI system?

In everyday life, just about everyone except for US! These countries do not use the metric system:

The United States of America Liberia Myanmar

ALL SCIENTISTS IN THE WORLD USE THE SI SYSTEM OF MEASUREMENT!

What are prefixes?

Pre means “before” A prefix is a small part of a word that comes

before the word. Metric prefixes equal a number.

Common Metric Prefixes

Prefix Symbol Meaning

Giga- G 1 000 000 000 or 109

Mega- M 1 000 000 or 106

kilo- k 1000

hecto- h 100

deka- da 10

deci- d 0.1 (one tenth)

centi- c 0.01 (one hundredth)

milli- m 0.001 (one thousandth)

nano- n 0.000 000 001 or 10-9

How can you put those numbers in your calculator?

Try these: 104

10-4

10-2

102

103

Adding prefixes

When we measure, we can add a prefix to change the value.

1 nanosecond = how many seconds? Find nano- on your chart. What does it mean?

1 nanosecond = 10-9 seconds 1 kilometer = 1000 meters 1 milligram = 0.001 grams

Rules for writing metric symbols

Do not use a period. 7 s [not 7sec.]

Leave a space. 6 kg [not 6kg]

Do not add an s to the symbol. 10 Kilometers = 10 km [not 10 kms]

Do not capitalize, unless it is supposed to be capital. Milliliter = ml [not Ml]

Do not use p for per. miles per hour = mi/hr [not mph]

Write the correct units

mm = millimeter

mg = milligrams

L = liter

Mg = Megagram

m = meter

dam = decameter

 

g = gram cm = centimeters ns = nanosecond

Which number is bigger?

4 cm or 4 hm

10 km or 10 mm

12g or 12 kg

What will we measure?

Length Distance between two points.

Mass Amount of material in an object.

Temperature Amount of heat a material has.

Volume Amount of space an object takes up.

What are BASE UNITS?

A base unit is the standard unit of measurement that we will use to measure.

We will add prefixes to the base units.

Measuring LENGTH

The SI base unit of measurement for length is the METER.

1 meter = 1m Your desk is about one meter tall. You can use a METRIC RULER or a METERSTICK

to measure length.

Other units of length

If you wanted to measure between cities, you would use KILOMETERS.

A kilometer is equal to 1,000 meters. If you wanted to measure small lengths, you

would use a centimeter or a millimeter. There are 100 centimeters in a meter. Just like there are 100 cents in a dollar. There are 1000 millimeters in a meter.

SURFACE AREA

Surface area is the space that a surface covers.

If you wanted to buy carpet or floor tile, you will have to know the SURFACE AREA of the floor.

Calculating SURFACE AREA

To find the area of a rectangle, multiply length X width.

AREA = Length X Width What is the area of this rectangle?

10cm5cm

A = L X W= 10 cm X 5 cm= 50 cm2

Practice!

How much carpet do you need to cover the floor in a room that measures 7 meters long and 5 meters wide?

L = 7 m W = 5 m A = L X W

A = 7 m X 5 mA = 35m2

Measuring VOLUME of a liquid

The SI base unit of measurement for volume is the LITER.

1 Liter = 1L You will use different units and tools to

measure volume of a liquid or a solid. You can use a GRADUATED CYLINDER

to measure the volume of a liquid.

Graduated cylinders measure in mL or milliliters.

The plastic ring around a graduated cylinder prevents breaking.

To read a graduated cylinder: Move to eye level. Read the bottom of the meniscus.

How much water is in this graduated cylinder?

Image from ChemPages Laboratory Resources http://jchemed.chem.wisc.edu/JCESoft/Programs/CPL/Sample/modules/gradcyl/grad100mL.htm

VOLUME of a solid

If you are trying to find the volume of a solid, you cannot pour it into a graduated cylinder.

Methods: Water displacement Calculating volume

Water Displacement

What steps will you take to measure with water displacement?

Put water in the graduated cylinder. Record the measurement. Tilt the graduated cylinder to the side. Gently lower the object into the graduated cylinder.

(Make sure that the whole object is under water.) Record the measurement. Water & Object – Water = Object’s volume REMEMBER 1 ml = 1 cm3 = 1 cc

Calculating Volume of a Block

To find the volume of a regular (block or box shaped) solid, you need to measure the length, width and height IN THE SAME UNIT and multiply these three numbers together. V= L X W X H

What is the volume of the black cube? What is the volume of the bigger cube? Volume = length X width X height V = 3 cm X 2 cm X 2 cm V = 12 cm3

Units of VOLUME

1 liter = 1 L 1 milliliter = 1 mL 1 centimeter cubed = 1 cubic centimeter = 1 cm3 = 1 cc

1 L = 1000 mL 1 mL = 1 cm3

1 L = ___________cm3

Measuring MASS

The SI base unit of measurement for mass is the GRAM.

1 gram = 1g A paperclip is about 1 gram. You can use a TRIPLE BEAM BALANCE

or an ELECTRONIC SCALE to measure mass.

Using an electronic balance

They are very sensitive. DO NOT place heavy objects or press down

with your hand. DO NOT put liquid, powder or crystals

directly on the tray.

Other units of mass

If you wanted to measure large masses you would use KILOGRAMS.

1 Liter of pop has a mass of about 1 kilogram. If you wanted to measure the mass of smaller

objects, you would use milligrams or centigrams.

When have you heard someone say milligrams?

Measuring TEMPERATURE

The SI base unit of measurement for temperature is Kelvin (K).

A more common unit is DEGREES CELSIUS.

1 degrees Celsius = 1ºC You can use a THERMOMETER to measure

temperature.

Look at the picture to compare ºF and ºC.

Measuring TIME

The SI base unit of measurement for time is the SECOND.

1 second = 1s

We will use a STOPWATCH to measure time in science class.

Time (s)

How do you change from one unit to another?

From another system to metrics or changing metrics FACTOR LABEL METHOD.

From metrics to metrics, MOVE THE DECIMAL.

from Industry Week, 1981 November 30

FACTOR LABEL METHOD

Write down what you know. Write down what you know about those two

units. Multiply by a fraction. Cancel out like units. Do the math.

Let’s Practice!

600 mm = ? m 1 m = 1000 mm or 1 mm = 0.001 m 600 mm X 1 m = 0.6 m

1000 mm

0.35 liters = ? milliliters

1050 grams = ? kilograms

4 years = ? days

20 kilograms = ? milligrams

3500 seconds = ? hours

Moving the decimal

                         

Metric unit conversion is simply a matter of moving the decimal in the correct direction and the correct number of places.

Write this chart:

kilo hecto deca BASE UNIT deci centi milli

k h da gram (g)meter ( m)

liter (L) second (s)

d c m

1000 100 10 0.1 0.01 0.001

103 102 101 10-1 10-2 10-3

Find the unit you are starting with.

Find the unit you want to change to.

Count the number of spaces you have to move.

Which way did you move?

Move the decimal in that direction that number of spaces.

Convert these: 35 ml = ? dl 2000 mm = ? km 0.752 hg = ? cg

kilo hecto deca BASE UNIT deci centi milli

k h da gram (g)meter ( m)

liter (L) second (s)

d c m

1000 100 10 0.1 0.01 0.001

103 102 101 10-1 10-2 10-3

How can we remember the order of the chart?

Kids Have Dropped OVER Dead Converting Metrics

Kilo Hecto Deca OVER Deci Centi Millimeterlitergram

What is your mnemonic device?

DENSITY

Pages 94- 95

ORGANIZING DATA

Pages 210-211

ANALYZING DATA

Pages 212-213

Images copied from:

http://lamar.colostate.edu/~hillger/brownridge.html#changing-prefixes

http://invsee.asu.edu/Modules/size&scale/unit2/unit2.htm