PS- 1.3

Scientific Measurements

Bad Joke…..

Why did the bottle insist on being at the front of the shelf?

Because it was a liter, not a follower!

Why was a system needed? Long ago, parts of

the human body were often used as units of measure.

Egyptian “cubit” was the length from your elbow to the tip of your middle finger.

The length of the kings foot or the distance from the tip of his nose to his fingertips were common units of measurement.

See any obvious problems with this line of thought?

Different from country to country

Existing measurements would change each time a new king was crowned

Different from body part to body part

The metric system was created with the purpose of establishing a universal system of measurement that could easily be used by people all over the world regardless of their country of origin.

Metric System Facts

Developed by the French in late 1700s and was officially adopted in 1790.

Named “Le Systeme International d’Unites”; Abbreviated SI

Was initially forced on all countries. The option for people to use the metric

system or not in the US became legal in 1866.

Metric System Facts Cont’d:

USA opted out of using the system.

USA is the only technologically advanced country NOT using the Metric System as it’s main system of measurement; Still using the English System which is a combo

Especially important to scientists

Metric System Facts Cont’d:

Decimal based system

~ What the heck does that mean?

It’s based on powers of 10, so it is very simple to use

The Metric units most often used by average people are….

Meter: measures length Second: measures time Gram: measures mass Liter: measures volume Degree Celsius: measures temperature

YOU WILL SEE THIS AGAIN!!

Regardless of the unit, the entire metric

system uses the same prefixes.

Most common prefixes

Kilo – 1000 Deci – 1/10 or 0.1 Hecto – 100 Centi – 1/100 or 0.01 Deka – 10 Milli – 1/1000 0r 0.001 Meter/gram/liter – 1

“King Henry’s Daughter Usually Drinks Chocolate Milk”

Length

Length is the distance between 2 points

The SI base unit for length is the meter

Length

We use rulers or meter sticks to find the length of objects.

Mass

Mass is the amount of matter that makes up an object.

The SI unit for mass is the gram.The mass of an object will not

change unless we add or subtract matter from it.

Mass

A golf ball and a ping pong ball are the same size, but the golf ball has a lot more

matter in it.

Which has more mass?

~the golf ball has more mass

Mass

A paper clip has a mass of about one gram

Remember: the mass of an object will not change unless we add or subtract matter from it.

Measuring Mass

We will use a triple beam balance scale to measure mass.

Gravity pulls equally on both sides of a balance scale, so you will get the same mass no matter

what planet you are on.

Weight

Weight is a measure of the force of gravity on an object.

The SI unit for weight is the Newton (N).

The English unit for weight is the pound

Gravity

Gravity is the force of attraction between any two objects with mass.

Gravity depends on 2 things:

Distance and Mass

Gravity

More distance = less gravity= less weight

Less distance = more gravity = more

weight

More mass = more gravity = more weight

Less mass = less gravity = less weight

Weight vs Mass

Jill Earth Moon Jupiter Orbit

Gravity 1 gravity 1/6th gravity

2.5 gravities

0 gravity

Mass 30 kg 30 kg 30 kg 30 kg

Weight 300 N 50 N 750 N 0 N

** Notice that Jill’s mass never changes**

Jill is a 30 kg little girl no matter where she goes or what planet she is on.

Jill Earth Moon Jupiter Orbit

Gravity 1 gravity 1/6th gravity

2.5 gravities

0 gravity

Mass 30 kg 30 kg 30 kg 30 kg

Weight 300 N 50 N 750 N 0 N

Volume

Volume is the amount of space contained in an object.

We can find the volume of box shapes with this formula

V = L x W x H

Volume Cont’d…

In the case of box shapes, the units would be cubic centimeters (cm³).

So, a box that is 2cm x 3cm x 5cm would have a volume of……

30 cm³

Base Units

The base unit for volume is the Liter.

We measure volume with a graduated cylinder.

Graduated Cylinders

Liquids form curved, upper surfaces when poured into graduated cylinders (sticks to the sides)

To correctly read the volume, read the bottom of the curve called the meniscus

Liquid Volume

When the metric system was created, they decided that 1 cm³ of water would equal 1 milliliter of water.

That 1ml of water would have a mass of one gram.

1cm³ water = 1ml water = 1 gram of water

Water Displacement

You can use water displacement to find the volume of objects that are not box shaped.

Water Displacement

We can put water in a graduated cylinder. If a rock causes the level to rise from 7 ml to 9 ml, the rock must have a volume of 2ml.

Water Mass and Volume

Remember:

1 cm³ = 1 ml = 1 g What would be the mass of 50 ml of

water?

50 grams How many milliliters would you have if you

were given 23 cm³ of water?23 ml

Density

Density is the amount of matter (mass) compared to the amount of space (volume) an object occupies.

We will measure mass in grams and volume in ml or cm³

Density Formula

Density is mass divided by volume

Density = mass / volume

Remember: all fractions are division problems

Density Triangle

Cover the property you are trying to find, and do what is left.

To find density, cover the word density.

You have mass over volume left. So divide mass by volume to find density

Density Triangle

To find mass, you cover the word mass and do what is left.

You have density x volume left

Density Triangle

To find volume, cover volume.

You have mass over density left, so you divide mass by density to find volume

Water and Density

Since 1 gram of water has a volume of 1 ml, then the density of water will always be 1 g/ml.

Ex: A kg of water will have a volume of 1000 ml, so it’s density will be 1 g/ml.

1000g/1000ml = 1 g/ml

Floating vs Sinking

Floating vs Sinking

Remember: density of water is 1 g/ml

Less dense materials will float on top of more dense materials.

Floating and Sinking

Objects with a density of less than 1 g/ml will float on top of water.

Objects with a density greater than 1 g/ml will sink in water.

Neutral Buoyancy

Objects with a density = to the density of water will float in mid water, at whatever level you place the object

Fish and submarines control their depth by changing their density

Titanic sails the ocean blue

Titanic makes it’s maiden voyage. What is the density of this enormous, steel

hulled ship, dull of machinery, coal, people and all sorts of heavy things?

~It’s floating, so we know that it’s density has to be less than 1 g/ml.

How can that be?

~It is a hollow vessel that is full of air.

Wreck of the Titanic

The denser the ship became, the lower it settled into the water.

What is the density of the ship resting on the ocean floor?

~must be over 1 g/ml to have gone below the surface

Review

How much does the prefix Hecto- represent?

~ 100 What is the SI unit for measuring length?

~ meter What 2 things does the force of gravity depend

on?

~ mass and distance

Review

What are the 2 units that volume can be measured in?

~ cm³ for box shapes

~ml for liquids What is the density of water?

~ 1 g/ml

Dimensional Analysis is a way to convert measurements between different units to help compare them.

BUT First, we will practice the easy way…moving the decimal or the “ladder method”

KHD U DCM Kilo Hecto Deka UNIT (m, l, g) Deci Centi Milli

KILO1000Units

HECTO100

Units

DEKA10

UnitsDECI

0.1Unit

CENTI0.01Unit

MILLI0.001Unit

MetersLitersGrams

Ladder Method

How do you use the “ladder” method?

1st – Determine your starting point.

2nd – Count the “jumps” to your ending point.

3rd – Move the decimal the same number of jumps in the same direction.

4 km = _________ m

12

3

How many jumps does it take?

Starting Point Ending Point

4. __.1

__. 2 3

__. = 4000 m

Try these conversions using the ladder method.

1000 mg = _______ g 1 L = _______ mL 160 cm = _______ mm

14 km = _______ m 109 g = _______ kg 250 m = _______ km

Conversion Practice

Write the correct abbreviation for each metric unit.

1) Kilogram _____ 4) Milliliter _____ 7) Kilometer _____

2) Meter _____ 5) Millimeter _____ 8) Centimeter _____

3) Gram _____ 6) Liter _____ 9) Milligram _____

Try these conversions, using the ladder method.

10) 2000 mg = _______ g 15) 5 L = _______ mL 20) 16 cm = _______ mm

11) 104 km = _______ m 16) 198 g = _______ kg 21) 2500 m = _______ km

12) 480 cm = _____ m 17) 75 mL = _____ L 22) 65 g = _____ mg

13) 5.6 kg = _____ g 18) 50 cm = _____ m 23) 6.3 cm = _____ mm

14) 8 mm = _____ cm 19) 5.6 m = _____ cm 24) 120 mg = _____ g

Metric Conversion Challenge

Dimensional Analysis

WHAT YOU WANT

___________________

WHAT YOU HAVE

Dimensional analysis is also called the factor-label method of problem solving. It is a way of setting up a problem in a constant fashion that breaks the problem down into simple steps. Each step is a ratio that must equal 1, thus canceling out some preceding unit.

Examples

1. 11 mm = ______ cm

2. 261 g = _______ kg

3. 9474 mm = _______ cm

Precision vs. Accuracy

Precision is the amount of detail in measurements, or how closely two or more measurements agree.

Precision vs. Accuracy

Accuracy is how close a measurement is to the actual or accepted value for that measurement.

Practice