All About

measuring matters

mass

density

volume

Volume is the amount of space an object takes up.

The base unit of volume in the metric system in the liter and is represented by L or l.

Metric Units

1 liter (L) = 1000 milliliters (mL)

1 milliliter (mL) = 1 cm3 (or cc) = 1 gram*

Which is larger?

A. 1 liter or 1500 milliliters

B. 200 milliliters or 1.2 liters

C. 12 cm3 or 1.2 milliliters*

volume

Measuring Volume

We will be using graduated cylinders to

find the volume of liquids and other

objects.

Read the measurement based on the bottom of

the meniscus or curve. When using a real

cylinder, make sure you are eye-level with the level of the water.

What is the volume of water in the cylinder? _____mL

What causes the meniscus?

A concave meniscus occurs when the molecules of the liquid attract those of the container. The glass attracts the water on the sides.

Measuring Liquid Volume

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Pay attention to the scales for each cylinder.

Measuring Solid Volume

10 cm

9 cm

8 cm

We can measure the volume of

regular object using the formula

length x width x height.

_____ X _____ X _____ = _____

We can measure the volume of

irregular object using water

displacement.

Amount of H2O with object = ______

About of H2O without object = ______

Difference = Volume = ______

10 cm 8 cm 9 cm 720 cm3

200 ml

260 ml

60 ml

Mass refers to the amount of matter in

an object.

The base unit of mass in the metric system in the kilogram and is represented by kg.

Metric Units

1 Kilogram (km) = 1000 Grams (g)

1 Gram (g) = 1000 Milligrams (mg)

Which is larger?

A. 1 kilogram or 1500 grams

B. 1200 milligrams or 1 gram

C. 12 milligrams or 12 kilograms

D. 4 kilograms or 4500 grams

Measuring Mass

We will be using triple-beam balances to find mass.

Once you have balanced the scale, you add up the amounts on each beam to find the total mass.

What would be the mass of the object measured in the picture?

_______ + ______ + _______ = ________ 300g 70g 3.32g 373.32g

PRECISION & ACCURACY

Accuracy

We talk about accuracy when the question we ask is:

How close is the experimentally measured value to the accepted value?

Precision

We talk about precision when the question we ask is: How close is the experimentally measured value to the other experimentally measured values?

Why is this confusing?

• Precise, is often used non-scientifically to

mean exact (which sounds a lot like

accurate!)

Matt John Dan Pete

Assuming the center bull's-eye is our accepted value: Who is the most accurate at throwing darts? Who is the least precise? Describe John’s precision and accuracy to the other dart throwers. example: Pete’s darts are less accurate and less precise than Matt’s, less accurate and more precise than John’s, and more accurate and more precise than Dan’s.

example: Three students weigh a

sample of known weight (4.50 g), four times each

Donovan: 4.56 g, 4.55 g, 4.76 g, 4.58 g » Average = 4.6125 g

» Range 0.21

Mike: 4.55 g, 4.56 g, 4.66 g, 4.53 g » Average = 4.575 g

» Range 0.13

Kevin: 4.77 g, 4.78 g, 4.76 g, 4.79 g » Average = 4.775 g

» Range 0.03

• Who is the most accurate? – Mike is 0.08 g off, Donovan is 0.11 off, and Kevin is off by 0.28 g

– Mike is the most accurate because he is the closest to the true value

• Who is the least precise? – Donovan has the highest standard deviation and the largest range,

therefore he is the least precise.

How Precise are your Measurements?

DENSITY

A distinguishing property

Density is a measure of how

mass and volume are related in an

object.

An object’s density is the amount of

matter it has in a given space.

To find density:

• first measure mass (m)

• and volume (v)

• then use this formula

Density is an important physical property of an object.

1. The density of a substance is always the same (at a given T and p)

mythbusters

sulfer hexofluoride

sulfur hex2

2. The density of one substance is always

different than the density of another substance.

Density math challenge

You went panning for gold and

found a nice nugget.

How do you know if it’s

real or just “fool’s gold”?

mass: 96.6 g

volume: 5.0 cm3

Remember D = m/v

Density of gold 19.32 g/cm3

Density of fools gold (iron pyrite) 5.02 g/cm3

Let’s Try a few Calculations Fun with math in science!

1. A brick of salt with a mass of 433 g measures

10 cm x 10 cm x 2 cm. What is its density?

2.16 g/cm3

D = m/v m = 433 g v = 10 cm x 10 cm x 2 cm = 200 cm3

D = 433/200 = 2.16 g/cm3

5. An ice cube has a density of 0.917 g/ml and

measures 5.8 cm x 5.8 cm x 5.8 cm. What is its

mass? 178.9 g

D = m/v m = Dv v = 5.8 cm x 5.8 cm x 5.8 cm = 195.11 cm3

m = (0.917 g/ml)(195.11 cm3 = 178.9 g

6. Gasoline will float on water. 450 g of gasoline is

spilled into a puddle of water. If the density of

gasoline is 0.665 g/ml, what volume of gas was

spilled? 676.7 ml

D = m/v v = m/D

v = 450 g ÷ 0.665 g/ml = 676.7 ml

last one…

13. Rocks are sometimes used along coasts to prevent

erosion. If a rock needs to weigh 2,000 kg (about 2

tons) in order not to be shifted by waves, how big

(volume) does it need to be? You are using basalt

which has a typical density of 3200 kg/m3.

0.625 m3

v = m/D

= 2,000 kg

3,200 kg/m3

DENSITY MINI LAB

Floating and Sinking

A study of Density

What Makes something Float or

Sink in water?

Floating and sinking

Using what you know of density and the information that

the density of water is 1 g/ mL (or 1 kg/L) provide an

explanation about how you could predict if an object will

float or sink in water.

What’s the Difference?

Exploring density:

PHET – floating and sinking

PHET Lab

A CLOSER LOOK AT MATTER

Atoms, elements, compounds and mixtures

Which of these is matter?

air

water

smoke

light

heat

cold

darkness

jello sound

human

cloud

diamond

What is matter?

• Matter is anything that has mass and

takes up space.

• Matter can be classified by extensive or

intensive properties.

• Extensive properties depend on the

amount of matter in the sample.

• Intensive properties do not depend on the

amount but the type of matter in the

sample.

elements

Pure substances that cannot be broken

down by chemical changes.

Each element has unique properties.

Matter is made up of…

Combine in fixed ratios.

Hydrogen peroxide

Glucose C6H12O6

Property of almost all elements – the ability to

combine with other elements and form

compounds

Matter is made up of…

compounds

elements combine to form larger

particles called compounds.

CLASSIFICATION OF MATTER

mixtures

compounds

Classification model

Pure Substances A pure substance always has the same composition and

the same characteristics/properties (density, color, taste,

smell, boiling point)

compounds

Can be broken down into

simpler substances using

chemical methods

elements

Can’t be broken down any

further. Contain only one

type of atom. Approx. 109

elements

mixtures Made up of two or more substances that are

not combined chemically so do not create a

new substance. They can be separated by

“mechanical” means.

Most things in nature are mixtures

Mixtures

• Mixtures are physical blends of two or

more components.

• Mixtures are classified into two groups:

• Heterogeneous mixtures are not uniform.

Their components are not evenly

distributed.

• Homogeneous mixtures are uniform and

their components are evenly distributed.

What kind of mixture is it?

heterogeneous Homogeneous

heterogeneous

Homogeneous

Heterogeneous

Homogeneous

Classification model

Element, Compound, or

Mixture? Rocks

Element, Compound, or

Mixture? Copper

Element, Compound, or

Mixture? Jelly Beans

Element, Compound, or

Mixture? Table Sugar

Element, Compound, or

Mixture? Diamond

Element, Compound, or

Mixture? Tea

Element, Compound, or

Mixture? Salt

Element, Compound, or

Mixture? Neon Gas

Element, Compound, or

Mixture? Pure Water

Element, Compound, or

Mixture? Aluminum

Element, Compound, or

Mixture? Lemonade

Element, Compound, or

Mixture? Silver

Element, Compound, or

Mixture? Sand

Is a Glow Stick Compound or

Mixture?

Glow sticks give off light when two

solutions are mixed.

The sticks consist of a small, brittle containers within a

flexible outer container. Each container holds a unique

solution.

When the outer container is flexed, the inner container

breaks, allowing the solutions to mix, causing the

necessary chemical reaction. After breaking, the tube is

shaken to thoroughly mix the two compounds.

Separating mixtures Chromatography of inks

Why use chromatography?

remember: chromatography is

used to physically separate

components in a mixture by

passing it in solution across a

medium (the paper) in which the

different components move at

different rates.

chromatography can purify basically any

soluble or volatile substance if the right

adsorbent material, carrier fluid, and

operating conditions are employed.

Calculating Rf (retention factor)

basically it is the

distance traveled by

the compound

divided by the

distance traveled by

the solvent

It's a measurement of how

the compound is interacting

with both the solvent (liquid)

and the solid support (paper).

The Rf value tells you how well the solute dissolves in the solvent. The

higher it rises on the paper, the better it dissolves in the solvent.

Separating a

complex mixture

Another engineering challenge!