Mass, Volume, & Density

MassMeasurement of the amount of matter

(or stuff) in an object

– Measured in grams (g)

There are 3 states

of matter:

Solid

Liquid

Gas

There are 3 states

of matter:

Solid

Liquid

Gas

Volume

Measurement of the amount of space an

object takes up

– Measured in milliliters (ml) or cm3

Density is defined as mass per unit volume. It is a measure

of how tightly packed and how heavy the molecules are in

an object. Density is the amount of matter within a certain

volume.

Density

Which one is more dense?

How about this: Which square is more dense?

Which one is more dense?

Now which one is more dense?

To find the density

3- Divide Density = Mass g

Volume cm³

1- Find the mass of the object

2- Find the volume of the object

1- Find the mass of the object

ALWAYS

REMEMBER

UNITS!

1) Find the mass of the object

2) Find the volume of the object

3) Divide : Density = Mass / Volume

To find density:

Ex. If the mass of an object is 35 grams and it takes up 7 cm3

of space, calculate the density.

Let’s try some density problems together

Work on these problems with your

neighbor

1 Frank has a paper clip. It has a mass of 9g and a volume of

3cm3. What is its density?

2. Frank also has an eraser. It has a mass of 3g, and a volume

of 1cm3. What is its density?

3. Jack has a rock. The rock has a mass of 6g and a volume of

3cm3. What is the density of the rock?

4. Jill has a gel pen. The gel pen has a mass of 8g and a

volume of 2cm3. What is the density of the gel pen?

Change Mass AND Keep Volume Same

Increase the mass increase density

Decrease the mass decrease in density

Which container has more density?

A B

Ways to Affect Density

Change Volume AND Keep Mass Same

Increase the volume decrease density

Decrease the volume increase density

Which container has more density?

A B

Ways to Affect Density

In your notebook illustrate the answer to

the following question:

What 2 ways will INCREASE density?

What 2 ways will INCREASE density?

Keep the

same

mass AND

decrease

the

volume

Keep the

same

volume

AND

increase

the mass

If you have 2 or more

substances,

the MORE dense

substance will be on

bottom

The LESS dense substance

will be on top

Liquid Layers – Try with your

neighbor

• Which liquid has the

highest density?

• Which liquid has the

lowest density?

Liquid Layers

Try on your own!

Imagine that the

liquids on the right

have the following

densities:

– 15g/cm3 10g/cm3

– 3g/cm3 9g/cm3

– 7g/cm3 12g/cm3

Match the colors to

the correct densities.

3g/cm3

7g/cm3

9g/cm3

10g/cm3

12g/cm3

15g/cm3

Super Scientist

Question of the Day

• Jake has a book, a ruler, and a balance.

• How can Jake find the density of the

book with the tools he has?

Reading Equipment

• Precision – How close two or more

measurements are to each other

• Accuracy – How close a measurement is to

its standard or known value.

1. You are measuring the boiling point of

water without salt. Your three

measurements are 80.1 oC, 80.6 oC and

79.8 oC.

2. You take three more measurements and

measure 100.4 oC, 99.8 oC and 100.0 oC.

Examples: Precise or Accurate

Accurate and Uncertain

• When measuring a numerical value, you can only be so

certain.

– Your uncertain value is the value one decimal place to the right of

your certain value.

– What is the uncertain decimal place for the thermometers below?

Uncertainty in Measurement• All measurements have a degree of uncertainty regardless

of precision or accuracy.

• Uncertainty is caused by two factors, the limitation of

measuring instrument (systematic error) and the skill of the

experimenter making the measurements (random error).

• Example: A measurement of 5.07 g ± 0.02 g means that

the experimenter is confident that the actual value for the

quantity being measured lies between 5.05 g and 5.09 g.

The uncertainty is the experimenter's best estimate of how

far an experimental quantity might be from the "true

value."

Examples of Uncertainty

Bob weighs himself on the scale. The smallest

division on the scale are 1-pound marks. Bob reads

his weight close to the 142-pound mark. He knows

his weight is between 141.5 pounds and 142.5

pounds. What is Bob’s weight and uncertainty?

Weight = 142 ± 0.5 pounds

In general, the uncertainty in a single measurement

from a single instrument is half the least count of the

instrument.

Significant Figures

Rules on determining how many significant

figures are in a number:

1. Non-zero digits are ALWAYS significant

2. Any zeros between two significant digits

are significant

3. A final zero or trailing zeros in the decimal

portion ONLY are significant

Significant Figures Examples

1. 246.32

2. 100.3

3. 0.678

4. 0.0001

5. 1.0000

6. 700000

1. 5 sig figs

2. 4 sig figs

3. 3 sig figs

4. 1 sig fig

5. 5 sig figs

6. 1 sig fig

More on Significant Figures

Addition/Subtraction – Round to the least number of decimal

places of any number in the problem

Ex: 32.567+135.0+1.4567 = 169.0237

How many sig figs?? = 169.0

Multiply/Divide – Round to the least number of significant

figures of any number in the problem

Ex: 28.367/3.74 = 7.5847593583

How many sig figs?? = 7.58

More Significant Figure Examples

1. 246.24 + 238.278 + 98.3 =

2. 658.0 – 23.6278 =

3. 23.7 x 3.8 =

4. 4278 / 1.006 =

1.582.8

2.634.4

3.90.

4.4252