Do Now: 7th grade

Copy HW into CJ.

COPY MY STUDENT HOURS: Tues/Thurs 3:15 – 4:15 pm in 504.

Answer these questions in Box 1 of your handout:1. What piece of lab equipment is most accurate for measuring volume?

2. Volume can be expressed in liters, milliliters, and __________.

3. Which is larger: a milliliter or a centiliter?

4. Name the following sets of measurements as accurate, precise, neither, or both

if the correct volume is 9.49 mL.

a. 7.14 mL, 7.25 mL, 6.99 mL

b. 9.45 mL, 9.67 mL, 9.30 mL

Announcements: 7th grade

• Quiz this week – everything we’ve done up to today

• HOMEWORK points officially start today

• CJ notes officially start today

• Missing HW

• Grades ( or )

• Behavior ( or )

Unit Conversions

Textbook:

Modern Chemistry 2012

Sarquis & Sarquis

Order it if you haven’t done so already.

We will soon start using it for

homework/assignments.

Introduction:

The metric system’s many prefixes allow quantities to

be expressed in many different units.

Dimensional analysis is useful to convert from one

metric system unit to another.

SI Prefixes:

Prefix mega kilo Hecto Deka deci centi milli

Abbreviation M k h da d c m

Exponential

factor106 103 102 101 100 10-1 10-2 10-3

Meaning1,000,0000 1,000 100 10

0.1

1/10

0.01

1/100

.001

1/1000

SI Prefix examples:

1 kilometer = 1,000 meters

1 hectometer = 100 meters

1 dekameter = 10 meters

1 decimeter = 0.1 meters (“one tenth”)

1 centimeter = 0.01 meters (“one hundredth”)

1 millimeter = 0.001 meters (“one thousandth”)

Scientific Notation:

A mathematical expression used to represent a decimal number between

1 and 10 multiplied by ten, so you can write large numbers using less

digits.

Scientific Notation:

1,000,000.

How many times did we move the decimal?

Is the original number GREATER THAN or LESS THAN zero?

Scientific Notation:

1,000,000.

How many times did we move the decimal?

Is the original number GREATER THAN or LESS THAN zero?

= 1 x 106

What is in front of

the decimal

Number of

times we

moved the

decimal

POSITIVE NUMBER

because our

original number

was greater than

zero!

Scientific Notation:

0.00711

How many times did we move the decimal?

Is the original number GREATER THAN or LESS THAN zero?

= 7.11 x 10-3

What is in front of

the decimal

Number of

times we

moved the

decimal

NEGATIVE

NUMBER because

our original

number was

greater than zero!

Scientific Notation

1 x 106

COEFFICIENT

always between 1 and 10BASE is 10

EXPONENT number of

decimal places that the

decimal needs to be moved to

change the number to standard

notation

Scientific Notation

1. Coefficient is greater than or equal to 1 and less than 10.

2. Base is 10.

3. Exponent shows the number of decimal places that the

decimal needs to be moved to change the number to standard

notation. A negative exponent means that the decimal is

moved to the left when changing to standard notation.

Scientific Notation Practice

Unit Conversions:

Follow along to draw the general formula for calculating unit

conversions:

Do Now: 7Pb and 7Hg

1. Write today’s HW in CJ. Keep CJ out on desk.

2. Answer questions in Box 1 of today’s notes.

Density

• Density is the amount of matter in a given volume

• Equation: d = m/V

• Often expressed in grams per cubic centimeter (g/cm3)

• 1 cm3 = 1 mL, so g/mL is OK too

• Density can be used to identify substances

Archimedes

• Ancient Greek philosopher

• One of the earliest mathematicians

• Used density to solve a riddle of a king’s crown

The Riddle of the King’s Crown

• Did the goldsmith replace some of the gold given to him by an

equal weight of silver?

• Hiero asked Archimedes to determine whether the wreath was

pure gold.

• The wreath was a holy object - the could not disturb the wreath in

any way.

The Riddle of the King’s Crown

• SOLUTION = EUREKA! When he stepped into his bath and caused it

to overflow.

• PLAN!

• Put a weight of gold equal to the crown, and known to be pure,

into a bowl which was filled with water to the brim.

• Remove gold and king’s crown put in.

• An alloy of lighter silver would increase the bulk of the crown

and cause the bowl to overflow.

The Riddle of the King’s Crown

Relied on density = gold is more dense than silver

Pure gold crown Gold + Silver crown

More dense Less dense

Displaces less water Displaces more

water (size is bigger)

Archimedes’ Principle

Definition: the buoyant force experienced by a submerged

object is equal to the weight of the water it displaces.

Application: the volume of water displaced by an irregularly

shaped solid that is not buoyant equals the volume of the

solid.

EXIT TICKET – just write answers down

1. Write 43,000 in scientific notation.

2. 1 km = ______ meters

3. 2,730 liters = ______ kiloliters

Prefix mega kilo hecto deka deci centi milli

Abbreviation M k h da d c m

Exponential

factor106 103 102 101 100 10-1 10-2 10-3

Meaning