Jeremy decides to make some Macaroni and Cheese from a box. He notices the directions ask him to add salt to water before bringing it to a boil. The next day, Jeremy asks his science teacher “How does adding salt to water affect the way it boils?” They plan an experiment to find out the answer. The following graph summarizes Jeremy’s findings.

List all of the materials and equipment that Jeremy would have to use in his experiment.

Using Jeremy’s experiment, identify:

1. the independent variable.

2. the dependent variable.

3. the experimental control group.

4. Jeremy’s probable conclusion.

Which formula represents a molecular compound?(1) HI (3) KCl(2) KI (4) LiCl

Which type of matter is composed of two or more elements that are chemically combined in a fixed proportion?(1) solution(2) compound(3) homogeneous mixture(4) heterogeneous mixture

EX 1: Convert 1006051 to scientific notation.

1006051Decimal will move here

The natural decimal point

is here

1.006051 x 1066 because the decimal moved 6 times

Determine the number of protons, neutrons, electrons,

and the mass number

Zn6530

2+

30 protons, 35 neutrons, 28

electrons, mass number = 65

EX 2: Convert 0.0052300 to scientific notation.

0 0052300Decimal will move here

The natural decimal point

is here

5.2300 x 10-3

Negative because the original number is less than 1 and 3 because the decimal moved 3 times

EX: Determine the number of significant figures in a) 4b) 4.0c) 40d) 0.0400e) 4004f) 0.0004

12

1

341

Practice

EX 1: Determine the number of significant figures in:

a) 2b) 5.0c) 10d) 0.0400e) 8005f) 3.00 x 103

121

343

EX 2: Convert each of the values into scientific notation while retaining the same number of sig figs

a) 60000 b) 20 c) 4004d) 0.0900

6 x 104

2 x 101

4.004 x 103

9.00 x 10-2

Lets practice together…

Round the following numbers to 3 sig figsa) 51.234b) 51.38c) 51.3587d) 51,358e) 0.050554

51.2

51.451.4

51,400

0.0506

Or 5.12 x 101

Or 5.14 x 101

Or 5.14 x 101

Or 5.14 x 104

Or 5.06 x 10-2

YOUR Practice

• EX: Round the following numbers to 3 sig figsa) 51.234 51.2b) 51.38c) 51.3587d) 51,358e) 0.050554f) 5,135,593

51.2

51,400

51.4

0.0506

51.4

5,140,000

Example:

It is expected that you will always report all sig figs on any laboratory

reading!

1 2 3 4 5 6 7 8 9 10

2.8

Example:

It is expected that you will always report all sig figs on any laboratory

reading!

1 2 3 4 5 6 7 8 9 10

2.71

Which Lewis electron-dot diagram representscalcium oxide?

Explain which of the following represent pure substances and which represent mixtures.

Practice

1) 22.101 mL – 0.9307 mL =

2) 2.5 g / 3.42 g = 3) 2.33 cm x 6.085 cm x 2.1 cm

= 4) 23.1 in + 4.77 in + 125.39 in +

3.581 in =

21.170 mL0.73 g

30. cm3

156.8 in

• EX: 37.24 mL + 10.3 mL =

• 27.87 g – 2.2342 g =

47.5 mL

25.64 g

Rules for Math Operations with Significant Figures

Addition and Subtraction

Ex. 37.24mL

+ 10.3 mL

47.54mL

Reported as 47.5mL

Rules for Math Operations with Significant Figures

Addition and Subtraction

Ex. 27.87 g

- 21.2342 g

6.6358 g

Reported as 6.64g

2. Multiplication and Division

• The measurement with the fewest sig figs determines the number of sig figs in the answer

• EX: 12.34 cm X 0.23 cm = 2.8 cm2

Practice

• 2. Determine the number of g in 0.03455 kg

want given

0.03455 kg

1000 g g1 kg

= 34.61

Relationship1000g = 1kg

Start with what’s given

1.06 qt.

• Ex. 2 Convert 323 mL to cups

wantgiven

323 mL 1 L

cups

1000 mL

= 1.37

1

Relationships1000 mL = 1L

1L = 1.06 quarts

1 quart = 4 cups

Start with what’s given

1 L 1 qt.

4 cups

2.54 cm

• Practice 1: Convert 7.005 ft to mm

wantgiven

7.005 ft12 in

mm

1 ft

= 2135

1

Relationships1 foot = 12 inches

2.54cm = 1 in

100 cm = 1 m

1 m = 1000 mmStart with what’s given

1 in 100 cm1 m 1000

mm1 m

1 hr

• EX 1: Convert 0.083 km/h to m/s

wantgiven

0.083km 1000m

m/s

1 km

= 2.31 X 10-2

1hr

Relationships1km = 1000m

1h = 60 min

1 min = 60 s

Start with what’s given

60 min 60 s1 min

1 ft

• 1. Convert 3.56 cm/s to ft/h

wantgiven

3.56 cm1 in

ft/hr

2.54 cm

= 420

1 s

Relationships2.54 cm = 1 in

12 in = 1 ft

60 s = 1 min

1 hr = 60 min

Start with what’s given

12 in 1 min

60 s

1 hr

60 min

1 ft

• 2. Convert $25.00/feet to cents/cm

wantgiven

$ 25.00100 cents

cents/cm

$1

= 82.0

1 ft

Relationships$1 = 100 cents

2.54 cm = 1 in

12 in = 1 ft

Start with what’s given

12 in 2.54 cm

1 in

Determine the number of centimeters in 1.76 kilometers

(Show all dimensional analysis.)

Determine the number of inches in 697 mm.

Note: 2.54 cm = 1 inch(Show all dimensional analysis.)

Determine the number of atoms in 5.20 moles of C6H12 .

(Show all dimensional analysis.)

How many significant figures do the following numbers contain?

A) 4,250.00

B) 4040

C) 0.009

D) 325.08

E) 6.02 x 1023

Find the answer to the following using the correct number of significant figures.

A) 4,250.38 + 25.1

B) 4040 x 32

Read the following to the correct number of significant figures.

Which statement describes a chemical property of bromine?(1) Bromine is soluble in water.(2) Bromine has a reddish-brown color.(3) Bromine combines with aluminum to

produce AlBr3.(4) Bromine changes from a liquid to a

gas at 332 K and 1 atm.

An atom of aluminum in the ground state and an atom of gallium in the ground state have the same - (1) mass(2) electronegativity(3) total number of protons(4) total number of valence

electrons

In an atom of argon-40, the number of protons – (1) equals the number of electrons(2) equals the number of neutrons(3) is less than the number of

electrons(4) is greater than the number of

electrons

Which type of substance can conduct electricity in the liquid phase but not in the solid phase?(1) ionic compound(2) molecular compound(3) metallic element(4) nonmetallic element

Why is a molecule of CO2 nonpolar even though the bonds between the carbon atom and the oxygen atoms are polar?(1) The shape of the CO2 molecule is

symmetrical.(2) The shape of the CO2 molecule is asymmetrical.(3) The CO2 molecule has a deficiency of electrons.(4) The CO2 molecule has an excess of electrons.

The relatively high boiling point of water is due to water having- (1) hydrogen bonding(2) metallic bonding(3) nonpolar covalent bonding(4) strong ionic bonding

Matter is classified as a - (1) substance, only(2) substance or as a mixture of substances(3) homogenous mixture, only(4) homogenous mixture or as a heterogeneous mixture

Which substance can not be decomposed by a chemical change?(1) ammonia (3) propanol(2) copper (4) water

A beaker contains both alcohol and water. These liquids can be separated by distillationbecause the liquids have different

(1) boiling points (3) particle sizes(2) densities (4) solubilities

A sample of an element is malleable and can conduct electricity. This element could be - (1) H (3) S(2) He (4) Sn

Identify the element in Period 3 of the Periodic Table that reacts with

oxygen to forman ionic compound represented by

the formula X2O.

Based on data collected during a laboratory investigation, a student determined an

experimental value of 322 joules per gram for the heat of fusion of H2O. Calculate the

student’s percent error. Your response must include a correct numerical setup and the

calculated result.

Calculate the density of a 129.5-gram sample of bronze that has a

volume of 14.8 cubiccentimeters. Your response must include a correct numerical setup

and the calculatedresult.

8.75 g/cm3

Atomic StructureQuestions

Answers

Determine the number of protons, neutrons, and electrons in an ion of magnesium with a 2+ charge

and a mass number of 25.

p+ = 12n0 = 13e- = 10

True or False?

Elements cannot be created, divided,

or destroyed

False

Elements can be divided

(particle accelerators/atom smashers)

Determine the element’s identity:

Element – 28 92.23%Element – 29 4.67%Element – 30 3.10%

Relative Abundance

Silicon

The Gold Foil experiment resulted in the discovery of

the ______

Nucleus!

Europium has two naturally-occurring isotopes: europium-

151 with an abundance of 47.82% and europium-153 with

an abundance of 52.18%. Determine the average atomic

mass for europium.

152.0436 amu

Who developed the plum pudding

model?

JJ Thompson

How can you determine the mass

number?

Protons + neutrons

What is fluorine’s most abundant

isotope?

Fluorine - 19

All atoms of an element are

________ from another element

All atoms of an element are

different from another element

Who discovered the electron?

JJ Thompson

Determine the number of protons, neutrons, and the

mass number

H31

1 proton, 2 neutrons, mass

number = 3

If 3 protons could be removed from the nucleus of an Nitrogen atom,

what nucleus remains?

Beryllium7p – 3p = 4p

Determine which element has a mass number of 45 and has 14

neutrons.

Gallium

Determine the number of protons, neutrons, and electrons in an atom of silicon-29.

protons = 14neutrons = 15 electrons = 14

Write the isotope for the element given that it has 12 protons and 14 neutrons. Show the isotope

in both ways.

Magnesium – 26

Mg2612

What part of the atom takes up the most amount of

space?

electrons

What element is used as the

standard for atomic mass units?

carbon

The end of an electron configuration says 4d4. What element is represented?

What does n represent?

Why can’t we have two up spins next to each other?

What is the roman numeral of the group found at np3?

How many orbitals have electrons in the configuration:

1s2 2s2 2p6 3s1

***hint***you probably want to write out the orbital notation.