Chapter 2 Example Explainations and Practice

​Chemistry: Chapter 2 Explained

By Chelsea McBride

Mixtures

When we talk about types of matter, we can place the matter into categories; mixtures and pure substances. Today is an introduction into mixtures.

Homogeneous Mixtures

The first type of mixture is homogenous. "Homo-" means the same so a homogenous mixture is the same throughout the entire matter.

Heterogeneous Mixtures

The second type of mixture is heterogeneous. "Hetero-" means different so a heterogeneous. mixture is different throughout the entire matter.

Multiple Choice

Is cereal homogeneous or heterogeneous?

• homogeneous

• heterogeneous

Multiple Choice

Is the drink "Hawaiian Punch" homogeneous or heterogeneous?

• homogeneous

• heterogeneous

Multiple Choice

Are M&M's homogeneous or heterogeneous?

• homogeneous

• heterogeneous

Multiple Choice

Is a cheeseburger homogeneous or heterogeneous?

• homogeneous

• heterogeneous

Multiple Choice

Is coffee homogeneous or heterogeneous?

• homogeneous

• heterogeneous

Multiple Choice

Is this cake homogeneous or heterogeneous?

• homogeneous

• heterogeneous

Multiple Choice

Is lemonade homogeneous or heterogeneous?

• homogeneous

• heterogeneous

Multiple Choice

Is guacamole homogeneous or heterogeneous?

• homogeneous

• heterogeneous

Multiple Choice

Is water (H₂O) homogeneous or heterogeneous?

• homogeneous

• heterogeneous

• Wait, this is a trick question. H₂O is a chemical compound.

Pure Substances

There are 2 types of pure subtances: elements and compounds.

Elements

• ALL are listed on the periodic table

• Made of only 1 type of atom

• Cannot be broken down with a physical or chemical changes

• Have consistent properties

Compounds

• Are made of two or more types of atoms chemically combined

• Can be broken down with chemical changes, but not physical

• Have consistent properties

Multiple Select

Select all of the ELEMENTS from the list below.

• Water

• Aluminum

• Oxygen

• Air

• Copper

Multiple Select

Select all the COMPOUNDS from the list below.

• Table Salt (NaCl)

• Air

• Oxygen (O₂)

• Carbon Monoxide (CO)

• Baking Soda

Multiple Choice

Which describes COMPOUNDS?

• made of one type of atom

• made of two or more types of atoms

Multiple Select

Select all of the ELEMENTS shown below.

Multiple Select

Select all the COMPOUNDS shown below.

Multiple Choice

Which best describes ELEMENTS?

• made of only 1 type of atom

• made of 2 or more types of atoms

Multiple Select

Select all the ELEMENTS shown below.

Multiple Select

Select all the COMPOUNDS shown below.

Multiple Select

Select all the COMPOUNDS shown below.

Density

You know, just a general measure of how much "stuff" is in there, very technical...

Particle Diagrams and Density

• We can imagine the "stuff" as particles and recognize that both the amount of particles (mass) and the space they occupy determine the density

• Let's compare and discuss A and B...

• Now let's compare and discuss A and C...

Multiple Choice

Which diagram shows the MOST dense object?

• left

• center

• right

Multiple Choice

Which diagram shows the LEAST dense object?

• left

• center

• right

Multiple Choice

Rank the objects from MOST dense to LEAST dense.

• left, center, right

• right, center, left

• left, right, center

• right, left, center

• center, left, right

Calculating Density

• This is in the Edpuzzle video for the week and the Notes so make sure you get it down!

• mass is typically in units of g or kg

• volume of liquids is in mL

• volume of liquids is in cm³

• density has a "combined" unit of g/mL or g/cm³

Practice calculating density

Multiple Choice

A block of aluminum occupies a volume of 15.0 mL and weighs 45.0 g. What is its density?

• 3 g/mL

• 0.3333 g/mL

• 675 g/mL

• I have no idea

Multiple Choice

A sample of liquid has a mass of 300 g and occupies 50 mL in a graduated cylinder. What is the density?

• 15,000 g/mL

• .16667 g/mL

• 6 g/mL

• Yup, still no clue

Multiple Choice

What is an isotope? 

• A charged atom
• An atom with different amounts of neutrons
• An atom with different amounts of protons
• A neutral atom

Multiple Choice

Isotopes of an element have a different number of...

• Protons

• Neutrons

• Electrons

• Mass

Multiple Choice

How many neutrons does an atom of the isotope Neon-22 have?

• 12
• 10
• 22
• 20

Multiple Choice

How many neutrons does a Sodium 24 isotope have?

• 12
• 13
• 14
• 15

Multiple Choice

How many neutrons in C-14?

• 6
• 7
• 14
• 8

Multiple Choice

Using the atomic masses and relative abundance of the isotopes of nitrogen given below, determine the average atomic mass of nitrogen.

N-14: 14.003 amu; 99.63% N-15: 15.000 amu; 0.37%

• 14.003 amu

• 14.007 amu

• 14.506 amu

• 15.000 amu

Multiple Choice

Gallium has two stable isotopes. The mass of gallium-69 is 68.926 amu and has an abundance of 60.11%. The mass of gallium-71 is 70.925 amu and has an abundance of 39.89%. Which is the average atomic mass of gallium?

• 69.93 amu

• 69.72 amu

• 292.47 amu

• 139.85 amu

Fill in the Blanks

Oxygen has three stable isotopes. Oxygen-16 has a mass of 15.99 amu and an abundance of 99.76%. Oxygen-17 has a mass of 17.00 amu and an abundance of 0.04%. Oxygen-18 has a mass of 18.00 amu and an abundance of 0.20%. What is the average atomic mass of oxygen using this data?

Intro to mole

By Monica Youssef

1. What is a mole?

​2. Avogadro's number

Multiple Choice

Which of the following statements regarding the mole is NOT correct?

• A mole is a counting unit

• Equal to 6.02 x 10²³ particles.

• The concept of mole is similar to the concept of dozen

• none of the above

Multiple Choice

When comparing a mole of oxygen and a mole of sulfur, how many atoms does each have?

• oxygen has 16 grams of atoms

• sulfur has 32.06 grams of atoms

• both contains 6.02 x 10²³ atoms

• can not be determined

Multiple Choice

Which would have more atoms?

• 1 mole of Li

• 1 mole of Au

• 1 mole of Si

• None, all are equal

Multiple Choice

Which has more molecules?

• 1 mole H₂O

• 1 mole Al(OH)₃

• 1 mole NaCl

• There are all the same

Multiple Choice

^{The photo above shows the isotopic notation for which isotope?}

• Carbon 12
• Carbon 13
• Carbon 14
• Carbon 15

Multiple Choice

How many atoms of iodine are in a mole of iodine?

• 53

• 63.55g

• 126.9

• 6.02 x 10²³

Multiple Choice

How can you figure out how particles (atoms) there are in 2 moles?

• 2

• 2 x (6.02 x 10²³)

• 2 x (atomic mass)

• 2 ÷ (6.02 x 10²³)

Multiple Choice

How many Carbon Atoms are in 4 moles of Carbon?

• 6.02 x 10²³

• 1.33 x 10²³

• 4.52

• 2.408 x 10²⁴

Multiple Choice

A mole = Avogadro's number = 6.022x10²³

• true

• false

Multiple Choice

The number 6.02 x 10²³ is called...

• Molar number

• Bohr's number
• Scientist's number

• Avogadro's number

Multiple Choice

Which of the following statements regarding the mole is correct?

• A mole is a counting unit equal to 6.02 x 1023 particles.

• The number of particles in a mole is known as Avogadro’s number.

• 1 mole = Avogdro's number

• all of the above

Molar Mass

• molar mass = 1 mole

• CO₂

• C=12 O=16x2

• 44 g/mol

Multiple Choice

CO₂ = 44 g/mol

How much would 3 moles of CO₂ equal?

• 132

• 33

• 404

Multiple Choice

Molar Mass of CH₄

• 12 g/mol

• 16 g/mol

• 4 g/mol

Multiple Choice

Molar Mass of K₂CO₃

• 138.205 g/mol

• 35 g/mol

• 78.2 g/mol

Multiple Choice

Molar Mass of Ag₂O

• 231.7 g/mol

• 56.2 g/mol

• 734.4 g/mol

Mass converted to molar mass

to find the moles of any molecule

mole = mass/molar mass

20 grams of H₂O is how many moles?

Molar mass of H₂O = 18

Moles = 20/18

1.1 moles of H₂O

Multiple Choice

88 grams of H₂O (18 g/mol) is how many moles?

• 4.88 moles

• .54 moles

• 6.67 moles

Multiple Choice

52 grams of O₂ (32 g/mol) is how many moles?

• 1.63 moles

• .615 moles

• 26 moles

Multiple Choice

73 grams of AlBr₃ (267 g/mol) is how many moles?

• .273 moles

• 263 moles

• 4.23 moles

Multiple Choice

800 grams of 2NH₃ (34 g/mol) is how many moles?

• 23.52 moles

• .0425 moles

• 834 moles