ch 2 matter & atoms

Ch 2 Matter & Atoms

Natural Approach to ChemistryLab Aids

Condensed

2.1 Frames 2-28 2.2 Frames 29-62 2.3 Fr. 63-106

2.1 Matter & the Elements

• Standards:• SC.912.P.8.5 relate properties of atoms & their

position in the periodic table to the arrangement of their electrons

• SC.912.P.8.9 apply the mole concept and the law of conservation of mass to calculate quantities of chemicals participating in reactions

The “stuff” that we are made of is called matter.

Chemistry tells us how one kind of matter can be changed into a completely different kind of matter.

What are things made of?

substance: a kind of matter that can’t be separated into other substances by physical means such as heating, cooling, filtering, drying, sorting, or dissolving.

Corn oil is a pure substance

mixture: matter that contains more than one substance.

Corn oil is a pure substance

Oil and vinegar dressing is a mixture of substances

Examples: MassDensityColor

Physical properties can be measured or seen through direct observations.

Physical properties

Physical changes include changes in shape, phase or temperature.

Chemical properties are observed when a substance changes into a different substance.

Iron RustChemical change

Signs that a

chemical change has occurred

Each element is a unique type of atom.

All oxygen atoms are identical.

An oxygen atom is different from a silicon atom or a potassium atom.

element: a substance that cannot be separated into simpler substances by chemical means.

1 grain of rice = 0.01 gram

1 hydrogen atom = 1.678 x 10–24 grams

= 0.000000000000000000000001678 grams

How small is an atom?

The periodic table

The periodic table organizes elements according to how they combine with other elements (based on their chemical properties).

HydrogenLightest elementAtomic number: 1

UraniumHeaviest naturally occurring elementAtomic number: 92

Increasing atomic number

Incr

easin

g at

omic

num

ber

Elements that belong to the same group (column) have similar chemical properties.

Reminder

1 atomic mass unit (amu) = 1.66 x 10-24 g

The atomic mass is the mass of:

1) a single atom in amu.

2) a mole of atoms in grams.

One single hydrogen atom weighs 1.01 amu.

One mole of hydrogen atoms weighs 1.01 g.

What does that mean?

The atomic mass is the mass of:

1) a single atom in amu.

2) a mole of atoms in grams.

One single carbon atom weighs 12.0 amu.

One mole of carbon atoms weighs 12.0 g.


One mole contains 6.02 x 1023 atoms

Avogadro’s number

How many moles are in 100 g of sulfur (S)?


Asked: The number of molesGiven: The element is sulfur and there are 100 gRelationships: One mole of sulfur has a mass of 32.065 g


Asked: The number of molesGiven: The element is sulfur and there are 100 gRelationships: One mole of sulfur has a mass of 32.065 g

Solve:

Answer: 100 g of sulfur contains 3.12 moles of sulfur atoms.

110032.065

3.12mole Sg Sg S

moles S

How many grams of calcium (Ca) do you need to have 2.50 moles of calcium?

Asked: The number of gramsGiven: The element is calcium and there are 2.50 molesRelationships: One mole of calcium has a mass of 40.078 g

How many grams of calcium (Ca) do you need to have 2.50 moles of calcium?

Asked: The number of gramsGiven: The element is calcium and there are 2.50 molesRelationships: One mole of calcium has a mass of 40.078 g

Solve:

Answer: 2.50 moles of calcium has a mass of 100. g.

40.0782.501

100.2g Camoles Camole Ca

g Ca

Physical properties can be seen and measured

Chemical properties are observed when one substance is changed into another

Elements are organized in a periodic table This allows to convert

grams to moles and vice versa.

2.2 Molecules and Compounds

Sc.912.P.8.7 interpret formula representations of molecules and compounds in terms of composition and structure.Sc.912.P.8.9 mole concept and law of conservation of mass

One H2 moleculeOne O2 molecule

molecule: a group of atoms chemically bonded together.

molecule: a group of atoms chemically bonded together.

compound: a substance containing more than one element in which atoms of different elements are chemically bonded together.

One H2O moleculeOne H2 moleculeOne O2 molecule

What do all these have in common?

What do all these have in common?

They are made up of only 3 types of atoms: carbon, oxygen and hydrogen.

More than 200,000 words in the English language

Trillions of substances that make up the universe

The alphabet of chemistry

The chemical formula

Write a chemical formula for a compound that has three hydrogen (H) atoms for each atom of nitrogen (N).


Asked: Chemical formulaGiven: 3 hydrogen (H) and 1 nitrogen (N)Relationships: The subscript tells the number of each element in the

compound.


Asked: Chemical formulaGiven: 3 hydrogen (H) and 1 nitrogen (N)Relationships: The subscript tells the number of each element in the

compound.Answer: NH3

The properties of a compound depend more on the exact structure of the molecule

than on the individual elements from which it is made.

F

U

N

E

RA

L

F U N E R A L F U NER A L

The arrangement of letters matters!

The arrangement of atoms matters!

Representation

There are many ways of representing the same thing.

Representation

Ionic compounds

Salt (NaCl) is not a molecule!

ionic compound: a compound such as a salt in which positive and negative ions attract each other to keep matter together.

ion: an atom or small molecule with an overall positive or negative chare as a result of an imbalance of protons and electrons.

Formula mass

The formula mass of water (H2O) is 18 g.

What is the mass of 1 mole of methane (CH4)?


Asked: The mass of 1 mole of methane

Given: Methane (CH4) contains 1 carbon (C) and 4 hydrogen (H) atoms

Relationships: The formula mass is the sum of the atomic masses for each atom in the compound


Asked: The mass of 1 mole of methane

Given: Methane (CH4) contains 1 carbon (C) and 4 hydrogen (H) atoms

Relationships: The formula mass is the sum of the atomic masses for each atom in the compound

Solve:

Answer: One mole of methane (CH4) has a mass of 16.04 g. 44 4 1.0079 12.0 16.0411 g CH

moH

eC

l

How many moles are in 100 grams of water (H2O)?


Asked: The moles in 100 g of water

Given: Water (H2O) contains 2 hydrogen (H) atoms and 1 oxygen (O)

atom.

Relationships: The formula mass is the sum of the atomic masses for each atom in the compound.


Asked: The moles in 100 g of water

Given: Water (H2O) contains 2 hydrogen (H) atoms and 1 oxygen (O)

atom.


Solve:

Answer: 100 g of water (H2O) contains 5.55 moles.

2

5

2 2 1.0079 15.999 18.015

110018.01

55

. 5

gH O H Omole

molegg

moles

How many grams are in 2.300 moles of butane (C4H10)? Butane is used as a lighter fluid in disposal lighter.


Asked: The mass in grams of 2.300 moles of butane

Given: 2.300 moles of C4H10



Asked: The mass in grams of 2.300 moles of butane

Given: 2.300 moles of C4H10


Solve:

Answer: 133.7 g are in 2.300 moles of butane (C4H10).

4 1

2

4 10

00

4 1

4 10 4 12.011 10 1.0079 58.12

133.7

3

58.1232.300

1

gH O H Omole

g C Hgmo

gle mole C

C HH

How many oxygen atoms are in 200.0 g of glucose (C6H12O6)?

Asked: Number of oxygen atoms

Given: 200.0 g of C6H12O6

Relationships: Formula mass of glucose:

6 12 6

6 12.011 12 1.0079 6 15.9 19 80.159

C Og

m e

H

ol

Remember: Avogadro’s number indicates that one mole contains 6.02 x 1023 atoms

Solve: First we find how many moles are in 200.0 g of glucose:

6 12 66 12 6

6 16 12 6

2 6

1200.0

180.1.11

150

mole C molesH O Cg C H Og H

H OC O


Next we find how many molecules are contained in 1.11 moles of glucose:

6 12 66 12 6 6 12 6

6 12 6

1200.0 1.110

180.15mole C H Og C H O moles C H O

g C H O

236 12

2

66 12 6

6 12 6

36 12 6

6.022 101.110

1

6.684 10

molecules C H Omoles C H

molecules

O

C

mole C

O

H O

H



Then we find how many O atoms are contained in 6.684 x 1023 molecules of glucose:

6 12 66 12 6 6 12 6

6 12 6

1200.0 1.110


g C H O

236 12 6

6 12 66 12 6

236 12 6

6.022 101.110

1

6.684 10

molecules C H Omoles C H Omole C H O

molecules C H O

236 12 6

6 1 6

24

2

4.66.684 101

010 10O atomsmolecules C H Omolecule C H O

O atoms



Then we find how many O atoms are contained in 6.684 x 1023 molecules of glucose:

Answer: There are 4.010 x 1024 atoms of O in 200.0 g of glucose (C6H12O6).

6 12 66 12 6 6 12 6

6 12 6

1200.0 1.110


g C H O

236 12 6

6 12 66 12 6

236 12 6

6.022 101.110

1

6.684 10

molecules C H Omoles C H Omole C H O

molecules C H O

236 12 6

6 1 6

24

2

4.66.684 101

010 10O atomsmolecules C H Omolecule C H O

O atoms

We can build compounds using atoms- The type of atom matters

- The arrangement of atoms also matters

We can calculate the formula mass of compounds:

2.3 Mixtures and Solutions

Sc.912.P.8.9 mole concept and law of conservation of massSc.912.P.12.12 explain how various factors such as concentration, temperature, and presence of a catalyst affect the rate of a chemical reaction

CHAPTER 2

Matter and Atoms

2.3 Mixtures and Solutions

A recipe calls for you to “mix until homogeneous.”


A mixture that is uniform throughout.

A mixture that is uniform throughout. Different samples may have different compositions.

What happens when sugar is added to water?

What happens when sugar is added to water?

A solution is obtained.

Is orange juice a solution?

Hint: Are things dissolved in orange juice?

Is orange juice a solution?

It is partially a solution because some chemicals are dissolved in water, but some bits (like pulp) are not.

These four solutions contain the same solvent and solute.

Which one is the most concentrated solution?Which one is the most dilute solution?

concentration: the amount of each solute compared to the total solution.

• Can you dissolve salt in water?

VariablesAmount of saltAmount of water


• Can you continue adding more and more salt, and still get a solution?

Variables

Amount of saltAmount of water


• Can you continue adding more and more salt, and still get a solution?

• Can you dissolve more salt when you increase the temperature?

Variables

Amount of saltAmount of water

Amount of saltAmount of waterTemperature

solubility: the amount of a solute that will dissolve in a particular solvent at a particular temperature and pressure.

Solubility of common substances in water at 25oC

If the concentration of a sugar solution is 75 g/L, how much solution do you need if you want 10 g of sugar?


Asked: Volume of solution

Given: 10 g of solute and concentration of 75 g/L

Relationships:mass of soluteLiters of solution

concentration in g L



Given: 10 g of solute and concentration of 75 g/L

Relationships:

Solve:

mass of soluteLiters of solutionconcentration in g L

10 0.1 1333375

g L org

LL

m

How much menthol do you need to make 10 kg of mouthwash if the concentration of menthol must be 0.05%?


Asked: Mass of solute

Given: 10 kg of solution, solute concentration of 0.05%

Relationships: %100

concentration inmass of solute mass of solution


Asked: Mass of solute

Given: 10 kg of solution, solute concentration of 0.05%

Relationships:

Solve:

%100

concentration inmass of solute mass of solution

0.05%10 0.00510

50

kg kg or g

molarity: the number of moles of solute per liter of solution.

( )( )

amount of solute moles molesmolarityvolume of solvent liters L

moles ML

If 10.0 g of citric acid (C6H8O7) is added to 500 mL of water, what is the molarity of the resulting solution?

Asked: The molarity of a solution

Given: The amount of solute (citric acid) and the volume of solution

Relationships:

moles solutemolarityvolume of solution L




Relationships:

Solve: Start by calculating the formula mass of C6H8O7:

moles solutemolarity

volume of solution L

6 12.011 8 1.0079 7 1 192.5. 12999 g mole




Relationships:


Next we calculate the number of moles in 10.0 g of C6H8O7:



6 12.011 8 1.0079 7 15.999 192.12 g mole

1# 10.0192.12

0.0521molemoles gg

moles





Relationships:


Next we calculate the number of moles in 10.0 g of C6H8O7:

Answer:



6 12.011 8 1.0079 7 15.999 192.12 g mole

1# 10.0 0.0521192.12molemoles g moles

g

0.05210.500

0.104molesmolarityL

M

Ascorbic acid = Vitamin C

Vitamin C acts as a food preservative by reacting with oxygen (O2)Ascorbic acid

C6H8O6

How much (volume) of a 1 M ascorbic acid solution will completely react with 0.02 moles of oxygen (O2)?


Given: Concentration (1M) and balanced reaction

Relationships:

According to the balanced reaction we need 2 moles of ascorbic acid for every mole of O2.






Relationships:


Solve: That means we need 0.04 moles of ascorbic acid:

0.04 0 41

0.04moles solute molesvolume L L ormolarit

LM

my






Relationships:


Solve: That means we need 0.04 moles of ascorbic acid:

Answer: 40 mL of the solution contains 0.04 moles of ascorbic acid, which is enough to react with 0.02 moles of oxygen (O2).

0.04 0 41

0.04moles solute molesvolume L L ormolarit

LM

my




The air you breathe is a mixture!

Air takes up less space under high pressure.

Standard

Temperature and

Pressure

molar volume: the amount of space occupied by a mole of gas at STP. It is equal to 22.4 L.

0oC

1 atm

Partial pressures

The total pressure in a mixture of gases is the sum of

the partial pressures of each individual gas

in the mixture.

Gas A

Gas BGas C

Gas A Gas B

Gas CTotal pressure

=

+

+

Partial pressure of A

Partial pressure of C

Partial pressure of B

Partial pressures

If 1 L of helium (75%) and neon (25%) is at STP, what is the partial pressure of helium?

Asked: Partial pressure of helium

Given: 75% He and 25% Ne at STP conditionsStandard pressure is 101,325 Pa or 1 atm

Relationships: The total pressure is the sum of the partial pressures of each gas.





Solve: 75,9940.75 101,30.75

250.75 1

Paor

Paatmatm

or





Solve:

Answer: The partial pressure of helium is 75,994 Pa or 0.75 atm.

75,9940.75 101,30.75

250.75 1

Paor

Paatmatm

or


STP conditions:

Standard

Temperature (0oC)

Pressure (1 atm)

Air is a mixture of gases. Based on Dalton’s law of partial pressures:

2 2...air N O ArP P P P

Concentration of a solution can be expressed in:mass per volumemass percentmolarity

moles of solutemolarity Mliters of solvent

ch 2 matter & atoms

Documents

mole of sulfur

mole of atoms

single atom

moles of sulfur atoms

g of sulfur s

properties of atoms

mole of hydrogen atoms

silicon atom