UNIT 2: WATER

SECTION 1: CLASSIFICATION OF

MATTER

WATER IS CLASSIFIED AS A COMPOUND.

So what’s a compound?

MatterAnything that has mass and

volume (occupies space)

PURE SUBSTANCES

- Each sample __________=

pure!

- Each piece has exact same make-

up (____________)

MIXTURES

- ____________________

________combined but

__________________

- _______________from

sample to sample

Cannot be separated by

physical means

Can be separated by physical

means

I. CLASSIFICATION OF MATTER

looks the same

fixed composition

2 or more different pure

substances

not chemically bonded together

Composition can vary

PURE SUBSTANCE

Element

(made up of ____________)

Two kinds of elements:

1. Monoatomic =

ex:

2. Diatomic =

ex:

Compound

(____________________

_________________)

Two types:

1. Ionic=Metal + nonmetal

ex:

2. Molecular/Covalent= nonmetal

+nonmetal

ex:

Cannot be separated by

chemical means

Can be separated by

chemical means

1 type of atom

one atom

Na2 atoms

Cl2

H2O (water)

NaCl (table salt)

2 or more different elements

chemically combined

MIXTURES

Homogeneous

(evenly mixed, distinct pattern)

Words to look for:

Ex:

**

Heterogeneous

(______________, no

pattern)

Hints to look for: 2 different

phases that don’t blend together

Ex:

**

Same composition

throughout

Different composition

throughout

solution, aqueous (aq),

dissolved in water

Salt water, iced tea

Homo = same

not evenly mixed

Sand and water,

cereal, trail mix

Hetero = unlike

PRACTICE1. A compound differs from an element in that a compound

a. Is a pure substance

b. Has a definite composition

c. Has a definite melting point

d. Can be decomposed by a chemical reaction

*Hint: Decomposed means ___________

2. Which of the following substances cannot be separated by chemical change?

a. Nitrogen (g)

b. Sodium chloride (s)

c. Carbon dioxide (g)

d. Magnesium Sulfate (aq)

*Hint: If it _____________by a physical OR chemical change it must be an ________. An

element is as simple as it gets so it can’t be broken down at all!

broken down

can’t be separated element

3. A pure substance that is composed only of identical atoms is classified as a

a. A compound

b. An element

c. A heterogeneous mixture

d. A homogeneous mixture

4. An example of a homogenous mixture is

a. Iron pieces in water

b. Kool Aid

c. Soup

d. Sand and Water

*Hint: If it appears to be one substance, it’s a ___________ mixture. If you can see

two or more different parts, it’s a ___________mixture.

homogenous

heterogeneous

II. REPRESENTING MATTER

1. Chemical Symbols and Formulas

A. Elements vs. Compounds

• Element = formula that contains ___________(note: a symbol is represented by a capital

letter)

• Compound = formula which contains ______________________

Examples:

Circle all the elements and underline the compounds below. Then, on the line provided, record the

number of different types of symbols within the species.

LiCl __ Mg __ NaOH ___ H2 __

Questions:

1. Does each compound have the same number of different types of symbols? ____

2. For each ELEMENT above, how many different types of symbols are there?__

3. What is the minimum number of different symbols that must be present in order for a species to be

considered a compound? __

*Hint – one capital letter = one element!

2 1 1

No

3

1

2

only one symbol

2+ different symbols/elements

B. Understanding Compound Formulas:

• Within a compound, you may see subscripts. These subscripts tell you the number of each type of atom that is present.

Example: CO2

# carbon atoms __ # oxygen atoms __

• If there are parentheses present around two or more atoms, the subscript applies to all atoms within the parentheses.

Example: Al(CN)3

# aluminum atoms __ # carbon atoms __ # nitrogen atoms __

1 2

1 3 3

• If one of the atoms within the parentheses has a subscript, you multiply this number by the number

outside of the parentheses.

Example: Fe2(SO4)3

# iron atoms __ # sulfur atoms __ # oxygen atoms ___

• Sometimes when you look at a chemical equation you will see a number IN FRONT OF a molecule.

That number tells how many there are of the entire molecule.

Example: 3H2O means that I have 3 molecules of H2O. Therefore it contains:

# hydrogen atoms (H) ___

# oxygen atoms (O) ___

2 3 12

6

3

C. Understanding Element Formulas

• The Common Elements—see periodic table!

• Rules for writing element symbols:

1) 1st letter is always capitalized.

2) If a second letter exists, it is lower case.

Example: Ca, C, Be, B --- Never CA or cA

**Warning: Be careful not to get tricked! Bi is the symbol for the element Bismuth. BI3

is the formula for Boron Triiodide, a compound containing the elements boron and

iodine. The capital letter is the clue that it is a different element!

Now that you know what a compound is and

what it looks like, let’s look at water again

and see why it is a compound.

1. What is the chemical formula for water?

2. Is water a pure substance or mixture?

Water is a pure substance because water has a fixed composition. It does not vary. Water is always H2O

3. Why, out of the two types of pure substances, is water a compound?

Water is a compound because it is made up of two or more different elements (hydrogen and oxygen) chemically bonded together

2. Particle Diagrams

• A particle diagram is a visual representation of the particles of a substance, with the particles typically

represented as circles.

• Different colors/shapes represent atoms of different elements. A key is used to identify the different

elements.

A single element Diatomic element (2

of same circle) Compound (2 or

more DIFFERENT

circles touching)

Key:

=Na (sodium)

= Cl (chlorine)

2 atoms of Na

Atom - one circle Molecule - two or more

circles

Mixture

(combination of

atoms/molecules)

2 molecules of

Cl2

2 molecules of

NaCl

Mixture of all

three

**Particle Diagrams:

https://www.youtube.com/watch?v=HzO_rUGj2zE

Practice

1. Which particle diagram(s) represent a mixture?

*Hint – for a ________, look for ___________________________mixed together

2. Which particle diagram(s) represent a pure substance?

*Hint – for a ___________, look for a diagram that is pure or in other words, _______________!

mixture 2 or more different types of particles

pure substance only has 1 type of particle

3. Which of the following particle diagrams represents a mixture of one compound and

one element?

4. Which particle diagram represents a diatomic element?

Now you know what a particle diagram is,

draw 3 molecules of water

Key:

=H (Hydrogen)

= O (Oxygen)

III. PROPERTIES OF MATTERA. Physical properties are the constants about a substance; can use our senses

to observe them; _________________________________

Examples:

B. Chemical properties are behaviors of a substance when it undergoes a

chemical change or reaction: _____________________________

Examples:

can be measured or observed without changing the substance

melting point, color, texture, density

describes the ability to change into a new substance

Flammability, reactivity

Practice

Identify the following as a physical (P) or chemical (C) property.

_____P_____ 1. The mass of copper wire is 255 g.

_____P_____ 2. The boiling point of ethyl alcohol is 77°C.

_____C_____ 3. Baking soda reacts with vinegar to make carbon dioxide

gas.

_____P_____ 4. The density of mercury is 13.6g/mL.

_____P_____ 5. The solubility of sodium chloride in water is 40g/100mL of

water

*Hint – for chemical properties, look for the word ______react!

Now that you know the difference between a

physical and chemical property, identify the

following properties of water as physical (P) or

chemical (C)

1. Water’s boiling point is 100 °C

2. Water dissolves a variety of substances

3. Water is cohesive, meaning its particles like to stick

together

4. Water reacts violently with certain metals like sodium

and cesium

P

P

P

C

IV. CHANGES IN MATTER• Matter is always changing. Ice in your drink melts. Wood in your fire burns. There are

two main types of changes in matter:

A. Physical Change – a change that does NOT change the chemical make-up of

a substance; ____________________________

*PHYSICAL changes can be reversed easily

Examples: melting, boiling, dissolving

*Hint – look for ____________ or changes in size or shape

appearance affected but not composition

phase changes

B. Chemical Change – a change in which the composition of a substance is

changed;_______________________________

*chemical changes are difficult to reverse

Examples: rusting, burning, any signs of a chemical reaction*

*recall the signs of a chemical reaction

1. _________– be careful! Not just to a lighter color like red to light red but like

red to yellow!

2. _____________– seen through ______________

3. Energy produced or consumed— in form of heat (__________), light, etc.

4. __________________(a solid in a solution)

new substance(s) formed with new properties

Color change

Gas is produced bubbling/fizzing

change in temp

Formation of a precipitate

Changes in Matter…Physical or Chemical?

Burning Toast Chemical

Making Ice Cubes Physical-can reverse by melting

Lighting a Candle Chemical

Spoiling Milk Chemical

Making Kool-Aid Physical-can reverse by evaporating water off

Practice

*Hint – ask yourself, does the change make a new substance with a new

composition? If it does, it’s a _______________. If the substance just

looks different but still has the same composition, it’s a _______________

chemical change

physical change

Now that you know the difference between a

physical and chemical change, identify the

following changes in water as physical (P) or

chemical (C)

1. Water reacting with sodium metal to produce a base and

hydrogen gas

2. Water dissolving sugar to make sugar water

3. Ice melting into liquid water

4. Water boiling into a gas

5. Water decomposing into hydrogen and oxygen

C

P

P

C

P

V. PHASES OF MATTER

• Matter exists in three phases or states

State of

Matter

Shape Volume Density Particle

Diagram

Solid (s) _______ Shape ______ volume High

Liquid (l) No definite shape-

___________

________

______ volume Medium

Gas (g) No definite shape

– _________

________

No definite volume

– ________

________

Low

*Hint – definite means fixed. It doesn’t change no matter what it’s in

Definite Definite

Definite

takes shape of

container

takes shape of

containerexpands to fill

container

THINK ABOUT THIS

What happens to the spacing and speed of particles at each of the

phases?

SOLID LIQUID GAS

https://www.brainpop.com/science/matterandchemistry/matterchangingstates/

VI. PHASE CHANGES

• A phase change is an example of a ________ change.

• Substances change phases by _____________________

• The motion or _____ of the molecules determines states of matter

• The more _______ molecules have, the _______ they move!

physical

absorbing or releasing energy

speed

energy faster

melting

boiling

Note: **__________________are two substances that readily sublime, or readily undergo

sublimation, at room temperature

https://www.youtube.com/watch?v=PaOFohqjZ1s

s g

freezing

condensation

CO2(s) (Dry ice) and I2(s)

Practice:

1. What is another name for boiling?

2. In what phase do the molecules have the most energy?

3. What is the temperature (in Celsius) that water starts to melt? ____ Label where this would be on

the diagram above.

4. What is the temperature (in Celsius) that water starts to boil? _____ Label where this would be

on the diagram above.

Evaporating/vaporization

gas

O°C

10O°C

Boiling point

Melting point

VII. SEPARATING MATTER

•Certain types of matter can be separated using various methods.

o _________________________________.They

cannot be separated at all

o ________can only be separated ________

o ________can be separated _________

•Physical separation = separating matter based on ___________

o ___________________of the substances being separated

•Chemical separation = separating matter through ___________

o _________________of the substances being separated.

Elements cannot be separated physically or chemically

Compounds chemically.

Mixtures physically

Doesn’t change the make-up

Changes the make-up

physical properties

a chemical change

Examples of Separation Techniques

Separation Apparatus Type of Separation

(Physical or

Chemical)

Description of

Technique

What types of matter will

it separate?

Tweezers

Sifting

Magnet

Physical

Physical

Physical

Separates mixtures

based on different

shape/size particles

Heterogeneous mixtures

(or things in different

phases)

Ex: Salad

Separates mixtures

based on different

shape/size particles

Heterogeneous

mixtures (or things in

different phases)

Ex: Sand and Rocks

Separates mixtures

based on magnetic

properties

Heterogeneous Mixtures (or

things in different phases)

Ex: Iron and Sand

Warning: not all metals are

magnetic

Examples of Separation Techniques

Separation Apparatus Type of Separation

(Physical or

Chemical)

Description of

Technique

What types of matter will

it separate?

Filtration

Evaporation

Physical

Physical

Separates mixtures

based on different

shape/size particles

Separates mixtures

based on different

boiling points

Heterogeneous

mixtures (or things in

different phases)

Ex: Sand and Water

Homogenous mixtures

(solutions, things

dissolved in water)

Ex: Salt Water!

Examples of Separation Techniques

Separation Apparatus Type of Separation

(Physical or

Chemical)

Description of

Technique

What types of matter will

it separate?

Distillation

Chromatography

Physical

Separates mixtures

based on different

boiling points

*it’s basically fancy

evaporation!

Homogenous mixtures

(solutions, things

dissolved in water)

Ex: Sugar and water

Physical

Separates mixtures

based on different

particle size and

solubility

Homogenous mixtures

(solutions, things

dissolved in water)

Ex: Different colored dyes

in ink

• What do you notice about the type of separation for all these techniques?

• What do you notice about the types of matter that these techniques can separate?

• What is the main difference between compounds and mixtures that makes mixtures

able to be separated physically but not compounds?

• Can you separate salt water using filtration?

– Why or why not?

All physical separation

Only mixtures

Mixtures have 2 or more substances only physically combined; compounds are 2

or more things chemically bonded together

NOBecause salt dissolves in water so it would go right

through the filter with the water. Salt water is a

homogenous mixture!

QUESTIONS