Review of 7.6A/B/C Changes in Matter

Review of 7.6A/B/C Changes in Matter

CLASSIFYING MATTER:

ELEMENTS,

COMPOUNDS, AND
MIXTURES REVIEW

(1)PURE SUBSTANCES

•A sample of matter that has definite
chemical and physical properties.

(2)ATOMS

The smallest unit of an element
that maintains the properties
of that element. An atom is a
single building block of an
element. All matter is made up
of atoms.

(3)ELEMENTS

Pure substances made up of only one type of
atom. Elements are listed on the Periodic
Table.

(4) MOLECULES

Composed of two or more atoms that
are joined by chemical bonds.

• Molecule can be made up of elements of the

same type – Ex: O2, H2, N2

• Molecules can also be made up of different

types of elements – Ex: C6H12O6, H2O, NaCl

Elements represented in a Chemical Formula only have ONE Capital Letter.

(5)COMPOUNDS

Pure substance composed of two or more
different elements joined by chemical bonds.
•Made of elements in a specific ratio

that is always the same

•Has a chemical formula
•Can only be separated by chemical means,
not physically
•Compounds have their own physical and
chemical properties that are different from
other substances

Compounds represented in a Chemical Formulas have TWO OR MORE Capital Letters.

Multiple Choice

Elements are made of 

• many types of atoms 

• the periodic table

• one type of atom 

• molecules 

Multiple Choice

Two or more atoms chemically bonded together are called a

• atom

• element

• molecule

• mixture

Multiple Choice

Which of the following is a molecule but is NOT a compound?

• sodium chloride (NaCl)

• ozone (O₃)

• carbon dioxide (CO₂)

• water (H₂O)

Multiple Choice

Which of the following is a characteristic of compounds?

• they are always metals

• they can be found on the periodic table

• They are made up of two or more different elements

• they cannot be divided into a simpler substance

Counting Atoms in a Chemical Formula

Chemical Formulas

Chemical Formulas are a shorthand way to communicate the parts of a molecule.

Examples: H2O, NaCl, CO2

Subscrips

Subscripts are the small lowered numbers used to identify how many atoms of a particular element are in a chemical formula.

Examples: H₂O = 2 hydrogen atoms + 1 oxygen atom

               CO₂ = 1 carbon atom + 2 oxygen atoms

              C₆H₁₂O₆ = 6 carbon atoms + 12 hydrogen atoms + 6 oxygen atoms

Coefficients

Coefficients are the numbers in front of a chemical formula to indicate the number of molecules of a compound.

Examples: 2 H₂O = 2 x 2 hydrogen atoms + 2 x 1 oxygen atom

                   = 4 hydrogen atoms + 2 oxygen atoms

Multiple Choice

Number of C's in 2Na₂CO₃

• 1

• 2

• 3

• 5

Multiple Choice

How many total atoms are in the compound C₂H₈O ?

• 11

• 2

• 8

• 1

Multiple Choice

How many atoms are there TOTAL in:
H₂SO₄

• 6

• 5

• 7

• 3

Multiple Choice

How many atoms of Carbon are in this formula? $$C_{6\ }H_{12}O_6$$  

• 6

• 1

• 12

Multiple Choice

Which element has the greatest number of atoms? $$AgNO_3$$  

• Silver

• Gold

• Nitrogen

• Oxygen

Physical vs. Chemical Changes

PHYSICAL CHANGE

• Physical change: a change that occurs

that does not change the identity of the
substance

• Some common physical changes include:

SIGNS OF A PHYSICAL CHANGE

A physical change has occurred if it ONLY:

1.Changes size
2.Changes shape
3.Changes state of matter

CHEMICAL CHANGES

• Chemical change: a change that occurs causing

the identity of the substance to change

• In a chemical change where there is a chemical

reaction, a new substance is formed and energy
is either given off or absorbed.

SIGNS OF A CHEMICAL CHANGE

If it ALSO:

1.

Production of a gas (bubbles)

2. Changes temperature (without added heat/cooling source)

3. Forms a solid in a liquid - precipitate

4. Gives off light, heat, or electricity

5. Changes color

6. Reacts with Oxygen

7. Gives off a new odor

Remember
COLD PIG!

Multiple Choice

Is this a physical or chemical change?

• Physical

• Chemical

Multiple Choice

Is this a physical or chemical change?

• Physical

• Chemical

Multiple Choice

In the picture below, two liquids are combined and a yellow solid is formed. Which of these is the best evidence that a chemical reaction occurs when the liquids are mixed?

• The density of one liquid is different from the other.

• Two substances are combined.

• A new substance with different properties is formed.

• The volume of the beaker changes.

Multiple Choice

Which statement(s) about chemical and physical changes is correct?

1. 1. Chemical changes break apart and move substances from one place to another.

2. 2. Physical changes alter a substance’s properties such as size, shape, or state of matter.

3. 3. Chemical changes form new substances.

4. 4. Physical changes break down substances into simpler molecules

• Statement 1 only

• Statements 2 and 3

• Statement 4 only

• Statement 2 only

Multiple Choice

Is this an example of a physical or chemical change?

• physical

• chemical

Multiple Choice

Is this an example of a physical or chemical change?

• physical

• chemical

Multiple Choice

Melting a chocolate bar?

• Physical Change

• Chemical Change 

Multiple Choice

Which of the following is NOT an example of a physical change?

• crumpling paper

• sharpening a pencil

• clothes shrinking

• sour milk