Transcript physical change

Bellringer # 6

1. What is matter?

2. How would you classify matter?
Complete the right column of the table below, using
the following names: boron, bromine, calcium,
magnesium, neon, nitrogen, silicon, sulfur, zinc.
Today, there are rules for how a newly discovered element is to be
named. However, in earlier times, elements were named for people,
places, and foreign words, among other things. Match each element
to how it was named. You may also use an element’s symbol as a
clue. Write the correct letter in the space provided.
___ Berkelium (Bk)
a. Noble Prize winner who studied relativity
___ Curium (Cm)
b. Latin name (ferrum)
___ Einsteinium (Es)
c. powerful mythological beings
___ Gold (Au)
___ Iodine (I)
d. home of the university in California where
the element was first made
e. Greek word for violet (iodes) ___ Iron (Fe)
f. Nobel Prize winner who studied radioactive
elements
g. Greek word for hidden (kryptos)
___ Titanium
h. Latin name (aurum)
___ Krypton (Kr)
Bellringer #7

Do you think there are elements inside the
human body?

If yes, list several examples.
Chapter 2 Overview
Matter and atoms
 elements
 distinguishes between elements and
compounds.
 Molecules and chemical formulas
 the differences between pure substances
and mixtures.
 Physical and chemical properties
 The concept of density
 Physical and chemical changes of matter

Chapter 2 – Matter Key Ideas
〉 How
can matter be classified?
〉 Why
are carbon and copper classified as
elements?
〉 How
are elements related to compounds?
〉 What
is the difference between a pure
substance and a mixture?
What is matter?

Matter is anything that has mass and
takes up space.

Chemistry is about the study of matter
and its changes.

Many items that you use each day are
chosen for their chemical properties.

Examples: soaps, foods, carbonated drinks,
gasoline.
Questions?

Is the air that you breath matter?


Is light matter?


yes
NO
Is sound matter?

NO
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Light and sound are not considered matter
because they have no mass or volume.
〉How
1.
can matter be classified?
One important part of Chemistry is
classification. Look at Figure 1 on page 45.
〉 One
useful way to classify matter is based on
what makes up the matter.
Every sample of matter is either an element,
a compound, or a mixture.
Example: gold is an element, water is a
compound, and vegetable salad is a mixture.
Elements
〉 Why
are carbon and copper classified as
elements?
〉 Each
element is made of one kind of atom.

element: a substance that cannot be
separated or broken down into simpler
substances by chemical means

atom: the smallest unit of an element that
maintains the properties of that element

Elements are represented by symbols.
 The symbols are either one capital letter
or one capital and one lowercase letter.
 Examples: C=Carbon, Ne=Neon

Atoms that make up a molecule act as a unit.
 Atoms can join to make millions of
molecules just as letters of the alphabet
combine to form different words.

Molecule: the smallest particle of a
substance that has all of the chemical
properties of that substance

A molecule is made up of one atom or two or
more atoms bonded together

Look at Figure 4 on page 47.
Compounds
〉 How
•
are elements related to compounds?
Each molecule of a compound contains two or
more elements that are chemically combined.
•
〉 Elements
combine chemically to form a
compound.

Compound: a substance made up of atoms of
two or more different elements joined by
chemical bonds

Example: Water -made from oxygen and hydrogen
atoms.
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Compounds have unique properties.

Every compound differs from the
elements that it contains.

Example 1: Hydrogen, Oxygen and
Nitrogen are colorless gases but they
combine with carbon to form nylon, a
flexible solid.
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Example 2: Likewise, the properties of
water differ from those of hydrogen and
oxygen, which make up water.
Chemical formulas represent compounds.
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The following chemical formula represents the
compound for indigo:
Pure Substances and
Mixtures
〉
What is the difference between a pure substance and
a mixture?
〉
Elements and compounds are pure substances,
but mixtures are not.

pure substance: a sample of matter, either a single
element or a single compound, that has definite
chemical and physical properties

mixture: a combination of two or more substances
that are not chemically combined
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
Mixtures are classified by how thoroughly the
substances mix.
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heterogeneous mixture: substances aren’t
mixed uniformly and are not evenly
distributed

homogeneous mixture: substances are
evenly distributed, and the mixture is the
same throughout

miscible: substances that can be mixed

immiscible: substances that cannot be
mixed
Gases can mix with liquids.
Types of Mixtures
Quick Lab Mystery Mixture
 Look
in your book on page 48.
 Listen
carefully for directions.
Homework
 Classifying
Matter
 Ch 2 Vocab 13 words pg. 69
Bellringer # 7
 Look
 How
at figure 1 on page 51.
many physical properties can you
observe?
Changes of Matter

Leaves change color in the fall, and ice
cube melts in your glass, and bread dough
turns into bread when it bakes in the oven.

Such changes occur in matter as a result
of a physical or chemical changes.
Physical Properties
〉 Why
are color, volume, and density classified as
physical properties?
〉 Physical
properties are characteristics that can
be observed without changing the identity of the
substance.
Physical properties can help
identify substances.

Many physical properties remain constant.
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Example 1: Height and hair color.
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Example 2: At room temperature and under
atmospheric pressure, all samples of pure
water are colorless and liquid.

Pure water is never a powdery green solid.
The physical properties of water help you
identify water.
Physical properties can be
observed or measured
Examples: shape, color, odor, texture, state
(solid liquid or gas), melting point, boiling
point, strength, hardness, magnetism, the
ability to conduct electricity or heat
 Water
can be in the form of solid ice, liquid water,
or gaseous steam.

melting point: the temperature and pressure
at which a solid becomes a liquid

boiling point: the temperature and pressure
at which a liquid becomes a gas
Physical properties can help
determine uses
Copper is used in power lines etc.
because it conducts electricity.
 Antifreeze is used in car radiators because
it remains a liquid at temperatures that
would freeze or boil water.
 Aluminum is used in foil because it is light
weight yet durable and flexible.

Durable- able to withstand wear and damage.
 Flexible- capable of bending easily without
damage.
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
Density is a physical property.

density: the ratio of the mass of a substance
to the volume of the substance
mass
m
density 
, or D 
volume
V

common unit of density is g/cm3
 Density
is different from weight.
Density is different from Weight





Look at Figure 4 on page 55
The brick and sponge have similar volumes but
the brick is more massive than the sponge.
Because the brick has more mass per unit than
the sponge it is denser.
Two pounds of feathers are heavier than one
pound of steel.
But the feathers are less dense than the steel,
so two pounds of feathers have a greater
volume than one pound of steel does.
Chemical Properties
〉A chemical property describes how a substance
changes into a new substance, either by combining
with other elements or by breaking apart into new
substances.
 There are two types of chemical properties.
 1. Flammability is a chemical property.


flammability: the ability to burn
2. Reactivity is a chemical property.

reactivity: the capacity of a substance to combine
chemically with another substance

Look at Figure 5 on page 56.
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Physical and chemical properties are different.

Physical properties can be observed without
changing the identity of a substance.

Chemical properties can be observed only in
situations in which the identity of the
substance changes.
Homework

Worksheet: Properties of matter due
tomorrow

Interpreting Charts and Graphs
Bellringer #8

Read “Aerogel” on page 53.

Answer questions 1 and 2 in your journal.
Quick Lab Reactivity

Open your book to page 58.
Changes of Matter

Leaves change color in the fall, an ice
cube melts in your glass, and bread dough
turns into bread when it bakes in the oven.

Such changes occur in matter as a result
of physical or chemical changes.
Physical Changes

A physical change affects one or more
physical properties of a substance without
changing the identity of the substance.
Look in your book at Figure 1 page 59
 Examples of physical changes: cutting,
crushing, reshaping, changing state


Sanding a piece of wood, and mixing oil and vinegar
Melting a gold nugget to form a gold
ring involves several physical changes.
Look at Figure 2 on page 60
 The gold changes from solid to a liquid
and back to a solid.
 The shape of the gold changes.
 The gold nugget becomes a ring of gold.
 But these physical changes do not change
all of the properties of the gold.


The gold’s color, melting point and density do
not change.
Physical changes do not change a
substance’s identity.

During a physical change energy is
absorbed.

After a physical change, a substance may
look different but the arrangement of
atoms that make up the substance is not
changed.

A gold nugget, molten gold and gold rings
are all made of gold atoms.
Physical Changes

Physical changes do not change a
substance’s identity.

Dissolving is a physical change.
Look at Figure 3 on page 60.
 When you stir sugar into water, the sugar
dissolves and seems to disappear. But the
sugar is still there. You can taste the
sweetness of the water so what happened to
the sugar?

Chemical Changes
〉Why
is baking bread an example of a
chemical change?
〉A
chemical change happens when one
or more substances are changed into
entirely new substances that have
different properties.

chemical change: a change that occurs when
one or more substances change into entirely
new substances with different properties
Chemical Changes

Chemical changes happen everywhere.

Examples of chemical changes: burning, rusting, digesting,
decomposing

Chemical changes form new substances.
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Chemical changes can be detected.

Signs include: change of color, change of smell, fizzing,
production of heat, production of sound, production of light

Chemical changes cannot be reversed by
physical changes.

Look at figure 4 on page 61.
Breaking Down Mixtures and
Compounds
〉How
can mixtures and compounds be
broken down?
〉Mixtures
can be separated by physical
changes
〉Compounds
must be broken down by
chemical changes.
Breaking Down Mixtures
•
Mixtures can be physically separated.

Examples of separating a mixture:

Separating saltwater into its parts by heating it:
When the water evaporates, the salt remains.

Using a distillation device to heat a mixture
whose components have different boiling
points: The component that boils and
evaporates first separates from the mixture.

Using a centrifuge: The mixture spins rapidly
until the components separate.
Breaking Down Compounds
•
Some compounds can be broken down through
chemical changes.

Examples of separating a compound:
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When mercury(II) oxide is heated, it breaks
down into the elements mercury and oxygen.
Look at Figure 8 on page 64.
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When a current is passed through melted
table salt, the elements sodium and chlorine
are produced.

When you open a bottle of soda, carbonic
acid in the soda breaks down into carbon
dioxide and water.
Homework
CH 2 Vocab 13 words the list is on pg.69
 CH 2 starts on page 45


Choosing materials for Bicycle Frames
Bellringer #9

Read How glass is made page 65

Answer question1 in your journal.
Matter can go through both physical and chemical changes and
can exist as mixtures and compounds. See how matter interacts
when Jordan makes oatmeal bread.
To make bread, Jordan must do several things before it is ready
to be baked. For each step, decide whether a physical or a
chemical change occurs, or whether a mixture or compound is
formed. Circle the correct answer.
a. stir flour and dry oatmeal
b.heat the water
c. melt the shortening
d.beat the eggs
e. blend molasses with water
f. bake the bread
mixture
physical
physical
physical
mixture
physical
compound
chemical
chemical
chemical
compound
chemical
Inquiry Lab: Can You Separate a Mixture?

Open your books to page 63.

Listen carefully to the directions.
Bellringer # 12
 Read
Identiying mysterious
substances pg 57
 Answer
questions 1 and 2 in
your journal.
Chapter 2 Vocab Quiz
 Take
out your parent signed
sheet
 Your homework crossword puzzle
 Look
over your vocab for 5
minutes.
Chapter 2 Review pg. 70
Do
#1-27
Due
Friday
Bellringer #13
 Read
how tv’s work page 116
 Answer
question 1 in your journal
Bellringer # 14
 Read
careers using chemistry pg
214
 Answer
journal
both questions in your
Bellringer #15
 Read
“Nuclear Medicine” on page
123 and answer the question in your
journal.