Transcript chemical and physical properties

Page 64
Nov. 5, 2012
Focus: Chemical and Physical
Properties / Changes
Objective: pre-test, define physical and
chemical property, physical and
chemical change
HW: article, data – analysis - graph due
Warm-Up:
• Is Humpty Dumpty falling off the wall
and cracking on the ground a
physical or chemical change?
• Explain your answer.
Pre-Assessment / Formative
•
•
•
•
Name
November 5, 2012
Block
Title: Formative of Objectives 6.P.2.3,
6.P.3.1, 6.P.3.3
No more than 25 minutes
Homework pg. 63
• Science Fair Project
• Article and questions
• Bring back card for My
Energy Kit
Physical versus Chemical
Properties
Reviewing MATTER
• Matter: anything that has mass and takes
up space
– Mass – the amount of matter in something
– Volume – the amount of space something
occupies
• Which of the following is matter?
– A car?
– A box?
– You?
What is a property?
• Property: a
characteristic of a
substance that can
be observed
http://www.gpb.org/chemistryphysics/chemistry/201
States, Boiling Point, Melting
Point, and Solubility
Solid
Liquid
Gas
Defining States of Matter
• States of matter are NOT defined by what
they are made of.
– Example: solids can be elements (gold), compounds
(Salt = NaCl), or mixtures (butter)
Element (Au)
Compound (NaCl)
Mixture (Milk, Salt, etc)
Defining States of Matter
• States of matter are defined by whether
they hold SHAPE and VOLUME
Element (Au)
Compound (NaCl)
Mixture (Milk, Salt, etc)
ALL KEEP THE SAME SHAPE AND VOLUME = Solids
Defining States of Matter
• Solids – have a definite SHAPE and
VOLUME.
Element (Au)
Compound (NaCl)
Mixture (Milk, Salt, etc)
ALL KEEP THE SAME SHAPE AND VOLUME
Particle View of a Solid
• Particles in a solid are PACKED
CLOSELY together and they are in a
FIXED POSITION.
Particles vibrate in place
Liquids
• Liquids – has definite VOLUME but no
defined SHAPE
100 ml
Particle View of a Liquid
• Packed CLOSELY (like a solid), but move
FREELY around each other (must stay in
contact).
Gases
• Gases - do NOT have definite SHAPE or
VOLUME.
Bromine gas fills up the entire volume of the container
Particle view of a Gas
• Particles can MOVE FREELY and will
either fill up or squeeze into available
space.
Changes in States of Matter
• Thermal Energy – heat energy.
• More thermal energy = More particle movement
Changing States
Increase Thermal Energy (Heat up)
Solid
Liquid
Decrease Thermal Energy (Cool off)
Gas
Melting point
• Melting - change from solid to liquid
• Melting point - SPECIFIC temperature when
melting occurs.
• Each pure substance has a SPECIFIC melting
point.
–
–
–
–
–
Examples:
M.P. of Water = 0°C (32°F)
M.P. of Nitrogen = -209.9 °C (-345.81998 °F)
M.P. of Silver = 961.93 °C (1763.474 °F)
M.P. of Carbon = 3500.0 °C (6332.0 °F)
Melting Point
• Particles of a solid vibrate so fast that they
break free from their fixed positions.
Increasing Thermal Energy
Solid
Liquid
Melting point
Vaporization
• Vaporization – change from liquid to gas
• Vaporization happens when particles in a
liquid gain enough energy to form a gas.
Increasing Thermal Energy
Liquid
Boiling point
Gas
Two Kinds of Vaporization
• Evaporation – vaporization that takes
place only on the surface of the liquid
• Boiling – when a liquid changes to a gas
BELOW its surface as well as above.
Boiling Point
• Boiling Point – temperature at which a
liquid boils
• Each pure substance has a SPECIFIC
boiling point.
– Examples:
– B.P. of Water = 100°C (212°F)
– B.P. of Nitrogen = -195.79 °C (-320.42 °F)
– B.P. of Silver = 2162 °C (3924 °F)
– B.P. of Carbon = 4027 °C (7281 °F)
Boiling Point and Melting Point
WATER – H20
200
Boiling point
Temperature
150
100
Melting point
50
0
-50
-100
-150
time
Solubility
• Maximum amount of a substance that can
be dissolved in a liquid (at a specific
temperature).
Salt (NaCl)
Water (H20)
at 20°C
Solubility
• Solute – substance being dissolved
• Solvent – liquid substance that solute is
dissolved into
Salt (NaCl)
Water (H20)
at 20°C
Solubility
• Solute – ?????? Salt
• Solvent – ????? Water
Salt (NaCl)
Water (H20)
at 20°C
Solubility can change
• Increased Temp = Increased Solubility
• Different substances have different
solubility curves
Solubility of Unknow n Substance at different tem peratures
substance/ml of H20
mg of unknown
3
2.5
2
1.5
1
0.5
0
1
3.8
6.6
9.4
12.2
15
17.8
tem perature (degrees Celcius)
20.6
23.4
26.2
Physical Property
Physical property: a property that can be
observed without changing the identity of the
substance.
Examples:
• luster
• melting point
• malleability: the ability
to be hammered into a
thin sheet
• boiling point
• ductility: the ability to
be stretched into a wire
• solubility
• density
• specific heat
Special Physical Properties
• Melting point: the temperature at
which a substance changes from a
solid to a liquid at a given pressure
water = 0oC
• Boiling point: the temperature at
which a substance changes from a
liquid to a gas at a given pressure
water = 100oC
Chemical Properties
• Chemical property: a property that
can only be observed by changing the
identity of the substance
Examples:
•flammability
•ability to rust
•reactivity with vinegar
Chemical
Properties &
Physical and
Chemical
Changes
Physical changes are those
changes that do not result in the
production of a new substance. If
you melt a block of ice, you still
have H2O at the end of the
change.
If you break a bottle, you still
have glass. Painting your nails
will not stop them from being
fingernails. Some common
examples of physical changes
are: melting, freezing,
condensing, breaking, crushing,
cutting, and bending.
Some, but not all physical changes
can be reversed. You could
refreeze the water into ice, but you
cannot put your hair back together
if you don’t like your haircut!
Special types of physical changes
where any object changes state,
such as when water freezes or
evaporates, are sometimes called
change of state operations.
CHEMICAL PROPERTIES
Chemical properties can ONLY
be observed AS the substances
are changing into different
substances.
Chemical changes, or chemical
reactions, are changes that result
in the production of another
substance.
FLAMMABILITY: A material’s ability
to BURN in the presence of OXYGEN
REACTIVITY:
How readily (easily) a substance
combines chemically with other
substances.
When you burn a log in a
fireplace, you are carrying out a
chemical reaction that releases
carbon. When you light your
Bunsen burner in lab, you are
carrying out a chemical reaction
that produces water and carbon
dioxide.
Common examples of chemical
changes that you may be
somewhat familiar with are;
digestion, respiration,
photosynthesis, burning, and
decomposition.
Physical or Chemical Change?
• Painting Wood
• PHYSICAL
Physical or Chemical Change?
• Burning Paper
• CHEMICAL
Physical or Chemical Change?
• Digestion of food
• CHEMICAL
Physical or Chemical Change?
• Sugar dissolving in
water
• PHYSICAL
Physical or Chemical Change?
• Iron turning red when
heated
• PHYSICAL
Physical or Chemical Change?
• Evaporation
• PHYSICAL
Physical or Chemical Change?
• A pond freezing in
winter
• PHYSICAL
Physical or Chemical Change?
• Melting ice
• PHYSICAL
Physical or Chemical Change?
• Cutting wire
• PHYSICAL
Physical or Chemical Change?
• Painting fingernails
• PHYSICAL
Physical or Chemical Change?
• Cutting fabric
• PHYSICAL
Physical or Chemical Change?
• Baking muffins
• CHEMICAL
Physical or Chemical Change?
• Shattering glass
• PHYSICAL
Physical or Chemical Change?
• Decomposition of old
leaves
• CHEMICAL
Physical or Chemical Change?
• Wrinkling a shirt
• PHYSICAL
Physical or Chemical Change?
• An old nail rusting
• CHEMICAL
Density
• Density is the amount of mass per
unit of volume.
• Density can be used to identify a
substance.
• The density of water is 1.0g/mL
Density Calculations
• Calculations:
D = m/V = g/mL = g/cm3
• Ex: A cube has a mass of 2.8 g and
occupies a volume of 3.67 ml. Would
this object float or sink in water?
Mass = 2.8 g
Volume = 3.67 mL
D = 2.8g/3.67 mL= 0.76 g/mL
– This object would float in water because
its density is less than water (1.0 g/mL).
More Density Calculations
• Ex: A liquid has a mass of 25.6 g and a
volume of 31.6 mL. Use the table below
to identify the substance.
Substance
Density (g/mL)
D = 25.6 g/31.6 mL
Mercury
13.6
D= 0.81 g/mL
Water
1.00
Ethanol
0.81
M=25.6 g
V=31.6 mL
The substance is ethanol.
• Bingo
• clickr