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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 dueWarm-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
• 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?
Reviewing MATTER
What is a property?
• Property: a characteristic of a substance that can be observed
http://www.gpb.org/chemistry-physics/chemistry/201
States, Boiling Point, Melting Point, and Solubility
Solid GasLiquid
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
Solid GasLiquid
Increase Thermal Energy (Heat up)
Decrease Thermal Energy (Cool off)
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.
Solid Liquid
Increasing Thermal Energy
Melting point
Vaporization
• Vaporization – change from liquid to gas
• Vaporization happens when particles in a liquid gain enough energy to form a gas.
GasLiquid
Increasing Thermal Energy
Boiling point
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
Melting point
Boiling point
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 – ??????
• Solvent – ?????
Salt (NaCl) Water (H20) at 20°C
SaltWater
Solubility can change
• Increased Temp = Increased Solubility
• Different substances have different solubility curves
Solubility of Unknown Substance at different temperatures
0
0.5
1
1.5
2
2.5
3
1 3.8 6.6 9.4 12.2 15 17.8 20.6 23.4 26.2
temperature (degrees Celcius)
mg
of
un
kn
ow
n
su
bsta
nce/ m
l o
f H
20
Physical Property
Physical property: a property that can be observed without changing the identity of the substance.
Examples:
• luster
• malleability: the ability to be hammered into a thin sheet
• ductility: the ability to be stretched into a wire
• melting point
• boiling point
• density
• solubility
• 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 mLD = 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)
Mercury 13.6
Water 1.00
Ethanol 0.81
M=25.6 g V=31.6 mL
D = 25.6 g/31.6 mL
D= 0.81 g/mL
The substance is ethanol.
• Bingo
• clickr