unit 2: matter and change
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Unit 2: Matter and Change. OBJECTIVES. Students will be able to: define matter describe the states of matter (solid, liquid, gas) identify the characteristics of of a substance, element and compound distinguish between physical and chemical change - PowerPoint PPT PresentationTRANSCRIPT
Unit 2: Matter and Change
OBJECTIVESStudents will be able to:1. define matter2. describe the states of matter (solid, liquid,
gas)3. identify the characteristics of of a substance,
element and compound4. distinguish between physical and chemical
change5. identify properties of matter (chemical,
physical, intensive, extensive)6. identify changes in matter that occur (physical
and chemical change)7. explain the law of conservation of mass
WHAT IS MATTER?• Matter is anything that takes up
space and has mass• Matter or not?
– gold– sound
– sunlight– air
– water– heat
– thoughts
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MASS & WEIGHT• Mass is the measure of the amount of
matter that makes up an object• Weight is a measure of the force of gravity on
an object– weight = mass x gravity– weight varies depending on distance from the
earth’s surface• Because the value never changes,
scientists use mass, not weight to measure matter
Shape Takes the shape of container
Takes the shape of container
Definite shape
Volume Fills volume of container Definite volume Definite
VolumeArrangeme
nt of particles
Random, far apart Random, close Fixed, close
Attraction between particles
Essentially none Strong Very strong
STATES OF MATTER
GAS vs. VAPOR• Gases and vapors are similar, but
terms should not be used interchangeably– Gas refers to a substance that is
naturally in the gaseous state at room temperature: hydrogen gas
– Vapor refers to the gaseous state of a substance that is a solid or a liquid at room temperature: water vapor
solid liquid gas
THE PHASES OF WATER
MatterAnything that has mass and takes up space
Pure SubstanceMatter with an
unique and unchanging composition
MixturesA combination of 2
or more pure substances
ElementPure
substance that cannot be broken into more simpler
substances
CompoundAtoms of two
or more elements that are
chemically united in a
fixed proportion
Homogeneous
Mixture/Solution
Mixture with a uniform
composition
Heterogeneous
MixtureMixture does not appear to be the same throughout
physical change
chemical
change
(PURE) SUBSTANCE • A substance is a form of matter with an
unique and unchanging composition (composition doesn’t change from sample to sample)
• Examples: Water, salt• What about salt water?• All pure substances are either elements or
compounds
ELEMENT• An element is a substance that cannot be
broken into more simpler substances• Examples: gold (Au), oxygen (O2)• To date, there are 118 elements
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COMPOUNDS• Compounds are substances composed of
atoms of two or more different elements that are chemically united in a fixed proportion– Water (H2O), sugar (sucrose, C12H22O11),
ammonia (NH3)• Compounds can be separated back into its
elements (by chemical means)– Electrolysis of water:
•2H2O 2H2 + O2
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PROPERTIES OF MATTER• Every pure substance has a unique set of
properties• A property is a characteristic that allows us
to recognize a certain type of matterPhysical properties of
waterclear liquid at room
temperatureboils at 100oCfreezes at 0oC
density at 4oC is 1.000 g/cm3
PHYSICAL PROPERTIES• Physical properties
are those properties that can be measured without changing the identity of the substance:– color, odor, melting point,
boiling point, density, hardness, taste
• Physical properties are either extensive or intensive
Extensive property
Intensive property
•A property that depends on the amount of a substance present•Example: Mass, volume, length•value will change when the amount of substance changes: 1 mL of water has a mass of 1 g while the mass of 1 L has a mass of 1000 g
•A property that is independent of the amount of substance present•Example: Density, boiling point, melting Point•value will not change when the amount of substance changes: The density of water is always 1.00 g/mL
CHEMICAL PROPERTIES• Chemical properties describe the way a substance may
change or react to form other substances– Corrosion, flammability
• The inability of a substance to change is also a chemical property– Argon gas is inert
• To observe a chemical property a chemical change must occur
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PROPERTIES OF COPPERPhysical properties Chemical properties
reddish brown, shiny
Forms a green copper carbonate compound when in contact with moist air
good conductor of heat
Forms new substances when combined with nitric & sulfuric acid
Density = 8.92 g/cm3 Forms deep blue
solution when in contact with ammonia
Melting point = 1085oCBoiling Point = 2570oC
CHANGES IN MATTER• A physical change is a change that
alters the appearance of the substance drastically but leaves its composition unchanged:– bend, grind, split, crush, boil, freeze,
melt, vaporize
Chemical Change (Chemical Reaction)
• In a chemical change a substance is transformed into a chemically different substance– When hydrogen burns in air it reacts with
oxygen to form water• The new substances formed have different
compositions and different properties• Terms: Explode, rust, oxidize, corrode,
tarnish, ferment, burn, rot etc.
EVIDENCE OF CHEMICAL CHANGEFormation of a gas or solid; color change;
energy change; odor
PHYSICAL OR CHEMICAL CHANGE?• Plants use carbon dioxide and
water to make sugar.• On a cold day, water vapor in the
air forms frost.
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THE LAW OF CONSERVATION OF MASS• Mass (matter) is neither created
nor destroyed during a reaction…mass is conserved:
Massreactants = Massproducts2HgO 2Hg + O216 g 200 g + 16
greactants products
PRACTICE PROBLEM1. In a complete reaction of 22.99 g
of sodium with 35.45 g of chlorine, what mass of sodium chloride is formed?
2. A 12.2-g sample of X reacts with a sample of Y to form 78.9 g of XY. What is the mass of Y that reacted?