Transcript Properties and Changes in Matter

Working with the Properties
and Changes of Matter
What is Chemistry ?!
• What’s a chemical?
S1T2C6
Any substance that has a definite composition.
• Why study this stuff?
To be able to use the information to your benefit.
• What’s a chemical reaction?
A change in the chemical structure of a substance.
• Is this gonna be difficult ?
That’s up to you …
You depend on chemicals everyday !
…JUST TO NAME A FEW…
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Water
Polyethylene
Carbon Dioxide
Oxygen
Niacin
Sucrose
Aluminum
Cellulose
DEET
ingredients in toothpaste
acetylsalicylic acid
nitrogen
acetylene
polyester
silicon dioxide
calcium carbonate
So Where does Chemistry fit in ?
Biology : matter that is alive
Chemistry :
how matter is put together
how atoms combine to form molecule
how molecules combine to make different kinds
of matter
Physics :
The nature of basic things such as motion, forces,
energy, matter, heat, sound, light & the composition of
atoms.
So, What is Matter ?
• Matter is defined as anything that has :
Mass (inertia:
a resistance to change in movement
Takes up space (volume)
Physical States of Matter
There’s 4 of them !
• SOLIDS
Have definite (or fixed) shape and volume
The particles in a solid are held fairly rigidly in place.
Physical States of Matter
There’s 4 of them !
• LIQUIDS
Have a definite volume but no fixed shape.
The particles in a liquid are free to flow around each other
Physical States of Matter
There’s 4 of them !
• GASSES
Have neither definite or fixed shape or volume.
The particles in a gas are:
widely disbursed,
interact weakly,
move independently at high speed,
and completely fill any container they occupy.
Physical States of Matter
There’s 4 or more of them !
• PLASMAS
Gases whose particles are so hot they have acquired an
electrical charge.
• Bose-Einstein Condensates
Groups of atoms at such low temperatures that they
behave as a single unit or super atom. (0.001 K)
• Neutron Stars
Matter that has collapsed due to gravity to leave nothing
but a pile of neutrons touching each other with no space
in between. (about 78,000 tons per teaspoon)
Changes in Matter ….
• Physical Changes :
* Changes in which the basic identity of the substance
does not change.
* The physical state (solid, liquid, or gas) may change
Examples:
Salt or sugar dissolving in water
wax melting in a candle
crushing a rock
Changes in Matter ….
• Chemical Changes :
There is a change in the identities of the substances
and new substances with different identities are formed.
Example:
mercury(II) oxide
sodium iodide + lead nitrate
mercury + oxygen (gas)
lead iodide + sodium nitrate
Changes in Matter ….
• In any reaction :
• Left side
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Right side
+
• Methane + oxygen forms carbon dioxide + water vapor
• REACTANTS
• Used up in the reaction
PRODUCTS
Produced in the reaction
• The reactants and products are THE SAME atoms just
rearranged as time has passed.
Evidence of a chemical change
• The evolution of a gas …
evidenced by bubbling or a change in color
• The formation of a precipitate
A solution turns cloudy or a solid drops out of solution
• The release or absorption of energy
The temperature changes – either hotter or cooler
or the solution or substance glows!
• A color change
Elements, Compounds, and Mixtures
Elements are pure substances
composed of only one type of matter
Compounds are substances made
up of more than one type of matter
acting like a single pure substance.
Mixtures are made up of more than
one substance in which each part
Retains its chemical identity.
ELEMENTS
• Elements can be found as single ATOMS
• EXAMPLE : He, Ne, Ar, Kr, Ra
• Elements can be found as MOLECULES
made up of 2 or more atoms of the same
substance.
• EXAMPLE : H2, O2, N2, F2, Cl2, Br2, I2
• Some elements have more than one form and
are called ALLOTROPES.
• EXAMPLE : Oxygen, Phosphorus, Sulfur,
Carbon
Allotropes
• Oxygen : Oxygen O2 and Ozone O3
• Phosphorus : Red and White Phosphorus
• Sulfur : Yellow S8
• Carbon : soot, graphite, diamond, and
fullerines (C60) or nanotubes
COMPOUNDS
• Compounds are pure substances
• They are represented by formulas
• Molecular formulas tell what elements and how much
of each element is present
• EXAMPLE : C12H22O11 = ?
(Hint: It’s sweet!)
• Structural formulas show how the atoms are connected
MIXTURES
• Mixtures are physical combinations of
substances.
• Each part retains its chemical identity.
• Mixtures can vary in composition and
properties.
• A mixture of metals is called an ALLOY
• EXAMPLES : gold in jewelry is mixed with silver, copper or nickel
to add strength and wear resistance.
• Copper and zinc make brass
• Copper and tin make bronze
Types of Mixtures
• Homogeneous Mixtures - physical
combinations of substances in which the
components are UNIFORMLY
DISTRIBUTED
• Heterogeneous Mixtures - physical
combinations in which the substances are
UNEVENLY DISTRIBUTED
Types of Mixtures
• EXAMPLES :
• Homogeneous : solutions
• tea,
stainless steel,
14 kt gold,
maple syrup
• Heterogeneous: Colloids and suspensions
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Orange or Tomato juices
Chocolate chip cookies
Granite
Salads
fog
shaving cream
jello or gelatin
clouds
Mixtures and Compounds
• Mixtures can be separated by physical
methods
• Chemical methods must be used to
separate compounds
• The components of a mixture can be
present in varying proportions
• Compounds have DEFINITE proportions
of the elements that make them up
Separating Mixtures
• Physical properties are exploited to
separate the substances in a mixture.
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Boiling point
Solubility
Melting point
Density
Magnetic suseptability
Chemical reactivity
used in petroleum refining
used in purifying salt etc.
used in metallurgy
used in gold mining
used in iron and nickel
used in purifying
SUMMARY
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Matter
• can be
• Pure Substances
• Element
Compound
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methane
ammonia
proteins
salt
Gold
Mercury
Nitrogen
Silicon
has mass and volume
can be
Mixtures
Heterogeneous
Homogeneous
suspensions colloids solutions
mud puddle
smog
coffee
salad
whipped cream tea
sandwitch
gel
Koolade