File - Chemistry with Mrs. Roys

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Divisions
of Matter
Pure Substances and
Mixtures
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Pure Substance
 Cannot
be broken down and retain its
properties.
 Has
a fixed composition.
 Every
sample of a pure substance has
EXACTLY the same composition AND exactly
the same characteristics - homogeneous
 Examples
 Salt
NaCl
 Copper
 Water – H2O is always 11.2% Hydrogen and
88.8% Oxygen
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Elements
 Simplest
form of
matter
 Made
up of ONE
type of ATOM
 All
atoms in an
element have same
number of protons
in nucleus.

Atom- Smallest unit of an
elements that KEEPS the
IDENTITY of the element
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PERIODIC TABLE
 Elements
are represented by symbols
 NEED to know Symbols. (handout)
 92
naturally occurring elements
 93-112
Made only under lab conditions
 Information
on periodic table
 Symbol
 Atomic
# - which tells us the number of protons
 Atomic Mass – Average mass of the element
(Number of neutrons plus protons)
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COMPOUNDS

Made up of atoms from 2 or
more different elements.

Can be broken down into its
elements BUT those elements
have different properties
than the compound.
 All
samples of a compound have the same ratio of
elements.
 Subscripts tell us the number of atoms or groups
of atoms in a formula
 Coefficient (the number in front) refers to the
entire unit.
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Law of conservation of Energy
The total amount of energy
remains the same in a system.
Energy can be absorbed or
released in a system, it can
change forms, but it is not
destroyed or created.
PAGE 11 IN YOUR BOOK
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MIXTURES
A mixture is a blend of two or more kinds
of matter, each of which retains it’s own
identity and properties.
Web site to interact with
KS3 Bitesize
http://www.bbc.co.uk/schools/ks3bitesize/science
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Mixtures
http://www.bbc.co.uk/schools/ks3bitesize/science
 Homogeneous
 Uniform
composition
 Same proportions of
components
throughout
 Also called solutions
 Examples
 Salt water
 Sugar water
 Stainless steel

Heterogeneous
 NOT uniform throughout
 Heavier particles may
concentrate at bottom of
container
 2 types/ colloids & suspensions
 Examples
 Granite
 Wood
 Blood
 Clay in water
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Heterogeneous mixtures
Suspensions
 Often
large visible
particles that tend to
settle out
 Tend
to block light
 Example: corn
starch
and water, clay and
water
Colloids
 Often
suspended
microscopic particles
 Exhibit Tyndale
effect –
which is when light is
scattered by very small
particles in its path , it
makes a beam of light
visible
 Example: gelatin
milk, mayonnaise
in water,
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Tyndale effect:
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