notes: 2.2-2.3 elements, compounds, and mixtures
TRANSCRIPT
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NOTES: 2.2-2.3 Elements, Compounds, and
Mixtures
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RECALL…
• MATTER: anything that has mass and occupies space
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Matter
Pure Substances
Mixtures
Elements
Compounds
Homogeneous
Heterogeneous
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PURE SUBSTANCES:
• A pure substance is made of only one kind of material and has definite properties.
• EXAMPLES: elements, compounds
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What are the Differences Between an
Element and a Compound?
• ELEMENTS – simplest form of matter that can exist under normal laboratory conditions
• Elements cannot be separated into simpler substances by chemical means
• Building blocks for all other substances
• Examples: nitrogen (N2), hydrogen (H2), and carbon (C)
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ELEMENTS (continued)…
• The smallest particle of an element that has the properties of that element is called an ATOM.
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**Currently we have about 115 kinds of atoms. In the natural world there are 88 different kinds of atoms.
The others have been artificially produced in laboratories.
Making stuff nature
never dreamed of.
The Elements Song
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PERIODIC TABLE:
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Abundance of the elements, by
weight
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The Earth’s interior is rich in IRON (Fe)
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Sand is made of
silicon & oxygen
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The ocean waters are made
of oxygen & hydrogen
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Atoms are made up of protons, neutrons, and electrons.
Protons and neutrons are found in the nucleus of atoms -- roughly at the center
Electrons travel around the nucleus.
Of course real atoms don’t look anything like
this!
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Different kinds of atoms, or elements, are different because they have different numbers of protons.
They don’t look anything like this
either!
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We list the elements by their atomic numbers - the number
of protons they have.
Hydrogen, number 1 Helium, number 2
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COMPOUNDS
• COMPOUNDS = pure substances that can be separated into simpler substances only by chemical means
• made of more than one element bound together
• Examples: water, table salt, and carbon dioxide
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sodium (Na) chlorine (Cl) Sodium chloride (NaCl)
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CHEMICAL SYMBOLS:
• CHEMICAL SYMBOL – one or two letter symbol representing an element on the periodic table
• First letter is always capitalized
• Second letter is always lower case
• Examples:
sodium – Na iodine – I
lead – Pb iron – Fe nickel – Ni
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CHEMICAL FORMULAS:
• Chemical formulas: Chemical symbols and numbers indicating the type and number of atoms contained in the basic unit of a substance.
• Examples:
water – H2O
sodium chloride – NaCl
sucrose – C12H22O11
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Matter
Pure Substances
Mixtures
Elements
Compounds
Homogeneous
Heterogeneous
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MIXTURES:
• MIXTURE = physical blend of two or more substances
(that are NOT chemically combined)
• can be classified as:
HOMOGENEOUS or HETEROGENEOUS
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Homogeneous Mixture
• Uniform in composition;
• Exhibits identical properties throughout the mixture;
• Examples: air, salt water, soda water, solutions, whipped cream, mixture consisting of one phase
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Heterogeneous Mixture
• Not uniform in composition;
• Exhibits portions with different properties;
• Examples: salad, sand, muddy water, oil and water, soup, granite, soil, mixture consisting of two or more phases, etc.
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How are Mixtures Separated?
Many mixtures can be separated by simple PHYSICAL means:• Boiling point differences• Melting point differences• Particle size• Density• Magnetism• Solubility• Color• Smell