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Elements, compounds and mixtures
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Atom – An atom is the smallest particle of an element which exhibits the physical and chemical characteristics of that element. - Postive - Neutral - Negative
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Element: A pure substance that cannot be separated
into simpler substances by physical or chemical means. Only contains one type of atom: lead (Pb), silver (Ag), hydrogen (H2), oxygen (O2).
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Elements can be divided into nonmetals, metals, metalloids
Elements are organized by physical and chemical properties on the Periodic Table Elements can be divided into nonmetals, metals, metalloids Interactive periodic table
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Compound: a pure substance composed of two or more different elements that are chemically combined.
can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means), has properties that are different from its component elements always contains the same ratio of its component atoms. carbon dioxide (CO2), calcium oxide (CaO), sodium hydroxide (NaOH).
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All compounds are molecules, but not all molecules are compounds
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What is a molecule? A molecule must contain 2 or more atoms different or the same.
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Molecules are the smallest parts of a substance that still retain the properties of that substance
Note: A compound is always a molecule, but a molecule is not always a compound. Elements can be molecules, but not always. Individual atoms are not molecules. Molecules of elements - H2, N2, O2, F2, Cl2, Br2, I2, P4, S8 Molecules of compounds - Na2O, KOH, CaSO4, HBr, H2CO3
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PURE SUBSTANCES consist of the same type of MOLECULE
All of the below are pure substances because all of the molecules are the same. Note that compounds are pure substances – it doesn’t matter that not all of the atoms are the same element!
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MIXTURES consist of the DIFFERENT TYPES of MOLECULES
All of the below are MIXTURES because the molecules are NOT the same. Note that mixtures can consist of elements – they don’t have to consist of compounds!
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Other terms used Monatomic- One atom– (Ag)
Diatomic – 2 atoms (N2, O2, F2, H2, CO) Triatomic – 3 atoms (H2O, O3)
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Mixtures A combination of 2 or more different substances not bonded together. All mixtures can be broken down or separated by physical means. Mixtures are not pure substances. Homogeneous- Uniform throughout. The same throughout. Example: Milk, lemonade, Gatorade, Air Heterogeneous- Not uniform throughout. Different throughout. Example: Oil and vinegar, dirty water.
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Suspension: a mixture in which particles of a material are dispersed throughout a liquid or gas but are large enough that they settle out.
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Colloid: a mixture in which the particles are dispersed throughout but are not heavy enough to settle out
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Solution: A homogenous mixture that appears to be a single substance but is composed of particles of two or more substances that are distributed evenly amongst each other
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yes no Yes* - opaque Hetero-geneous TYPE OF MIXTURE Solution
Homo-geneous or Hetero-geneous? Are particles dissolved or not? Do the particles scatter light? relative size of particles can the particles settle out? Solution yes no smallest Suspension Hetero-geneous Yes* - opaque largest Colloids medium
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MATTER: is either/or Pure Substance Mixture Compound Element metals
mMM Pure Substance Mixture Homogen-ous Hetero-geneous Compound Element metals Met.oids Non-metals Suspension Solution Colloid
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