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The Nature of Matter

The Nature of Matter. What’s in an atom?. Atom- the smallest unit of matter that cannot be broken down by chemical means. Made up of subatomic particles Protons- positive charge Neutrons- neutral charge Electrons- negative charge. Elements.

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The Nature of Matter

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  1. The Nature of Matter

  2. What’s in an atom? • Atom- the smallest unit of matter that cannot be broken down by chemical means. • Made up of subatomic particles • Protons- positive charge • Neutrons- neutral charge • Electrons- negative charge

  3. Elements • An element is a pure substance made of only one kind of atom. • Elements differ in the number of protons their atoms contain. • The number of neutrons in an atom is often but not always equal to the number of protons in the atom. • Isotope- atoms of the same element with different mass numbers (# of neutrons)

  4. Compounds & Molecules • Atoms can join with other atoms to form stable substances. • A force that joins atoms is called a chemical bond. • A molecule is formed when 2 or more atoms bond together • A compound is a substance made of the joined atoms of two or more different elements.

  5. Compounds and Molecules • A compound is always a molecule but a molecule is not always a compound!

  6. Chemical bonds • Atoms can join with other atoms to form stable substances. • Three types of bonds • Covalent • Ionic • Hydrogen

  7. Ionic Bond • An atom or molecule that has gained or lost one or more electrons is called an ion. • Ions have an electrical charge because they contain an unequal number of electrons and protons. Ions of opposite charge may interact to form an ionic bond. • Ex. Na+ and Cl- Bond to form Salt

  8. Ions • Cations- Ions with a positive charge (More protons than electrons) • Anions- Ions with a negative charge (More electrons than protons)

  9. Covalent Bonds • Covalent bonds form when two or more atoms share electrons. • An atom becomes stable when its outer electron level is full. If the outer electron level is not full, an atom will react readily with atoms that can provide electrons to fill its outer level. • Ex. Carbon Dioxide

  10. Hydrogen Bond • Hydrogen bond—a weak chemical attraction between polar molecules • Molecules with an unequal distribution of electrical charge are called polar molecules. • Ex. The attraction between two water molecules • In a water molecule, the shared electrons are attracted more strongly by the oxygen nucleus than by the hydrogen nuclei.

  11. Properties of H2O • Cohesion is an attraction between substances of the same kind. • Because of cohesion, water and other liquids form thin films and drops. • Adhesion is an attraction between different substances. • Adhesion powers a process, called capillary action, in which water molecules move upward through a narrow tube, such as the stem of a plant.

  12. Acids and Bases • Compounds that form hydrogen ions (H+) when dissolved in water are called acids. • Compounds that reduce the concentration of hydrogen ions in a solution are called bases. • Many bases form hydroxide (OH-) ions when dissolved in water. • The pH scale measures the concentration of hydrogen ions in a solution.

  13. Mixing Acids and Bases • Sodium Bicarbonate aka Baking Soda- Basic • Acetic Acid aka Vinegar- Acidic • NaHCO3 + CH3COOH ---> CH3COONa + H2O + CO2 • Baking Soda + Vinegar --- Sodium Acetate + Water + Carbon Dioxide

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