Science mid term jan 28-29

Midterm Study Notes

Key Concepts in Chemistry

Exothermic Graph

• Understand the characteristics and representation of exothermic reactions on a graph.

• Exothermic reactions release heat, showing a downward slope in energy as reactants convert to products.

Atomic Structure

• Definition of Atomic Number: The number of protons in an atom, which defines the element.

• Atomic Number Calculation Example: If an atom contains 3 protons, 4 neutrons, and 3 electrons, the atomic number is 3.

• Mass Number: The total number of protons and neutrons in the nucleus of an atom.

• Example for Mass Number Calculation: An atom with 11 protons, 12 neutrons, and 11 electrons has a mass number of $11 + 12 = 23$.

Ions and Atoms

• Ion: An atom that has gained or lost one or more electrons, thus acquiring a charge.

  • Negative Ion (Anion): Atom that gains electrons.

  • Neutral Atom: Atoms with an equal number of protons and electrons.

Electron Shells

• Shell Configuration: Atoms have electrons arranged in shells, commonly represented as 2 electrons in the first shell, and 8 in the second and third shells (2, 8, 8).

Noble Gases

• Noble gases possess full valence electron shells, making them stable and chemically inert.

Covalent Bonds

• Definition: Bonds formed when two or more atoms share electrons.

• Properties: Molecules formed do not conduct electricity and generally have low melting points.

• Example: Water (H₂O) is formed from two hydrogen atoms and one oxygen atom.

Chemical Changes and Properties

• Chemical Change Examples:

  • Rusting of a metal (chemical property).

  • Flammability (chemical property).

• Physical Change Examples:

  • Slicing bread.

  • Water condensation and vaporization.

  • Wet pavement drying after rain.

Specific Processes in Chemistry

• Deposition: The direct transition from gas to solid.

• Ionization: The transition of a solid, liquid, or gas into plasma.

• Vaporization: The formation of bubbles during boiling, indicating a phase change from liquid to gas.

Periodic Table Insights

• Periods: Seven on the periodic table; elements in the same period share the same number of electron shells.

• Groups: Elements in a group have the same number of valence electrons, influencing their chemical behavior.

Mixtures and Solutions

• Suspension: A mixture that can be separated by filtration and consists of larger particles that settle over time.

• Colloid: Contains intermediate-sized particles that scatter light. Cannot be separated by filtration.

• Solution: Composed of two parts; the solvent (larger component) and solute (substance dissolved).

  • Soluble Salt: Reactants that exist before a chemical reaction occurs.

Measurement & Reaction Rates

• Gram: A unit of measure in the metric system.

• Catalyst: A substance that increases the speed of a chemical reaction without being consumed in the process.

Historical Models of the Atom

• Plum Pudding Model: An early representation of atomic structure suggesting that electrons are scattered within a 'soup' of positive charge.

• Rutherford's Nuclear Model: Introduced the nucleus, demonstrating that atoms consist mostly of empty space.

Conservation Laws

• Law of Conservation of Mass: Matter cannot be created or destroyed; it only changes forms. This principle underlies all chemical reactions and processes.

Conservation Laws

Law of Conservation of Mass

• Matter cannot be created or destroyed; it only changes forms. This principle underlies all chemical reactions and processes.

Historical Models of the Atom

Plum Pudding Model

• An early representation of atomic structure suggesting that electrons are scattered within a 'soup' of positive charge.

Rutherford's Nuclear Model

• Introduced the nucleus, demonstrating that atoms consist mostly of empty space.

Atomic Structure

Atomic Definitions

• Atomic Number: The number of protons in an atom, which defines the element.

• Mass Number: The total number of protons and neutrons in the nucleus of an atom.

Calculations

• Atomic Number Example: If an atom contains $3$ protons, $4$ neutrons, and $3$ electrons, the atomic number is $3$.

• Mass Number Example: An atom with $11$ protons, $12$ neutrons, and $11$ electrons has a mass number of $11 + 12 = 23$.

Electron Shells

• Shell Configuration: Atoms have electrons arranged in shells, commonly represented as $2$ electrons in the first shell, and $8$ in the second and third shells ($2, 8, 8$).

• Noble Gases: These possess full valence electron shells, making them stable and chemically inert.

Periodic Table Insights

• Periods: There are $7$ periods on the periodic table; elements in the same period share the same number of electron shells.

• Groups: Elements in a group have the same number of valence electrons, influencing their chemical behavior.

Ions and Atoms

• Ion: An atom that has gained or lost one or more electrons, thus acquiring a charge.

• Negative Ion (Anion): An atom that gains electrons.

• Neutral Atom: Atoms with an equal number of protons and electrons.

Covalent Bonds

• Definition: Bonds formed when two or more atoms share electrons.

• Properties: Molecules formed do not conduct electricity and generally have low melting points.

• Example: Water ($H_{2}O$) is formed from two hydrogen atoms and one oxygen atom.

Chemical Changes and Properties

• Chemical Change Examples:

  • Rusting of a metal (chemical property).

  • Flammability (chemical property).

• Physical Change Examples:

  • Slicing bread.

  • Water condensation and vaporization.

  • Wet pavement drying after rain.

Specific Processes in Chemistry

• Deposition: The direct transition from gas to solid.

• Ionization: The transition of a solid, liquid, or gas into plasma.

• Vaporization: The formation of bubbles during boiling, indicating a phase change from liquid to gas.

Mixtures and Solutions

• Suspension: A mixture that can be separated by filtration and consists of larger particles that settle over time.

• Colloid: Contains intermediate-sized particles that scatter light. Cannot be separated by filtration.

• Solution: Composed of two parts; the solvent (larger component) and solute (substance dissolved).

• Soluble Salt: Reactants that exist before a chemical reaction occurs.

Measurement & Reaction Rates

• Gram: A unit of measure in the metric system.

• Catalyst: Speed up the chemical reaction