Unit A: Chemistry Overview

Unit A: Chemistry

• Chemistry is the branch of science that identifies the substances matter is made of
• It investigates their properties and how they interact, combine and change
• It also uses processes to make new substances

Terms You Should Know

• Matter: A physical substance with mass that occupies space
• Energy: Power derived from chemical or physical resources
• State: A physical condition determined by molecular structure (solid, liquid, gas)

Physical Properties of Matter

• Boiling Point/Condensation Point: The temperature at which a substance boils or condenses
• Freezing Point/Melting Point: The temperature at which a substance freezes or melts
• Malleability: The ability to be beaten or rolled into sheets without crumbling
• Ductility: The ability to be stretched out without breaking
• State: Existence as a solid, liquid, or gas
• Crystal Formation: Crystalline appearance
• Magnetism: the ability to attract other objects with magnetic properties
• Conductivity: The ability to conduct heat or electricity
• Solubility: The ability to dissolve
• Color: The color of the material

Chemical Properties of Matter

• Ability to Burn: Combustion (flame, heat, light)
• Flash Point: Temperature needed to ignite a flame
• Behavior in Air: Tendency to degrade, react, or tarnish
• Reaction with Water: Tendency to corrode or dissolve
• Reaction with Acids: Corrosion, sometimes with bubble formation
• Reaction with Heat: Tendency to melt or decompose
• Reaction to Red/Blue Litmus: Red (acid), blue (base), no change (neutral)

Properties & Classification of Matter

• Matter: Pure substances (elements, compounds) or mixtures (solutions, mechanical mixtures, suspensions, colloids)
• Pure Substances: Contain only one type of particle that cannot be broken down further by physical means
• Elements: Made up of one type of atom (e.g., gold, oxygen, diamond)
• Compounds: Made up of more than one type of element chemically combined in specific ratios (e.g., water, salt, crystals)
• Mixtures: Contain two or more pure substances
• Homogeneous Mixtures: Appear to be made of one substance and look the same throughout (e.g., sugar & water)
• Heterogenous Mixtures: Separate components are visible (e.g., suspensions, colloids)
• Suspensions: Particles dispersed throughout a fluid (e.g., sand and water)
• Colloids: Particles that cannot be filtered out easily (e.g., gelatin, milk)

Matter can Change

• Chemical Change: A chemical reaction forms new products
• Physical Change: Matter changes form but not its chemical identity
  • Examples: Combustion, Rotting, Melting, Shredding, Rusting, Digestion, Boiling, Chopping

Identifying Chemical Reactions

• All chemical reactions are characterized by the formation of a new substance with new physical and chemical properties.
• All chemical reactions involve the release or absorption of energy.

Ancient Chemistry

• Metallurgy: Science of producing and using metals
• Annealing: Heating copper to make it stronger and less brittle
• Smelting: Separating metals from compounds by melting them

Food Chemistry

• Development of food preservation techniques essential for human survival

Atomic Theory

• Our understanding of the atom has changed over time, with new models emerging from experimental evidence
• Different models include: Dalton's "Billiard Ball" Model, Thomson's "Plum Pudding" Model , Rutherford's "Planetary" Model, Bohr's Model, the Quantum Mechanical Model

Idea 1: Spontaneous Generation

• Aristotle's idea that living things can be generated from non-living things
• Pneuma (vital heat) and Anima (soul)

Idea 2: The Billiard Ball Model

• John Dalton's idea that all elements are made of atoms.
• Atoms of the same element are identical
• Atoms are indivisible
• Atoms combine in fixed ratios to form compounds

Idea 3: The Raisin Bun Model

• J.J. Thomson's idea that atoms have a large positive charge.
• Small negative charges (electrons) are embedded within the positive charge

Idea 4: The Planetary Model

• Ernest Rutherford's idea that an atom has a tiny, dense, positively charged nucleus.
• Negative electrons orbit the nucleus like planets around the sun

Idea 5: The Bohr Model

• Niels Bohr's idea that electrons are arranged in specific orbits or energy levels around the nucleus

Idea 6: The Quantum Mechanical Model

• The modern model describing the positions of electrons in an atom in terms of probabilities.
• Electrons can be found at any distance from the nucleus, but they tend to be more frequently in certain regions depending on energy level