Science Review Highlights

Overview

The lecture reviewed key chemistry, electricity, and ecosystem topics for end-of-course summative exams, focusing on properties, atomic structure, circuits, and ecological concepts.

Physical and Chemical Properties and Changes

• Physical properties can be observed or measured without changing a substance's identity (color, density, melting point, etc.).
• Physical changes alter physical properties without changing chemical composition (melting, shredding, boiling).
• Chemical properties describe a substance's ability to react and form new substances (flammability, acidity, reactivity).
• Chemical changes result in new substances through bond breaking/forming (burning, digestion, color changes).

Periodic Table & Atomic Structure

• The atomic number equals the number of protons and electrons in a neutral atom.
• Atomic mass equals the number of protons plus neutrons.
• Protons (positive), electrons (negative), neutrons (neutral); neutrons = atomic mass - atomic number.
• Isotopes are atoms with the same protons but different neutrons (e.g., Carbon-12, Carbon-13, Carbon-14).
• Groups (columns) share similar chemical properties; periods (rows) have differing properties.
• Metals are on the left, non-metals on the right, metalloids on the diagonal.
• Metals tend to lose electrons (become positive ions), non-metals gain electrons (become negative ions).
• Ionic bonds form between metals and non-metals; name non-metal compounds with "ide" ending.
• Valence electrons are found by group number (1-2, 13-18).

Bohr-Rutherford Diagrams & Ions

• Standard notation shows symbol, atomic number, and mass.
• Ions have net charge from losing/gaining electrons; show ionic charge with brackets in diagrams.
• The first electron shell holds 2 electrons; pair electrons after the 5th on outer shells.
• For neutral atoms, protons = electrons; adjust electrons for ion charge.

Electricity: Static and Current

• Like charges repel, opposite charges attract, neutrals attract charged objects (only electrons move).
• Static electricity is an imbalance of charges that can discharge suddenly.
• Charging by contact gives both objects the same charge; induction gives them opposite charges.
• Friction can transfer electrons to/from objects, changing their charge.

Electric Circuits: Series and Parallel

• Series circuits have a single path; if one bulb fails, all go out.
• Parallel circuits have multiple paths; one bulb failing does not affect others.

Voltage and Current in Circuits

• Voltage (V) is energy per electron, measured by a voltmeter; divided among loads in series, same across loads in parallel.
• Current (amps, A) is the rate of electron flow; same through all loads in series, split among loads in parallel.

Ecosystems: Key Terms and Organization

• Abiotic factors are non-living (temperature, water); biotic factors are living (plants, animals).
• Producers make food (photosynthesis); consumers eat others; decomposers break down dead matter.
• Photosynthesis turns CO₂ and water into glucose and O₂; respiration uses O₂ to produce energy from glucose.
• Energy pyramids show energy flow; numbers/mass pyramids show population or biomass at each level.
• Food webs illustrate interconnected feeding relationships in ecosystems.

Key Terms & Definitions

• Physical property — Observable/measurable quality without chemical change.
• Chemical property — Substance's ability to react and form new substances.
• Isotope — Atom with same protons, different neutrons.
• Ion — Atom with net electric charge due to electron loss/gain.
• Valence electron — Electron in the outermost shell.
• Static electricity — Charge imbalance on an object's surface.
• Series circuit — One path for current.
• Parallel circuit — Multiple paths for current.
• Voltage — Energy per electron in a circuit.
• Current (Ampere) — Rate of electron flow.
• Abiotic factor — Nonliving environmental component.
• Biotic factor — Living environmental component.
• Producer — Organism that makes its own food.
• Consumer — Organism that eats other organisms.
• Decomposer — Organism breaking down dead matter.

Action Items / Next Steps

• Review and practice filling in tables for physical vs. chemical properties and changes.
• Use the periodic table to practice finding atomic number, mass, electrons, protons, neutrons, and drawing Bohr-Rutherford diagrams.
• Draw series and parallel circuits using correct symbols.
• Study key ecosystem terms and review photosynthesis, respiration, and food web structures.