From Particles to Solutions

Particle Theory of Matter

• All matter is made of tiny particles.
• Particles are always moving.
• Particles have spaces between them.
• Particles are attracted to one another.
• Temperature affects the speed of particles.

Compounds

• A compound is a pure substance made from two or more elements chemically combined (e.g., $H_2O$).
• Compounds have properties different from the elements that form them.

Pure Substances vs. Mixtures

Physical Properties

• Characteristics that can be observed/measured without changing the substance.

Quantitative vs. Qualitative

Qualitative Properties Discussed

• Color
• Texture
• State (solid, liquid, gas)
• Malleability
• Ductility
• Clarity

Chemical Change

• A change where a new substance is formed.

Evidence of a Chemical Change

• Color change
• Gas produced (bubbles, odor)
• Temperature change
• Light produced
• Precipitate forms (solid in liquid)

Characteristic Physical Properties

• Unique to a substance and help identify it.

Examples:

• Melting Point
• Freezing Point
• Boiling Point
• Density

Density Formula:

$\text{Density} = \frac{\text{Mass}}{\text{Volume}} \quad \text{(g/cm³ or g/mL)}$

Be able to solve for:

• Mass: $\text{Density} \times \text{Volume}$
• Volume: $\frac{\text{Mass}}{\text{Density}}$

Metals vs. Non-metals on the Periodic Table

• Metals: Left side (and center)
• Non-metals: Right side
• Metalloids: Stair-step line between metals and non-metals

Important Groups

• Group 1: Alkali Metals – very reactive
• Group 2: Alkaline Earth Metals – reactive
• Group 17: Halogens – very reactive non-metals
• Group 18: Noble Gases – stable, non-reactive

Subatomic Particles

Atomic Structure

• Atomic Number = number of protons (and electrons in a neutral atom)
• Mass Number ≈ protons + neutrons

Finding Subatomic Particles from the Periodic Table

• Protons = Atomic number
• Electrons = Same as protons (if atom is neutral)
• Neutrons = Mass number – Atomic number

Static Electricity

How Objects Gain Charge

• Electrons can move; protons cannot.
• If an object gains electrons, it becomes negatively charged.
• If it loses electrons, it becomes positively charged.

Creating Static Charges

• Friction (e.g., rubbing a balloon on hair) causes electrons to transfer.
• Example: Balloon gains electrons → becomes negatively charged.

Law of Electric Charges

• Like charges repel (e.g., + and + or – and –).
• Opposite charges attract (e.g., + and –).
• Charged objects attract neutral objects due to induced charge separation.

Charging by Induction

• A charged object near a neutral object can rearrange its charges.
• No contact is made.
• Can cause temporary attraction.

Electrostatic Series

• A list of materials showing their tendency to gain or lose electrons.
• Materials higher on the list lose electrons (become positive).
• Materials lower on the list gain electrons (become negative).

Charging by Friction

• When two materials are rubbed together:
  • One loses electrons (positive charge),
  • One gains electrons (negative charge),
  • Use the electrostatic series to predict the direction of transfer.

Charging by Contact

• A charged object touches a neutral object.
• Electrons move from one object to another → both become charged.

Grounding

• Connecting an object to Earth allows electrons to enter or leave.
• This neutralizes the charge.

Current Electricity & Circuits

What is Current Electricity?

• The flow of electrons through a conductor (e.g., wire).
• Needs a closed circuit and a source of energy.

Key Terms

Circuit Diagrams Symbols

• Cell: |‒‒| (long = positive, short = negative)
• Battery: multiple cells in a row
• Wire: straight line
• Switch: break in wire with hinge
• Bulb/Load: circle with filament or zigzag
• Ammeter: circle with "A"
• Voltmeter: circle with "V"

Types of Circuits

Current, Voltage, and Resistance

Ohm’s Law

$V = I \times R$

• Rearranged:
  • $I = \frac{V}{R}$
  • $R = \frac{V}{I}$

Series vs. Parallel Circuits

Series Circuit

• Current: Same throughout
• Voltage: Split across components
• Resistance: Adds up
  $R<em>{\text{total}} = R</em>1 + R_2 + \dots$

Parallel Circuit

• Voltage: Same across each branch
• Current: Splits among branches
• Resistance: Total resistance is less than any one resistor
  $\frac{1}{R<em>{\text{total}}} = \frac{1}{R</em>1} + \frac{1}{R_2} + \dots$

Solving Circuits

• Identify if series or parallel.
• Use Ohm’s Law and rules for combining resistances.
• Solve step by step for:
  • Total resistance
  • Total voltage/current
  • Values for individual components