Metals

Location on the Periodic Table:

• Found on the left and center of the periodic table.
  
  

Physical Properties:

• Luster: Shiny

• Malleable: Can be hammered into sheets

• Ductile: Can be drawn into wires

• Conductivity: Good conductors of heat and electricity

• State: Mostly solid at room temperature (except mercury)
  
  

Examples:

• Iron (Fe), Copper (Cu), Aluminum (Al), Gold (Au)

Importance:

• Used for building materials, wires, coins, vehicles, tools, and electronics.
  
  

Nonmetals

Location on the Periodic Table:

• Found on the right side of the periodic table.

Physical Properties:

• Luster: Dull (not shiny)

• Malleability: Brittle (break easily)

• Conductivity: Poor conductors (insulators)

• State: Can be solid, liquid, or gas at room temperature

Examples:

• Oxygen (O), Carbon (C), Sulfur (S), Nitrogen (N)

Importance:

• Found in living organisms, air, and fuels; essential for life processes like breathing and photosynthesis.

Metalloids

Location on the Periodic Table:

• Found along the zigzag line (stair-step line) separating metals and nonmetals.

Physical Properties:

• Have properties of both metals and nonmetals

• Can be semiconductors (conduct electricity only under certain conditions)

• Often shiny but brittle

Examples:

• Silicon (Si), Boron (B), Arsenic (As)

Importance:

• Used in computer chips, electronics, and solar panels because of their semiconductor properties.

1. Elements

• Definition: A pure substance made of only one type of atom.

• Cannot be broken down into simpler substances by chemical means.

• Examples: Hydrogen (H), Oxygen (O), Iron (Fe), Gold (Au).
  
  

• Characteristics:

  • Each element has unique properties (melting point, density, reactivity).

  • Found on the Periodic Table.
    
    

2. Compounds

• Definition: A pure substance made of two or more different elements chemically combined in a fixed ratio.

• Can be broken down into simpler substances only by chemical reactions.

• Examples: Water (H₂O), Salt (NaCl), Carbon dioxide (CO₂).
  
  

• Characteristics:

  • Has properties different from the elements that form it.

  • Always has a chemical formula showing the exact ratio of atoms.
    
    

3. Mixtures

• Definition: A combination of two or more substances that are not chemically combined.

• Can be separated by physical means (filtering, evaporation, magnetism, etc.).

• Types of mixtures:

  • Homogeneous mixture (solution):

    • Uniform composition; looks the same throughout.

    • Example: Salt water, air, vinegar.

  • Heterogeneous mixture:

    • Composition is not uniform; different parts can be seen.

    • Example: Salad, trail mix, sand and water.
      
      

• Characteristics:

  • Each substance in the mixture keeps its own properties.

  • No fixed ratio; proportions can vary.
    
    

Evidence of Chemical Change

A chemical change occurs when a substance changes into a new substance with different properties. You can usually tell a chemical change has happened if you observe one or more of these signs:

1. Color Change

• The substance changes color without mixing dyes or pigments.

• Example: Iron rusting (metal turns reddish-brown).
  
  

2. Gas Production (Bubbling or Fizzing)

• Gas forms without boiling or adding heat.

• Example: Baking soda reacting with vinegar produces carbon dioxide gas.
  
  

3. Temperature Change

• The reaction releases or absorbs energy, causing the temperature to change.

• Example: Hand warmers get hot due to a chemical reaction.
  
  

4. Formation of a Precipitate

• A solid forms when two liquids react.

• Example: Mixing solutions of silver nitrate and sodium chloride forms solid silver chloride.
  
  

5. Change in Odor

• A new smell appears that wasn’t present before.

• Example: Food spoiling produces a foul odor.
  
  

6. Light or Sound Production

• Some chemical reactions release energy as light or sound.

• Example: Fireworks, burning wood.
  
  

Important Notes

• Not all changes are chemical. Some physical changes may also produce bubbles, color change, or temperature change (like melting ice or boiling water).

• A chemical change produces new substances; physical changes do not.
  
  

Quick Trick to Remember

Bad Puppies Like To Chew Stuff:

• Bubbles (Gas)

• Precipitate (New Solid)

• Light

• Temperature Change (unexpected)

• Color Change (unexpected)

• Smell/Sound

🔹 1. Subscripts

• A subscript is the small number written to the right of an element symbol.

• It tells how many atoms of that element are in one molecule or formula unit.

  • Example: H₂O → 2 hydrogen atoms and 1 oxygen atom.
    
    

🔹 2. No Subscript Means “1”

• If an element has no subscript, it means only one atom of that element is present.

  • Example: NaCl → 1 sodium atom and 1 chlorine atom.

🔹 3. Coefficients

• A coefficient is the big number in front of a chemical formula.

• It multiplies all atoms in the formula.

  • Example: 3H₂O → 3 × (2 H + 1 O) = 6 hydrogen atoms and 3 oxygen atoms.
    
    

🔹 4. Parentheses

• Parentheses group atoms together.

• The subscript outside the parentheses multiplies everything inside.

  • Example: Ca(OH)₂ → 1 Ca, 2 × (1 O + 1 H) = 1 calcium, 2 oxygen, 2 hydrogen.
    
    

🔹 5. Combining Coefficients and Parentheses

• Multiply coefficient × subscript × parenthesis subscript.

  • Example: 2Al₂(SO₄)₃

    • 2 × (Al₂) = 4 Al

    • 2 × 3 × (S) = 6 S

    • 2 × 3 × (O₄) = 24 O
      → 4 Al, 6 S, 24 O

🔹 6. Total Atom Count

• Add up the number of atoms for each element to get the total number of atoms in the formula.

  • Example: H₂SO₄ → 2 + 1 + 4 = 7 total atoms.

🔹 7. Distinguish Elements

• Each capital letter starts a new element symbol.

  • Example: NaOH → Na, O, and H are three different elements.

🔹 8. Practice Tip

• Always look right after the symbol for subscripts.

• Then check for parentheses and coefficients.

• Work from inside to outside of the formula.

⚖️ IT'S ALL ABOUT BALANCE!  WHAT GOES IN, MUST COME OUT!

Law of Conservation of Mass

• Matter cannot be created or destroyed in a chemical reaction.

• The total mass of the reactants equals the total mass of the products.

• Atoms are rearranged, not lost or gained — they just form new substances.

• Example:

  • Hydrogen + Oxygen → Water

  • 2H₂ + O₂ → 2H₂O

  • The number of each type of atom is the same on both sides (4 H and 2 O).

🔹 Chemical Equations Basics

• A chemical equation shows what happens in a chemical reaction.

• It has reactants (starting materials) and products (new substances formed).

  • Example: Na + Cl₂ → NaCl

    1. • Reactants: Na and Cl₂

       • Product: NaCl
         
         

🔹 Parts of a Chemical Equation

Reactants

• Substances that start the reaction

• H₂ + O₂

Products

• Substances formed by the reaction

• H₂O

Arrow (→)

• Means “yields” or “produces”

• Reactants → Products

Coefficients

• Big numbers that show the number of molecules

• 2H₂ + O₂ → 2H₂O

Subscripts

• Small numbers that show the number of atoms in a molecule

• H₂ = 2 H atoms

🔹 Balanced vs. Unbalanced Equations

• A balanced equation has the same number of each type of atom on both sides.

• An unbalanced equation has different numbers of atoms on each side.

  • Example:

    1. Unbalanced: H₂ + O₂ → H₂O (4 atoms on left, 3 on right)

    2. Balanced: 2H₂ + O₂ → 2H₂O (4 atoms on left, 4 on right)

• The equation must follow the Law of Conservation of Mass — atoms are not created or destroyed.
  
  

🔹 Evidence of the Law of Conservation of Mass

• Total mass before = total mass after

  • 1. If you start with 50 g of reactants, you end with 50 g of products.

• In closed systems, no matter escapes, so mass stays the same.

• If mass seems to change, gas may have been released or absorbed.
  
  

🔹 Common Misconceptions

• Atoms disappear → ❌ False

• Atoms change type → ❌ False

• Atoms are rearranged → ✅ True

• Coefficients show how many molecules are involved, not whether the equation is balanced.
  
  

🔹 Study Tip

• To check if an equation follows the Law of Conservation of Mass:

  • List all elements on both sides.

  • Count the number of atoms for each element.

  • Compare both sides to see if the numbers match.