Study sheet: Foundations of Chemistry and Physics

📋 Course Outline

1. Lewis Structures and Valence Rules
2. Chemical Bonds and Molecular Structures
3. Chemical Formulas and Moles
4. Equation Balancing and Oxidation
5. Reaction Energy and Respiration
6. Organic Chemistry and Hydrocarbons
7. Branches of Physics

📖 1. Lewis Structures and Valence Rules

🔑 Key Concepts & Definitions

• Chemical bond : the force of attraction that holds atoms together in a compound
• Ionic bond : forms by complete transfer of electrons from one atom to another; the atom losing electrons becomes a positively charged cation and the atom gaining electrons becomes a negatively charged anion

★ Must-know

📌 The octet rule describes the tendency of an atom to gain 8 electrons in its valence shell, while the duplet rule applies to hydrogen and helium and involves 2 electrons.

Further detail

📌 When different atoms are present in the same number in a Lewis structure, the atom with the greater need for electrons is placed in the center; between carbon and nitrogen, nitrogen has 5 valence electrons and carbon has 4.

💡 Memory Hook

Octet seeks 8 electrons, whereas duplet seeks 2.

📖 2. Chemical Bonds and Molecular Structures

🔑 Key Concepts & Definitions

• Non-polar covalent bond : can occur between different atoms when their electronegativity difference is small; the source gives carbon at 2.5 and hydrogen at 2.1, producing a difference of 0.4

📝 Essential Points

• The Lewis structure of hydrogen cyanide is H–C≡N, with a single bond between hydrogen and carbon and a triple bond between carbon and nitrogen.

• Carbon dioxide has the structure O=C=O, with two carbon–oxygen double bonds.

💡 Memory Hook

Picture Na⁺ and Cl⁻ held together after an electron crosses from sodium to chlorine.

📖 3. Chemical Formulas and Moles

🔑 Key Concepts & Definitions

• Molecular formula : shows the exact number of atoms present in a compound, as in C₆H₁₂O₆ for glucose
• Empirical formula : shows the simplest whole-number ratio of atoms in a compound; glucose has the empirical formula CH₂O because 6:12:6 reduces to 1:2:1

★ Must-know

📐 Formula — The number of moles is calculated by $n = \frac{m}{M}$, where m is mass and M is molar mass.

Further detail

📌 When the subscripts in a molecular formula cannot be divided by a single common number, the molecular and empirical formulas are the same, as for H₂O.

• For 12.5 g of NaCl with a molar mass of 58.5 g/mol, the amount is 0.213 moles.

• The mass of one mole of BaSO₄ is 353.32 grams per mole.

💡 Memory Hook

Molecular formula gives exact numbers, whereas empirical formula gives the simplest ratio.

📖 4. Equation Balancing and Oxidation

★ Must-know

• 🔄 The balancing order is:

  1. Balance atoms other than oxygen and hydrogen
  2. Balance oxygen
  3. Balance hydrogen

• For aluminium reacting with oxygen, restarting the balancing process after detecting disturbed aluminium gives 4Al + 3O₂ → 2Al₂O₃.

📌 In the source, reduction is associated with the oxidizing agent, while oxidation is associated with the reducing agent.

Further detail

• The equation CH₄ + O₂ → CO₂ + H₂O requires coefficients to correct the unequal oxygen counts before the final hydrogen check.

• The listed oxidation-state targets are:

  • Fe in Fe₂O₃
  • Mn in MnO₄
  • Cr in Cr₂O₇²⁻
  • N in NH₃
  • Cu in CuSO₄
  • S in Na₂S₂O₃
  • C in HCO₃⁻
  • I in IO₄⁻

💡 Memory Hook

Balance other atoms, then oxygen, then hydrogen.

📖 5. Reaction Energy and Respiration

🔑 Key Concepts & Definitions

• Activation energy : the extra energy required for an effective collision because it overcomes electron repulsion between approaching atoms
• Catalyst : a substance that increases the rate of a reaction and remains unchanged at the end of the reaction
• Cellular respiration : a reaction in which glucose reacts with oxygen to release energy along with carbon dioxide and water, and it takes place in a cell

★ Must-know

📌 An effective collision forms products, whereas an ineffective collision does not form products because the reacting molecules have an improper orientation.

Further detail

• A catalyst reduces activation energy by providing a new pathway for the reaction.

💡 Memory Hook

Catalysts lower activation energy, so effective collisions increase and reactions speed up.

📖 6. Organic Chemistry and Hydrocarbons

🔑 Key Concepts & Definitions

• Organic chemistry : the study of hydrocarbons and their derivatives
• Alkane : contains carbon–carbon single bonds and follows the general formula $C_nH_{2n+2}$

★ Must-know

📌 Carbon can form 4 bonds.

Further detail

• Hydrocarbons are compounds containing carbon and hydrogen, while derivatives are compounds formed from hydrocarbons such as C₂H₆ in the illustrated substitution example.

• For an alkane containing 3 carbon atoms, substituting n = 3 into $C_nH_{2n+2}$ gives C₃H₈.

💡 Memory Hook

Alkanes follow CnH2n+2.

📖 7. Branches of Physics

🔑 Key Concepts & Definitions

• Mechanics : the branch of physics that studies objects in motion, their causes, and their effects
• Thermodynamics : the study of heat flow and the conversion of heat into work and other forms
• Oscillation : the back-and-forth motion of a body about its mean position
• Wave : a disturbance in a medium that causes the particles of the medium to vibrate

📊 Synthesis Tables

Main Physics Branches

Branch	Subject	Distinguishing idea
Mechanics	Objects in motion	Studies causes and effects of motion
Thermodynamics	Heat	Studies heat flow and conversion into work and other forms
Oscillations and waves	Oscillations and waves	Studies back-and-forth motion and disturbances in a medium