10TH CHEMISTRY CHAPTER 01 HISTORY OF CHEMISTRY FEDERAL BOARD

 Unit 1 

History of Chemistry Full Explanation 

1.1 Principles and Methods in Chemistry

 • Conservation of Mass and Energy: Mass cannot be created or destroyed. 

 • Logical Thinking: Use observations to form theories (e.g., Mendeleev’s periodic table).

 • Controlled Experiments: Change one variable at a time for accuracy. 

 • Peer Review: Research must be reviewed before publication. 

Be Objective: Focus on Objectives

Skepticism & Proofing: Always double check new discoveries 

1.3 Scientific Paradigms 

• Frameworks that help understand chemical properties. 

• Guide research and explain chemical behavior. 

• Help develop new materials and technologies. 

ATOMIC MODELS 

Plum Pudding Model 

J.J. Thomson’s model (1904): Atom is a positively charged sphere with embedded electrons. Rejected: Couldn’t explain Rutherford’s experiment. 

Rutherford Model: 

Nuclear Model (1911): Atom has a dense, positively charged nucleus; electrons orbit around it. 

 Based on Gold Foil Experiment: Most of the atom is empty space ATOMIC MODELS 

Bohar’s Model: 

Electron Orbits (1913): Electrons revolve in fixed circular paths (energy levels) around the nucleus. 

 Energy Quantization: Electrons emit or absorb energy only when jumping between these levels. ATOMIC MODELS 

1.4 Confidence and Uncertainty 

 • Confidence Intervals: Range of values likely containing the true result. 

 • P-Values: Check if result is due to chance (low p-value = significant). 

 • Standard Deviation: Measures how much results vary. 

 • Bayesian Probability: Updates confidence with new evidence. 

 • Quantifying Uncertainty: Expressed as ± value. 

1.5 Repeatability & Reproducibility 

• Repeatability: Same result under same conditions and tools. 

• Reproducibility: Same result in different labs with different scientists. 

• Importance: Ensures experiment is reliable and accepted. 

Key Points Summary 

• Mass and energy are conserved. 

• Logical thinking and observation are key. 

• Use of statistics ensures accuracy. 

• Scientific methods must be repeatable and reproducible. 

• Peer review maintains research quality.