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Understanding Units and Atomic Theory
Sep 17, 2024
Lecture Notes: Units, Conversion, and Atomic Theory
Introduction
Challenges with technology, particularly the projector.
Discussing dimensional analysis and conversion of units.
Dimensional Analysis
Conversion Example:
Converting 17.5 cm to meters:
1 cm = 10^-2 m.
Different ways of expressing conversions (e.g., dividing units cancels them).
Example:
x times x = x².
x³ divided by x = x².
Conversion Example: Volume
Problem:
Convert 6.83 m³ to milliliters.
Use conversion: 1 cm³ = 1 mL.
Convert m³ to cm³ using: 1 m³ = 1000000 cm³.
Result: 6.83 x 10^6 mL.
Units and Mathematical Operations
Multiplying units increases power; dividing decreases power.
Addition and subtraction don't cancel units, they factor them.
Density and Units
Density = mass/volume (e.g., g/mL). Units do not cancel out.
Formation of Elements
Elements formed during the Big Bang.
Fundamental particles formed: protons, neutrons.
Stars fuse elements (e.g., hydrogen atoms form helium).
Dalton's Atomic Theory
Elements made of tiny particles: atoms.
Atoms cannot be created/destroyed.
All atoms of an element are identical (mostly true).
Atoms of different elements are different.
Atoms combine to form compounds.
Law of Multiple Proportions
Elements combine in whole number ratios (e.g., CO and CO₂).
Mass ratios reflect these combinations.
Structure of Atoms
Atoms consist of a nucleus and electron cloud.
Nucleus:
Contains protons (+ charge) and neutrons (neutral).
Electron Cloud:
Contains electrons (- charge).
Rutherford's Experiment
Tested the plum pudding model.
Most alpha particles passed through gold foil, indicating empty space.
Small positive charge concentrated in the nucleus.
Conclusion
Atomic theory continues to develop; understanding of units and conversions critical for chemistry.
Prepare for next class: read Chapter 2 and print activity sheet.
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