Week 1: chem 111

Problem Solving in Chemistry

• Introduction

  • Einstein emphasized that the formulation of a problem is often more crucial than its solution.

  • Creative imagination is key in advancing scientific inquiry and formulating new questions from existing problems.

Definitions

• Problem

  • A situation indicating difficulty, uncertainty, or perplexity.

• Question

  • A request for data; it includes inquiries, interrogations, and queries.

• Answer

  • A spoken or written reply to a question.

• Solution

  • A method developed to explain, resolve, or address a problem.

~Albert Einstein

Natural Laws

Law of Definite Proportions

• When elements combine to form a compound, their masses are in a fixed, definite ratio.

• Example based on Gay-Lussac's Experiment:

  • 1 volume of hydrogen combines with 1 volume of chlorine to produce 2 volumes of hydrogen chloride.

  • Equation with volumes:

    • $1H<em>2 + 1Cl</em>2 <br>ightarrow 2HCl$

Law of Multiple Proportions

• Describes the ratio of masses when two elements combine to form more than one compound.

• The mass of element A that combines with a fixed mass of element B has a simple whole number ratio in different compounds.

Law of Conservation of Mass

• Mass or matter cannot be created or destroyed; it remains constant in a closed system.

Law of Conservation of Energy

• Energy cannot be created or destroyed in a non-nuclear system; this is the First Law of Thermodynamics.

Einstein's General Theory of Relativity

• Presented by the equation $E=mc^2$ which indicates the interrelation of mass and energy.

• As energy changes, so does the mass of a body, although these changes are usually too minor to detect in macroscopic phenomena.

• Matter can materialize from energy (e.g., a photon creating an electron-positron pair) or be destroyed (e.g., annihilation leading to photon production).

Scientific Theories

• Information Theory

  • Foundation for electronic communication and computer science.

• Game Theory

  • Developed for economics, applies to daily activities including negotiating and sports.

• Combustion Theory

  • Explains the chemical processes of combustion or burning.

• Plate Tectonics Theory

  • Emerged over decades, establishing that the Earth's lithosphere is divided into tectonic plates.

• Statistical Mechanics

  • Explains thermodynamics statistically, providing insights into atomic behavior and validating atomic theory.

• Quantum Mechanical Theory

  • Challenges classical physics concepts; reshapes understanding of reality and causation at the subatomic level.

• Heliocentrism Theory

  • Established by ancient Greeks and affirmed that celestial bodies revolve around the sun.

Scientific Method

Steps in the Scientific Method

1. Make an Observation

2. Form a Hypothesis

3. Test Hypothesis

4. Show Fit with Current Laws and Theories

5. Develop New Scientific Law/Theory

6. Communicate with Others

Variables

• Independent Variable: The variable that is changed or controlled in an experiment.

• Dependent Variable: The variable being tested and measured.

Types of Data

• Qualitative Data: Descriptive and non-numerical information.

• Quantitative Data: Numerical information that can be measured.

Laboratory Safety and Equipment

Lab Coat Features

• Elastic fitted cuffs, snap or Velcro closure, collar fit, and pockets.

Safety Eyewear

• Goggles, face shields, and safety glasses (any color, untinted lens).

Real-World Examples

Experimental Setup

• Using Centifuge Tubes with Rice and a Steel Ball Bearing exemplifies the Scientific Method.

Measurement Data

• G25 Chrome Steel Bearing Balls:

  • Diameter: 12.7 mm, Weight: 8.419 grams

  • Diameter: 19.05 mm, Weight: 28.25 grams

• Grain of Rice:

  • Weighs about 1/64 of a gram (length: 7-9 mm, width: 2 mm).

• Particle Sizes:

  • Coarse sand: 0.1-0.2 inch diameter

  • Fine sand: 0.075-0.425 mm diameter.