1 - Measurements and Math in Chemistry

Overview of Science and Math in Chemistry

  • Discussion of basic science and math concepts used in chemistry measurements.

  • Emphasis on the importance of the scientific method.

Scientific Method

Four Parts

  1. Observations

    • Facts obtained by observing and measuring nature.

    • Example: Noticing how far a ball goes when kicked.

  2. Hypothesis

    • A statement that explains an observation.

    • Example: Suggesting a force acts on an apple falling.

  3. Experimentation

    • Tests or procedures to validate the hypothesis.

    • Example: Dropping different objects to observe falling speeds.

  4. Theory

    • A model that describes how observations occur using experimental results.

    • Example: Developing a theory of gravitational force based on experiments.

Significant Figures

Importance

  • Essential for accuracy in measurements and lab work.

Rules

  1. Non-zero numbers are significant.

  2. Sandwiched zeros are significant.

  3. Leading zeros are not significant.

  4. Trailing zeros are significant if there is a decimal point; otherwise, they are not.

  5. Exact numbers (e.g., counted items) are infinitely significant.

Rounding Off Numbers

  • Round down if the last number is 4 or less; round up if it is 5 or more.

  • Example: Rounding 53.811 to 3 significant figures results in 53.8; rounding 2.4884 to 2 significant figures results in 2.5.

Operations with Significant Figures

Multiplication and Division

  • The final answer should match the least number of significant figures in any number used.

Addition and Subtraction

  • The final answer should have the fewest decimal places from the numbers involved.

Conversion Factors and Dimensional Analysis

  • Conversion factors should be known, such as:

    • 1 inch = 2.54 cm

    • 1 liter = 1.06 quarts; 1 gallon = 4 quarts.

  • Problem-solving example of converting between liters and gallons using dimensional analysis:

    • Convert 4.65 liters to gallons using the relevant conversion factors.

Temperature Conversions

Formulas

  • Celsius to Fahrenheit:[ C = (F - 32) / 1.8 ]

  • Celsius to Kelvin:[ K = C + 273 ]