Chapter 1: Chemistry and Our Lives

Introduction to Chemistry

Chemistry is the scientific study of matter and its properties. Matter is defined as anything that has mass and occupies space. Chemists investigate the composition, structure, properties, and changes of matter to understand the world at a molecular level.

• Matter: Anything that has mass and volume.

• Chemical: A substance with a definite composition and set of properties, regardless of its source.

• Example: Toothpaste contains chemicals such as calcium carbonate, sorbitol, sodium lauryl sulfate, and titanium dioxide.

The Scientific Method

The scientific method is a systematic approach used by scientists to explore observations, answer questions, and solve problems.

• Steps:

  1. Observation

  2. Hypothesis

  3. Experiment

  4. Model (Theory)

  5. Further Experimentation

Qualitative vs. Quantitative Analysis

Scientists study matter using two main approaches:

• Qualitative Analysis: Describes qualities or characteristics (e.g., color, smell, texture).

• Quantitative Analysis: Involves measurements and numerical data (e.g., mass, length, volume, temperature).

Chapter 2: Chemistry and Measurements

SI Units and Measurement

Scientific measurements are expressed in SI units, a standardized metric system used globally. SI units include seven base units and many derived units.

• Base Units:

  • Mass: kilogram (kg)

  • Length: meter (m)

  • Time: second (s)

  • Temperature: kelvin (K)

  • Amount of substance: mole (mol)

  • Electric current: ampere (A)

  • Luminous intensity: candela (cd)

• Derived Units: Formed by combining base units (e.g., area: m2, volume: m3, density: kg/m3, velocity: m/s).

Decimal Prefixes and Scientific Notation

To handle very large or very small numbers, scientists use decimal prefixes and scientific (exponential) notation.

• Scientific Notation: Expresses numbers as a product of a decimal part (≥1 and <10) and a power of ten.

  • Example:

  • Example:

• Decimal Prefixes: Used to simplify numbers by replacing powers of ten with prefixes.

  • kilo (k):

  • centi (c):

  • milli (m):

  • micro (\mu):

  • nano (n):

  • mega (M):

  • deci (d):

Rules for Scientific Notation

• The decimal part must be ≥1 and <10.

• Adjust the exponent to reflect the movement of the decimal point.

• Examples:

Significant Figures

Significant figures (sig figs) reflect the precision of a measurement. Only meaningful digits are retained to minimize error.

• Rules:

  • Leading zeros are not significant.

  • Trailing zeros after a decimal point are significant.

  • Trailing zeros before a decimal point are significant if the decimal is shown.

  • Use scientific notation to clarify the number of significant figures.

• Examples:

  • 0.0012 (2 sig figs)

  • 10.002 (5 sig figs)

  • 10.00200 (7 sig figs)

  • 11000. (5 sig figs)

  • 1.10 × 104 (3 sig figs)

Arithmetic with Significant Figures

• Addition/Subtraction: The result should have the same number of decimal places as the measurement with the fewest decimal places.

• Multiplication/Division: The result should have the same number of significant figures as the measurement with the fewest significant figures.

• Examples:

  • 1.11 cm + 0.222 cm = 1.33 cm (rounded to 3 sig figs)

  • 2.222 × 0.11 = 0.24 (2 sig figs)

Unit Conversions and Dimensional Analysis

Unit conversions are essential in chemistry for translating between different measurement systems. Conversion factors are ratios that express how many of one unit are equal to another unit.

• Example: 1 dozen = 12 eggs

• Example: 1.000 kg = 2.205 lbs

• Dimensional Analysis: Units cancel algebraically, just like variables.

• Example Calculation: To convert 2.0 kg to pounds:

Practice Problems and Applications

• Rewrite 123000 m as km using the kilo prefix:

• Rewrite 0.00000012 s as microseconds:

• Round 44.981 g to three significant figures: 45.0 g

• Type 3.14 × 103 in standard notation: 3140

• Type 8.75 × 10−4 in standard notation: 0.000875

Key Takeaways

• Chemistry is the study of matter and its changes.

• Measurements in chemistry use SI units and require careful attention to significant figures and unit conversions.

• Scientific notation and decimal prefixes simplify the expression of very large or small numbers.

• Dimensional analysis ensures correct unit conversions and meaningful results.