Foundations of Chemistry: Matter, Scientific Method, and Mathematical Skills

Chemistry and Chemicals

Introduction to Chemistry

Chemistry is the scientific study of the composition, structure, properties, and reactions of matter. It seeks to understand what substances are made of, how they interact, and the changes they undergo.

• Chemistry: The study of composition, structure, properties, and reactions of matter.

• Matter: Anything that has mass and takes up space. Examples: water, oxygen, carbon dioxide, you.

• Chemicals: Substances with the same composition and properties wherever found. Examples: toothpaste ingredients, milk, fruit, breakfast cereal.

Key Questions Chemistry Asks

• Composition: What is it made of?

• Structure: How is it put together?

• Properties: What characteristics does it have?

• Reactions: How does it behave?

The Scientific Method

Definition and Steps

The scientific method is a systematic approach used by scientists to solve problems and explain observations. It involves making observations, forming hypotheses, and conducting experiments to test those hypotheses.

• Observation: Noticing facts or events. Example: Itchy eyes near cats.

• Hypothesis: A possible explanation for an observation. Example: "I may be allergic to cats."

• Experiment: Testing the hypothesis through controlled investigation. Example: Leaving the house, visiting another cat.

Everyday Example: Allergies → Observations + repeated experiments = confirmed cat allergy.

Learning Check: Practice identifying steps (observation, hypothesis, experiment, theory).

Key Math Skills

Essential Mathematical Tools for Chemistry

Mathematical skills are crucial in chemistry for analyzing data, performing calculations, and solving problems. Understanding place value, operations, and percentages is foundational for success in the subject.

• Place Values: Identify digits in whole and decimal numbers. Example: In 15.24, 1 = tens, 5 = ones, 2 = tenths, 4 = hundredths.

• Positive/Negative Numbers:

  • (+) × (+) or (−) × (−) = positive

  • (+) × (−) or (−) × (+) = negative

• Operations:

  • Addition/Subtraction: With mixed signs, subtract the smaller number from the larger and keep the sign of the larger.

  • Multiplication/Division: Follow sign rules above.

• Percentages:

  • Formula: (Part ÷ Whole) × 100

  • Example: 325 mg aspirin + 545 mg tablet × 100 = 60%

• Solving Equations: Isolate the variable by rearranging terms.

Writing in Scientific Notation

Expressing Large and Small Numbers

Scientific notation is a method for expressing very large or very small numbers using powers of 10. This is especially useful in chemistry for dealing with quantities like Avogadro's number or atomic masses.

• Definition: A way to express very large or small numbers using powers of 10.

• Format: Coefficient × 10n

  • Coefficient: ≥1 and <10

  • n = number of decimal places moved

• Examples:

  • 64,000 = $6.4 \times 10^4$

  • 0.021 = $2.1 \times 10^{-2}$

  • 0.000008 = $8.0 \times 10^{-6}$

  • 72,000,000 = $7.2 \times 10^7$

• Calculator Use: Use EE/EXP key for entering scientific notation.