CHEM 1123 Unit 1: Introduction to Chemistry, Matter, and Scientific Method

Introduction to Chemistry and Chemical Calculations

Definition of Chemistry

Chemistry is the study of the composition, structure, properties, and reactions of substances. It explores how substances interact, combine, and change to form new substances.

• Substance: Any form of matter that has a definite composition and distinct properties.

• Example: Water (H2O), table salt (NaCl), and oxygen (O2).

Chemicals in Our Daily Lives

Chemicals are present in many everyday items and are essential to modern life.

• Examples: Drinking water, plastics, baking soda, detergents, gasoline, processed foods, medicines.

Chemical Reactions

Chemical reactions involve processes where substances are transformed into new substances with different properties.

• Examples: Using a battery, digesting food, burning a match.

• Chemical reactions produce new substances.

What is a Chemical?

A chemical is any substance used in or produced by a chemical process. All matter is made up of chemicals.

• Examples: Salt, sugar, baking soda, bleach.

Matter and Its Classification

Definition of Matter

Matter is the physical "stuff" that makes up all things. It has mass and occupies space (has volume).

• All substances (chemicals) are forms of matter.

Pure Substances

A pure substance contains only one kind of matter and has a specific composition.

• Types of pure substances:

  • Elements: Substances that cannot be broken down into simpler substances by chemical means.

  • Compounds: Substances composed of two or more elements chemically combined in fixed proportions.

Elements

Elements are pure substances that cannot be broken down into anything simpler using chemical reactions. Each element is made up of only one type of atom.

• Each element has a unique chemical symbol.

• There are at least 118 known elements, each listed on the periodic table.

• Atom: The smallest unit of matter that can be identified as an element.

Origin of Element Names

• Carbon: From Latin "carbo" (coal).

• Iodine: From Greek "ioeides" (violet).

• Curium: Named in honor of Marie Curie.

Element Symbols

Each element is represented by a unique symbol, usually one or two letters. The first letter is always capitalized, and the second letter (if present) is lowercase.

• Examples: C (carbon), N (nitrogen), F (fluorine), Co (cobalt), Ca (calcium), Mg (magnesium).

• Some symbols are derived from Latin names: Cu (copper, cuprum), Fe (iron, ferrum), Au (gold, aurum).

Writing and Memorizing Element Symbols

• Always use correct capitalization.

• Do not use symbol letters incorrectly (e.g., CO is cobalt, not carbon and oxygen).

• Memorize the correct spelling and symbols for common elements.

Compound Formulas

Compound formulas show the elements that make up the compound and the ratios of those elements. Subscripts indicate the number of atoms of each element in the compound.

• Examples:

  • Table salt: $\mathrm{NaCl}$

  • Water: $\mathrm{H_2O}$

  • Table sugar: $\mathrm{C_{12}H_{22}O_{11}}$

Mixtures

A mixture is a type of matter that consists of two or more substances that are physically mixed, not chemically combined. The composition of a mixture can vary.

• Mixtures can be separated by physical methods.

• Examples: Air, salad, salt water.

Physical Methods of Separation

• Filtration

• Evaporation

• Distillation

• Chromatography

Types of Mixtures

• Homogeneous mixture: The composition is uniform throughout; the different parts are not visible (e.g., salt water, air).

• Heterogeneous mixture: The composition varies from one part to another; the different parts are visible (e.g., salad, sand in water).

Classification of Matter Table

The following table summarizes the classification of matter:

Type	Definition	Examples
Pure Substance	Has a fixed composition; can be an element or compound	Water, gold, sodium chloride
Element	Cannot be broken down by chemical means	Oxygen, iron, carbon
Compound	Composed of two or more elements chemically combined	Water (H2O), sodium chloride (NaCl)
Mixture	Physical blend of two or more substances; variable composition	Air, salad, salt water
Homogeneous Mixture	Uniform composition throughout	Salt water, air
Heterogeneous Mixture	Non-uniform composition; different parts visible	Salad, sand in water

The Scientific Method

Definition and Steps

The scientific method is a general approach to problem-solving and understanding natural phenomena. It involves systematic observation, experimentation, and analysis.

1. Make observations (collect data).

2. Formulate a hypothesis (a tentative explanation or prediction).

3. Test the hypothesis by performing experiments.

4. Analyze the data and draw a conclusion.

5. Develop a theory if the hypothesis is supported by repeated experiments.

Key Terms

• Observation: Information obtained through the senses.

• Hypothesis: A testable statement or prediction.

• Experiment: A controlled procedure to test a hypothesis.

• Conclusion: A judgment based on the results of the experiment.

• Theory: A well-tested explanation for a broad set of observations.

Example of the Scientific Method

• Observation: My phone is missing.

• Hypothesis: I left my phone in the car.

• Experiment: Check the car for the phone.

• Conclusion: If the phone is found in the car, the hypothesis is supported.

Additional info: This study guide covers the foundational concepts of chemistry, including the nature of matter, classification of substances, and the scientific method, as introduced in a typical GOB Chemistry college course.