BackChapter 1: Matter, Measurements, and Problem Solving – General Chemistry Study Notes
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Matter, Measurements, and Problem Solving
Introduction
This chapter introduces the foundational concepts of matter, its classification, and the measurement systems used in chemistry. Understanding these basics is essential for problem solving and further study in chemistry.
Elements
Definition and Properties
Element: A pure substance made up of only one type of atom.
Elements have a constant composition and cannot be broken down into simpler substances by chemical means.
All known elements are listed on the Periodic Table.
Examples: Cu (Copper), H2 (Hydrogen), O2 (Oxygen)
Elements and Composition
There are currently 118 named elements.
Only five elements (oxygen, silicon, aluminum, iron, calcium) make up about 90% of the Earth's crust by mass.
Only three elements (oxygen, carbon, hydrogen) make up about 90% of the human body by mass.
Application: The abundance of elements in different environments (Earth's crust vs. human body) highlights the diversity of chemical composition in nature.
Compounds
Definition and Examples
Compound: A substance composed of two or more different types of atoms chemically bonded together.
Compounds have a fixed, definite composition.
Examples: H2O (water), NaHCO3 (baking soda), NaCl (table salt), C12H22O11 (sucrose)
Application: Everyday substances such as water, baking soda, and table sugar are all compounds, each with unique properties resulting from the specific combination of elements.
Classification of Matter
Elements vs. Compounds
Elements consist of only one type of atom and are represented by symbols on the periodic table.
Compounds consist of two or more types of atoms bonded in fixed ratios, represented by chemical formulas.
Example Table: Comparison of Elements and Compounds
Property | Element | Compound |
|---|---|---|
Composition | One type of atom | Two or more types of atoms |
Representation | Symbol (e.g., H, O, Cu) | Chemical formula (e.g., H2O, NaCl) |
Separation | Chemically indivisible | Can be separated into elements by chemical means |
Additional info:
The periodic table organizes elements by increasing atomic number and groups elements with similar chemical properties together.
Compounds exhibit properties distinct from the elements that compose them due to chemical bonding and structure.
