Chapter 1: Chemistry Basics—Matter and Measurement (GOB Chemistry Study Notes)

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Classifying Matter

Pure Substances and Mixtures

Matter is anything that occupies space and has mass. It can be classified into two main categories: pure substances and mixtures.

Pure substances are made up of only one type of substance and can be represented by a single chemical formula or symbol.
Elements are the simplest type of pure substance, consisting of only one type of atom.
Compounds are pure substances composed of two or more elements chemically joined together.
Mixtures are combinations of two or more substances that can be separated by physical means.
Homogeneous mixtures have a uniform composition throughout (e.g., salt water).
Heterogeneous mixtures have a non-uniform composition that varies throughout (e.g., salad).

Classification Table

The following table summarizes the classification of matter:

Type	Definition	Example
Element	Pure substance of one type of atom	Copper (Cu)
Compound	Pure substance of two or more atoms chemically bonded	Water (H2O)
Homogeneous Mixture	Uniform composition throughout	Brass (copper and zinc atoms)
Heterogeneous Mixture	Non-uniform composition	Water and copper atoms

Elements, Compounds, and the Periodic Table

The Periodic Table

The periodic table of the elements is a systematic arrangement of all known elements. Each element is represented by a chemical symbol, usually one or two letters, and is organized into blocks with numbers indicating atomic number and other properties.

Symbols are often derived from the English or Latin name of the element (e.g., Na for sodium from natrium, Au for gold from aurum).
Vertical columns are called groups and contain elements with similar chemical behaviors.
Horizontal rows are called periods and are numbered from 1 to 7.
The staircase line separates metals from nonmetals; elements bordering the line (except aluminum) are metalloids.

Essential Elements for Life

Macronutrients (needed in >100 mg/day): sodium, magnesium, potassium, calcium, chlorine.
Micronutrients (needed in <100 mg/day): iodine, fluorine, iron, zinc, and others.

Chemical Formulas

A chemical formula shows the elements present in a compound and the number of atoms of each element. For example:

Water: (2 hydrogen atoms, 1 oxygen atom)
Salt: (1 sodium atom, 1 chlorine atom)

How Matter Changes

Physical and Chemical Changes

Matter can undergo changes that are classified as physical or chemical:

Physical change: Alters the form or appearance of matter but does not change its identity (e.g., melting ice).
Chemical change: Alters the chemical identity of a substance, resulting in a chemical reaction (e.g., burning wood).

Chemical Equations

A chemical equation represents a chemical reaction, showing reactants and products. For example:

States of matter are indicated by (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous.

Balancing Chemical Equations

The number of atoms of each element must be the same on both sides of the equation (law of conservation of mass).
Balance equations by adding coefficients in front of chemical formulas.

Math Counts

SI Units and Metric System

Chemistry uses the Système International d’Unités (SI), a modern version of the metric system:

Mass: kilogram (kg)
Volume: liter (L)
Length: meter (m)

Unit Conversion and Dimensional Analysis

Equivalent units can be used as conversion factors (e.g., ).
Dimensional analysis involves converting units to the desired unit using conversion factors.

Significant Figures

Significant figures reflect the precision of a measurement.
All nonzero digits are significant; zeros may or may not be significant depending on their position.
Exact numbers (from counting or defined conversions) have infinite significant figures.

Calculations and Rounding

For addition/subtraction: answer should match the least number of decimal places.
For multiplication/division: answer should match the least number of significant digits.
Rounding rules: If the digit to be dropped is 5 or greater, increase the last retained digit by 1.

Scientific Notation

General form: where and is an integer.
Positive exponent: number greater than 1; negative exponent: number between 0 and 1.

Percent Calculations

Percent (%) = (part/whole) × 100
Convert fractions or decimals to percent by multiplying by 100.

Matter: The “Stuff” of Chemistry

Mass and Volume

Mass is the amount of material in an object, measured in grams (g).
Volume is the three-dimensional space occupied by matter, measured in liters (L), milliliters (mL), or cubic centimeters (cm3).
1 mL = 1 cm3; 5 mL ≈ 1 teaspoon.

Density and Specific Gravity

Density (d) is the ratio of mass to volume:
Density of water at 4°C is 1.00 g/mL.
Specific gravity (sp gr) is the ratio of the density of a sample to the density of water:

Temperature Scales

Fahrenheit (°F), Celsius (°C), and Kelvin (K) are common temperature scales.
Kelvin is the SI unit for temperature.
Conversion formulas:

Energy and Specific Heat

Energy is the capacity to do work or supply heat.
Potential energy is stored energy; kinetic energy is energy of motion.
Law of conservation of energy: energy is neither created nor destroyed.
SI unit for energy: joule (J); 1 calorie (cal) = 4.184 J; 1 Calorie (nutritional) = 1000 cal.
Specific heat (SH) is the amount of heat needed to raise the temperature of 1 g of a substance by 1°C:

States of Matter

Solid: Definite shape and volume; particles are closely packed and vibrate in place.
Liquid: Definite volume, takes shape of container; particles move more freely.
Gas: No definite shape or volume; particles are far apart and move rapidly.

States of Matter Table

Property	Solid	Liquid	Gas
Shape	Definite	Adopts container	Adopts container
Volume	Definite	Definite	Fills container
Particle arrangement	Orderly, close-packed	Less orderly, close	Far apart, random
Energy	Lowest	Intermediate	Highest

Measuring Matter

Accuracy and Precision

Accuracy: Measurements close to the true value.
Precision: Measurements that are consistent with each other.
Best practice: Take multiple measurements and average the values.

Units in Health and Dosage Calculations

SI/metric units are standard, but U.S. customary units are also used.
Common conversions: 1 deciliter (dL) = 0.1 L = 100 mL; 1 millimole (mmol) = 0.001 mole.
Dosage calculations involve determining the final units, given information, and appropriate conversion factors.
Delivery of medications may be measured in drops per milliliter (gtt/mL).

Percent in Health

Percent active ingredient: Used to calculate the amount of medicine in a pill.
Percent of adult dose: Used to adjust dosages for children.
Percent daily value (%DV): Used in nutrition labeling to show contribution to daily dietary requirements.

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