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# Chapter 1: Chemical Foundations ## 1.1 Chemistry: An Overview **Chemistry** - The study of matter and its properties, as well as the changes that matter undergoes. ### The Scientific Method A process for understanding the world, involving: 1. Making observations (gathering data) 2. Formulat...

# Chapter 1: Chemical Foundations ## 1.1 Chemistry: An Overview **Chemistry** - The study of matter and its properties, as well as the changes that matter undergoes. ### The Scientific Method A process for understanding the world, involving: 1. Making observations (gathering data) 2. Formulating a hypothesis (a possible explanation) 3. Experimenting (testing the hypothesis) **Theory (Model):** A set of tested hypotheses that gives an overall explanation of some natural phenomenon. **Natural Law:** When the same observation applies to many different systems, it is summarized as a natural law. ### Units of Measurement * Scientists use the **SI system** (International System of Units). * Important SI 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) * **Volume** is a derived unit (length x length x length). * commonly used unit: liter (L) * $1 \text{ mL} = 1 \text{ cm}^3$ * **Uncertainty in Measurement** * All measurements have some degree of uncertainty. * **Accuracy:** How close a measurement is to the true value. * **Precision:** How close measurements are to each other. * **Random Error (Indeterminate Error):** Measurement has an equal probability of being high or low. * **Systematic Error (Determinate Error):** Measurement is consistently high or low. ### Significant Figures & Calculations * **Significant Figures:** The digits in a measurement that are known with certainty plus one uncertain digit. * **Rules for counting significant figures:** 1. Nonzero integers always count as significant figures. 2. Zeros * Leading zeros do not count as significant figures. * Captive zeros always count as significant figures. * Trailing zeros are significant only if the number contains a decimal point. 3. Exact numbers have an infinite number of significant figures (e.g., counting numbers, conversion factors). * **Rules for significant figures in calculations:** * **Multiplication/Division:** The number of significant figures in the result is the same as the number in the least precise measurement used in the calculation. * **Addition/Subtraction:** The number of decimal places in the result is the same as the number in the least precise measurement used in the calculation. * **Rounding** * If the digit to be removed: * is less than 5, the preceding digit stays the same. * is equal to or greater than 5, the preceding digit is increased by 1. ## 1.2 Classification of Matter * **Matter** - Anything that has mass and occupies space. * **States of Matter** - Solid, liquid, gas. * **Mixtures** - Something with variable composition. * **Homogeneous mixture:** Visibly indistinguishable parts. * **Heterogeneous mixture:** Visibly distinguishable parts. * **Pure substances** - Something with constant composition. * **Elements:** Cannot be broken down into simpler substances by chemical means. * **Compounds:** Can be broken down into simpler substances by chemical means. ## 1.3 Elements and Compounds * **Elements** * Each element has a unique name and symbol (one or two letters). * The periodic table organizes elements by their properties. * **Compounds** * Compounds are made of elements combined in fixed ratios. * Chemical formulas represent compounds (e.g., $H_2O$, $CO_2$). ## 1.4 Chemical Reactions ### Evidence of a chemical reaction 1. The color changes 2. A solid forms 3. Bubbles form 4. Heat and/or a flame is produced or heat is absorbed. ## 1.5 Separation of Mixtures * **Distillation:** Separates liquids based on boiling points. * **Filtration:** Separates solids from liquids. * **Chromatography:** Separates substances based on their affinity for a stationary phase. ## 1.6 Density * **Density** - The amount of mass per unit volume of a substance. * $\text{Density} = \frac{\text{mass}}{\text{volume}}$ ## 1.7 Temperature * **Temperature** - A measure of the average kinetic energy of the particles in a sample. * Scales $$ \begin{aligned} &{ }^{\circ} \mathrm{C}=\frac{5}{9}\left({ }^{\circ} \mathrm{F}-32\right) \\ &{ }^{\circ} \mathrm{F}=\frac{9}{5}\left({ }^{\circ} \mathrm{C}\right)+32 \\ &\mathrm{K}={ }^{\circ} \mathrm{C}+273.15 \end{aligned} $$ ## 1.8 Energy and Heat * **Energy** - The capacity to do work. * **Potential energy:** Energy due to position or composition. * **Kinetic energy:** Energy due to motion. $$ \mathrm{KE}=\frac{1}{2} m v^{2} $$ ### Law of Conservation of Energy * Energy can be converted from one form to another but can neither be created nor destroyed. ### Heat and Changes of State * **Heat** - A form of energy that flows from a warmer object to a cooler one. * **Endothermic process:** A process that absorbs heat. * **Exothermic process:** A process that releases heat. ### Specific Heat Capacity * The amount of energy required to raise the temperature of one gram of a substance by one degree Celsius. $$ \text{Energy Required} = \text{Specific Heat Capacity} \times \text{mass} \times \text{temperature change} = s \times m \times \Delta T $$