Chemistry Notes PDF

Pure Substances vs. Mixtures ​ Pure Substance: A material made of only one type of particle (atom or molecule). It has a fixed composition. ○​ Examples: Water (H₂O), Oxygen gas (O₂), Gold (Au) ​ Mixture: A combination of two or more substances that are physically blended but...

Pure Substances vs. Mixtures ​ Pure Substance: A material made of only one type of particle (atom or molecule). It has a fixed composition. ○​ Examples: Water (H₂O), Oxygen gas (O₂), Gold (Au) ​ Mixture: A combination of two or more substances that are physically blended but not chemically combined. ○​ Examples: Saltwater, Air, Salad Atoms, Molecules, and Compounds ​ Atom: The smallest unit of an element (e.g., Hydrogen (H), Oxygen (O)). ​ Molecule: Two or more atoms chemically bonded together (e.g., O₂, H₂O). ​ Atomic Element: An element made up of single atoms (e.g., Helium (He), Iron (Fe)). ​ Molecular Element: An element that exists as molecules (two or more atoms of the same element bonded together) (e.g., O₂, N₂). ​ Compound: A substance made of two or more different elements chemically bonded (e.g., H₂O, CO₂). Homogeneous vs. Heterogeneous Mixtures ​ Homogeneous Mixture: Uniform composition; looks the same throughout (e.g., Saltwater, Air, Coffee). ​ Heterogeneous Mixture: Uneven composition; different parts are visible (e.g., Salad, Oil and Water, Cereal with Milk). Physical vs. Chemical Properties ​ Physical Property: Can be observed or measured without changing the substance (e.g., color, density, melting point). ​ Chemical Property: Describes a substance's ability to change into a new substance (e.g., flammability, reactivity with acid). Definition of Chemistry Chemistry is the study of matter, its properties, and how it changes. Qualitative vs. Quantitative Data ​ Qualitative Data: Describes qualities (e.g., color, smell, texture). ​ Quantitative Data: Includes numbers and measurements (e.g., mass = 5g, temperature = 100°C). Chemistry Lab Safety Guidelines ​ Wear safety goggles and gloves. ​ No eating or drinking in the lab. ​ Handle chemicals with care. ​ Know emergency procedures. Accuracy and Percent Error ​ Accuracy: How close a measurement is to the true value. ​ Percent Error Formula: Percent Error=(∣Experimental Value−Actual Value∣Actual Value)×100%\text{Percent Error} = \left( \frac{|\text{Experimental Value} - \text{Actual Value}|}{\text{Actual Value}} \right) \times 100\%Percent Error=(Actual Value∣Experimental Value−Actual Value∣​)×100% Example Calculation: If the actual value is 50g and the measured value is 48g: Percent Error=(∣48−50∣50)×100=4%\text{Percent Error} = \left( \frac{|48 - 50|}{50} \right) \times 100 = 4\%Percent Error=(50∣48−50∣​)×100=4% Precision and Range Calculation ​ Precision: How close multiple measurements are to each other. ​ Range Formula: Range=Highest Value−Lowest Value\text{Range} = \text{Highest Value} - \text{Lowest Value}Range=Highest Value−Lowest Value Finding Density Density is how much mass is packed into a given volume.  ​ Formula: Density=MassVolume\text{Density} = \frac{\text{Mass}}{\text{Volume}}Density=VolumeMass​ ​ Example: If a substance has a mass of 10g and a volume of 2mL: Density=102=5 g/mL\text{Density} = \frac{10}{2} = 5 \text{ g/mL}Density=210​=5 g/mL Identifying Physical vs. Chemical Properties ​ Physical Properties (don’t change the substance): Color, Shape, Melting Point, Density. ​ Chemical Properties (change the substance): Rusting, Burning, Reactivity with Acid.