Chemistry Notes PDF

What is Chemistry? ● Chemistry is the study of matter ○ Study of elements and their chemical composition, structure, and reactions ○ Chemical interactions between elements, atoms, and molecules Matter Matter is anything that takes up space and can be weighed. It can be categorized into the follo...

What is Chemistry? ● Chemistry is the study of matter ○ Study of elements and their chemical composition, structure, and reactions ○ Chemical interactions between elements, atoms, and molecules Matter Matter is anything that takes up space and can be weighed. It can be categorized into the following 2 categories: - Pure substance - when all of the particles are identical - Mixture - if there are different types of particles present Matter can exist in various states, including solids, liquids, gases, and plasma (an ionized gas), and it can change between these states through physical processes. Atoms - Atoms are the basic units of matter and the defining structure of elements. They are the smallest units of an element that retain all the chemical properties of that element. - An atom is composed of a nucleus, which contains protons (positively charged particles) and neutrons (neutral particles), and electrons (negatively charged particles) that orbit around the nucleus. - The arrangement and number of these subatomic particles determine the atom's chemical properties. Molecules - Molecules are chemical structures consisting of at least two atoms bonded together. These atoms can be the same (as in O2, which is a molecule of oxygen) or different (as in H2O, which is a molecule of water). - Molecules are held together by chemical bonds, which involve the sharing or transfer of electrons. Elements - Elements are pure substances consisting entirely of one type of atom, distinguished by their atomic number, which is the number of protons in the nucleus of their atoms. Elements cannot be broken down into simpler substances by chemical means. Density Definition: How much mass is in a given space ● High densities sink to the button ● Low densities sit at the top Density = mass/volume Imagine that a metal rod has a density of 3.5 g/mL. If you were to slice the metal rod in half, what would the density of each half be? Mention a numerical value in your explanation. If a metal rod has a density of 3.5 g/mL, it means that for every milliliter (mL) of the rod, there are 3.5 grams (g) of metal in it. When you cut the rod in half, each half still has the same amount of metal in it as the original rod because you're not changing the metal's composition. So, the density of each half of the rod is still 3.5 g/mL. Cutting the rod in half doesn't change its density. How can objects that are the same size have different masses? Objects that are the same size can have different masses because their materials or substances are different. The mass of an object is determined by the amount of matter it contains, while the size or volume of an object refers to the amount of space it occupies. Do two objects with the same mass always have the same volume? Explain why or why not. No, two objects with the same mass do not always have the same volume. The mass of an object is a measure of the amount of matter it contains, while the volume of an object is a measure of the amount of space it occupies. These two properties are related through the concept of density, but they are not the same thing. Scientific Method 1. Identify the Problem 2. Form a Hypothesis 3. Create an Experiment 4. Perform an Experiment 5. Analyze the Data a. 6. Iterate/Modify Experiment Communicate Results Water Displacement Water levels rise when you put an object into a container of water. This is known as water displacement. Find the difference between water displacement before and after Your mass that you are putting in water has to be taller than the amount of water in the graduated cylinder Qualitative vs. Quantitative (vs. Inference) Qualitative: info that describes color, odor, shape, or some physical appearance. Quantitative: numerical information (measurement, weight) Inference: a guess, conclusion, or opinion formed from what you see, evidence, or facts Lab Tools (Graduated Cylinder & Meniscus) Used to find volume of liquids Usually measured in milliliters Meniscus → read the bottom of the curve Read it at eye level Metric System ● ● ● Originated in France in the late 1700s The USA uses the imperial system (one of the 3 places in the world that uses the metric system) Real-world examples of metric vs. Imperial system ○ Kilometers per hour vs Miles per hour ○ Centimeters vs Inches ○ Meters vs Feet ○ Kilograms vs Pounds ○ Celsius vs Fahrenheit ○ Liter vs. Cups Why we use the metric system: Almost all countries use the metric system International companies refuse to buy products from the U.S. if not labeled in the metric units. ● Scientists need a universal way to communicate data ● ● Standard Units: ● Mass = Kilograms (kg) ● Volume = Liters (L) ● Distance = Meters (M)