Physical Properties in Science PDF

Physical Properties in Science Physical properties are characteristics of a substance that can be observed or measured without changing the substance into something new. These properties help us identify and describe different materials. Key Physical Properties 1.​ Luster describes how...

Physical Properties in Science Physical properties are characteristics of a substance that can be observed or measured without changing the substance into something new. These properties help us identify and describe different materials. Key Physical Properties 1.​ Luster describes how a material reflects light. ​ Examples: ​ Metallic luster: Shiny like metals (e.g., gold or silver). ​ Non-metallic luster: Dull, glassy, shiny, brilliant... (e.g., wood or rubber). 2.​ Texture is how a material feels to the touch. ​ Examples: ​ Smooth (e.g., glass). ​ Rough (e.g., sandpaper). ​ Soft (e.g., cotton). 3.​ Malleability is the ability of a material to be hammered or rolled into thin sheets without breaking. ​ Examples: ​ High malleability: Aluminum, gold. ​ Low malleability: Glass, ceramics. 4.​ Electrical Conductivity measures how well a material allows electricity to pass through it. ​ Examples: ​ Good conductors: Copper, silver.  ​ Poor conductors (insulators): Plastic, rubber. 5.​ Density is the amount of mass in a given volume. ​ Formula: D = M/V (Density = mass / volume) ​ ​Units: grams per centimeter cubed (g/cm3) ​ Examples: ​ High density: Lead, gold. ​ Low density: Styrofoam, cork. ​ ​ Melting Point is the temperature at which a solid changes into a liquid. ​ Examples: ​ High melting point: Iron (1538°C). ​ Low melting point: Ice (0°C). Why Are Physical Properties Important? Physical properties are used in: ​ Identifying unknown substances. ​ Selecting materials for specific purposes (e.g., building, electronics). Comparing and classifying different substances. ​ Mixtures and Solutions What is a Mixture? A mixture is a combination of two or more substances where: ​ Each substance retains its original properties. ​ The substances can be physically separated. Mixtures can be categorized as:  1.​ Homogeneous Mixture: The components are evenly distributed, and you cannot see the individual parts (e.g., saltwater). 2.​ Heterogeneous Mixture: The components are not evenly distributed, and the individual parts are visible (e.g., a salad). What is a Solution? A solution is a special type of homogeneous mixture where one substance dissolves in another: ​ The solute is the substance that dissolves (e.g., salt in saltwater). ​ The solvent is the substance that does the dissolving (e.g., water in saltwater). Example: ​ In a saltwater solution: ​ Salt is the solute. ​ Water is the solvent. Saturation and Solubility: ​ A solution becomes saturated when it cannot dissolve any more solute at a specific temperature. ​ Saturation Point - when no more solute can dissolve. ​ Unsaturated Solution: Can dissolve more solute. ​ Supersaturated Solution: Contains more dissolved solute than a saturated solution due to being heated and then cooled carefully. Using a Solubility Curve: A solubility curve is a graph that shows how much solute can dissolve in a solvent at different temperatures. ​ The x-axis typically represents temperature. ​ The y-axis represents the amount of solute (usually in grams) that can dissolve in a specific amount of solvent (usually 100 grams of water) ​ Solids usually become more soluble as temperature increases. ​ Gasses become more soluble as temperature decreases. ​ Solubility increases as pressure increases. Steps to Use a Solubility Curve: 1.​ Locate the temperature on the x-axis. 2.​ Find the corresponding point on the curve for your solute. 3.​ Determine the solubility by reading the value on the y-axis. 4.​ Compare your solution: ​ If the amount of solute is below the curve, the solution is unsaturated. ​ If the amount of solute is on the curve, the solution is saturated. ​ If the amount of solute is above the curve, the solution is supersaturated. The history of the atomic model is an excellent way to tie key principles of science to real-world examples. Here's how each principle can connect to the development of the atomic model: The natural world is understandable Scientists sought to understand the nature of matter, starting with Democritus's idea of "atomos" (indivisible particles) and evolving into more detailed models as understanding grew. This demonstrates the belief that the natural world can be comprehended through systematic inquiry. Science demands evidence - Each stage of the atomic model's development was supported by experimental evidence: Dalton’s atomic theory relied on chemical reaction observations. Thomson’s cathode ray tube experiments revealed the electron.  Rutherford’s gold foil experiment provided evidence for a dense nucleus. Bohr’s model explained the quantized nature of electron orbits using spectroscopic data. Science is a blend of logic and imagination Thomson, Rutherford, Bohr, and others used imagination to propose models (like the plum pudding and planetary models), yet these were logically based on evidence from experiments. Scientific knowledge is durable While models have been refined, the foundational ideas such as atoms being the building blocks of matter remain valid. Each new model builds on past insights rather than discarding them entirely. Scientific knowledge is subject to change The atomic model has evolved dramatically—from indivisible particles (Democritus) to electrons embedded in a positive sphere (Thomson), to a dense nucleus with orbiting electrons (Rutherford and Bohr), and now to quantum mechanics. This reflects the self-correcting nature of science. Scientists attempt to identify and avoid bias Scientists like Dalton and Rutherford conducted rigorous experiments and relied on repeatable observations rather than preconceived notions. This commitment helped refine models and correct earlier misconceptions. Science is a complex social activity The development of the atomic model was a collaborative effort over centuries. Ideas were shared, debated, and refined by scientists from different backgrounds and time periods, such as Thomson, Rutherford, Bohr, Schrödinger, and Heisenberg. Atoms and Their Structure What is an Atom? ​ Definition: The smallest unit of matter that retains the properties of an element. ​ Components: Atoms are made of three main particles: protons, neutrons, and electrons. Key Feature Atom Carbon (C) Smallest unit of matter ​ Nucleus: ​ The dense, central part of an atom. ​ Contains protons (positively charged) and neutrons (neutral/no charge). ​ Most of the atom’s mass is concentrated here. ​ Electron Cloud: ​ Surrounds the nucleus. ​ Contains electrons (negatively charged). ​ Electrons move in regions of space called orbitals. Subatomic Particles Particle Charge Location Relative Mass Proton Positive (+) In the nucleus Heavy Neutron Neutral (0) In the nucleus Heavy Electron Negative Electron Very light (-) cloud Key Concepts ​ Ions:  ​ Atoms that have gained or lost electrons, giving them a charge. ​ Cation: Positively charged ion (lost electrons). ​ Anion: Negatively charged ion (gained electrons). ​ Isotopes: ​ Atoms of the same element with different numbers of neutrons. ​ Example: Carbon-12 and Carbon-14. ​ Atomic Number: ​ The number of protons in an atom. ​ Determines the element. ​ Mass Number: ​ The total number of protons and neutrons in an atom. Atoms vs. Elements, Compounds, and Mixtures ​ Element: ​ A pure substance made of only one type of atom (e.g., Oxygen, O₂). ​ Compound: ​ A substance made of two or more elements chemically bonded (e.g., H₂O). ​ Mixture: ​ A combination of two or more substances that are not chemically bonded (e.g., saltwater). Periodic Table · Dmitri Mendeleev organized elements in the 19th century by atomic mass, noticing repeating patterns in properties. Later, the table was rearranged by atomic number (number of protons). Organization of the Periodic Table · Periods (rows) run left to right and show the number of electron shells. · Groups (columns), or families, contain elements with the same number of valence electrons, leading to similar properties. o Valence electrons – electrons in the outer shell of an atom that is responsible for the chemical properties of the atom. Patterns in the Periodic Table · Groups share properties due to the same valence electron count (e.g., Group 1 elements have 1 valence electron and are highly reactive). · Reactivity varies:  o Metals (left side) and halogens (Group 17) are reactive. o Noble gases (Group 18) have full outer shells and are non-reactive. Metals, Nonmetals, and Metalloids · Metals: Shiny, malleable, conductive, and lose electrons to form positive ions. · Nonmetals: Found on the right; often gases or brittle solids; gain electrons to form negative ions. · Metalloids: Along the zigzag line; have properties of both metals and nonmetals. Key Groups of Elements  · Alkali Metals (Group 1): Most reactive metals with 1 valence electron; react with water. · Alkaline Earth Metals (Group 2): Reactive, with 2 valence electrons; found in rocks. · Halogens (Group 17): Very reactive nonmetals with 7 valence electrons; form salts with alkali metals. · Noble Gases (Group 18): Unreactive gases with full outer shells (e.g., helium). Why Elements Combine · Atoms combine to achieve full outer shells, making them stable: o When atoms are close to a full shell, they become increasingly reactive. § Such as when valence electrons are low (Sodium) or high (Chloride). o Noble gasses have no valence electrons so are extremely stable and nonreactive. Periodicity · The periodic table shows repeating patterns in properties like reactivity and atomic size, based on valence electrons. · Each period starts a new electron shell of valence electrons. ​ Element - A pure substance made up of only one type of atom, such as oxygen or gold. ​ Atom and atomic model - The smallest unit of matter that retains the properties of an element. Atomic Models are a  representation of the structure of an atom, including the nucleus and electron cloud. ​ Nucleus - The small, dense center of an atom containing protons and neutrons. ​ Proton - A positively charged particle found in the nucleus of an atom. ​ Neutron - A particle with no charge, located in the nucleus of an atom. ​ Electron cloud - The region around the nucleus where electrons are likely to be found. ​ Electron - A negatively charged particle that orbits the nucleus in the electron cloud. ​ Valence Electron - An electron in the outermost energy level of an atom, important for bonding and reactivity. ​ Energy Level - A specific region around the nucleus where electrons are found, representing different amounts of energy. ​ Periodic Table - A chart organizing all known elements by their properties, atomic number, and groups. ​ AZE Notation - A shorthand way to represent an atom, including its atomic number (Z), mass number (A), and element symbol (E). ​ Atomic Number - The number of protons in the nucleus of an atom, unique to each element. ​ Atomic Mass - The average mass of an element's atoms, including protons and neutrons. ​ Periods - The horizontal rows on the periodic table, showing elements with increasing atomic numbers. ​ Groups - The vertical columns on the periodic table, containing elements with similar properties and the same number of valence electrons.  ​ Isotope - Atoms of the same element with different numbers of neutrons, giving them different atomic masses. ​ Reactivity - How easily an element combines with other substances in a chemical reaction. WHAT TO STUDY Physical Properties ​ Distinguish properties of elements from compounds. ​ Distinguish properties of a pure substance from a mixture. ​ Identify elements from a list of common substances. ​ Describe the areas within an atom represented in an atomic model. ​ Explain why compounds have different properties than the elements it is made from. ​ Analyze particle diagrams for mixtures or elements. Subatomic Particles ​ Know the electric charge of a proton, neutron, or electron. ​ Identify a charged ion from a list with protons, neutrons, and electrons. ​ Recognize a mixture of elements and compounds from a particle diagram. ​ Predict the charges of particles (atoms) when electrons are transferred. ​ Identify the movement of electrons around the nucleus. ​ Identify the most modern atomic model. ​ Match atomic nuclei to specific elements. Periodic Table Trends ​ Identify which elements share characteristics in a group or period. ​ Explain why elements in the same group have similar properties. ​ Determine an atom’s reactivity based on valence electrons. ​ Predict the placement of elements based on atomic structure. ​ Identify the most reactive element in a group. ​ Analyze common properties of elements in the same group. Periodic Table Applications ​ Determine the unique characteristic of isotopes. ​ Determine the number of neutrons from AZE notation. ​ Classify elements based on malleability and conductivity. ​ Identify the most metallic element in a group based on trends in the periodic table. ​ Compare the reactivity of elements based on trends in the periodic table. ​ Recognize trends among elements in the same period.