Chemistry Notes-Grade 9 PDF

**Chemistry Notes-Grade 9** **History of the Atom** **Democritus (460-370 BCE)** Idea: Proposed the concept of indivisible particles called \"atoms.\" Model: Suggested that atoms were solid, differed in shape and size, and were constantly moving. **John Dalton (1766-1844)** Idea: Developed th...

**Chemistry Notes-Grade 9** **History of the Atom** **Democritus (460-370 BCE)** Idea: Proposed the concept of indivisible particles called \"atoms.\" Model: Suggested that atoms were solid, differed in shape and size, and were constantly moving. **John Dalton (1766-1844)** Idea: Developed the first modern atomic theory. Model: Suggested that: Each element is composed of unique atoms. Atoms are indivisible and indestructible. Atoms of the same element are identical in mass and properties. Atoms of different elements combine in simple whole-number ratios to form compounds. **J.J. Thomson (1856-1940)** Discovery: Discovered the electron in 1897 using cathode ray tubes. Model: Proposed the \"plum pudding\" model, where electrons were scattered throughout a positively charged sphere. **Ernest Rutherford (1871-1937)** Discovery: Conducted the gold foil experiment in 1909 and discovered the nucleus. Model: Proposed the nuclear model, where most of the atom\'s mass and positive charge are concentrated in a small, dense nucleus, while electrons orbit the nucleus. **Niels Bohr (1885-1962)** Idea: Introduced the Bohr model in 1913. Model: Suggested that: Electrons orbit the nucleus in specific energy levels or shells. Electrons can only move between energy levels by emitting or absorbing energy. The Bohr model was a major step towards understanding atomic structure but was later replaced by the quantum mechanical model. **Physical and Chemical Properties** **Physical Properties: A physical property is a characteristic of a substance that can be observed without changing the substance into another substance.** Color Melting point Density Solubility **Chemical Properties:A chemical property is a characteristic of a substance that goes a under a change to another substance** Reactivity with acids Flammability Oxidation states Stability **Physical and Chemical Changes** **Physical Change** **Does not alter the chemical composition or identity of the substance, only the form.** Melting ice (change in state or phase) Freezing Kool-aid Tearing paper Boiling water (change in state or phase) Stretching silly putty Making a mixture (ex. Sugar water) Unmixing a mixture (ex. sorting) **Chemical Change\ Does alter the chemical composition or identity of a substance and makes new substances.** Burning paper Digesting food Rotting Iron reacting with oxygen gas Odour Change Color change Temperature change Light produced A chemical change is also called a chemical reaction. **Groups and Periods on the Periodic Table** **Alkali Metals:** **Located in Group 1.** Highly reactive, especially with water. Examples: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb). **Alkaline Earth Metals:** **Group 2.** Reactive, but less so than alkali metals. Examples: Beryllium (Be), Magnesium (Mg), Calcium (Ca), Barium (Ba) **Halogens:** **Group 17.** Very reactive nonmetals. Examples: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I). **Noble Gases:** **Group 18.** Inert and non-reactive due to full valence shells. Examples: Helium (He), Neon (Ne), Argon (Ar), Xenon (Xe). **Transition Metals:** **Groups 3-12.** Often form colorful compounds and are good conductors. Examples: Iron (Fe), Copper (Cu), Gold (Au), Silver (Ag). **Metalloids** **Groups 13-16 (excluding boron).Staircase** **Characteristics:** Appearance: Can have a metallic or nonmetallic luster. Conductivity: Intermediate between metals and nonmetals. Examples: Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Polonium (Po) **Nonmetals** Groups 14-17 (excluding noble gases). Characteristics: Appearance: Dull, brittle, and non-conductive. Reactivity: Can be highly reactive or inert. Examples: Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), Fluorine (F), Chlorine (Cl), Phosphorus (P), Sulfur (S), Selenium (Se), Bromine (Br), Iodine (I), Xenon (Xe) **Ions and Isotopes** **Ions** Definition: An ion is an atom that has gained or lost electrons, resulting in a net electric charge. Types: Cations: Positively charged ions (lost electrons). Anions: Negatively charged ions (gained electrons). Naming: Cations: Add \"ion\" to the element name (e.g., sodium ion). Anions: Change the ending to \"ide\" (e.g., chloride ion). Example: Sodium atom (Na) loses one electron to become a sodium ion (Na+). **Isotopes** Definition: Isotopes are atoms of the same element with different numbers of neutrons in their nuclei. Properties: Same atomic number (number of protons) but different atomic mass (number of protons + neutrons). Some isotopes are radioactive, while others are stable. Example: Carbon-12, Carbon-13, and Carbon-14 are isotopes of carbon. They have 6 protons each, but Carbon-12 has 6 neutrons, Carbon-13 has 7 neutrons, and Carbon-14 has 8 neutrons. **Atoms, Molecules, and Compounds** Atoms: Basic units of matter, consisting of protons, neutrons, and electrons. Molecules: Two or more atoms bonded together, can be the same or different elements Compounds: Substances formed when two or more different elements chemically bond **Bohr-Rutherford Diagram** Nucleus: Center of the atom containing protons (positive charge) and neutrons (neutral). Electron Shells: Electrons (negative charge) orbit the nucleus in defined energy levels. Shell capacity: 1st shell holds 2, 2nd shell holds 8, 3rd shell holds 8, 4th shell holds 2. Nucleus at the center. Big circles representing electron shells. Dots or small circles indicating electrons in their shells. HHPS SAFETY  Definitions Physical properties: A **physical property** is a characteristic of a substance that can be observed without changing the substance Examples: Color, Hardness, Odor, Taste, State of matter, Texture, Luster, Flexibility, Heat conductivity, Solubility, Shape, Viscosity, Ductility, Malleability, and Density. Chemical Properties: any of the properties of matter that can be observed and measured only by performing a chemical change or chemical reaction. Examples:flammability, toxicity, solubility, heat from combustion, Physical Changes: **[Does not]** alter the chemical composition or identity of the substance, **only the form**. Or state. Examples Chemical Changes [Does] alter the chemical composition or identity of a substance and **makes new substances**. - Burning paper - Digesting food - Rotting - Iron reacting with oxygen gas - A chemical change is also called a *chemical reaction.* Examples: The cut apple turns brown, Marshmallow being toasted on a campfire. State Of Matter: a way to describe the behavior of atoms and molecules in a substance. Matter: Anything that has mass and takes up space for example; Air, Water, Paper, and Dog. Flammability: How quickly something burns and lights on fire. Reactivity: the state or power of being [reactive](https://www.google.com/search?client=opera-gx&hs=caY&sca_esv=a705397e3bbcc753&q=reactive&si=ACC90nx67Z8g0WkBmnrPB4IqtqGvHqRIHWa39hXB_IvRLAub-gC98Ayk-kRLG7AS1WTH5b1AbgacWnx3sXfVb5bgMZOQQ4ah5zYYBaWjYKeq7oFj_EceTNY%3D&expnd=1&sa=X&ved=2ahUKEwjG95zew5qJAxWNEDQIHSUBEsMQyecJegQIHBAO). Decomposition: the state or process of rotting; decay. Combustion: a chemical process in which a substance reacts rapidly with oxygen and gives off heat. Examples are burning any type of candle or wood to heat your home, and cars burn petrol to run. Combustibility: Ability to burn and light on fire. Corrosion:the degradation of a metal due to a reaction with its environment. Examples; rusting of iron, tarnishing of silver, and the appearance of green colour in copper. Ductility: the quality of being pliable and flexible, like a piece of metal that can be bent into a thin wire. Texture:the feel, appearance, or consistency of a surface or substance. Example is this feels very rough. Luster: the state or quality of shining by reflecting light; glitter, sparkle, sheen, or gloss: Odour: a distinctive smell, especially an [unpleasant](https://www.google.com/search?client=opera-gx&sca_esv=a705397e3bbcc753&q=unpleasant&si=ACC90nz-2feRzoY4yuySkO-aQE81nU0V4XU8iyHCMD_RYA0aK5uHwxD6D_yFXsobX0YI9DRV3Qlmr5UDrd6E42HYo9LfvTTd7mGCOfiCgRg_hGQ0ReVR9yg%3D&expnd=1&sa=X&ved=2ahUKEwixxrCDxpqJAxVfHzQIHSHdOoEQyecJegQIMxAO) one. For example, the odor of that cigarette is terrible. Inert: lacking the power to move. 2. : very slow to move or act. Malleability: the quality of something that can be shaped into something else without breaking, example when someone shapes iron into something else without breaking it. Conductivity: the property of allowing heat or electricity to go through something, Density: the relationship between the mass of the substance and how much space it takes up (volume). Solubility: degree to which a substance dissolves in a solvent to make a solution Viscosity: a measure of a fluid\'s resistance to flow.