Science 9 Chemistry Notes - Investigating Matter PDF

# Science 9: Chemistry ## Investigating Matter - **Matter:** Anything that has mass and volume. - **Mass:** Is the amount of matter in a substance or object. Measured in grams or kilograms. - **Volume:** Is the space that a substance or object occupies. Measured in liters or milliliters....

# Science 9: Chemistry ## Investigating Matter - **Matter:** Anything that has mass and volume. - **Mass:** Is the amount of matter in a substance or object. Measured in grams or kilograms. - **Volume:** Is the space that a substance or object occupies. Measured in liters or milliliters. - **Properties of Matter:** Matter can be described by physical or chemical properties: - **Physical Properties:** Can be observed or measured without changing the chemical identity of the substance (examples: color, texture, state of matter, melting point, boiling point, hardness, solubility). - **Chemical Properties:** Describe the ability of matter to react with another substance to form new substances (examples: combustibility, reactivity with acids, reactivity with oxygen, lack of reactivity). ## Changes in Matter - **Chemical Change:** A change in matter that occurs when substances react to form new substances. Examples: fireworks, explosions, ice packs. - **Physical Change:** There may be a change in the appearance of a substance, but no new substances are formed. Examples: ice melting into water (change of state). ## States of Matter - **Solid:** Holds a definite shape and volume. Examples: sugar, chair, pencil. - **Liquid:** Has a definite volume but takes the shape of its container. Examples: juice. - **Gas:** Volume and shape determined by its surroundings. Examples: air in balloons. ## The Particle Model of Matter - Describes the arrangement of matter. - All matter is made of particles. - There are spaces between the particles. - Gas particles have more space than liquid particles. - Liquid particles have more space than solid particles. - Particles are constantly moving. - Particles are attracted to each other. The strength of attraction depends on the type of particle. ## The Kinetic Molecular Theory - Describes what happens to matter when the temperature of the particles change. - **Kinetic Energy:** The energy of motion. - **Main Points of the KMT:** - Matter is made of particles. - There is space between particles. - Particles are constantly moving. - Solid particles are packed together and cannot move freely. - Liquid particles can slide past each other. - Gas particles are far apart and move around freely. - Energy makes particles move. ## Investigating Matter - Part 2 - **Solid:** Particles are closely packed together, fixed in position. - **Liquid:** Particles are still close but, can slide past one another. - **Gas:** Particles are highly energetic and move freely. - **Pure Substance:** Made up of one type of particle. They cannot be separated into simpler substances by any physical means. Examples: Gold, water, oxygen, salt. - Can be either an **element** (cannot be broken down into simpler substances) or a **compound** (made up of two or more elements chemically combined). - **Examples:** Gold, H$_2$O. ## Classifying Matter - Matter can be classified into two categories: **pure substances** and **mixtures**. - **Mixture:** Made up of two or more pure substances that can be separated by physical means. - **Heterogeneous mixture:** Mixtures where components can be easily distinguished. Examples: sand and water, salad. - **Homogeneous mixture:** Components are evenly distributed and cannot be easily distinguished. Example: salt dissolved in water, air. ## Making Molecules - **Atom:** The smallest unit of an element (e.g., oxygen, carbon). - **Molecule:** Two or more atoms chemically bonded together. - **How to make molecules:** - Get two different colored pencils and colors a set of circles one color, then another set a different color. - Each circle represents an atom. - Place the atoms together to form a molecule of at least three larger particles that are exactly the same. - What kind of substance resulted: element or compound? Explain why. ## Physical and Chemical Changes - **All chemical reactions involve some sort of change.** - **Chemical Changes:** Changes that produce entirely new substances. Occur when chemical bonds are broken and formed.. - *Evidence of a chemical change:* - Formation of gas. - Change in color. - Change in temperature. - Production of a precipitate. - Release of light or sound. - **Physical Changes:** Changes where only the appearance of the substance changes, no new substances are formed. - Example: When ice melts into water, it is a change of state. There is no new substance. - Examples: changes in state, dissolving sugar or salt in water. ## Reactants and Products - **Reactants:** Substances that react in a chemical change. - **Products:** Substances that are formed as a result of a chemical change. ## Energy Changes - **Energy Change:** Occurs during physical and chemical changes. - Energy can be transferred between the system and its surroundings. - **Exothermic Reaction:** A chemical reaction that releases heat or light. - *Examples:* Burning wood, combustion of fuels. - **Endothermic Reaction:** A chemical reaction that absorbs heat or light. - *Examples:* Melting ice cubes, cooking an egg. # Chemical Elements - **Chemistry:** The study of matter and its changes. - **Element:** A pure substance that cannot be broken down into simpler substances. - **Atomic Symbol:** A one or two letter abbreviation for an element. The first letter is always capitalized, the second letter is lowercase. Examples: H (hydrogen), O (oxygen), C (carbon). - **Importance of Elements:** - Each element is made of a specific type of atom. - By studying elements, we can learn more about the composition of matter. ## Organizing the Periodic Table - **Periodic Table:** A table that organizes all the known elements. Elements with similar properties are grouped together. - **Groups:** Vertical columns on the periodic table. - **Periods:** Horizontal rows on the periodic table. - **Key Groups to Know:** - **Group 1 (Alkali Metals):** Highly reactive metals that readily form ionic bonds. Examples: lithium (Li), sodium (Na), potassium (K). - **Group 2 (Alkaline Earth Metals):** Reactive metals that also readily form ionic bonds. Examples: beryllium (Be), magnesium (Mg), calcium (Ca). - **Group 17 (Halogens):** Non-metals that easily gain electrons. Examples: fluorine (F), chlorine (Cl), bromine (Br). - **Group 18 (Noble Gases):** Highly unreactive non-metals. They have full outer shells and do not readily form bonds. Examples: helium (He), neon (Ne), argon (Ar). ## Properties of Metals and Non-Metals - **Metals:** Typically shiny, solid, malleable, ductile, good conductors of heat and electricity. Examples: Iron, gold, copper. - **Non-Metals:** Non-shiny, often brittle, poor conductors of heat and electricity. Examples: Sulfur, carbon. - **Metalloids:** Have properties intermediate between metals and non-metals. Located in a zig-zag line on the periodic table. Examples: Silicon, germanium. - **Chemical Families:** Groups of elements on the periodic table that exhibit similar chemical properties because they have the same number of valence electrons in their outer shell. # Atomic Structure of Elements - **Atom:** The smallest particle of an element that retains the chemical properties of the element. - **Subatomic Particles:** Particles that make up an atom. - **Protons:** Positively charged particles found in the nucleus. - **Neutrons:** Neutral particles found in the nucleus. - **Electrons:** Negatively charged particles that orbit the nucleus in energy levels called "shells." - *The number of protons determines the atomic number of an element.* - **Mass Number:** The total number of protons and neutrons in the nucleus. The mass number is approximately equal to the atomic mass. - **Atomic Number:** The number of protons in an atom. - **Nuclear Charge:** The charge of the nucleus due to the number of protons. # Bohr Diagrams - **Niels Bohr** proposed a model of the atom that depicts electrons orbiting the nucleus in specific energy levels. - **Electron Shells:** Energy levels that electrons occupy around the nucleus. - **Bohr Diagrams:** Diagrams used to represent the arrangement of electrons in shells. - Rules to follow: The first shell holds up to two electrons, the second shell up to eight, the third up to 18. ## Trends on the Periodic Table - **Atomic Size:** The radius of an atom. - **Down a Group (Column):** As atomic size increases, the atomic radius increases. - **Across a Period (Row):** As you move from left to right across a period, the atomic radius decreases. - **Electronegativity:** - **Down a Group (Column):** Electronegativity decreases. - **Across a Period (Row):** Electronegativity increases. - **Ionization Energy:** The amount of energy it takes to remove an electron from an atom. - **Down a Group (Column):** Ionization energy decreases. - **Across a Period (Row):** Ionization energy increases. ## Making Ions from Atoms - **Ion:** An atom that has gained or lost electrons. - **Cation:** A positive ion (formed when an atom loses electrons). - **Anion:** A negative ion (formed when an atom gains electrons). - **Ionic Bonds:** Attractive forces between oppositely charged ions caused by the transfer of electrons. - **Rules for Forming Ions:** - **Metals:** Tend to lose electrons to form cations. - **Non-Metals:** Tend to gain electrons to form anions. - **Noble Gases:** Have a full outer shell and typically do not form ions. ## Bohr Diagrams of Atoms and Ions - **Bohr Diagrams:** A simple model used to represent the arrangement of electrons in atoms and ions. - **Electrons in ions:** The number of electrons in an ion is different from the number of electrons in a neutral atom. - **Cations:** Have fewer electrons than protons. - **Anions:** Have more electrons than protons. - **Note:** Sodium (Na) readily loses one electron to form a positive ion (Na$^+$ ). Oxygen (O) readily gains two electrons to form a negative ion (O$^{2-}$ ). - **Valence Shell:** The outermost shell of an atom or ion. Ions will attempt to achieve the same valence shell electron configuration as the nearest noble gas. - **To find the overall charge of an ion:** Subtract the number of electrons from the number of protons. ## Summary Table of Subatomic Particles | Name | Symbol | Mass | Charge | Location | |--------------|--------|------------|-----------|-----------------------| | Proton | p$^+$ | 1 amu | +1 | Nucleus | | Neutron | n$^0$ | 1 amu | 0 | Nucleus | | Electron | e$^-$ | Negligible | -1 | Energy Levels/Shells | .