TEAS 7 Chemistry: Physical Properties, States of Matter, and Water Question and answer 2023

TEAS 7 Chemistry: Physical Properties, States of Matter, and Water Question and answer 2023Kinetic Molecular Theory Theory that all matter is composed of particles (atoms and molecules) moving constantly in random directions. Molecule motion changes as is heat added or removed. What does the phase of a substance depend on? 1. Temperature 2. Pressure Mass Amount of matter in an object, the number of molecules Volume Amount of space occupied by a specific number of molecules 3 states of matter 1. Solid 2. Liquid 3. Gas Solid 1. Fixed shape and volume 2. High pressure 3. Low temperature 4. High atomic attraction Liquid 1. Fixed volume but changing shape (takes shape of container) 2. High pressure 3. Higher temperature 4. Weaker physical bonding Gas 1. Changing volume and shape 2. Low pressure 3. Higher temperature 4. Weaker atomic attraction Phase change Change from one state (solid or liquid or gas) to another without a change in chemical composition. Involves adding or removing heat. Exothermic reaction A reaction that releases energy in the form of heat Endothermic reaction A reaction that absorbs energy in the form of heat 2 external factors that affect matter state 1. Temperature 2. Pressure Vaporization Liquid -- Gas Spontaneous phase change Adding heat = endothermic reaction Evaporation Liquid -- Gas Phase transition Adding heat Happens at boiling point and depends on atmospheric pressure Condensation Gas -- Liquid Phase change Removing heat = exothermic reaction Freezing Liquid -- solid Phase change Removing heat = exothermic reaction Sublimation Solid -- gas Skips over liquid phase Phase change Adding heat = endothermic Sublimation = solid skips phase. Deposition Gas -- solid Phase change Removing heat = exothermic reaction Physical properties of matter Characteristics of matter that can be observed without changing the substance into something else: color, shape, hardness, mass, volume, density Most important for the TEAS Extensive physical properties Properties that do depend on the amount of matter present 1. Mass 2. Volume 3. Heat Capacity Intensive physical properties Properties that do not depend on the amount of matter present 1. Boiling Point 2. Melting Point 3. Density 4. Molarity Chemical properties of matter Characteristics of matter that can be observed when a substance interacts with another substance to change composition and identity. How a substance can change or not change based on interaction like burning and rusting Melting Solid -- Liquid Phase change Heat added = endothermic Melting point The temperature at which a solid becomes a liquid Boiling point The temperature at which a liquid changes to a gas (vapor). The boiling point of water at sea level is 100°C (212°F). Depends on pressure. Molecular motion The motion of atoms in an object Affected by the temperature Gasses have the most amount of molecular motion; solids have the least amount of molecular motion. Molecular motion increases as heat is added. Crystalline Solid A solid that is made up of crystals in which particles are arranged in a regular, repeating pattern Density Mass/volume "Mass divided by volume" How compact a substance is Memorize this formula for the TEAS. You might need to calculate the density in a question. Triple Point The temperature and pressure conditions at which the solid, liquid, and gaseous phases of a substance coexist at equilibrium Critical Point The point on a phase diagram at which the liquid and gas phases of a substance have the same density, and are therefore indistinguishable. Dependent on temperature and pressure for gas and liquid states of a substance to coexist. List the important general properties of water for the TEAS. 1. Water is tasteless, odorless, and colorless/transparent. 2. Water can dissolve almost any solid, liquid, or gas, earning it the term universal solvent. 3. Water's polar bonds create high surface tension and cohesion. List the important chemical properties of water. 1. Water has polar covalent bonds (oxygen has negative charge; hydrogen has positive charge). 2. Water has a neutral pH of 7. 3. Water has a high specific heat capacity and high heat of vaporization. 4. Water has a maximum density at 4 degrees Celsius, which is about 39 degrees Fahrenheit. 5. Water's triple point is near absolute zero (273.1 degrees K), where it exists as a solid, liquid, and a gas all at once. Why is water's high specific heat capacity important? Water changes temperature more slowly than the environment. Large amounts of heat can absorbed with little change to water's temperature. Specific Heat Capacity Amount of heat energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius Does water's boiling point change? Yes. Water's boiling point changes based on altitude. Why does ice float? Ice is less dense than liquid water. As water freezes, it expands, which increases its volume, so density decreases. (Water's maximum density is about about 39 degrees Fahrenheit.)