7th Grade Science Cheat Sheet PDF

# Elements and Compounds - Elements - One capital letter - Substance made entirely of one type of atom - Examples: - Cl, H, N, O - Al, Be, Ne - Compounds: - Two or more capital letters - Two or more elements chemically bonded - Examples: - H2O...

# Elements and Compounds - Elements - One capital letter - Substance made entirely of one type of atom - Examples: - Cl, H, N, O - Al, Be, Ne - Compounds: - Two or more capital letters - Two or more elements chemically bonded - Examples: - H2O - NaCl - C6H12O6 - NH3 # Chemical Symbols and Formula - Chemical Symbol - A notation of one or two letters representing a chemical element - Examples: - H = Hydrogen - Mg = Magnesium - Ca = Calcium - S = Sulfur - Chemical formula - Tells us the number of atoms in each compound or molecule - Examples: - H2O = water - NaCl = salt - C6H12O6 = glucose - NH3 = ammonia # Physical and Chemical Changes - Physical Change - Can be reversed - No new substance - State of matter change - Shape change - Size change - Dissolving salt/sugar - Examples: Cutting hair, ice melting - Chemical Change - Cannot be reversed - New substance - Gas bubbles - Color change - Temperature change - Light appears - Smell - Precipitate forms - Examples: Fireworks, rusty bike # Aqueous Solutions - Solute: - The substance that is dissolved in a solution. - Examples: Salt in water, sugar in Kool-Aid. - Solvent: - The substance that dissolves the solute. - Examples: Water in coffee, or Kool-Aid. - Concentration: - The amount of solute dissolved in a certain amount of solvent (More solute = higher concentration) - Dilution: - Reduces the concentration of a solution by adding more solvent (More solvent = less concentration). **Diagram of Diluted and Concentrated Solutions:** - A drawing shows a container with a small amount of solute and a large amount of solvent. It is labeled "Diluted". - A drawing shows a container with a large amount of solute and a small amount of solvent. It is labeled "Concentrated". # Rate of Dissolution - Measures how fast a solute dissolves in a solvent. - Stirring a solute into a solvent speeds up the dissolution and is called "agitation". - The temperature of the solvent affects how fast a solute dissolves. A solute dissolves faster in a warmer solvent than a cooler solvent. - The size of the solute particles affects the rate of dissolution. The greater the surface area, the more contact between particles. For example, granulated sugar will dissolve more quickly than a sugar cube. # Calculating Distance, Speed, and Time - D = Distance - S = Speed - T = Time - D = S x T - S = D ÷ T - T = D ÷ S # Speed vs. Velocity vs. Displacement - **Speed:** How fast something is moving. - **Velocity:** How fast something is moving and direction. - **Displacement:** The distance from start to end. # Balanced vs. Unbalanced Forces - **Balanced Forces:** - Net force is 0 - Equal force causes no change in motion. - **Unbalanced Forces:** - Net force is greater than 0 - Unequal force causes a change in motion. # Thermal Energy Transfer - **Conduction:** Direct contact (touch) - **Convection:** Circulating air of water - **Radiation:** Feel through empty space. # Heat Transfer - When something is hot, it will transfer its heat to something colder until it reaches equilibrium. # Kinetic Energy and Temperature - **Hot:** Molecules move fast. - **Cold:** Molecules do not move. # Solar System Physical Properties, Locations, and Movements - **Comet:** - Physical Properties: Ice, dust, and rock. - Location: Around the Sun - Movement: Long, narrow ellipse around the Sun. - **Galilean Moons:** - Physical Properties: Io, Europa, Ganymede, and Callisto - Location: Jupiter - Movement: Revolves around Jupiter - **Kuiper Belt:** - Physical Properties: Small icy bodies, comets, asteroids, frozen objects - Location: Beyond the orbit of Neptune - Movement: Orbits the Sun - **Meteors:** - Physical Properties: Rock/dust - Location: Earth's atmosphere - Movement: Streak of light in the sky - **Asteroids:** - Physical Properties: Rock, minerals, elements, gas - Location: Between Mars and Jupiter in the asteroid belt - Movement: Revolves around the Sun - **Oort Cloud:** - Physical Properties: Trillions of icy objects. - Location: Surrounds the solar system in a spherical shell - Movement: Highly elliptical and random orbit - **Moons:** - Physical Properties: Rock/dust - Location: Orbit around planets - Movement: Revolves around the Sun - **Sun:** - Physical Properties: Massive, hydrogen and helium. - Location: Milky Way galaxy - Movement: Orbits around the Milky Way # Gravity - The force that governs the motion of our solar system. - Gravity is the force of attraction between two objects. # Earth's Perfect Distance from the Sun - Earth is at the perfect distance from the Sun. - If we were closer we would burn up. - If we were farther, we would freeze. - We have water on Earth. - Earth's atmosphere protects us from the Sun.