Science & Engineering Comparisons

AC Current vs DC Current Alternating current reverses direction periodically and powers electrical grids; Direct current flows in one direction and powers batteries and electronics. Mitosis vs Meiosis Mitosis produces two genetically identical diploid daughter cells for growth and repair; Meiosis produces four genetically unique haploid cells for sexual reproduction. DNA vs RNA DNA is double-stranded deoxyribose that stores genetic information long-term; RNA is single-stranded ribose that helps express and transport that information. Speed vs Velocity Speed is a scalar quantity measuring how fast something moves; Velocity is a vector quantity that includes both magnitude and direction. Atom vs Molecule An atom is the smallest unit of a chemical element retaining its properties; A molecule is two or more atoms chemically bonded together. Convection vs Conduction Convection transfers heat through bulk fluid movement (liquids/gases); Conduction transfers heat through direct molecular contact in solids. Genotype vs Phenotype Genotype is the inherited genetic code; phenotype is what you can actually observe — the result of those genes interacting with the environment. Fahrenheit vs Celsius Two scales for the same temperature, with different reference points and a quick mental shortcut to convert. Acid vs Base Acids donate hydrogen ions and have pH below 7; bases accept hydrogen ions and have pH above 7. Alligator vs Crocodile Alligators have wide U-shaped snouts and live in freshwater; Crocodiles have narrow V-shaped snouts and tolerate saltwater. Cell Membrane vs Cell Wall Every cell has a flexible membrane controlling what enters and leaves; only plants, fungi, bacteria and some others have a rigid wall outside it. Climate Change vs Global Warming Global warming: rise in Earth's temperature; Climate change: broader shifts in temperature, precipitation, weather patterns. Comet vs Asteroid Comets are icy bodies with tails when near the Sun; asteroids are rocky or metallic bodies. Conduction vs Convection vs Radiation Conduction moves heat by direct contact, convection by the flow of a liquid or gas, and radiation by electromagnetic waves that can cross a vacuum. Solar Eclipse vs Lunar Eclipse A solar eclipse is the Moon blocking the Sun from your view; a lunar eclipse is the Earth blocking sunlight from reaching the Moon. Element vs Compound An element is a pure substance made of one type of atom; A compound is a substance made of two or more elements chemically bonded. Force vs Pressure Force is a push or pull; pressure is force spread over an area. Heat vs Temperature Heat is thermal energy transferred because of a temperature difference, measured in joules; temperature measures the average kinetic energy of particles, measured in °C, °F or kelvin. Homogeneous Mixture vs Heterogeneous Mixture A homogeneous mixture has the same composition throughout (salt water, air); a heterogeneous mixture has visibly different parts (sand and water, salad). Hurricane vs Typhoon vs Cyclone Hurricanes, typhoons and cyclones are the same kind of storm — a strong tropical cyclone — named differently by ocean basin. Hypothesis vs Theory A hypothesis is a testable prediction or proposed explanation for a specific observation; a scientific theory is a broad explanation supported by extensive, repeatedly tested evidence. Igneous vs Sedimentary vs Metamorphic Igneous rock forms from cooled magma; sedimentary from deposited and compacted layers; metamorphic from heat and pressure transforming existing rock. Indica vs Sativa Indica strains: shorter, bushier plants with sedating effects; Sativa: taller with energizing effects. Kinetic Energy vs Potential Energy Kinetic energy is the energy of motion; potential energy is stored energy due to position or configuration. Latitude vs Longitude Latitude lines run east-west and measure north-south position; longitude lines run north-south and measure east-west position. Magma vs Lava Magma is molten rock below Earth's surface; lava is magma that has erupted onto the surface. Mass vs Weight Mass is the amount of matter (constant); Weight is gravitational force on mass (varies by location). Mixture vs Compound A mixture combines substances physically and can be separated by physical means; a compound bonds elements chemically in a fixed ratio. Molecule vs Compound A molecule is two or more atoms held together by covalent bonds; a compound is a substance made of two or more different elements in a fixed ratio. Ocean vs Sea An ocean is a vast open body of saltwater covering major portions of the globe; A sea is a smaller body of saltwater partially enclosed by land. Organic vs Inorganic In chemistry, organic compounds contain carbon-hydrogen bonds; inorganic compounds usually don't. Photosynthesis vs Cellular Respiration Photosynthesis turns light, water, and CO2 into sugar and oxygen. Physical Change vs Chemical Change A physical change alters form or appearance without creating new substances; A chemical change produces entirely new substances with different properties. Plant Cell vs Animal Cell Plant cells have a rigid cell wall, chloroplasts, and large central vacuole; Animal cells lack these but have centrioles and irregular shapes. Prokaryote vs Eukaryote Prokaryotes are simple cells without a membrane-bound nucleus (bacteria, archaea); Eukaryotes have a defined nucleus and complex organelles (animals, plants, fungi). Series vs Parallel Circuits In a series circuit, components share one path; current is the same everywhere, voltage divides. Tornado vs Hurricane A tornado is a narrow rotating column of air over land lasting minutes; a hurricane is a huge tropical storm over warm ocean lasting days. Tornado Watch vs Tornado Warning A tornado watch means conditions are favorable for tornadoes over a large area in the next several hours — be prepared. Virus vs Bacteria Viruses are non-living particles needing a host; Bacteria are single-celled living organisms. Voltage vs Current Voltage is the electrical pressure pushing charges; current is the flow rate of charge. Weather vs Climate Weather is short-term atmospheric condition; Climate is long-term average of weather patterns over decades. Weathering vs Erosion Weathering breaks rock down where it sits; erosion picks up the pieces and moves them away by water, wind, ice or gravity. Work vs Power Work is force times distance — the energy transferred.