Mix and Flow of Matter (Fluids and Density)
What is a fluid?
Any substance that flows, including liquids and gases.
What is a cell?
The basic unit of life; the smallest living part of an organism.
What is the law of reflection?
The angle of incidence equals the angle of reflection.
What is a simple machine?
A device with few or no moving parts that makes work easier by changing the size or direction of a force.
What percentage of Earth's water is fresh water?
About 3% (or 2.5-3%)
What is the formula for calculating density?
Density = Mass ÷ Volume (D = m/V)
What is the difference between a plant cell and an animal cell? Name two differences.
Plant cells have cell walls, chloroplasts, and large central vacuoles; animal cells don't have these structures (any two differences).
What is the difference between transparent, translucent, and opaque?
Transparent allows light through clearly; translucent allows some light but not clear images; opaque blocks all light.
Name the six types of simple machines.
Lever, wheel and axle, pulley, inclined plane, wedge, and screw.
What is the water cycle? Name the three main processes.
The continuous movement of water on Earth. Processes: evaporation, condensation, and precipitation.
Explain why a steel ship floats even though steel is denser than water.
The ship's hollow shape displaces a large volume of water, and the overall density of the ship (including air inside) is less than water.
What is the function of the mitochondria?
The powerhouse of the cell; produces energy (ATP) through cellular respiration.
What causes refraction?
Light bends when it travels from one medium to another because it changes speed.
What is mechanical advantage and how do you calculate it?
The amount a machine multiplies force. MA = Output Force ÷ Input Force (or MA = Input Distance ÷ Output Distance).
What is a watershed (drainage basin)?
An area of land where all water drains into a common body of water (river, lake, or ocean).
What is viscosity and give examples of high and low viscosity fluids?
Viscosity is a fluid's resistance to flow (thickness). High: honey, molasses, ketchup; Low: water, alcohol, gasoline (one example each)
Explain the difference between diffusion and osmosis.
Diffusion is movement of particles from high to low concentration; osmosis is specifically the diffusion of water through a semi-permeable membrane.
How does a convex lens differ from a concave lens?
Convex lenses are thicker in the middle and converge (focus) light rays; concave lenses are thinner in the middle and diverge (spread out) light rays.
Identify the three classes of levers and give one example of each.
First class: fulcrum in middle (seesaw, scissors); Second class: load in middle (wheelbarrow, nutcracker); Third class: effort in middle (tweezers, fishing rod).
Explain how ocean currents affect climate.
Warm currents carry heat from the equator toward poles, warming coastal areas; cold currents bring cool water from poles toward the equator, cooling coastal regions.
Explain how a hydraulic system works and why it provides a mechanical advantage.
Pressure applied to a fluid in a closed system transmits equally throughout; a small force on a small piston creates a larger force on a larger piston (Pascal's Law).
Describe the levels of organization in living things from smallest to largest.
Cell → Tissue → Organ → Organ System → Organism
Explain how your eye focuses light to create an image.
Light enters through the cornea, passes through the pupil, the lens focuses it by changing shape, and an inverted image forms on the retina; the brain interprets it right-side up.
Explain why no machine can be 100% efficient.
Some energy is always lost to friction, heat, sound, or other forms; output work is always less than input work in real machines.
What is the difference between point-source and non-point-source pollution? Give an example of each.
Point-source comes from a single, identifiable source (factory pipe, sewage outlet); non-point-source comes from many scattered sources (agricultural runoff, street runoff).