RISE Science Grade 7 cheat sheet

The net force is the single combined result of all forces on an object: forces in the same direction add, forces in opposite directions subtract.

Balanced forces are equal in size and opposite in direction; they change neither the speed nor the direction of motion. Unbalanced forces cause acceleration.

Newton's second law: net force = mass × acceleration (F = m × a), with force in newtons, mass in kilograms, and acceleration in m/s².

Newton's third law: for every action force there is an equal and opposite reaction force, and the two act on different objects so they never cancel each other.

Gravity is a noncontact force: near Earth's surface all falling objects accelerate downward at about 9.8 m/s² when air resistance is ignored, regardless of mass.

Mass is the amount of matter (kilograms); weight is the gravitational force on that mass (newtons), calculated as weight = mass × 9.8 N/kg.

Friction is a contact force opposing motion between touching surfaces; it converts motion energy into thermal energy and slows objects.

Speed = distance ÷ time; acceleration = change in velocity ÷ time, and velocity differs from speed because it includes direction.

Like magnetic poles and like electric charges repel each other; opposite poles and opposite charges attract, both acting at a distance without contact.

Earth's interior, from outside in: thin rocky crust, hot slowly flowing mantle, liquid outer core of metal, solid inner core; temperature and pressure rise with depth.

Plate tectonics: the rigid lithosphere is broken into plates that ride on the hotter, slowly flowing asthenosphere, driven by convection in the mantle.

Divergent boundary (plates separate): magma rises, forming mid-ocean ridges and new seafloor, or a rift valley where plates split on land.

Convergent boundary (plates collide): a denser oceanic plate subducts, producing deep ocean trenches, volcanic mountain chains, and earthquakes.

Transform boundary (plates slide past each other): crust is neither created nor destroyed, and grinding motion produces faults and earthquakes.

Earthquake terms: the focus is the underground origin of the rupture; the epicenter is the surface point directly above it, where shaking is usually strongest.

Law of superposition: in undisturbed sedimentary layers the oldest rock is at the bottom and the youngest at the top.

Index fossils come from species that were widespread and existed only briefly, so they identify and match rock layers across regions.

Weathering breaks rock apart, erosion carries the sediment away, and deposition drops it, building new landforms and sedimentary rock; these present-day processes, acting over long spans, explain Earth's 4.6-billion-year history.

Cell theory: all living things are made of one or more cells, the cell is the basic unit of structure and function, and new cells arise from existing cells.

Cell membrane controls what enters and leaves the cell; nucleus holds DNA and directs activities; mitochondria release energy from food through cellular respiration.

Plant cells have a cell wall for support, chloroplasts for photosynthesis, and a large central vacuole; animal cells lack cell walls and chloroplasts.

Photosynthesis occurs in chloroplasts: sunlight + water + carbon dioxide → sugar + oxygen; cellular respiration releases the sugar's energy for the cell.

Levels of organization in multicellular organisms: cell → tissue → organ → organ system → organism.

Organ systems have specialized jobs: circulatory transports materials, respiratory exchanges gases, digestive breaks down food, nervous carries signals, skeletal supports and protects.

Structure matches function: root hairs and intestinal villi increase surface area for absorption; flat disc-shaped red blood cells carry oxygen efficiently.

Homeostasis keeps internal conditions such as temperature, water balance, and blood sugar steady when the environment changes.

In single-celled organisms, one cell performs every life function, so the organelles act as the organism's complete body systems.