Saga Public High School Entrance Examination - Science flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Newton's Second Law

The acceleration of an object equals the net force acting on it divided by its mass (a = F/m). Doubling the force doubles the acceleration; doubling the mass halves it.

Conservation of Energy

Energy cannot be created or destroyed, only transferred or transformed between forms. In a closed system the total energy stays constant, though friction may convert useful energy into heat.

Ohm's Law

For a conductor at constant temperature, current is directly proportional to voltage and inversely proportional to resistance, written V = IR. Doubling the voltage doubles the current.

Wave Speed Equation

Wave speed equals frequency multiplied by wavelength (v = fλ). When a wave crosses into a new medium, its speed and wavelength change but its frequency remains fixed.

Mechanical Advantage

The ratio of load force to effort force in a simple machine. A lever balances when effort times effort arm equals load times load arm, allowing a small force to lift a larger load.

Element Versus Compound

An element contains only one kind of atom and cannot be split chemically. A compound contains two or more elements chemically combined in fixed proportions, such as water or carbon dioxide.

Ion Formation

An ion is formed when an atom gains or loses electrons. Losing electrons gives a positive ion (cation); gaining electrons gives a negative ion (anion). Proton number never changes.

Neutralisation Reaction

A reaction between an acid and a base that produces a salt and water. Hydrogen ions from the acid combine with hydroxide ions from the alkali, moving the pH towards neutral.

Balancing Chemical Equations

Adjusting coefficients so each element has equal atom counts on both sides of the arrow. This reflects conservation of mass; subscripts inside formulas must never be changed to balance.

pH Scale

A scale from 0 to 14 measuring acidity. Values below 7 are acidic, 7 is neutral, and above 7 is alkaline. Each unit step represents a tenfold change in hydrogen ion concentration.

Reaction Rate Factors

Reactions speed up with higher temperature, higher concentration, greater surface area, or a catalyst. These increase the frequency of successful collisions between reacting particles.

Plant Versus Animal Cells

Plant cells have a cellulose cell wall, chloroplasts, and a large permanent vacuole. Animal cells lack these but both cell types share a nucleus, cytoplasm, and cell membrane.

Photosynthesis Equation

Carbon dioxide plus water, using light energy absorbed by chlorophyll, produces glucose and oxygen. It occurs in chloroplasts and stores energy in chemical bonds of glucose.

Mitosis Versus Meiosis

Mitosis produces two genetically identical cells for growth and repair. Meiosis produces four gametes with half the chromosome number, so fertilisation restores the normal diploid number.

Dominant and Recessive Alleles

A dominant allele is expressed when at least one copy is present. A recessive allele is expressed only when two copies are present, so recessive traits can skip generations.

Natural Selection

Individuals with inherited variations better suited to their environment survive and reproduce more successfully. Over many generations, the alleles for those advantageous traits become more common in the population.

Energy in Food Chains

Energy flows from producers to consumers along a food chain, with only about ten percent transferred to the next level. The rest is lost mainly as heat through respiration.

Aerobic Respiration

Glucose reacts with oxygen to release energy, producing carbon dioxide and water. It yields far more energy per glucose molecule than anaerobic respiration and occurs mainly in mitochondria.

Day, Night, and Seasons

Earth's rotation on its tilted axis causes day and night. Its yearly orbit around the Sun, combined with the tilt, changes the angle and duration of sunlight, producing the seasons.

Moon Phases

The changing shape of the illuminated part of the Moon seen from Earth. Phases result from the changing angle between Earth, Moon, and Sun over a roughly 28-day cycle.

Three Rock Types

Igneous rock forms from cooled magma or lava, sedimentary rock from compacted sediment layers, and metamorphic rock from heat and pressure acting on existing rock.

Weather Versus Climate

Weather is the short-term condition of the atmosphere at a place, such as today's rain. Climate is the long-term average pattern of weather over many years.

Air Pressure and Wind

Air pressure decreases with altitude. Wind blows from high-pressure regions to low-pressure regions, and the greater the pressure difference between them, the stronger the wind.

Earth's Layers

Earth has a solid inner core, a liquid outer core, a rocky mantle, and a thin crust. Convection in the mantle drives the movement of tectonic plates on the surface.

Speed and Velocity

Speed is distance travelled per unit time, a scalar quantity. Velocity is speed in a stated direction, so a car going round a bend at constant speed still changes velocity.

Work and Power

Work equals force multiplied by distance moved along the force's direction. Power is work done per second, measured in watts, so a more powerful machine does the same work faster.

Kinetic and Potential Energy

Kinetic energy is ½mv², depending on mass and speed. Gravitational potential energy is mgh, depending on mass, height, and gravity. Falling objects convert potential energy into kinetic energy.

Diffusion and Particles

Diffusion is the spreading of particles from high to low concentration due to random motion. Higher temperature increases particle speed, so diffusion happens faster in warm conditions.

Acids and Alkalis

Acids release hydrogen ions in water and have a pH below 7. Alkalis release hydroxide ions and have a pH above 7. Both are corrosive in concentrated form and conduct electricity in solution.

Food Webs and Decomposers

A food web links several food chains in an ecosystem. Decomposers such as bacteria and fungi break down dead organisms, returning nutrients like carbon and nitrogen to the soil.

Solar and Lunar Eclipses

A solar eclipse happens when the Moon passes between Earth and the Sun, blocking sunlight. A lunar eclipse happens when Earth's shadow falls across the Moon.

Metamorphic and Sedimentary Rock

Sedimentary rock forms when layers of sediment are compacted and cemented over time, often containing fossils. Metamorphic rock forms when existing rock is altered by heat and pressure.