Praxis Elem CKT Science flashcards

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

Cell theory

All living things are made of one or more cells, cells are the basic unit of life, and new cells come only from existing cells.

Photosynthesis equation

Six carbon dioxide plus six water molecules, given light energy, yield one glucose and six oxygen molecules: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, catalyzed inside chloroplasts.

Mitosis versus meiosis

Mitosis produces two genetically identical diploid cells for growth and repair; meiosis produces four genetically different haploid gametes, each carrying half the original chromosome number.

Punnett square ratios

A tool that predicts offspring genotype and phenotype probabilities; crossing two heterozygotes for a simple dominant trait gives a 3:1 phenotype ratio.

Natural selection conditions

Heritable variation among individuals, more offspring than can survive, and differential reproduction based on traits cause allele frequencies to shift across generations.

Trophic energy transfer

Only about ten percent of energy at one trophic level passes to the next; most is lost as heat, so food chains rarely exceed four or five links.

Xylem and phloem

Xylem carries water and dissolved minerals upward from roots to leaves; phloem carries sugars made in photosynthesis from leaves to roots and growing tissue.

Complete metamorphosis

An insect life cycle with four stages-egg, larva, pupa, adult-as in butterflies and beetles; the larva differs completely in form and diet from the adult.

Newton's three laws

Objects keep constant velocity unless a net force acts; acceleration equals net force divided by mass; forces occur in equal, opposite pairs acting on different objects.

Speed and acceleration formulas

Speed equals distance divided by time; acceleration equals change in velocity divided by time; velocity is speed with a stated direction.

Kinetic and potential energy

Kinetic energy equals one-half mass times velocity squared; gravitational potential energy equals mass times gravity times height; total energy is conserved.

Density and floating

Density equals mass divided by volume; an object floats in water when its density is below 1 gram per cubic centimeter, regardless of sample size.

Atomic number

The number of protons in a nucleus, which identifies the element; in a neutral atom electrons equal protons, and mass number adds protons plus neutrons.

Series versus parallel circuits

A series circuit has one current path, so one break stops everything; a parallel circuit has multiple paths, so other branches keep operating.

Wave speed equation

Wave speed equals frequency times wavelength; in a fixed medium, increasing frequency shortens wavelength, linking pitch or color to measurable wave properties.

pH scale

Runs from 0 to 14: below 7 acidic, 7 neutral, above 7 basic; each whole step is a tenfold change in hydrogen ion concentration.

Rock types

Igneous rock forms when magma or lava cools, sedimentary rock forms from compacted and cemented sediments, and metamorphic rock forms when existing rock is altered by heat and pressure.

Plate boundaries

Divergent boundaries pull plates apart, convergent boundaries push them together causing subduction or mountains, and transform boundaries slide plates past each other, producing earthquakes.

Earth's layers

From outside inward: a thin rocky crust, a solid mantle that flows very slowly, a liquid iron-nickel outer core, and a solid inner core.

Water cycle processes

Evaporation and transpiration add water vapor, condensation forms clouds, precipitation returns water, and runoff or infiltration moves it to oceans and groundwater.

Rotation versus revolution

Rotation spins Earth on its axis once about every 24 hours, causing day and night; revolution orbits the sun once in about 365.25 days, defining a year.

Why seasons happen

Earth's 23.5-degree axial tilt changes the angle and duration of sunlight through the year; distance from the sun is not the cause of seasons.

Moon phase cycle

The moon's appearance changes over about 29.5 days as its position relative to Earth and the sun shifts; phases are not caused by Earth's shadow.

Solar system order

From the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune; the inner four are rocky, the outer four are gas or ice giants.

5E instructional model

A lesson sequence of Engage, Explore, Explain, Elaborate, and Evaluate in which students investigate phenomena before the teacher formalizes the scientific explanation.

Science and engineering practices

Eight NGSS practices: asking questions, developing models, planning investigations, analyzing data, using mathematics, constructing explanations, arguing from evidence, and obtaining and communicating information.

Crosscutting concepts

Themes spanning all science domains, including patterns, cause and effect, scale and proportion, systems and system models, energy and matter, structure and function, and stability and change.

Fair test variables

A fair test changes one independent variable, measures one dependent variable, and keeps all other conditions constant as controlled variables so results can be attributed to the manipulation.

Formative and summative assessment

Formative assessment occurs during instruction to guide feedback and next steps; summative assessment occurs at the end to judge achievement against standards.

Misconception: plants eat soil

Students often think plants obtain food from soil; plants make glucose through photosynthesis using carbon dioxide and water, while soil supplies water and minerals.

Misconception: heavier objects fall faster

In air, heavier objects often land first because of air resistance; in a vacuum all objects accelerate at the same rate regardless of mass.

Laboratory safety rules

Wear goggles, waft odors instead of sniffing directly, never taste materials, wash hands after activities, and follow teacher directions for chemical disposal.