10Th Chem V

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vaccination the administration of treated microorganisms into humans or animals to induce an immune response

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vaccination

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vaccine a substance prepared from killed or weakened pathogens and introduced into a body to produce immunity

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vaccine

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vacuole a fluid-filled vesicle found in the cytoplasm of plant cells or protozoans

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vacuole

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vagina the female reproductive organ that connects the outside of the body to the uterus and that receives sperm during reproduction

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vagina

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valence electron an electron that is found in the outermost shell of an atom and that determines the atom's chemical properties

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valence electron

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value a principle or standard that an individual considers to be important

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value

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valve a fold of membranes that controls the flow of a fluid

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valve

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vane the web of a feather; consists of barbs and other structures

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vane

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vapor pressurethe partial pressure exerted by a vapor that is in equilibrium with its liquid state at a given temperature

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vapor pressure

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variable a factor that changes in an experiment in order to test a hypothesis

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variable

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variety a division of a species or of a subspecies

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variety

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varve a banded layer of sand and silt that is deposited annually in a lake, especially near ice sheets or glaciers, and that can be used to determine absolute age

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varve

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vascular bundle in a plant, a strand of conducting tissue that contains both xylem and phloem

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vascular bundle

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vascular cambium in a plant, the lateral meristem that produces secondary xylem and phloem

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vascular cambium

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vascular plant a plant that has a vascular system composed of xylem and phloem, specialized tissues that conduct materials from one part of the plant to another

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vascular plant

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vascular system a conducting system of tissues that transport water and other materials in plants or in animals

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vascular system

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vascular tissue the specialized conducting tissue that is found in higher plants and that is made up mostly of xylem and phloem

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vascular tissue

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vas deferens a duct through which sperm move from the epididymis to the ejaculatory duct at the base of the penis

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vas deferens

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vector in biology, any agent, such as a plasmid or a virus, that can incorporate foreign DNA and transfer that DNA from one organism to another; an intermediate host that transfers a pathogen or a parasite to another organism

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vector in biology

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vector in physics, a physical quantity that has both magnitude and a direction

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vector

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vegetative part any nonreproductive part of a plant

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vegetative part

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the growth of plants by some means of asexual reproduction

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vegetative propagation

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a type of asexual reproduction in which new plants grow from non reproductive plant parts

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vegetative reproduction

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vein in biology, a vessel that carries blood to the heart

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vein

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vein in geology, a thin, tubular or sheet like deposit of minerals that fills a fracture or joint in a rock

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vein

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velocity the speed of an object in a particular direction

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velocity

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vena cava one of the two large veins that carry blood from the body tissues to the heart

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vena cava

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venation the arrangement of veins in a leaf

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venation

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vent an opening at the surface of the Earth through which volcanic material passes

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vent

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ventifact any rock that is pitted, grooved, or polished by wind abrasion

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ventifact

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ventral the lower or abdominal part of an organism

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ventral

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ventricle one of the two large muscular chambers that pump blood out of the heart

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ventricle

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venule a small vessel that collects blood and that joins with other vessels to form veins

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venule

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vernal equinox the moment when the sun passes directly above the equator from south to north; day and night are of equal length on the day that the vernal equinox occurs

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vernal equinox

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vernalization in plants, the exposure of seeds or seedlings to a period of cold

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venule in plants

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vertebra one of the 33 bones in the spinal column (backbone)

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vertebra

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vertebrate an animal that has a backbone; includes mammals, birds, reptiles, amphibians, and fish

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vertebrate

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vesicle a small cavity or sac that contains materials in a eukaryotic cell; forms when part of the cell membrane surrounds the materials to be taken into the cell or transported within the cell

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vesicle

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vessel in plants, a tube like structure in the xylem that is composed of connected cells that conduct water and mineral nutrients; in animals, a tube or duct that carries blood or another bodily fluid

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vessel

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vessel element in plants, one of the cellular components of a xylem vessel

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vessel element

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vestigial structure a structure in an organism that is reduced in size and function and that may have been complete and functional in the organism's ancestors

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vestigial structure

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vibrationa repetitive, back-and-forth motion of an object around its rest position

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vibration

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villus one of the many tiny projections from the cells in the lining of the small intestine; increases the surface area of the lining for absorption

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villus

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viper a venomous snake that has two large, mobile fangs at the front of the mouth

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viper

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viroid an infectious agent that consists of a small strand of RNA and that causes disease in plants

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viroid

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virology the study of viruses and viral infections

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virology

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virtual image an image that forms at a point from which light rays appear to come but do not actually come

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virtual image

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virulent describes a microorganism or virus that causes disease and that is highly infectious

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virulent

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virus a nonliving, infectious particle composed of a nucleic acid and a protein coat; it can invade and destroy a cell

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virus

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visceral mass the central section of a mollusk's body that contains the mollusk's organs

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visceral mass

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viscosity the resistance of a gas or liquid to flow

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viscosity

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visible spectrum the portion of the electromagnetic spectrum that includes all of the wavelengths that are visible to the human eye

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visible spectrum

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vitamin an organic compound that participates in biochemical reactions and that builds various molecules in the body; some vitamins are called coenzymes and activate specific enzymes

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vitamin

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viviparous an organism whose offspring develop within the mother's body and are born alive

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viviparous

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volatile liquid a liquid that evaporates readily or at a low temperature

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volatile liquid

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volatile substance a substance that evaporates readily or at a low temperature

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volatile substance

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volcanic ash fine pyroclastic particles, less than 4 mm in diameter, that are blown out from a volcanic explosion; also called volcanic dust

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volcanic ash

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volcanic bomb a large, individual fragment of volcanic material that acquired a rounded form as it solidified before hitting the Earth

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volcanic bomb

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volcanic dust fine pyroclastic particles, less than 4 mm in diameter, that are blown out from a volcanic explosion; also called volcanic ash

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volcanic dust

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volcanic neck a mass of hardened volcanic magma that has remained upright after the surrounding material has been eroded

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volcanic neck

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volcanism any activity that includes the movement of magma toward or onto the Earth's surface

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volcanism

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volcano a vent or fissure in the Earth's surface through which magma and gases are expelled

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volcano

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voltage the potential difference or electromotive force, measured in volts; it represents the amount of work that moving an electric charge between two points would take

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voltage

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voltaic cell a primary cell that consists of two electrodes made of different metals immersed in an electrolyte; used to generate voltage

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voltaic cell

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volume a measure of the size of a body or region in three-dimensional space

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volume

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voluntary muscle a muscle whose movement can be consciously controlled

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voluntary muscle

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VSEPR theory a theory that predicts some molecular shapes based on the idea that pairs of valence electrons surrounding an atom repel each other

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VSEPR theory

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vulcanization a chemical reaction that causes the cross-linking of rubber with sulfur

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vulcanization

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vulva the external part of the female reproductive organs

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vulva