Science Terms D-G

Question 1

decibel

Answer 1

a unit of measure for the relative intensity of sounds

Question 2

declination

Answer 2

the celestial coordinate similar to that of latitude on the Earth. Declination measures how many degrees, minutes, and seconds north or south of the celestial equator an object is.

Question 3

delta

Answer 3

a fan-shaped deposit of material at the mouth of a river

Question 4

density

Answer 4

the mass of a substance for a given unit volume. A common unit of density is grams per milliliter (g/ml).

Question 5

displacement

Answer 5

the change in position of an object, computed by calculating the final position minus the initial position. Common units of measure are meters (m).

Question 6

divergent boundary

Answer 6

a boundary between two of the Earth’s plates that are moving away from each other

Question 7

DNA

Answer 7

contains all genetic material for an organism. The smallest units of DNA are called nucleotides.

Question 8

ecliptic

Answer 8

the apparent path of the Sun across the sky over the course of a year

Question 9

electric potential energy

Answer 9

the energy due to an object’s position within an electric field

Question 10

electromagnetic wave

Answer 10

a light wave that has an electric field component and a magnetic field component. An electromagnetic wave does not require a medium to travel through.

Question 11

electrostatic force

Answer 11

the force that exists between particles due to their charge. Particles of like charge repel, particles of unlike charge attract.

Question 12

element

Answer 12

the smallest entity that has distinct chemical properties. It cannot be decomposed by ordinary chemical reactions.

Question 13

ellipse

Answer 13

a geometric shape that is formed when a plane intersects with a cone. In this case, the plane intersects the cone at an angle, so that a shape similar to a circle but stretched in one direction is formed. The orbits of the planets around the Sun represent ellipses.

Question 14

endoplasmic reticulum

Answer 14

an organelle that is used to transport proteins throughout the cell

Question 15

energy

Answer 15

the ability to do work or undergo change. Kinetic energy is the energy of motion, while potential energy is stored energy.

Question 16

epicycle

Answer 16

smaller circles on which the planets traveled around the Earth in the geocentric model of the solar system. Epicycles were used to explain the retrograde motion of planets and help make the predicted positions of the planets match the observed positions.

Question 17

equilibrium

Answer 17

a state at which the forward and reverse reactions proceed at the same rate

Question 18

focal length

Answer 18

the distance from a focal point to a mirror or lens

Question 19

force

Answer 19

that which acts on an object to change its motion; a push or pull exerted on one object by another. Common units are newtons (N).

Question 20

freefall

Answer 20

an object in one-dimensional motion that is only acted on by the force of the Earth’s gravity. In this case its acceleration will be -g or g downward.

Question 21

frequency

Answer 21

the number of cycles or repetitions per second. Frequency is also often measured as the number of revolutions per second. The common units of frequency are hertz (Hz), where one hertz equals 1 cycle/second.

Question 22

frictional force

Answer 22

the force that acts parallel to surfaces in contact opposite the direction of motion or tendency of motion

Question 23

functional group

Answer 23

a group of atoms that give a molecule a certain characteristic or property

Question 24

gel electrophoresis

Answer 24

a process used in laboratories to determine the genetic makeup of DNA strands. This process involves the movement of chromosomes through a gel from one pole to the other. Magnetism is used to pull the chromosomes through the gel.

Question 25

geocentric model

Answer 25

the model of the solar system that places the Earth at the center with the planets and the Sun orbiting around it

Question 26

geology

Answer 26

the study of rocks and minerals

Question 27

glacier

Answer 27

a large mass of snow-covered ice

Question 28

Golgi apparatus

Answer 28

an organelle that packages proteins so that they can be sent out of the cell

Question 29

gravitational force

Answer 29

the attractive force that exists between all particles with mass