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Eighth Grade Science Essential Knowledge 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. Matter – anything that has mass and volume. Matter exists usually as a sold, liquid or gas Mass – a measure of how much matter an object is made of Space – the unlimited 3 dimensional realm in which all material objects and all events occur Law of Conservation of Mass – a law stating that atoms are not created nor destroyed in a chemical reaction Mixture – a combination of 2 or more substances that do not combine chemically but remain the same individual substances. Mixtures can be separated by physical means Element – a substance that cannot be broken down into a simpler substance by ordinary chemical changes. An element consists of atoms of only one type Compound – a substance made up of 2 or more different types of atoms bonded together Atom – Smallest particle of an element that has the chemical properties of that element Molecule – a group of atoms held together by covalent bonds so that they move as a single unit Solid – matter that has a definite shape and a definite volume. The molecules in a solid are in fixed positions and are close together Liquid – matter that has a definite volume but does not have a definite shape. The molecules in a liquid are close together but not bound to one another Gas – matter with no definite volume and no definite shape. The molecules in a gas are very far apart, and the amount of space between them can change easily Density – a property of matter representing the mass per unit volume Volume – an amount of three-dimensional space, often used to describe the space that an object takes up Fluid - a substance that can flow easily, such as a gas or a liquid Melting point – the temperature at which a substance changes from its solid state to its liquid state through melting Boiling point – the temperature at which a substance changes from its liquid state to its gas state through boiling Freezing point – the temperature at which a substance changes from its liquid state to its solid state through freezing Solubility – the amount of solute that dissolves in a certain amount of a solvent at a given temperature and pressure to produce a saturated solution Solute – in a solution a substance that is dissolved in a solvent Solvent – in a solution the substance that dissolves a solute and makes up the largest percentage of a solution Chemical change – a change of one substance into another substance Physical Change – a change in a substance that does not change the substance into a different one Chemical property – characteristics that describe how a substance interacts with other substances to produce a different kind of matter Physical property – characteristics of a substance that can be observed without changing the identity of the substance Mechanical energy – a combination of the kinetic energy and potential energy an object has Thermal energy – the energy an object has due to the motion of its particles; the total amount of kinetic energy of particles in an object Kinetic energy - the energy of motion. A moving object has the most kinetic energy at the point where it moves the fastest Combustion – the act or process of burning Friction – a force that resists the motion between 2 surfaces in contact Electric motors – a device that converts electrical energy to mechanical torque Generator – a device that converts kinetic energy into electrical energy. Generators produce electric current by rotating a magnet within a coil or wire within a magnetic field 33. Electrical energy – energy made available by the flow of electrical charge through a conductor 34. Respiration – the exothermic process by which living things release energy from glucose and oxygen and produce carbon dioxide and water 35. Photosynthesis - in green plants the endothermic process in which light is absorbed and used to change carbon dioxide and water into glucose and oxygen 36. Temperature – a measure of the average amount of kinetic energy of the particles in an object 37. Conduction – the process by which energy is transferred from a warmer object to a cooler object by means of physical contact 38. Convection – a process by which energy is transferred in gases and liquids, occurring when a warmer, less dense area of gas or liquid is pushed up by a cooler, more dense area of the gas or liquid 39. Radiation – energy that travels across distances in the form of electromagnetic waves 40. White light – light that contains all the wavelengths of visible light 41. Prism – an optical tool that uses refraction to separate wavelengths that make up white light 42. Light colors – reflect sunlight, reflecting heat 43. Dark colors – absorbs heat from light 44. Wave – a disturbance that transfers energy from one place to another without requiring matter to move the entire distance 45. Wavelength – the distance from one wave crest to the next crest; the distance form any part of one wave to the identical part of the next wave 46. Frequency – the number of waves that pass a fixed point in a given amount of time, usually 1 second; the number of cycles per unit of time 47. Speed – a measure of how fast something moves through a particular distance over a definite time period; speed is distance divided by time 48. Wave motion – a disturbance that travels through space and time, usually accompanied by a transfer of energy 49. Sound waves – a type of wave that is produced by a vibrating object and that travels through matter 50. Light waves – electromagnetic waves that we can see as the colors of the rainbow, each color has a different wave length 51. Medium – a substance through which a wave moves 52. Motion – a change in position over time 53. Frame of reference(point of reference) – an indicator that orients you 54. Position – an object’s location 55. Acceleration – the rate at which velocity changes over time 56. Velocity – a speed in a specific direction 57. Force – a push or a pull; something that changes the motion of an object 58. Balanced force – opposing forces that are equally pushing or pulling against each other 59. Unbalanced force - forces that produce a change in an object’s motion 60. Currents – steady motion in one direction 61. Electric current – a continuous flow of electric charge, which is measured in amperes 62. Cell – smallest unit of an organism that can carry on life functions 63. Organism – any living thing 64. Multi-cell organism – cells that work and function together to create a living organism, as in plants and animals 65. Single-cell organism – made up of only one cell as in bacteria 66. Parts of plant cell – cell membrane, vacuole, nucleus, chloroplasts, cell wall, cytoplasm 67. Cell wall – rigid structure that encloses, supports, and protects the cells of plants, algae, fungi and most bacteria 68. Vacuole – a small cavity in cytoplasm of a cell, bound by a membrane, containing water, food or waste 69. Chloroplast – green, chlorophyll-containing, plant cell organelle that uses light energy to produce sugar from carbon dioxide and water 70. Chlorophyll – green, light-trapping pigment in plant chloroplasts that is important in photosynthesis 71. Mitosis – cell process in which the nucleus divides to form 2 nuclei identical to each other and identical to the original nucleus, in a series of steps(prophase, metaphase, anaphase, telophase) 72. Respiration – process by which producers and consumers release stored energy from food molecules, series of chemical reactions used to release energy stores in food molecules 73. Glucose – a type of sugar the body uses for energy 74. Nerve cell – a specialized cell that conducts nerve impulses, spinal cord for example 75. Muscle cell – an elongates contractile cell that forms the muscles of the body 76. Skin cell – any of the cells making up the skin 77. Bone cell – a cell found in bone 78. Blood cell – cells that circulate in the blood as white blood cells or red blood cells 79. Tissue – group of similar cells that work together to do one job 80. Organ – structure, such as the heart, made up of different types of tissue that all work together 81. Organ system – a group of organs that work together to perform a certain task 82. Muscle – organ that can relax, contract, and provide the force to move bones and body parts 83. Cardiac muscle – striated, involuntary muscle found only in the heart 84. Striated muscle – the muscle involved with moving skeletal parts to which it is usually attached 85. Smooth muscle – muscles involving involuntary movement, as in the intestines, blood vessels 86. Digestive system – helps convert food into usable nutrients 87. Respiratory system – supplies the blood with oxygen in order to deliver oxygen to all parts of the body 88. Circulatory system – a body-wide network of blood, blood vessels and lymph, empowered by the heart 89. Excretory system - removes metabolic waste and maintains the proper amount of water in the body 90. Skeletal system – framework of the body which protects and supports it with bones 91. Nervous system – made up of the brain, spinal cord and nerves that serve as the processing center to control the body 92. Environment – conditions and surrounding that influence development and behavior 93. Adaptation – any variation that makes an organism better suited to its environment 94. Ectotherm – vertebrate animal whose internal temperature changes when the temperature of its environment changes, cold-blooded 95. Endotherm – vertebrate animal with a nearly constant internal temperature, warm blooded 96. Behavioral responses – the way in which an organism interacts with other organisms and its environment; can be innate or learned 97. Dichotomous key – a key for the identification of organisms based on a series of choices between alternative characteristics 98. Kingdom – first and largest category used to classify organisms 99. Protist – one or many-celled eukaryotic organism that can be plantlike, animal-like, or funguslike 100. Producers – organism, such as a green plant or alga, that uses an outside source of energy like the Sun to create energy-rich food molecules 101. Consumers – organism that cannot create energy-rich molecules but obtains its food by eating other organisms 102. Pollutant – substance that contaminates any part of the environment 103. Deforestation – the clearing of trees 104. Population - all organisms that belong to the same species living in a community 105. Ecosystem – community of organisms and the environment they inhabit 106. Biotic – features of the environment that are alive or were once alive 107. Abiotic – nonliving, physical features of the environment, including air, water, sunlight, soil, temperature, and climate 108. Physical factors that affect ecosystems 109. Genetic s – the study of how traits are inherited through the action of alleles 110. Gregor Mendel – the founder of the science of genetics 111. Inherited traits – characteristics of a parent being passed on to its offspring through heredity 112. Gene – section of DNA on s chromosome that contains instructions for making specific proteins 113. Chromosome – structure in a cell’s nucleus that contains hereditary material 114. Trait – a distinguishing characteristic or quality 115. Gamete – a reproductive cell that unites with another cell to form a new organism 116. Dominant genes – describes a trait the covers over, or dominates, another form of that trait 117. Recessive genes – describes a trait that is covered over, or dominated, by another form of that trait and seems to disappear 118. Punnett square – a tool to predict the probability of certain traits in offspring that shows the different ways that alleles can combine 119. Extinction – no longer in existence; has died out 120. Survival of the fittest – the survival of those best adapted to the environmental conditions 121. Genetic diversity – advantage to sexual reproduction 122. Asexual reproduction – a type of reproduction – fission, budding and regeneration – in which a new organism is produced from one organism and has DNA identical to the parent organism 123. Evolution – change of living things over time 124. Fossil – trace or remains of a plant or an animal in sedimentary rock 125. Biological adaptation – the adjustment of an organism to its environment 126. Natural selection – parts of Earth’s environment that supply materials useful or necessary for the survival of living organisms 127. Biological evolution – change in inherited traits over time 128. Diversity of species 129. Photosynthesis – process by which plants and many other producers use light energy to produce a simple sugar from carbon dioxide and water and give off oxygen 130. Food web – model that shows the complex feeding relationships among organisms in a community 131. Food chain – the chain from a food source to the ultimate consumer 132. Closed system- an isolated region where no matter or energy can cross 133. Decomposer – an organism that breaks down the cells of dead plants and animals 134. Disease – an impairment of normal functioning cells 135. Biological agents(microorganism) – have the ability to negatively affect life 136. Bacteria – a very large group of microorganisms; can be harmful or beneficial 137. Virus – a strand of hereditary material surrounded by a protein coating that can infect and multiply in a host cell 138. Environmental factors – factors that affect or influence any living organism 139. Genetic – The study of how traits are inherited through the actions of alleles 140. Genetic disorders – a disease that is caused by an abnormality in DNA 141. Reproductive system – the system of organs and parts which function in reproduction 142. Homeostasis – the tendency of a system to maintain internal stability 143. Plate tectonics – theory that the lithosphere is made up of plates that float on the asthenosphere and that the plates possibly are moved by convection 144. Earthquake – vibration of the earth’s crust 145. Epicenter – point on the earth’s surface directly above the focus of an earthquake 146. Volcano – lava and pyroclastic material built up on the earth’s surface around a vent 147. Seafloor spreading – movement of the ocean floor away from either side of a mid-ocean ridge 148. Mountain - a natural elevation of the earth’s surface greater than 2000 feet or 610 meters 149. Landforms – physical feature of the earth’s surface 150. Weathering – change in the physical form or chemical composition of rock materials exposed at the earth’s surface 151. Physical weathering – breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water, ice, pressure 152. Chemical weathering – breakdown of rocks, soil and minerals through direct contact with atmospheric chemicals 153. Erosion – process by which the products of weathering are transported 154. Sediment – fragments that result from the breaking of rocks, minerals, and organic matter 155. Landslide – sudden movement of loose rock and soil down a slope 156. Rock cycle – series of processes in which rock changes from one type to another and back again 157. Igneous rocks – rock formed from cooled and hardened magma 158. Metamorphic rock – rock formed from other rocks as a result of intense heat, pressure, or chemical process 159. Sedimentary rock – rock formed from hardened deposits of sediment 160. Relative age – age of an object compared with the ages of other objects 161. Rock strata – distinct layers in rock 162. Law of superposition – principle that a sedimentary rock layer is older than the layers above it and younger than the layers below it 163. Index fossils – guide fossil; fossil found in the rock layers of only one geological age and is used to establish the absolute age of the rock layers 164. Alpine Glaciers – form on the crest and slopes of mountain 165. Continental Glacier – a broad sheet of ice resting on a plain and spreading outward 166. Hardness – resistance to fracture, chip, bend or break 167. Cleavage – splitting of mineral along smooth, flat surfaces 168. Streak – the color a rock or mineral takes on when scratched on a surface 169. Luster – a shine by reflecting light, a sparkle 170. Ozone – form of atmospheric oxygen that has 3 atoms per molecule 171. Ozone depletion – a decline on the total volume of the ozone layer in the atmosphere 172. Heat transfer – 3 types of heat for the Earth 173. Conduction – type of energy transfer in which vibrating molecules pass heat along to other vibrating molecules by direct contact 174. Convection – transfer of eat through the movement of heated material 175. Radiation – the emission or transfer of radiant energy as particles or waves 176. Air current – air moving from an area of high pressure to an area of low pressure 177. Coriolis effect – deflection of wind and ocean currents caused by the earth’s rotation 178. Weather – general condition of the atmosphere at a particular time and place 179. Barometer – instrument that measures atmospheric pressure 180. Barometric pressure – atmospheric pressure 181. Dew point – temperature to which air must be cooled to become saturated 182. Wind - air in natural motion 183. Temperature – measure of motion 184. Precipitation – process by which water falls from clouds to the earth as rain, snow, sleet and hail 185. Clouds – a visible collection of particles of water or ice suspended in the air 186. Stratus cloud – cloud with a sheet-like or layered form that is the lowest cloud in the sky 187. Cumulus cloud – thick, billowy cloud that forms above stratus clouds and below cirrus clouds 188. Atmosphere – thick blanket of gases surrounding the earth 189. Stratosphere – layer of the atmosphere that extends upward from the troposphere to an altitude of 50km; contains most ozone atmospheric ozone 190. Ozone layer – layer of the uppermost atmosphere that protects organisms on earth from ultraviolet radiation 191. Ionosphere – lower region of the thermosphere ,at an altitude of 80 – 550 km 192. Thermosphere – the atmospheric layer above the mesosphere 193. Troposphere – atmospheric layer closest to the earth’s surface where nearly all weather occurs 194. Solar radiation – radiation for the sun 195. Electromagnetic spectrum – complete range of wavelengths of radiation 196. Revolution – movement of a planet around the sun 197. Earth’s axis – imaginary straight line running through the earth from pole to pole 198. Rotation – spinning of a plant on its axis 199. Equinox – the time when day and night are equal length 200. Solstice – 2 times during the year when the sun is the farthest from the equator 201. Light year – distance that light travels in one year, about 9.5 trillion km 202. Big Bang Theory – theory that all matter and energy in the universe was compressed into an extremely small volume that suddenly, billions of years ago, began expanding in all directions 203. Milky Way – spiral galaxy containing our solar system 204. Galaxy – large-scale group of stars 205. Hydrosphere – all the earth’s water 206. Theory – hypothesis or set of hypotheses supported by the results of experimentation and observation 207. Scientific Law – rule that correctly describes a natural phenomenon 208. Doppler Effect – apparent shift in the wavelength of energy emitted by a source moving away from or toward an observer 209. Spectroscope – instrument that splits white light into a band of colors 210. Seismic wave – vibration that travels through the earth 211. Crust – outermost zone of the solid earth; 1% mass of the earth, oceanic and continental 212. Mantle – zone of rock 2900 km thick below that earth’s crust, lithosphere and asthenosphere 213. Lithosphere – thin outer shell of the earth consisting of the crust and the rigid upper mantle 214. Asthenosphere – zone of mantle beneath the lithosphere that consists of slowly moving solid rock 215. Core – center of the earth, made of iron, 1/3 of the earth’s mass 216. Plasticity – ability for a solid to flow 217. Magnetosphere – a region of space that is affected by the earth’s magnetic field 218. Time Zone – one of 24 regions of the globe approximately marking an hour of time 219. International Date Line – line running from north to south through the Pacific ocean where the date changes from one day to the next 220. Parallel – any circle that runs east to west around the earth parallel to the equator 221. Latitude – angular distance north or south of the equator 222. Longitude – angular distance east to west of the prime meridian 223. Meridians(Prime meridian) – semicircle on the earth that runs from pole to pole 224. Geomagnetic poles – point on the earth’s surface above a pole of the earth’s imaginary internal magnet 225. Contour interval – difference in elevation between one contour line and the next 226. Topographic map – map that shows the surface features of the earth 227. Continental drift – hypothesis stating that the continents once formed a single landmass,Pangea, broke up and drifted to their present locations