Science Reviewer

September 5, 2017 | Author: Gem Zuñiga | Category: Solution, Solubility, Chemical Compounds, Chemical Elements, Liquids
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Reviewer for Grade 7 students...


 consists of crust, mantle, outer and inner core  CRUST: holds most of the natural resources  MANTLE: occupies biggest part o UPPER MANTLE: composed of silicates high in iron and magnesium o LOWER MANTLE: higher iron content than the upper mantle  CORE: consists mainly of nickel and iron o OUTER CORE: molten o INNER CORE: solid Mixtures  consists of two or more components that are not chemically combined and are not in any fixed proportion  components retain their characteristic properties Heterogeneous Mixtures  components are not uniformly distributed  composed of diff substances that remain physically separate  may be solid-solid; solid-liquid; liquid-liquid  immiscible –not having the ability to mix with other liquids in the mixture  suspension – consists of solid particles that may remain suspended momentarily or dispersed thoroughly throughout a liquid by mechanical agitation (shaking) o particles settle at the bottom o not clear or opaque  emulsion – mixture of liquid wherein small drops of one liquid are mixed throughout another liquid o mayonnaise Homogeneous Mixtures  made up of two or more substances that are spread out uniformly and look similar in appearance and composition throughout the mixture  also referred to as solutions o consists of a solvent (liquid) wherein a solute (solid) is being dissolved in

o as you add more solute, higher boiling point; thus lower freezing point than that of the pure solvent Separating the Components of a Mixture  DECANTATION: do sedimentation first (settling of particles in liquid), then pour the liquid out of the bottle, leaving the heavier particles  MECHANICAL SEPARATION: separated based on particle size; usually by picking  FILTRATION: separating solids from liquids  EVAPORATION: put sol’n in an open container under the sun, then allow water to evaporate  DISTILLATION: best used when mixture is composed of two liquids with diff boiling points; uses vaporization and condensation to collect the liquids one at a time  PAPER CHROMATOGRAPHY: when homogeneous mixtures are composed of a solvent and one or more solutes o various materials of a mixture is adsorbed selectively in a column or strip of paper; components are then separated on a surface o consists of stationary phase (solid like an adsorbed paper or liquid) and mobile phase (a liquid or a gas) which flows through the former  CENTRIFUGATION: spinning a container in circles at high speeds o centripetal force allows the denser substance to settle at the bottom Application of Separation Techniques in Food Processing  Physical Separation  Centrifugation – separation of vegetable oils from other liquid products; clarification of cloudy appearance in beverages


The Lithosphere

Nature of Solution

Factors affecting Solubility  Temperature o some solid solutes become more soluble in water as the temp rises o solubility decreases as temperature increases – for gases o when temp rises, average kinetic energy of particles in solution increase, then gas particles overcome the weak IMF and escape to the atmosphere  Pressure o profound effect on gases; but negligible impact on liquids and solids o more pressure, increased solubility @ constant temp o studied by William Henry o Henry’s law explained decompression sickness (also called bends)  Nature of Solute and Solvent o polar solvents dissolve polar and ionic substances o nonpolar solvents will dissolve nonpolar substances

Amount of Solute in Sol’n  saturated solution – max amount of solute has been dissolved in a given amount of solvent @ a given temp and when any more solute added will settle at the bottom  unsaturated - less than the max amount of solute that can be held  supersaturated – containing more solute than it normally contains o prepared by increasing tem to dissolve the excess solute and slowly cooling the sol’n o unstable condition

 Percentage Composition

o refer to page 80-81 for sample exercises


 solvent has a larger amount than a solute, and determines the state of the sol’n  all gases can be dissolved  refer to page 74 for the table of types of sol’ns  aqueous solutions – solutions in liquid form where water is the solvent  SOLID-SOLID SOL’N: alloy  soluble – qualitative description of substances that have the ability to be dissolved in significant amounts in a given solvent  miscible – qualitative description of the solubility of substances in a liquid-liquid and gas-gas system  solubility – quantitative term defined as the maximum amount of solute that will dissolve in a given amount of solvent at a specific temp

Pure substances  purified components which exhibit the same properties throughout and are homogeneous  cannot be separated into two or more substances by physical or mechanical means  has constant chem. composition

o refer to pg. 94 for the physical properties of metals and nonmetals USES OF METALS AND NONMETALS  Metals

Elements  pure substance that cannot be chemically decomposed  Mercury and Bromine – only elements that are liquids at normal room temp  11 elements are gases  represented by a chemical symbol, which symbol may be one or two letters, where the first letter is always capitalized o METALS o METALLOIDS – look like metals but have nonmetallic properties as well o NONMETALS  PERIODIC TABLE OF ELEMENTS o periods or series – horizontal rows o groups – vertical columns; often called a family bec elements in it have similar chem. properties

 Nonmetals o used to prevent thermal or electrical conductivity o Human body cells – carbon, oxygen, hydrogen, nitrogen, and sulfur o jewelry – carbon and diamond o sulfuric acids and drugs o bleaching – chlorine o antiseptic – iodine

o refer to pg. 93 for periodic table o Sanderson line – separates metals (left) from nonmetals (right); adjacent elements are metalloids



o BASES  bitter and biting taste  slippery, soap feeling  changers red to blue litmus paper  very few react with metals o SALTS  neutralization product between the rxn of an acid and base

Elements essential to life

Compounds  can be chemically separated into their component elements  proportion of elements in compound is fixed  Represented by formulas based on the symbols of fixed proportions of the elements in the compound. o ACIDS  tastes sour  reacts with some metals and/or produce hydrogen gas  changes blue to red litmus paper  reacts with base to form salt

HANDLING ACIDS AND BASES 1. use hand protection gloves appropriate to acids or bases 2. wear safety glasses or goggles 3. wear a lab gown 4. If the acids or bases enter your eyes or have contact with any part of your body, flush them with lots of water. Go to the clinic at once 5. Dispose these chemicals properly


1. Bulk or structural elements – major components of biomolecules 2. Macro minerals – for nutrition required in amounts greater than 100mg/day such as sodium, potassium, magnesium, calcium, chlorine, and phosphorus 3. Trace elements – needed in very small amounts such as iron, zinc, and copper a. iodine, selenium, arsenic, boron, manganese, molybdenum, vanadium, nickel, cadmium, tin, lead, fluorine, cobalt, chromium b. cerals, milk, bread, margarine

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