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Unit 2 Distinguish chemical properties of matter (including reactivity) from physical properties of matter (including boiling point, freezing/melting point, density [with density calculations], solubility, viscosity, and conductivity). (PS-3.1) Infer the practical applications of organic and inorganic substances on the basis of their chemical and physical properties. (PS-3.2) Illustrate the difference between a molecule and an atom. (PS-3.3) Classify matter as a pure substance (either an element or a compound) or as a mixture (either homogeneous or heterogeneous) on the basis of its structure and/or composition. (PS-3.4) Compare the properties of the four states of matter—solid, liquid, gas, and plasma—in terms of the arrangement and movement of particles. (PS-3.6) Explain the processes of phase change in terms of temperature, heat transfer, and particle arrangement. (PS-3.7) States of Matter • Solids • Particles held together by strong attractions • Vibrate in place • Definite shape & volume • Liquids • Particles move fast enough to overcome attractions and move past each other • Take shape of container • Volume cannot change because particles are close together States of Matter • Gases • Particles move fast enough to break all attractions • Expand to fill available space • Plasma • • • • No definite shape or volume Particles are electrically charged Conducts electricity Found in lightning, fire & aurora borealis States of Matter Phase Changes Kinetic Molecular Theory • All matter is made up of constantly moving particles. • In order for a substance to be a liquid or a solid at room temperature there has to be some force of attraction between the particles that make up the substance. Kinetic Molecular Theory • Different types of intermolecular forces of attraction: • Dispersion forces • Dipole-dipole • Hydrogen bonding • Important in biological functions • Keeps H2O molecules in liquid state at room temp Kinetic Molecular Theory • Kinetic energy is energy of moving things • At a given temperature the average kinetic energy of particles is the same. • Temperature is a measure of average kinetic energy. • The higher the temperature the higher the average kinetic energy and vice versa. Phase Changes • During a change in state (i.e. solid → liquid) • Energy is being added to the substance • Endothermic • Temperature stays constant because the energy is going into the atoms/particles to change the state of the substance. • IMAs are becoming weaker Phase Changes • During a change in state (i.e. liquid → solid) • Energy is being removed from the substance • Exothermic • Temperature stays constant because the energy is being removed from the atoms/particles • IMAs are becoming stronger Phase Changes Boiling – add heat; temp constant; weakening IMAs Melting – add heat; temp constant; weakening IMAs Liquid – add heat; increase temp Solid – add heat; increase Temp Gas – add heat; increase temp Physical v. Chemical Properties • Physical Properties: • Can be observed without changing the chemical makeup of a substance • Examples: solubility, mass, volume, MP, BP, color, hardness, conductivity, heat capacity • Chemical Properties: • Describes a chemical change & the kinds of chemical reactions that a substance undergoes • Examples: reactivity with H2O or air, reaction to being heated or cooled, exposed to sunlight, or mixed w/ another substance Extensive v. Intensive Properties • Extensive properties • Properties that depend on sample size • Examples: Mass, volume • Intensive properties • Properties that are independent of sample size • Examples: density, electrical conductivity Identification of Substances • Intensive properties more useful • • • • Density Boiling point Melting point Color • Chemical properties such as reactivity with oxygen when heated also useful (real gold v. fool’s gold) Density • Physical, intensive property • Ratio of an object’s mass to its volume • D = m/V • Decreases slightly with increasing temperature (except for water) • 3 methods for finding volume of object: • l x w x h (rectangular prisms) • Water displacement (oddly shaped solids) • Use graduated cylinder (for liquids) Mixtures • Combination of 2 or more pure substances in which each substance keeps individual chemical properties • Heterogeneous mixtures • Not blended evenly, separate substances remain distinct • Homogeneous mixtures • Constant composition throughout; always has single phase • Also called solutions Separation Techniques • Mixtures can be separated by differences in physical properties. • Centrifugation (using a centrifuge) • Separates mixtures of undissolved solids from liquids by density. • As the centrifuge spins the mixture, the larger particles fall to the bottom of the centrifuge tube. • This is how platelets are separated from the liquid portion of your blood at medical laboratories. Separation Techniques • Distillation: • Separates mixtures of liquids by boiling point. • A heating mantle would be held on the ring clamp on the left in order to heat the mixture to the boiling point of the liquid to be recovered. Separation Techniques • Filtration : • Separates mixtures of undissolved solids from liquids by particle size. • The filter can be paper as shown above, or a synthetic membrane, as shown on the below. • The solid particles in a mixture are trapped on the filter, and the liquid portion (the filtrate) is collected in a receiving flask, beaker, or other suitable container. Separation Techniques • Chromatography: • Separates mixtures based on attractive forces between the particles of two different phases. (solubility) • The more the component is attracted to the mobile phase (the liquid moving up the paper) the higher the component travels up the paper. • The more the component is attracted to the stationary phase (the paper which is not moving) the more it is retained or held back by the paper. Elements & Compounds • Element: • Pure substance that cannot be separated into simpler substances by physical or chemical means • Periodic Table: organizes elements based on physical and chemical properties • Compound: • combination of 2 or more elements that are combined chemically • Properties of cmpd differ from those of elements (salt and water)