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 H 2 O 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 Solid – add heat; increase Temp Melting – add heat; temp constant; weakening IMAs Liquid – add heat; increase temp Boiling – add heat; temp constant; weakening IMAs 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 H 2 O 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)