classification of matter chemistry apps chapter 9 mr. gilbertson
TRANSCRIPT
Classification of Matter
Chemistry AppsChapter 9
Mr. Gilbertson
Composition of Matter
Substances (Pure) – cannot be reduced to simpler substances by physical means.
Elements – all atoms in a sample are identical.
Simplest form of matter Cannot be subdivided by physical means
Elements
118 recognized elements90 natural elements28 synthetic elements (man-made)
Compounds Made up of two or more elements
chemically combined to form new substances.
Have properties which are significantly different from the properties of the elements from which they are formed.
Made up of particles which are either molecules or ion pairs.
Mixtures Heterogeneous – non-uniform composition
consisting of two or more distinct phases. Physical combination of two or more substances
which can be separated by physical means. Each part of the mixture maintains its distinct
properties. Homogeneous – uniform composition appearing to
be in a single phase. Solutions are the most common examples. One substance (solute) is completely dissolved in
another (solvent).
Solution Homogeneous mixtures in which
one substance it thoroughly distributed in another (single phase at equilibrium)
May exist in any phase (solid, liquid, gas)
Kool aid, Steel, air, and seawater, are all good examples.
Solution Two parts:
Solvent – the part that is in greatest quantity or the part in which the other is dissolved. (the water in kool-aid)
Solute – the substance being dissolved or distributed (the sugar and powder in kool-aid)
Important Terminology System – the total environment of the
reaction under study (must be defined) Phase – A region within the system
displaying uniform properties Interface – the boundary between two
adjacent phases Organic – containing carbon or being
produced as a result of life processes Inorganic – not organic
Heterogeneous Mixture
Classification of Matter
Special Mixtures Colloids – a heterogeneous mixture that does not
settle out. Exhibits Tyndall effect and Brownian Motion. Particle size is between those of solutions and
suspensions. Cannot be filtered out.
Suspensions – a heterogeneous mixture that has very large particles which always settle out. Exhibits Tyndall Effect. Can be filtered out.
Tyndall EffectProperty of all colloids and suspensions which causes them to scatter light as a result of the reflection of very large particles.
Describing Matter
Physical Properties Any characteristic of a material that
you can observe without changing the substances that make up the material.
Color, shape, size, density, melting point, etc.
Often can be measured directly. All substances have physical properties
which distinguish it from other substances.
Physical Properties Extensive – depend on the
amount of substance present (mass, dimensions, weight, etc.)
Intensive – independent of the amount of substance (Density, color, hardness, luster, etc.)
Physical Properties
Properties used to identify
Mixtures are often separated using physical means.
The differences between the properties of the substance in a mixture are used to separate the parts.
Magnetic properties, solubility, particle size, boiling point, color, are all properties that might be useful for separation.
Separation using physical properties
Panning for Gold
Distillation
Separation of matter
magnetism A refinery
Water purification using Colloids
Physical Changes Any change which does not involve a
change in composition (the identity of the material does not change).
Examples: cutting wood, breaking glass, tearing paper, melting, vaporizing, etc.
Changes in size, shape, or state, or arrangement of parts are considered to be physical changes.
Chemical Changes Always involve changes in composition,
one substance changes to another and its properties change.
Evidences: Gases given off, color changes, formation of a precipitate, energy changes (heat or light) are all evidences of a chemical change. (Rule of thumb)
May also absorb energy in the form of heat and light.
Energy Changes in Chemical Reactions
Exothermic reactions – Give off energy to the surroundings (heat up)
Endothermic reactions – absorb energy from their environment (cool down)
Activation Energy – the energy that is required to cause a reaction to begin.
Video about Chemical and Physical changes
Physical and Chemical Changes
Chemical Properties A characteristic of a substance which
indicates whether it can undergo a certain chemical change.
Describes how a substance will react in the presence of other substances.
Cannot be observed without changing the composition of the substances.
Flammability, corrosive, toxic, acidic, etc.
Flammability
Electrolysis
Used to separate elements in a compound by passing an electric current through a solution.
Chemical Properties
Conservation of Mass
First proposed by Antoine Lavoisier. The mass of products in a chemical
reaction must equal the mass of the reactants.
Matter cannot be created or destroyed during a chemical change.
Requires a closed system.
Antoine Lavoisier
Proposed Law of Conservation of Mass
Chemical Change
Mass is conserved in chemical reactions
Sometimes seems to be untrue, but if it is contained in a closed system so that no new matter can enter or exit the reaction vessel.Mass of all products must equal mass of reactants.
Silver AgProperties: The melting point of silver is 961.93°C, boiling point is 2212°C, specific gravity is 10.50 (20°C), with a valence of 1 or 2. Pure silver has a brilliant white metallic luster. Silver is slightly harder than gold. It is very ductile and malleable, exceeded in these properties by gold and palladium. Pure silver has the highest electrical and thermal conductivity of all metals. Silver possesses the lowest contact resistance of all metals. Silver is stable in pure air and water, although it tarnishes upon exposure to ozone, hydrogen sulfide, or air containing sulfur.
Heat and Temperature Heat is the transfer of energy from a
body at a higher temperature to a body at a lower temperature.
Temperature is a measure of the average kinetic energy in the particles of a system.
Often confused because the flow of heat will result in a temperature change.
Calorimeter
Used to measure heattransfer from one body to another
Insulated to restrict heat flow to the Environment.
Amount of heat required to raise the temperature of one gram of a substance 1 Celsius degree (1 Kelvin).
^Q =mc^T ^Q – heat change (Joules) m – mass (g) C – specific heat (J/goC) ^T – change in temp (oC or K)
Specific Heat
Conservation of energy and specific heat.
^Qloss = ^Qgained
Heat lost by sample must equal heat gained by the rest of the system in a calorimeter. So…..
mc^Tunknown = mc^Twater + mc^Tcup
mc^Twater + mc^Tcup
Cunknown = ---------------------------------------
m^T unknown
Where :^T = Tf-Ti calorimeter demo
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