chapter 5 elements, compounds, mixtures. section 1: elements
TRANSCRIPT
Chapter 5
Elements, Compounds, Mixtures
Section 1: Elements
Vocabulary
ElementPure substanceMetalNonmetalMetalloid
Vocabulary
• Element– Substance that cannot be broken down or
be separated into simpler substances by chemical means
• Pure substance– Either an element or a single compound,
that has definite chemical and physical properties
Vocabulary
• Metal – Element that is shiny, – good conductor of heat & electricity
• Non Metal– Does not conduct heat or electricity
• Metalloid– Element with properties of both metal and
nonmetal
Elements, the simplest substance
• Elements are pure• Made of atoms• Each element, only has one type of atom– Silver only has silver atoms in it
• Each atom in an element is identical to each other
Classifying Elements
• Each element is classified by its unique properties– These properties don’t change based
upon the amount of the element• 10 kilograms of silver has the same properties
of 1 milligram of silver
Classifying Elements
• Characteristic properties include both physical and chemical properties– Hardness, melting point, density– Reactivity or flammability
• These properties can be used to identify elements
Grouping Elements
• 3 major groups of elements– Metal– Nonmetal– Metalloid
Grouping Elements
• Metals– Good conductors of heat– Good conductors of electricity– Malleable• Can be shaped
– Ductile• Can be drawn into wires
Grouping Elements
• Nonmetals– Dull• Not shiny
– Poor conductors of heat & electricity– Solids tend to be brittle• Unmalleable
– Few objects made of purely of nonmetals
Grouping Elements
• Metalloids– Semi-metals– Have properties of both metals & nonmetals• some are shiny• Some conduct electricity• Some are dull• Some malleable• Etc….
Section 2: Compounds
Vocabulary
• Compound– Pure substance composed of 2 or more elements
that are chemically combined
Compound: Made of Elements
• Elements combine through chemical changes– Chemical changes mean a new substance– Think water• Hydrogen gas + oxygen gas = water
Compound: Made of Elements
• Chemical changes (reactions) rearrange the atoms– Form in various patterns
• Properties of new substance are different than original atom.
Properties of Compounds
• Compounds have unique properties from the elements that made it
• Always join in specific ratios
Breaking Down Compounds
• Compounds can only be broken by chemical changes– Example --- soda• Carbonic acid is release from the
water/sugar • Creates that fizz–Fizz or bubbles is a sign of chemical
change
Breaking Down Compounds
• Chemical breakdown is harder than physical changes
• Generally energy is needed for a chemical change
Compounds in Your World
• Compounds are everywhere in your world– Industry• Plastics• Metal alloys
– Nature• Water• Sucrose (sugar)
Section 3: Mixtures
Vocabulary
MixtureSolutionSoluteSolventConcentrationSolubility
Vocabulary
• Mixture– Combination of 2 or more substances that
are not chemically combined• Solution– Homogenous mixture• 2 or more substances are evenly dispersed
• Solute– Item to be dissolved
Vocabulary
• Solvent– substance that dissolves the solvent
• Concentration– Amount of a particular substance in a
given quantity of a mixture or solution• Solubility– Ability of a substance to dissolve
Properties of Mixtures
• No chemical changes– So substance still has same chemical make up
• Can be separated by physical method
Properties of Mixtures
• Common Ways to Separate mixtures
– Distillation
– Magnet
– Centrifuge
Properties of Mixtures
• Ratios of particles in a mixture can vary– Remember that in compounds, the ratio is
fixed
Solutions
• Homogenous mixture– Particles are evenly mixed throughout
Solutions
Solutions
• Examples– Soda– Gasoline– Air– Alloys• Mix of 2 or more metals
Concentration of Solution
• Amount of solute in solvent– Normally expressed in grams per milliliter
• Solubility of a solute depends on temperature– Normally higher solubility with higher
temperature