What is the difference between Elements , Compounds & Mixtures ? Unit 3 Structure and Organization of Matter
Feb 24, 2016
What is the difference between Elements,
Compounds & Mixtures?Unit 3
Structure and Organization of Matter
What ISN’T an Element?• Earth, wind, fire and
water are NOT elements!– Earth - most all
substances on the periodic table
– Wind - air is made up of multiple gases
– Fire - is plasma, anything burning
– Water - Hydrogen & Oxygen
What ARE Elements?• Pure substances• Any substance with a
single kind of particle• Those particles ALL
have the same kind of atoms
• The particles cannot be divided further.
Diamond = pure carbon
How are Elements Identified?
• Physical Properties– Boiling point– Melting point– Density
• Chemical Properties– Reactivity with acid– Reactivity with oxygen
How are Elements Categorized?• By their properties
– Physical & Chemical• Three major types of
elements– Metals– Metalloids– Non-metals
Draw a table like the one belowState Appearance Conductivit
yMalleablitity & Ductility
Metals
Non-metals
Metalloids
What are Metals?• Shiny, good
conductors of heat & electricity
• Malleable - can bend
• Ductile - pulled into wire
• 95% of all elements are metals
The Metals
State Appearance Conductivity
Malleability & Ductility
Metals -Solid at room temperature except Mercury
-Shiny luster - Good conductors of both heat & electricity
-All metals are malleable & ductile
Non-metals
Metalloids
What are Non-metals?
• Dull, not too shiny• Poor conductors of
heat & electricity• Solids are brittle and
break easily• Not many solid objects
are made up of non-metals
The Non-metals
State Appearance Conductivity
Malleability & Ductility
Metals -Solid at room temperature except Mercury
-Shiny luster - Good conductors of both heat & electricity
-All metals are malleable & ductile
Non-metals
-Some gases at room temperature-Some solids-One liquid (bromine)
- Not very shiny at all
- Poor conductors of heat and electricity
-Brittle- Not ductile
Metalloids
What are Metalloids?• They are semi-conductors
– Some conduct electricity – Electrical conductivity is not
as good as metals• Have some properties of
both metals & nonmetals– Shiny, metallic appearance
• Some are malleable & ductile
The Metalloids
State Appearance Conductivity
Malleability & Ductility
Metals -Solid at room temperature except Mercury
-Shiny luster - Good conductors of both heat & electricity
-All metals are malleable & ductile
Non-metals
-Some gases at room temperature-Some solids-One liquid (bromine)
- Not very shiny at all
- Poor conductors of heat and electricity
-Brittle- Not ductile
Metalloids -Solids at room temperature
-Some are very shiny
-Some may conduct electricity -Poor conductors of heat
-Brittle- Not ductile
What are Compounds?
A pure substance made of 2 or more elements.
What else can be said of Compounds?
• Elements combine through a chemical reaction
• Elements don’t randomly form compounds
• Elements combine in a very specific ratio - based on the element’s mass
What are the properties of Compounds?
• Physical properties are similar to Elements:– Melting point, density,
etc…• Chemical properties
can include:– Reactivity to oxygen– Reactivity to acid– Reactivity to light
Caffeine
Light can break this compound
down
Can Compounds be broken down?
• Through a chemical change
• Most time a lot of energy must be added to cause the change– Heat– Electricity – Light
What are common Compounds?• Common organic
compounds include carbon, nitrogen, hydrogen and oxygen
• Such as those found in caffeine
• Theobromine - the active ingredient in chocolate
What is a Mixture?
A combination of 2 or more substances that are NOT
chemically combined
What is a Mixture? (continued)
• Two or more substances will not react together
• No chemical change occurs • Each substance has the same chemical
makeup in the mixture– Salt water
• The salt (NaCl) is still there as well as the water (H2O)
Can Mixtures be separated?• Yes, through…. • Distillation
– Uses boiling points• Evaporation
– Atmospheric pressure• Magnet
– Removing iron • Centrifuge
– Uses the densities
Mixtures vs. Compounds• Made of elements,
compounds, or both
• No charge in original properties of components - not electrical
• Separated by physical means
• Formed using ANY ratio of components
• Made of elements only
• Change in original properties of components
• Separated by chemical means
• Formed using a set ratio of components
What about the ratio of components in a Mixture?
• Do not have to be mixed in any particular ratio
• Granite is an excellent example of this quality to mixtures
What is a solution?• A mixture that appears
to be a single substance
• Composed of 2 or more substances that are distributed evenly among each other
• Have the same appearance & properties throughout
What are parts to a solution?• The process of particles
separating spreading through a mixture is
called dissolving• Solute - the substance
that is dissolved• Solvent - the substance
in which the solute is dissolved
What are examples of different Solutions?
• Gas in gas -– dry air, O2 In N2
• Gas in liquid - – soft drinks, CO2 in H2O
• Liquid in liquid - – antifreeze, alcohol in H2O
• Solid in liquid - – Salt water, NaCl in H2O
• Solid in solid (Alloy)- – brass, zinc in copper
What is Solubility?• The ability of a solute
to dissolve in a solvent, like…
• Putting sugar in water – Only so much sugar
(solute) will dissolve in water (solvent)
What is the difference between Dilute & Concentrated
• Dilute solution contains less solute• Concentrated solutions contain more solute
Dissolving gases in Liquids
• As the solvent (water) becomes warmer the gas becomes less soluble
• This is why a warm can of Mountain Dew will go “flat” faster.
• Gas that is dissolved in the water can’t stay dissolved as the temperature rises.
On the other side, however…
Dissolving Solids in Liquids• Three ways to speed up the dissolving1. Mixing/stirring (agitating) the solute in the
solvent 2. Heating the solvent3. Crushing the solute before placing it in
the solvent
1 2 3
What is a Suspension?• A mixture in which the
particles are dispersed throughout but are large enough to settle out
• Heterogeneous• Must be shaken or stirred
periodically to remain mixed• The suspension can be
separated by use of a filter
Other Suspensions…
What are Colloids?• Mixtures with
properties in between solutions & suspensions
• Homogeneous • Particles are dispersed
throughout but are not heavy enough to settle out
Other Colloids….
Our Atmospher
e is a mixture
Next up ….. The Periodic Table of the Elements!