what is the difference between elements, compounds & mixtures? unit 3 structure and organization...
TRANSCRIPT
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 below
State Appearance Conductivity
Malleablitity & 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
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
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
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 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? (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.
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
What are Colloids?• Mixtures with
properties in between solutions & suspensions
• Homogeneous • Particles are dispersed
throughout but are not heavy enough to settle out