Transcript Chapter 4 Elements, Compounds, & Mixtures

Chapter 4
Elements, Compounds, &
Mixtures
Gold
Salt Fields
Granite
Elements
• Are pure substances that cannot be
separated into simpler substances by
physical or chemical changes.
• Elements are found on the periodic table
of elements
Pure Substance
• Contains only one type of particle.
• Example: 5 grams of the element gold is
like all other particles of gold.
• The particles of a pure substance are alike
no matter where that substance is found.
Identifying Elements
• Physical properties and Chemical properties are
ways in which you may identify an element.
• Examples of Physical Properties: melting point,
density, color, hardness, and texture.
• Examples of Chemical Properties: flammability,
reactivity with oxygen, acid & water.
Elements are Classified by their
Properties
• Elements are divided into three categories:
Metals, Nonmetals, & Metalloids.
• Elements are classified into groups
according to their shared properties.
• Example: Iron, Nickel & Cobalt are all
shiny and conduct electric current
therefore scientists have grouped them
into the metal section of the periodic table.
Metals
Are:
– Shiny
– Good conductors of thermal energy
– Good conductors of electric current
– Malleable (hammered into sheets)
– Ductile (drawn into thin wires)
Examples: Copper, Lead, Tin
Copper
Nonmetals
• Are:
– Dull
– Poor conductors of thermal energy
– Poor conductors of electric current
– Brittle
– Unmalleable
Examples: Sulfur, Bromine, Neon
Sulfur
Metalloids
• Are:
Silicon
– Have both properties of metals & nonmetals
– Some are shiny some are dull
– Somewhat Malleable and ductile
– Some conduct thermal energy and electric
current well
Examples: Silicon, Antimony, Boron
Compounds
• A pure substance composed of two or more
elements that are chemically combined.
• In order for elements to combine they must react
or undergo a chemical change with another.
• Examples:
Table salt- sodium and chlorine
Water- hydrogen and oxygen
• Once the chemical change occurs you have
another pure substance
• http://www.youtube.com/watch?v=0evGD
GkOMvc
Compounds…
• Each compound like elements has its own
unique set of physical and chemical properties
that helps you identify it.
• Example:
-boiling point
-melting point
-density
-color
-reactivity
Compounds in Nature
• Proteins are compounds found in all living
things.
• Nitrogen is needed to make proteins.
• Plants get their nitrogen compounds from
the soil. Animals get the nitrogen they
need by eating plants or animals that have
eaten plants.
Quiz
1. An element is a pure substance that cannot be _________ into other
substances.
A. combined
C. made
B. separated
D. burned
2. Which two categories of elements are good conductors of electricity?
A. Metals and Nonmentals
c. Metals and some Metalloids
B. Nonmetals and Metalloids
d. Water and Metals
3. Elements are divided into three categories
A. metals, nonmetals, metalloids
B. metals, solids, liquids
C. solids, liquids, gasses
D. cobalt, iron, nickel
Quiz Continued
4. Two or more elements that are chemically
combined are called___________.
A. metals
C. pure substance
B. elements
D. compounds
5. True or False
In order for elements to combine they
must react or undergo a chemical
change with another.
Mixtures
• Are a combination of two or more
substances that are not chemically
combined.
• Two or more materials together form a
mixture if they do not react to form a
compound.
Example: A Pizza: dough, sauce, pepperoni,
cheese, olives. They do not react when
put together.
Mixtures continued…
• Since no chemical change has occurred
the substance still has the same chemical
makeup it had before it was combined with
the other substances.
• Mixtures can be physically separated. If
you don’t like olives on your pizza you may
pick them off. This is a physical change of
the pizza.
Mixtures Continued…
• Mixtures are not all as easy to separate. Salt water can
be separated but you must separate the salt from the
water by heating the mixture. The water changes from a
liquid to a gas, and the salt remains.
• Other ways to separate mixtures:
- Distillation is a process that separates a mixture based
on its boiling point. (saltwater)
-Centrifuge separates according to the densities of the
components. (blood)
-Magnet can separate iron from aluminum.
Mixtures vs. Compounds
Mixtures
1. Are elements,
compounds, or both.
2. Separated by
physical means.
3. They keep original
properties.
Compounds
1. Are elements.
2. Lose their original
properties.
3. Separated by
chemical means.
Solutions
• A mixture that appears to be a single
substance but is composed of particles of
two or more substances that are
distributed evenly amongst each other.
• Example: Saltwater
Nerdy Science Joke of the day
• What did the compound say to
the solution?
• Answer: You’re all mixed up!
Solute vs. Solvent
• In solutions the Solute is the substance
that is dissolved.
• The Solvent is the substance in which the
solute is dissolved.
• Example: In saltwater salt is the solute
or the substance that is dissolved.
While water is the solvent which
dissolves the salt.
Solubility
• Is the amount of solute needed to make a
saturated solution.
• If a solution contains all the solute it can hold at
a given temperature it is saturated. An
unsaturated solution contains less solute than it
can hold at a given temperature.
• Mixing, Heating & Crushing all affect how quickly
solids will dissolve in liquids.
http://www.youtube.com/watch?v=3G472AA3SEs
Suspensions
• Are mixtures that have particles of a material
throughout it. They settle to the bottom but do
not dissolve.
• Example: When you shake a snow globe, the
snow moves around but eventually falls to the
bottom.
Nerdy Science Joke Alert!
• What did the • “Settle
Down!”
chemist say
to the
suspension?
Colloids
• Are mixtures in which
particles are dispersed
throughout but are not heavy enough to
settle to the bottom. The particles are small
and fairly well mixed.
• Example: Jello is an example of a colloid.
Quiz
1.
A.
B.
A mixture is a combination of ______ substance(s) that
are not ______ combined.
one, chemically
C. two, chemically
two, physically
D. one, physically
2. True or False
Mixtures can be physically separated.
3. The __________ is the substance that is dissolved, and
the _________is the substance that dissolves.
A. water, salt
C. solvent, solute
B. solute, solvent
D. solution, water
Quiz
4. Solubility is how much __________ can be dissolved.
A. metal
C. gas
B. water
D. solute
5. A snow globe is an example of a ______.
A. colloid
C. solvent
B. suspension
D. compound
6. A ________is a fairly well mixed mixture which the
particles are not heavy enough to settle out.
A. suspension
C. solution
B. colloid
D. ratio