Post on 07-Mar-2021
transcript
Matter and Change
Chemistry is…
Chemistry:
Is the study of the
composition, structure,
and properties of matter
and the changes it
undergoes
Reactants Products
C2H5OH + 3 O2 2 CO2 + 3 H2O + Energy
Reactants Products
Matter
Anything that has mass and occupies space
MassA measure of the amount of matter
Any property that describes physical attributes of a substance:• Color• Phase• Aroma• Mass• Length• Height• Ductility• Malleability• Conductivity• Boiling point• Melting point
Types of Physical Properties of Matter
Extensive properties
Intensive properties
Volume
Mass
Energy Content
depend on the amount of matter that is present.
do not depend on the amount of matter present.
Melting point
Boiling point
Density
Describes the chemical nature of a substance:• Reacts with oxygen
• Decomposes to produce a gas
• Oxidizes
• Is a reducer
• Reacts with sulfur
Chemical ChangeA change in which one or more substances are converted into different substances.
Heat and light are often evidence of a chemical change.
Production of Light
Unexpected color change
Production of heat
Formation of a precipitate
Liberation of a gas (w/out
heating)
Physical Change
A change in a substance that does not involve a change in the identity of the substance.
Example:
Phase Changes: A substance changing state from a solid to a liquid to a gas.
The same substance remains after the change
Examples of Physical Change:• Pounding
• Cutting
• Heating
• Dissolving into a solution
• Melting
• Boiling
Phase Differences
Solid – definite volume and shape; particles packed in fixed positions.Liquid – definite volume but indefinite shape; particles close together but not in fixed positions.
Gas – neither definite volume nor definite shape; particles are at great distances from one another.
Plasma – high temperature, ionized phase of matter as found on the sun.
Three Phases
Elements
Compounds
AtomThe smallest unit of an element that maintains the properties of that element
ElementA pure substance made of only one kind of atom
CompoundA substance that is made from the atoms of two or more elements that are chemically bonded.
Sucrose – C12H22O11
Sucrose is also known as table sugar!
Two or more substances physically combined. A mixture can be either heterogeneous or homogeneous.• Heterogeneous: A mixture of two or more substances with
visible interfaces Example: A bowl of peas and carrots
• Homogeneous: A mixture of two or more substances with no visible interfaces Example: Brass – a mixture of copper and nickel
Solution: A special type of homogenous mixture in where the particles are actually dissolved on the microscopic level Example: sugar water
The constituents of the mixture retain their identity and may be separated by physical means.
Mixtures
Can it be physically
separated?
Element CompoundHeterogeneous
Mixture
no yes
Is the composition
uniform?noyes
Can it be chemically
decomposed?yesno
Homogeneous
Mixture
MIXTUREPURE SUBSTANCE
MATTER
Element
• composed of identical atoms
• Ex:
copper wire
aluminum foil
Compound
• composed of 2 or more
elements in a fixed ratio
• properties differ from those
of individual elements
• Ex:
table salt (NaCl)
Law of Definite Composition
• A given compound always contains the same, fixed
ratio of elements.
Law of Multiple Proportions
• Elements can combine in different ratios to form
different compounds.
For example…
Two different compounds,
each has a definite composition.
Carbon, C Oxygen, O Carbon monoxide, CO
Carbon Dioxide, CO2Oxygen, OOxygen, OCarbon, C
Variable combination of 2 or more pure
substances.
Heterogeneous Homogeneous
Tyndall
Effect?no yes
Will mixture separate if
allowed to stand?yesno
Suspension (course solid in liquid) Emulsion (liquid in liquid)
Colloid
Suspension, Colloid, or EmulsionSolution
Homogeneous
Mixture (Solution)
Solid or liquid
particles?liquidsolid
Suspension or Emulsion
Solution
• homogeneous
• very small particles
• no Tyndall effect
• particles don’t settle
• Ex:
rubbing alcohol
Colloid
• homogeneous
• very fine particles
• Tyndall effect
• particles don’t settle
• Ex:
milk
Suspension
• homogeneous
• large particles
• Tyndall effect
• particles settle if
given enough time
• Ex:
Pepto-Bismol
Fresh-squeezed
lemonade
Emulsion
• homogeneous
• mixture of two
immiscible liquids
• Tyndall effect
• particles settle if
given enough time
• Ex:
Mayonnaise
Examples:
graphite
pepper
sugar (sucrose)
paint
coffee
-element (C)
-hetero. mixture
-compound
-suspension
-solution
The components of dyes such as ink may be separated by paper chromatography.
Separation of a Mixture
Separation of a Mixture
Distillation
Separation of a Mixture
Filtration
Separation of a Mixture
Evaporation
Magnetic
Separation
Decantation
Separation of a Pure CompoundThe Electrolysis of water
Water Hydrogen + Oxygen
H2O H2 + O2
Reactant Products
Compounds must be separated by chemical means.
With the application of electricity, water can be separated into its elements