chemistry – matter unit what is matter? what is chemistry? what is the organization of matter?...
TRANSCRIPT
Chemistry – Matter Unit
• What is matter?• What is
chemistry?• What is the
organization of matter?
• What is the nature of matter?
What is NOT Matter?
Energy !
Types of Energies
• Mechanical
• Chemical• Heat
• Atomic
• Light
• Electrical
Is Air matter?
• What are the two criteria for matter?–Does it take up
space?–Does it have
mass?
What is chemistry?
• “Chemistry is the study of the composition, structure, and the properties of matter and the changes it undergoes.”
• All chemical reactions involve energy.
What is the composition of matter?
Matter
Pure Matter Substance
Impure Matter Mixture
What is a pure substance?
• A pure substance has a definite composition (proportion).
• The composition of a substance will have the same percent of elements no matter where the sample was obtained. – Water from Lake Okechobee and water from
the Atlantic Ocean (once cleaned up) will have the same composition of hydrogen to oxygen.
– Gold is the same as other gold (once cleaned up).
What is a pure substance?
• A pure substance, by definition, is an element or a compound.
• A container with an almost pure compound:
Pure Substance
Pure Substance
Element Compound
What is an element?
• “a pure substance made of only one kind of atom”
• A substance that cannot be decomposed any farther by simple chemical means
• An element has a definite composition. Gold from South Africa is the same, when purified, as a sample from California.
Periodic Table of Elements
• Most elements on the periodic chart are metals.• Elements through 114 but not 113 have been discovered
or made.
Elemental Samples
• Zinc, copper, lead, carbon, sulfur
What is a compound?
• “A compound is a substance that is made from the atoms of two or more elements that are chemically bonded.”
• The definition is actually more involved than this.
What is a compound?
• A compound is a substance that cannot be decomposed any farther by simple physical means.
• A compound has a definite composition by mass.
• A compound is made up of two or more elements chemically combined.
What is a compound?
• A compound no longer has the properties of its constituent elements.
• Table salt, NaCl or sodium chloride, is a compound of the element sodium and the element chlorine.
Sodium
Sodium metal
• Soft, can be cut with a knife
• Shiny• Good
conductor of electricity
• Very reactive
Sodium in water
Chlorine gas
Chlorine gas
• Greenish gas
• Poisonous
• Heavier than air
Sodium in chlorine gas
Sodium chloride, NaCl
• Sodium chloride dissolves in water rather than reacts with water.
• Sodium chloride is a white solid, not a poisonous green gas.
• Sodium chloride is its own substance with its own properties, not those of either sodium or chlorine.
Samples of Other Compounds
• Sucrose (table sugar), Sodium Chloride, Water, Copper(II) sulfate
Colored Compounds
• Cobalt(II) chloride, Iron(II) sulfate, Potassium dichromate, Potassium chromate, Nickel(II)
nitrate, copper(II) sulfate
What is the composition of matter?
Matter
Pure Substance Impure Matter
Mixture
Impure Matter - Mixture
• “A mixture is a blend of two or more kinds of matter, each of which retains its own identity and properties.”
• A mixture is made up of two or more substances that are not chemically combined.
Mixtures• Mixtures can be separated by simple
physical means.• Two mixtures containing the same
substances may not have the same proportions.
• Example: Very salty water versus barely salty water. Very sweet sugar water versus slightly sweet sugar water.
Water and Dye Mixture
• Two mixtures of the same substances may have different proportions.
Mixtures
Mixtures
Homogeneous Mixture
Heterogeneous Mixture
?
Solutions
• Mixtures– Mixture = a blend of two or more kinds of
matter, each of which retains its own identity and properties
a) homogeneous mixture = a mixture that is uniform in composition throughout
Ex: Food coloring and water
b) heterogeneous mixture = a mixture that is NOT uniform in composition throughout
Ex: Oil and water
Heterogeneous Mixtures
• Sand and water on the left and sand and gravel on the right.
Heterogeneous Mixture
Types of Mixtures:1) solution = a homogeneous mixture
2) suspension = a mixture in which the particles are so large that they settle out unless the mixture is constantly stirred or agitated
Heterogeneous mixture
Ex: Sand and water
3) colloid = a mixture consisting of particles that are intermediate in size between those in solutions and those in suspensions
Heterogeneous mixture
Ex: Milk
Colloidal Suspension
• Fog
Tyndall Effect
THE NATURE OF SOLUTIONS: 1) Solvent = the substance that does the dissolving in a solution
a) Typically present in the greatest amount
b) Typically a liquid
c) Water is the most common or “universal” solvent
2) Solute = substance being dissolved in a solution
a) Typically present in the least amount
b) Typically a solid
9 Possible Solution Combinations:
Factors Affecting the Rate of Dissolving (Increase Solution Rate):
• 1) Grinding: increases surface area
• 2) Stirring: allows solvent continual contact with solute
• 3) Heating: increases kinetic energy; increases mixing
SOLUBILITY:1) Solubility = quantity of solute that will dissolve in specific amount of solvent at a certain temperature.
(pressure must also be specified for gases).
a)Ex: 204 g of sugar will dissolve in 100 g of water at 20°C
b)soluble and insoluble are relative terms
c)solubility should NOT be confused with the rate at which a substance dissolves
2) saturated solution = a stable solution in which the maximum amount of solute has been dissolved.
3) solution equilibrium = state where the solute is dissolving at the same rate that the solute is coming out of solution (crystallizing).
a) Opposing processes of the dissolving and crystallizing of a solute occur at equal rates.
b) solute + solvent solution
4) unsaturated solution = a solution that contains less solute than a saturated solution under existing conditions
5) supersaturated solution = a solution that temporarily contains more than the saturation amount of solute than the solvent can hold (unstable)
3 FACTORS EFFECTING SOLUBILITY:The extent to which a given solute dissolves in a solvent depends on the identity of the solute and solvent and also on the existing conditions of pressure & temperature
1) Nature of solute and solvent
a)“Like dissolves like” = rule of thumb for predicting whether or not one substance dissolves in another
• “Alikeness” depends on:
o Intermolecular forces
o Type of bonding
o Polarity or nonpolarity of molecules:
ionic solutes tend to dissolve in polar
solvents but not in nonpolar solvents
Solvent-Solute Combinations:
2) Pressure:
a)Pressure has little effect on the solubility of liquids or solids in liquid solvents.
b)The solubility of a gas in a liquid solvent
INCREASES when pressure increases. It is a direct relationship.
3) Temperature:
a)The solubility of a gas in a liquid solvent DECREASES with an increase in temperature.
b)The solubility of a solid in a liquid solvent MOST OFTEN increases with an increase in temperature. However, solubility changes vary widely with temperature changes sometimes decreasing with temperature increases.
Mixtures vs. Compounds
• Rocks are mixtures.
• Minerals are pure substances
• Granite rock
Mixtures vs Compounds
• Minerals are pure substances although many have impuities that must be cleaned up first.
Minerals
Amethyst
Halite
Diamond
What is the nature of matter?
• An atom is the smallest unit of an element that maintains the properties of that element– An atom is made up of electrons,
protons, and neutrons as well as other particles.• Protons and neutrons are made up of
quarks.
What is the nature of matter?
• A molecule is a unit that consists of more than one atom bonded together.
• A molecule can have atoms of the same element such as oxygen. These are called diatomic elements.
2O
Blue – diatomic elements
Diatomic elements – blue
Tetraatomic element – red
Octatomic element - yellow
What is the nature of mature?
• A molecule can have atoms of more than one type of element.
• Water
• Sugar (sucrose)
OH2
112212 OHC
Atoms and Molecules
• Three particles:– 2 atoms of
hydrogen– 1 atom of
oxygen
• One particle:– 1 molecule of
water
Atoms• How can an atom of an element be
broken up into atoms of other elements or into other smaller particles and energy?
•Nuclear Reaction
Compound• How is a compound broken up into its
elements or other simpler compounds?
–Use a chemical separation method.
• What are some examples of chemical separation methods?
Chemical Separation Methods
• Heat the compound.
Chemical Separation Methods
• Use Electrolysis which is using an electric current to decompose the compound.
• An electrolyte has been added to the water since water does not conduct.
Mixtures
• How can mixtures be separated?
–Use Physical Separation Methods.
What are examples of physical separation methods?
Physical Separation Methods
• Distillation is the separation of mixtures by using the difference in boiling points of liquids.
• A water cooled condenser is used.
Physical Separation Methods
• Filtration uses the difference in particle size to separate mixtures.
• Filter papers have different size pores.
Physical Separation Methods
• Chromatography uses the difference in solubility in various solvents.
• Gas, liquid, thin layer, and paper chromatography are widely used.
States of Matter
• Three states of matter:
• Liquid, solid, gas
Physical Changes
• During physical changes matter changes in appearance without forming new substances.
• What some examples of physical changes?
Physical Change Examples
• Breaking or tearing
Physical Change Examples
• Boiling or condensing
Physical Change Examples
• Freezing or melting
Physical Change Examples
• Sublimation
Physical Change Examples
• Sublimation:
• “The change of state directly to a gas is known as sublimation.”
• “The reverse process is called deposition, the change of state from a gas directly to a solid.”
Chemical Changes
• During chemical changes new substances are formed with different properties than the original substances.
• What is an example of a chemical change?
Chemical Change Example
• Heating baking soda, sodium hydrogen carbonate, forms sodium carbonate, carbon dioxide, and water. The formation of carbon dioxide is what causes cakes to rise.
Mixture or Pure Substance
• These bottles contain sodium chloride, sucrose, and a mixture of the two. Which is which and how can they be identified?
Physical and Chemical Properties
• What are some physical properties of this pen?
Physical Properties• Examples:
–Color–Hardness–Texture–Volume–Length–Mass
Physical Properties• More Examples:
–Density (mass/volume ratio)–Odor–Sound–Boiling point–Melting point–Magnetism
Physical Properties
• Melting Point and freezing point temperatures are the same.
Chemical Properties
• A chemical property is how something reacts.
• Does the pen float is physical.
• Does the pen dissolve is physical.
• Does the pen react with water is chemical.
Chemical Properties• Does the pen
burn is a chemical property.
• Whether and how something reacts is chemical.
Extensive vs Intensive
• Extensive Properties depend upon the amount of matter that is present.
• Intensive Properties do not depend on the amount of matter present. These properties are the same for a given substance regardless of how much of the substance is present.
Extensive vs Intensive
• Which of the properties listed earlier are extensive and which are intensive?
• Comparisons of several properties are used together to identify an unknown.
Matter UnitNow it is time to try “Chemistry Vocabulary Worksheet: Application of Matter”.
.
Chemistry Vocabulary• A Symbol is a
representation of an element.
• One or two letters may be used.
• The first letter is upper case while the second is lower case.
H C O
Fe Cl Ag
Cu Ba Cf
Chemistry Vocabulary
• A formula is a representation of a molecule of an element or a molecule of a compound.
42
2
SOH
O
Chemistry Vocabulary
112212 OHC• The subscript
represents the number of atoms of a particular element in the molecule.
12 atoms of carbon
22 atoms of hydrogen
11 atoms of oxygen
Chemistry Vocabulary
42SOH• If no subscript
is shown. An understood one is indicated.2 atoms of hydrogen
1 atom of sulfur
4 atoms of oxygen
Chemistry Vocabulary• A coefficient is a
number in front of a formula and represents the number of molecules.
• If no coefficient is shown, one molecule is indicated.
112212 OH2C
2 molecules of sucrose
24 atoms of carbon
44 atoms of hydrogen
22 atoms of oxygen
Chemistry Vocabulary
wateroxygen Hydrogen
22 222
OHOH
• An equation is a sentence showing what is happening in a chemical
reaction.
Chemistry Vocabulary
O2H2 222 OH• The reactants are the substances
(elements or compounds) that will react. They are on the left or starting side.
Chemistry Vocabulary
OH 222 2O 2H
• The products on the right side of the equation are what are formed or are produced during the reaction.
Chemistry Vocabulary• An atom is the smallest unit of an
element that maintains the properties of that element– An atom is made up of electrons,
protons, and neutrons as well as other particles.• Protons and neutrons are made up of
quarks.
Chemistry Vocabulary• A atom is made up of a nucleus and
particles outside the nucleus called electrons.
• Electrons are negatively charged particles.
• The mass of an electron is about 1800 times smaller than that of the proton and neutron.
Chemistry Vocabulary• The nucleus is the tiny positive core
of the atom.
• Two of the particles in the nucleus are the proton and the neutron.
• The proton is a positively charged particle.
Chemistry Vocabulary• What is wrong with
this commonly used picture?
• The nucleus is 1/10000 times smaller than the atom.
• The atom is mostly empty space.
Chemistry Vocabulary• Proton:
– The charge on a proton is equal in magnitude but opposite in sign to the charge on an electron.
• A proton is made up of three quarks.– Two quarks have a +2/3 charge.– One quark has a -1/3 charge.
Chemistry Vocabulary• The mass of a proton is approximately
1800 times heavier than an electron.
• ***The number of protons present is what determines the type of atom.***– If the number of protons change, an
atom of a different element is formed.
Chemistry Vocabulary• The number of protons found in
the nucleus is known as the atomic number.–Hydrogen with an atomic number of
1 has only one proton. If it had 2, it would be helium.
–Uranium with an atomic number of 92 has 92 protons.
Chemistry Vocabulary
• A neutron is an uncharged particle found in the nucleus.
• The mass of a neutron is almost the same as the mass of a proton.
• A neutron is made of three quarks.– One quark has a +2/3 charge.
– Two quarks have a -1/3 charge.
Chemistry Vocabulary
• Two atoms of the same element can have differing numbers of neutrons. These are called isotopes.
• Hydrogen has three isotopes:– Hydrogen with 1 proton and 0 neutrons
– Deuterium with 1 proton and 1 neutron
– Tritium with 1 proton and 2 neutrons
Chemistry Vocabulary• The different masses of these
isotopes give them different properties such as melting and boiling points and reactivities and stabilities.
• Regular uranium is not radioactive enough for a nuclear fuel. Only certain isotopes of uranium will work.
Chemistry Vocabulary
• The mass number is the total number of protons and neutrons in the nucleus of the atom.
• The mass number is not found on the periodic table.
• The masses on the table are the weighted averages of the isotopes.
Chemistry VocabularyParticle Symbol Charge Mass
Number
Electron 1- 0
Proton 1+ 1
Neutron 0 1
p
-e
0n
Chemistry Vocabulary• Nuclear Symbol:• Mass Number
– Number of protons and neutrons
• Atomic number– Number of protons– Found on Periodic
Table
U23592
Chemistry Vocabulary• Number of protons =• 17• Number of neutrons =• 18• Number of electrons=• 17• The number of
protons = number of electrons
Cl3517
Chemistry Vocabulary
Mg2512
• Number of protons =• 12• Number of neutrons = • 13• Number of electrons=• 12
Chemistry Vocabulary
• In a neutral atom the number of protons is equal to the number of electrons.
• The number of protons can never vary in an atom.
• The electrons are the particles that can be gained or lost in a reaction.
Chemistry Vocabulary• The sum of the
positive protons and the negative electrons give the overall charge of the atom.
• The term charge was once called valence.
• The charge is shown as a superscript to the upper right.
2Mg
Chemistry Vocabulary• Number of protons =• 17• Number of neutrons =• 19• Number of electrons=• 18• (17+) + (?-) = 1-
– So ? = 18-
-3617 Cl
Chemistry Vocabulary• Number of protons =• 12• Number of neutrons =• 12• Number of electrons=• 10• (12+) + (?-) = 2+
– ?- = 10
22412 Mg
Chemistry Vocabulary• An ion is a charged atom or group of
atoms.
• A cation is a positively charged ion.
• An anion is a negatively charged ion. The prefix an- can mean not or negative.
Chemistry Vocabulary• Free state – The atom or molecule is
not combined with atoms of other elements.– Gold can be found in the free state.– Because of its reactivity, sodium cannot.
• Combined state – The atom is part of a compound.
Matter Unit• Now it is time to try “Chemistry Vocabulary
Worksheet: Application of Matter”.
• The exam will cover the material in this unit, the lab safety material, and the lab drawer equipment.
• Know the examples and how the ideas go together. Know all parts of the definitions.