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### Bellwork Which of the following represents a mixture? a piece of copper wire oxygen in a pressurized tank a slice of mushroom pizza a lead fishing weight – PowerPoint PPT presentation

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Title: Bellwork

1
Bellwork
• Which of the following
• represents a mixture?
• a piece of copper wire
• oxygen in a pressurized tank
• a slice of mushroom pizza

2
Chapter 13 Review
• Matter anything that has mass and takes up
space
• Mass the amount of matter in something
• Volume the amount of space something occupies
• Which of the following is matter?
• A car?
• A box?
• You?

3
What is a property?
• A Property is a characteristic of a substance
that can be observed.

4
Physical Property
A physical property is one that can be observed
without changing the identity of the substance.
5
Examples
• Malleability the ability to be hammered into a
thin sheet
• Ductility the ability to be stretched into a
wire
• Melting/freezing point
• Boiling point
• Density
• Solubility
• Specific heat the amount of heat required to
heat a substance 1 degree Celsius
• Luster shiny, matt

6
Special Physical Properties
• Melting point the temperature at which a
substance changes from a solid to a liquid at a
given pressure
• water 0oC
• Boiling point the temperature at which a
substance changes from a liquid to a gas at a
given pressure
• water 100oC

7
Density
• Density is the amount of mass per unit of volume.
• Like many other properties it can be used to
identify a substance.
• The density of water is 1.0g/mL

8
Calculating Density
• D m/V g/mL g/cm3
• Ex A cube has a mass of 2.8 g and occupies a
volume of 3.67 ml. Would this object float or
sink in water?
• Mass 2.8 g Volume 3.67 mL
• D 2.8g/3.67 mL 0.76 g/mL

9
Identification by Density
• A liquid has a mass of 25.6 g and a volume of
31.6 mL.
• Use the table below to identify the substance.

M25.6 g V31.6 mL D 25.6 g/31.6 mL
D 0.81 g/mL The substance is ethanol.
10
Chemical Properties
• A Chemical property is a property that can
only be observed by changing the identity of the
substance
• Examples
• flammability
• ability to rust
• reactivity with vinegar

11
Element
• An element is a pure substance that cannot be
broken down into any other substance by chemical
or physical means.
• Examples
• aluminum
• zinc
• oxygen

12
Atom
• Elements are comprised of atoms, which are so
small they cannot be seen even with a microscope.

13
Molecule
• Atoms bond together chemically to form
molecules.

14
Compound
• A compound is a pure substance made of 2 or
more elements chemically combined in a set ratio.
Compounds cannot be easily separated.

15
Mixture
• A mixture is a pure substance made of 2 or
more elements, compounds, or both, that are
together yet not chemically bonded and therefore
can be separated by physical means.

Heterogeneous Homogeneous
16
Changes
• Physical change substance maintains its
chemical makeup
• Ex state changes, dissolving
• Chemical change substance becomes something else
entirely
• Ex burning, oxidation

17
Chemical Reactions
• Endothermic reactions must absorb heat/energy in
order for the reaction to take place.
• This intake of energy may be observed as a
decrease in temperature as the reaction proceeds.
• Exothermic reactions release heat from the
reaction.

18
Chemical Reactions
• Reactants are the chemicals that go into a
reaction.
• Products are the chemicals products that are
created by the reaction.

19
Law of Conservation of Matter
• States that the
• Mass of the reactants
• Mass of the Products
• (in a closed system)
• Ex 5 g of sodium(Na) 5 g of chloride (Cl)
yields 10g of table salt (NaCl)

20
Conservation of Matter Lab
• Objective
• To demonstrate the Law of Conservation of
Matter by reacting vinegar baking soda in a
closed system.

21
Bellwork
• What is the difference between a compound
and a mixture?

22
Venn Diagram
23
• ENERGY!

24
2 Main Types of Energy
25
Temperature Energy
26
Temperature
27
Law of Conservation of Matter
• States that the
• Mass of the reactants
• Mass of the Products
• Also stated as matter cannot be created nor
destroyed only transformed.

28
Law of Conservation of Energy
• Energy also cannot be created nor destroyed
only transformed or transferred.

29
Law of Conservation of Energy
30
Exothermic
Produces Heat
31
Endothermic
Soaks up heat from the surroundings observed
as a decrease in temperature
25 ml citric acid soln 15 g baking soda
32
Bellwork
• Which pure substance is composed of more
than one element?
• - carbon
• - gold
• - water
• - sodium

33
Intro.
• The PERIODIC TABLE contains information about
the different ELEMENTS that make up all the
solids, liquids, and gases in the known universe.

34
Natural vs. Synthetic
• The majority of the known elements are
naturally occurring, however all elements above
92, are known as SYNTHETIC elements having been
created in a lab.

35
Atoms
• Elements are one or more identical ATOMS and
each element has its own unique atom that looks
different than all the other elements.

36
Organization
• Elements are organized on the periodic table
by their ATOMIC NUMBER, which is the number of
PROTONS in the nucleus.

37
Isotopes
• Atoms of the same element can have different
numbers of NEUTRONS the different possible
versions of which are called ISOTOPES.

38
Calculate of Neutrons
• To determine the average number of neutrons
in an element Round the atomic mass to the
nearest whole number and subtract the atomic
number (of protons). Ex K 39 19 20 neutrons.

39
Atomic Mass
• The ATOMIC MASS listed on the periodic table
is an average of the mass of all known isotopes
of that element.

40
Symbols
• Hg Mercury
• Sn Tin Ag Silver
• Cu Copper Fe Iron
• K Potassium Na - Sodium

41
Patterns in the Table
• The PROPERTIES of an element can be
predicted by their location on the periodic table.

42
Group 1
• Alkali Metals do not occur uncombined in
nature highly chemically reactive

43
Group 2
• Alkaline Earth Metals also do not occur
uncombined good conductors

44
Groups 3-12
• Transition Metals also good conductors
form colorful compounds that last a long time
since they are not highly chemically reactive

45
Lanthanides
• Soft, shiny, malleable metals with high
conductivity

46
Actinides
• Most are synthetic and the nuclei are
unstable (meaning they break apart quickly)

47
Metalloids
• Along the stair step line
• (7) METALLOIDS that have properties of
metals and non-metals are very useful for their
varying abilities to conduct electricity (i.e.
silicon semi-conductors in computer chips).

48
Non-Metals
• The NON-METALS are not good conductors but
they combine with others readily to form
compounds.
• Many of these elements are crucial in
creating and maintaining life (C, N, O, P, S).

49
Group 17
• HALOGENS - meaning salt forming
• They are DIATOMIC, meaning they never exist
as a single atom.

50
Group 18
• NOBLE GASES do not bond with other
elements at all, hence why they are called noble

51
Bellwork
• The element silicon is best used for which
purpose?
• - as a container to keep coffee hot
• - as a semiconductor in a computer chip
• - as a material to make airplane frames
• - as a malleable material for coins and
jewelry

52
Protons Electrons
• Atoms are in general NEUTRAL since they
generally have the same number of protons as
electrons in their pure form. They strive at all
times to maintain their neutrality.

53
Electrons
• We know already that ELECTRONS are orbiting
around the nucleus of the atom. Where they are
orbiting helps us to make some predictions about
how and if an element will combine with other
elements (reactivity).

54
Energy Levels
• There are several ENERGY LEVELS within the
electron cloud and each can only hold a certain
number of electrons.
• The period/row on which an element can be
found will tell you how many energy levels there
are in an atom of that element.

55
Filling the Energy Levels
• 1st energy level holds 2 electrons
• 2nd energy level holds 8 electrons
• 3rd energy level holds 18 electrons
• There are 7 energy levels in total but we
will only concern ourselves now with the first 18
elements so we will only need to know about the
first 3.

56
Valence Electrons
• Not all energy levels will be filled and the
electrons that reside in the outermost energy
level are called the VALENCE ELECTRONS.
• You can find out at a glance how many
valence electrons an element has by looking at
the group number.

57
Bell Work
• How can a scientist, using the periodic
table, find an element with properties similar to
another element?
• - by comparing density
• - by finding its periodic group
• - by comparing malleability
• - by comparing atomic weight

58
Bell Work
• Which periodic group does the element
chlorine belong to?
• - alkali metals
• - alkali earth metals
• - noble gases
• - halogens

59
Bell Work
• How would you calculate the number of
neutrons in an atom of a given element?

60
Bell Work
• What is the NAME of the family/group that
fluorine belongs to?

61
Bell Work
• What is the NAME of the family/group that
Potassium belongs to?
• Dont forget to have your completed Periodic
Table from yesterday out when I come around with
the stamp ?

62
Bell Work
• Which of the following correctly
compares the elements on the right side of the
periodic table with the elements on the left?
• - The elements on the right side are generally
denser than the elements on the left side.
• - The elements on the left side are better
conductors of electricity than the elements on
the right side.
• - The elements on the right side are better
conductors of thermal energy than those on the
left side.
• - The elements on the left side have lower
melting point than the elements on the right
side.
• Dont forget to have your completed homework
out?

63
Bellwork
• Which element is LEAST likely to combine
with another element to form a molecule?
• Chlorine (Cl), a halogen
• Iron (Fe), a metal
• Neon (Ne), a noble gas
• Silicon (Si), a metalloid

64
Molecules
• 2 or more atoms help together by chemical
bonds

65
Valence Electrons
• Are the electrons on the outermost shell of
an atom that participate in bonding.

66
Lewis Dot Structures
• Diagrams that show electrons, bonding, and
lone pairs of electrons.

67
Covalent Bonds
• A chemical bond that involves the SHARING of
their valence electrons.

68
Ionic Bonds
• A bond that involves the TRANSFER of valence
electrons from one atom to another.

69
Ions
• Atoms that gain or lose electrons, therefore
having a charge.

70
Cations
• Atoms with a positive charge. These are
metals since they lose electrons because they
have one or 2 to spare.

71
Anions -
• Atoms with a negative charge. These are
nonmetals since they gain electrons because they
only need 1 or 2 to become stable.

72
Ionizing Energy
• The amount of energy required to remove an
electron from an atom.

73
Bellwork
• What do these chemicals have in common?
• Cu SO4 ZnCl4 Fe2O3
• Number of atoms
• Presence of oxygen
• Presence of metal
• Number of bonds

74
Bellwork
• You have a sample of an unknown element.
At room temperature, this element is a gas
reacts easily with other elements to form
compounds. In which column of the periodic table
does this element most likely belong?
• - IIA
• - VA
• - VIIA
• - VIIIA

75
Chemical Reactions
• Chemical change occurs when bonds break and
new bonds are formed.
• The chemical composition (makeup) of the
substance(s) has been altered.

76
Evidence of Chemical Change
• Change of properties
• heat absorbed -endothermic
• heat released exothermic
• gas formation (O2, CO2)
• Precipitate formation

77
Chemical Equations
• Reactants ? Products
• 2H2 O2 ? 2H20
• Coefficient of molecules
• Subscript - of atoms

78
Types of Chemical Reactions
• Synthesis
• A B ? C
• Decomposition
• C ? A B
• Replacement
• AB CD ? AD BC

79
Conservation of Mass
• Mass of Reactants
• Mass of Products

Remember the lab where we reacted baking soda and
vinegar and trapped the CO2 in the balloon!
80
BellWork
• Five molecules of methane contain five carbon
atoms and 20 hydrogen atoms. What is the
chemical formula of methane?
• CH4
• C2H8
• C4H20
• C5H20

81
Activation Energy
• Activation Energy is the minimum amount of energy
required to start a chemical reaction.
• It has a cascading effect.
• An endothermic reaction requires A LOT of
activation energy.

82
Surface Area
• If you break the reactants into smaller pieces
then there is more surface area in contact with
the other reactant. Thereby increasing the
chance that 2 oppositely charged atoms can bond
together.

83
Temperature
• If you increase the temperature then the
molecules are moving faster and thereby making
connections more frequently.

84
Concentration
• Concentration is the amount of a substance in a
given volume. Increasing the concentration of a
substance means there are more atoms or molecules
available for bonding.

85
Catalysts
• Catalysts increase the rate of reaction by
lowering the activation energy required to start
the reaction.
• They are not reactants and they are not consumed
during a reaction.

86
Inhibitors
• Inhibitors slow reactions by interfering with the
reactants ability to get to each other.

87
Demo Time
• Decomposition of Hydrogen Peroxide
• KI
• 2H2O2 ? 2H2O O2

88
• Answer on a sheet of notebook paper
• Describe what happened in this demonstration.
• Is this an endothermic or exothermic reaction?
• What is a catalyst?
• Name the catalyst in this demonstration.
• Could it be included as a reactant in the
chemical equation?

89
Acids
• Produce H ions in H2O
• Ex HCl ? H Cl-
• Properties
• Tastes sour
• Corrosive reaction w/metal
• Reacts w/CO32- to make CO2
• Turns blue litmus paper red

90
Examples of Acids
• HCl hydrochloric acid
• CH3CO2H acetic acid (vinegar)
• H2SO4 sulfuric acid
• Ascorbic Acid Vitamin C (citrus)
• Fertilizers
• Nitric Phosphoric Acid
• Lactic Acid

91
Bases
• Produce OH- ions in H2O
• Ex NH3 H2O ? NH4 OH-
• Tastes bitter
• feels slippery
• Turns red litmus paper blue

92
Examples of Bases
• NaHCO3 baking soda
• household cleaners including
• NH3- ammonia
• Drain Cleaner

93
Strength
• The strength of an acid or a base is based on how
well it produces ions in water.
• Strong Acids HCl H2SO4
• Strong Bases - NaOH

94
Measuring Strength
• pH Potential Hydrogen
• Range of values from 0 to 14 that describes the
concentration of H ions in a substance.
• Since we are measuring H ions and they are
produced by acids, we can expect the higher it is
on the scale, the more acidic it is!

95

96
Safety
• Know the pH (strength) of the acid or base you
are handling.
• Everything from 2-11 is in the safe zone.

97
Precautions
• When working with a strong acid or base (0-2 or
11-14) be sure to wear goggleseven if its a
dilute solution!
• For spills-
• Pour vinegar on a base sodium bicarbonate on an
acidbecause

98
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99
Acid Base Neutralization
• Displacement reaction
• Acid Base ?
• (liquid) water (solid) salt
• Salt Group 1-2 Metal a halogen

100
Demo Time
NaHCO3 NaOH ? Na2CO3 H2O
101
Precipitate Reactions
• If the ions in 2 solutions combine to form a
solid and that solid is NOT soluble with the
solvent produced a precipitate will form.
• ? Example
• Fe(NO3)3(aq) 3 NaOH(aq) ? Fe(OH)3(s) 3
NaNO3(aq)

102
Demo Time
• Cu(NO3)2(aq) 2 NaOH(aq) ? Cu(OH)2(s) 2
NaNO3(aq)