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The Chemical Nature of Matter

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Title: The Chemical Nature of Matter


1
The Chemical Nature of Matter
  • 7th Grade Science
  • Standard 7-5

2
Classification of Matter
  • Matter is something that has mass and takes up
    space
  • It can be classified by what it is made of
    (composition)

3
Solids
  • Take up Space
  • Have a fixed shape
  • Dont flow
  • Have weight

4
LIQUIDS
  • Takes Up Space
  • CHANGE Shape to fit container
  • Flow
  • Have weight

5
Gases
  • Takes up Space
  • Change Shape
  • Invisible (usually)
  • Have weight

6
Atoms
  • Atoms the smallest part of an element that has
    chemical properties of that element
  • Has mass and takes up space

7
Pure substances - Elements
  • Elements pure substances that cannot be changed
    into simpler substances,
  • Ex. Iron, hydrogen, oxygen, calcium
  • Elements are composed (made) of only one type of
    atom.
  • Elements are represented by symbols

Element Symbol
Sodium Na
Chlorine Cl
Hydrogen H
Oxygen O
Carbon C
Nitrogen N
8
Mixtures
Mixtures are composed of two or more different
substances that retain their own individual
properties and are combined physically (mixed
together). Mixtures can be separated by physical
means (filtration, sifting, or evaporation). Mixt
ures may be heterogeneous (DIFFERENT) or
homogeneous (SAME).
9
Compounds
Compounds are pure substances that are composed
of two or more types of elements that are
chemically combined. Compounds can only be
changed into simpler substances called elements
by chemical changes (7-5.10). One way that two
or more atoms can combine is to form a molecule.
10
MATTER ACTIVITY
11
Periodic Table
  • Periodic Table of the Elements a chart that
    organizes all of the elements
  • Elements of the periodic table are identified
    with numbers (called atomic numbers) increasing
    from left to right across each row.

12
Periodic Table Cont.
  • A horizontal row is called a period
  • The periodic table has a square for each element
    with the atomic number, atomic mass, element
    name, and the element symbol

Atomic number
Element symbol
Element name
Atomic mass
13
  • There are two large sections of the table. Find
    the zigzag line on the left are metals and on
    the right of that line are non-metals

14
Families of the Periodic Table
  • Families also called groups, vertical columns
    of elements that have similar properties

15
Metals
  • Metals Groups of elements generally located on
    the left side of the zig zag line of the table
  • Ex. Sodium (Na), Calcium (Ca), Iron (Fe), and
    Aluminum (Al)
  • Have the following properties in common - luster,
    are conductors, are malleable, ductile and have
    high density

16
Luster
  • Luster shiny surface, reflecting light brightly
  • ex. Aluminum (inside of a soda can)

17
Properties of Metals
  • Conductors heat and electricity move through
    them easily
  • Ex. Copper wire, aluminum pot
  • Malleable ability to be hammered into different
    shapes
  • Ex. Gold
  • Ductile ability to be drawn into wire
  • Ex. Wire
  • High Density heavy for their size
  • Ex. Bar of silver

18
Nonmetals
  • Nonmetals Groups of elements generally located
    on the right side of the table
  • Ex. Chlorine (Cl), Oxygen (O), Sulfur (S), and
    Iodine (I)
  • Have the following properties in common - are
    dull, nonconductors and are brittle.

19
Properties of Nonmetals
  • Dull not shiny
  • Nonconductors heat and electricity do no move
    through them
  • Brittle break or shatter easily

20
Chemical Symbols
  • Elements have chemical symbols.
  • Chemical Symbols
  • Na - Sodium
  • Cl - Chlorine
  • H - Hydrogen
  • O - Oxygen
  • C - Carbon
  • N - Nitrogen

21
Compound
  • Compounds pure substances that are composed of
    two or more types of elements ex. Water, salt,
    sugar
  • Can only be changed into simpler substances
    (elements) by chemical changes.

22
Mixtures
  • Mixtures composed of different substances that
    are mixed together
  • Ex. Italian dressing, garlic salt,
    iron filings and sulfur (pictured here)
  • Mixtures can be easily separated into their
    component substances by filtering, sifting,
    magnetic attraction, evaporation, chromatography
    and flotation.

23
Chemical Formulas
  • Compounds and some forms of elements have
    chemical formulas.
  • Molecule - The smallest part of a compound.
  • Chemical Formulas
  • H2O - Water
  • CO2 - Carbon Dioxide
  • NaCl - Sodium Chloride (or salt)
  • C6H12O6 - Simple Sugar

24
Diatomic Molecules
  • Some elements bond together to be more stable,
    the next two formulas are for diatomic (two atom)
    molecules. These occur abundantly in earths
    atmosphere.
  • O2 - Oxygen gas
  • N2 - Nitrogen gas

25
Solutions
  • Solutions a liquid (ex. Water solvent) that
    has something dissolved in it ex. Sugar (solute)
  • Concentration the amount of solute in a
    solution

26
pH
  • pH a measure of the concentration of solutions
    of acids and bases
  • Stands for power of Hydrogen or how many
    hydrogen ions are in a liquid
  • The pH scale goes from 1-14. 1 being the
    strongest acid, 14 being the strongest base, 7
    being neutral.
  • Water (non-polluted or distilled) should be
    neutral.

27
pH Scale
  • The pH scale goes from 1-14. 1 being the
    strongest acid, 14 being the strongest base, 7
    being neutral.
  • Water (non-polluted or distilled) should be
    neutral.

28
Acids
  • Acids 0-6 on the pH scale
  • Have a sour taste ex. Lemon, orange
  • NEVER use the taste test on laboratory chemicals
  • Reacts with metals (see evidence for a chemical
    reaction below)
  • Reaction with bases to form neutral pH solutions

29
Bases
  • Bases 8-14 on the pH scale
  • Bitter taste ex. Soapsuds
  • NEVER use the taste test or feel test on
    laboratory chemicals
  • Feel slippery ex. Chlorox, liquid soap
  • Reaction with acids to form neutral pH solutions

30
Neutral
  • Neutral neither an acid nor a base
  • Water (non-polluted or distilled) should be
    neutral

31
pH Scale
32
Indicators
  • Indicators substances that can be used to
    determine whether a solution is an acid or a base
  • Litmus Paper
  • pH Paper
  • Phenolphthalein

33
Litmus Paper
  • Litmus paper
  • blue litmus paper turns red in an acid and stays
    blue in a base
  • red litmus paper turns blue in a base and stays
    red in an acid
  • Both red and blue litmus paper turn purple in a
    solution that is neutral
  • Usually neither turn a color just get wet
    paper.

34
Litmus Paper
  • Always use a strip of red and blue paper when
    testing a substance. You need the results of both
    to compare to be sure you have an acid, base or
    neutral!

35
pH Paper Phenolphthalein
  • pH paper can turn a series of colors, the color
    of the paper is compared to the chart on the pH
    paper vial to determine the pH
  • Phenolphthalein turns magenta (hot pink) in a
    strong base and stays clear in an acid

36
Chemical Equations
  • Chemical Equations are used to represent
    chemical reactions, they contain the chemical
    formulas for the substances that are mixed and
    the new substance(s) that are formed. An arrow
    separates them.

37
Chemical Equations
  • Reactants the substances that are mixed in a
    chemical reaction, are on the left side of the
    arrow
  • Products the new substance(s) that are formed
    in a chemical reaction, are on the right side of
    the arrow

38
Law of Conservation of Matter
  • Law of Conservation of Matter matter is neither
    created nor destroyed, but can be changed in form
  • The amount of matter does not change during a
    chemical reaction only the atoms are rearranged
    to form new substances.
  • The total mass of the material(s) before the
    reaction is the same as the total mass of
    material(s) after the reaction

39
Balanced Chemical Equations
  • Balanced chemical equations A balanced chemical
    equation has the same number of each kind of atom
    on both sides of the arrow.

40
Physical Properties
  • Physical Properties properties that can be
    observed and measured without changing the kind
    of matter being studied
  • Color
  • Melting Point
  • Boiling Point
  • Density

41
Color Melting Point
  • Color can be distinctive and can be used to
    help identify a substance
  • Melting point temperature at which a solid can
    change to a liquid

42
Boiling Point Density
  • Boiling point temperature at which a liquid
    changes into a gas
  • Density the measure of the heaviness of
    objects with constant volume, the mass of a given
    volume of a substance
  • 1 mL H2O 1cm3 H2O 1 g H2O
  • Density of water 1 g/mL or 1 g/cm3 or 1g/cc

43
Chemical Properties
  • Chemical Properties properties that are not
    always visible, can be recognized only when
    substances react chemically with one another
  • Chemical reactivity is the tendency of a
    substance to undergo a chemical reaction usually
    with other specific substances
  • Burning - When a substance reacts with oxygen
    quickly and releases heat and light energy

44
Chemical Properties
  • Rusting when a substance reacts with oxygen and
    water slowly
  • Ex. iron

45
Physical Changes
  • Physical Changes DO NOT change the identity of
    the substance
  • Change of state (solid to liquid to gas)
    Ex. Ice to water
  • Change in shape like tearing or shredding Ex.
    Paper
  • Change in size like when crushing Ex.
    chalk

46
Chemical Changes
  • A Chemical Change changes the identity of the
    substance
  • Ex. Na -Sodium is a highly reactive metal it
    explodes when placed in water
  • Cl Chlorine is a poisonous gas
  • When they combine in a chemical reaction they
    make NaCl salt basically a harmless substance

47
Zip Lock Bag Chemistry Activity
  • Can you identify the evidence of a chemical
    reaction?

48
How can you tell a chemical change has happened?
  • Evidence of a chemical reaction or chemical
    changes
  • Color change when a substance changes color the
    chemical composition usually changes
  • Temperature change When substances change
    temperature after being mixed with
    other substances

49
Evidence of Chemical Change
  • Precipitate formation when two or more liquids
    are mixed and a solid (precipitate) is forms
  • Gas formation when two or more liquids are
    mixed or heated and a gas (bubbles)
    is given off
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