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Physical Properties and Changes

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Physical Properties and Changes Chapter 7, Lesson 3 What is a physical property? A physical property is any characteristic of a material that can be observed without ... – PowerPoint PPT presentation

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Title: Physical Properties and Changes


1
Physical Properties and Changes
  • Chapter 7, Lesson 3

2
What is a physical property?
  • A physical property is any characteristic of a
    material that can be observed without changing
    the identity of the material itself such as
    color, shape or length.
  • Some physical properties, such as mass and
    volume, depend on the amount of matter other
    physical properties do not depend on the amount
    of matter.

3
Physical Properties
  • The temperature at which a solid changes to a
    liquid is its melting point. This does not
    depend on the amount of matter.
  • The temperature at which a liquid changes to a
    gas is its boiling point. This does not depend
    on the amount of matter.

4
Physical Properties (contd)
  • Attractive forces determine the melting and
    boiling points of a substance.
  • Molecules with weak attraction have low melting
    and boiling points.
  • Molecules with strong attraction have high
    melting and boiling points.

5
Physical Properties (contd)
  • Pressure also affects the boiling point
  • The higher the air pressure, the higher the
    boiling point.

6
Physical Properties (contd)
  • Density is a physical property of a substance
    that does not depend on the amount of matter.
  • Density is the mass-per-unit volume of a
    substance.
  • A substances density is higher when its
    particles are packed more tightly together.
  • D

7
Physical Properties (contd)
  • Hardness is a physical property that shows how
    strongly the particles of a substance are held
    together.
  • Diamonds are a form of carbon and are the hardest
    substance found in nature.

8
Physical Properties (contd)
  • The table below shows the difference between the
    structure of diamonds and graphite, both of which
    are forms of carbon.

9
Physical Properties (contd)
  • Thermal conductivity is the ability of a material
    to transfer heat.
  • When one part of a metal is heated, the particles
    collide into other particles and the heat is
    transferred throughout.

10
Physical Properties (contd)
  • Electrical conductivity is the ability of a
    material to transfer electric charge.

11
What is a physical change?
  • A physical change is any change in size, shape,
    or state of matter in which the identity of the
    substance is not changed.
  • Dissolving is a physical change in which one
    substance is mixed into another substance to form
    a solution.
  • Mixing is a physical change that takes place when
    two substances are combined and neither substance
    dissolves.

12
What is a physical change? (contd)
  • Changes in the state of matter of a substance are
    physical changes and are reversible
  • Melting and freezing
  • Boiling and condensing
  • Subliming and deposing

13
What is a chemical change?
  • In comparison, a chemical change is the change of
    one or more substances into other substances.
  • A chemical change can not be reversed
  • Burning paper ash, CO2, H2O
  • Baking soda vinegar CO2, H2O
  • Rust FeO (iron oxide)
  • (more to come in Chapter 8)

14
7-3 Lesson Review Questions
  • 1) When water changes to ice, it is undergoing a
    ____.
  • A chemical change
  • B physical change
  • C radioactive decay
  • D metallic change

15
7-3 Lesson Review Questions
  • 2) Which of the following is NOT a physical
    change?
  • A ice melting into water
  • B sugar dissolving into water
  • C sand and sugar mixing
  • D burning a candle

16
7-3 Lesson Review Questions
  • 3) Which of the following is NOT a physical
    property?
  • A density
  • B conductivity
  • C hardness
  • D all are physical properties
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