What is Matter?

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What is Matter?
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Objectives

• Explain the relationship between matter, atoms,
  and elements
• Distinguish between elements and compounds
• Describe molecules, and explain how they are
  formed
• Interpret and write some common chemical formulas
• Categorize materials as pure substances or
  mixtures

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What is chemistry and matter?

• Chemistry the scientific study of the
  composition, structure, and properties of matter
  and the changes that matter undergoes.
• Matter anything that has mass and takes up
  space.

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• Element a substance that cannot be separated or
  broken down into simpler substances by chemical
  means.
• Atom the smallest unit of an element that
  maintains the properties of that element
• Compound a substance made of atoms of two or
  more different elements that are chemically
  combined.

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• Molecule the smallest unit of a substance that
  keeps all of the physical and chemical properties
  of that substance.
• A compound is made of two or more different
  elements, but a molecule may be of the same
  elements or different elements.

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• Remember some elements occur singly in nature
• Ex) Neon
• The atoms of other elements combine to form
  polyatomic molecules
• Ex) O2 H2 P4

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• Molecules can be represented by
• Formula
• Physical models
• Chemical formula- a combination of chemical
  symbols and numbers to represent a substance
• C16 H10 N2 O2 Indigo
• C8 H10 N4 O2 Caffeine

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• Mixture- a combination of two or more substances
  that are not chemically combined
• Pure substance- a sample of matter, either a
  single element or a single compound, that has
  definite chemical and physical properties
• Elements and compounds are pure substances, but
  mixtures are not

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Solids can mix with liquids

• Mixtures can be separated into their components
• Heterogeneous mixture- substances arent mixed
  uniformly and are not evenly distributed
• Ex) flour in water a suspension
• Homogeneous mixture- components are evenly
  distributed, mixture is same throughout
• Ex) sugar in water

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Liquids can mix with liquids

• Gasoline is a liquid mixture of 100 liquids
• Comprised of miscible liquids
• Miscibility- only miscible liquids that are
  combined (ex. Ethylene glycol and water) can
  dissolve in each other.
• They form a solution (a homogeneous liquid
  mixture)

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• Immiscible- liquids such as oil and water or
  toluene and water that are practically insoluable
• Instead, they form two layers, with the denser
  liquid on the bottom.

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Gases can mix with liquids

• Ex) Lava
• The molten rock in some types of volcanoes
  contains large quantities of gas. Pumice, a
  solid foam that occurs naturally on Earth, is a
  volcanic rock formed by the violent separation of
  these extremely hot gases from lava.
• As the exploding lava cools, it traps the bas
  bubbles.
• Some pumice is so soft that it is spongy, and has
  such a low density that it floats on water

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2.2

• Objectives
• Distinguish between the physical and chemical
  properties of matter, and give examples of each
• Perform calculations involving density
• Explain how materials are suited for different
  uses based on their physical and chemical
  properties
• Describe characteristic properties

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Physical properties

• Physical properties identify things by describing
  matter
• Examples
• Color
• Shape
• Height
• Mass
• Volume
• density

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• More examples of physical properties
• Melting point (temperature and pressure at which
  a solid becomes a liquid)
• Boiling point (temperature and pressure at which
  a solid becomes a liquid)
• Strength
• Hardness
• Ability to conduct electricity
• Magnetism
• Heat

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A characteristic of any pure substance is that
its boiling point and melting point are constant
if the pressure remains the same
substance Melting point º Celsius Boling point º Celsius
C 3550 4827
Au 1063 2970
Fe 1535 2750
Hg -39 357
N -209 -196
O -218 -183
NaCl 801 1413
H2O 0 100

• .

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• Density Mass
• Volume
• Density depends on the arrangement of atoms
  within that sample of matter
• Density determines whether an object will float
  or sink

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Densities of some substances
Substance Chemical formula Density in g/cm3
Air, dry Mixture 0.00129
Brick Mixture 1.9
Gasoline Mixture 0.7
Helium He 0.00018
Ice H20 0.92
Iron Fe 7.86
Lead Pb 11.3
Nitrogen N2 0.00125
Steel Mixture 7.8
Water H20 1.00
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• The density of a liquid or a solid is affected
  only slightly by a change in temperature or
  pressure.
• In a gas however, an increase in temperature or a
  decrease in pressure significantly reduces the
  density of a gas

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Chemical Properties

• Chemical property- describes how a substance
  changes into a new substance either by combining
  with other elements or by breaking apart into new
  substances.
• Examples
• Reactivity of element with other compounds
  (oxygen, acid, water, other)
• Oxidation of Fe creates rust
• Flammability (ability to burn)

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Changes of matter

• Objectives
• Explain physical change, give examples
• Explain chemical change, give examples
• Compare and contrast physical and chemical
  changes
• Describe how to detect whether a chemical change
  has occurred

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• A physical change affects one or more physical
  properties of a substance without changing its
  identity
• Ex) breaking chalk
• Getting a hair cut
• Dissolving sugar
• Melting ice
• Sanding wood
• Crushing a can
• Mixing oil and vinegar

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Mixtures can be physically separated because the
components are not chemically combined.

• Distillation device- can separate components of
  mixtures that have different boiling points.
  When heated, the component that boils and
  evaporates first, separates from the mixture and
  collects in the receiving tank

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• Magnets can be used to separate mixtures that
  have components containing iron.

• Centrifuge- tool used to separate mixtures. It
  spins a sample of a mixture rapidly until the
  components of the mixture separate

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• Changes in the state of matter are physical
  because they do not change the identity of the
  substance!!!

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Chemical changes

• A change that occurs when a substance changes
  composition by forming one or more new
  substances.
• Ex) soured milk (produces odor)
• Effervescent tablets (produce CO2)
• (copper penny?copper carbonate)
• Oxidation- (iron ? rust)
• Fruits ripening
• Food being digested

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• Chemical changes form new substances that have
  different properties
• Ex) baking a cake

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Chemical changes can be detected

• Clues suggesting that a chemical change occurred
• Change in odor or color
• Fizzing
• Foaming
• Production of sound, heat, light, odor

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• Chemical changes cannot be reversed by physical
  changes
• Ex) you can not unbake a cake
• However, some chemical changes can be reversed
  under the right conditions by other chemical
  changes.