Elements, Compounds, and Mixtures

1
Elements, Compounds, and Mixtures
Preview
Section 1 Elements Section 2
Compounds Section 3 Mixtures
Concept Mapping
2
Section 1 Elements
Objectives

• Describe pure substances.
• Describe the characteristics of elements give
  examples.
• Explain how elements can be identified.
• Classify elements according to their properties.

3
Section 1 Elements
Elements, the Simplest Substances

• Element pure substance that cannot be separated
  into simpler substances by physical or chemical
  means.

4
pure substance substance in which there is
only one type of atom
5
Section 1 Elements
Properties of Elements

• Each element can be identified by its unique set
  of properties.
• An element may share property w/ another
  element, but other properties help distinguish
  elements from each other.
• Elements can be identified by using physical
  properties and chemical properties.

6
Identification of Elements
7
Section 1 Elements
Classifying Elements by Their Properties, ctd

• Categories Are Similar
• By knowing category to which unfamiliar element
  belongs ? can predict some of its properties.
• The next slide show examples and properties of
  metals, nonmetals, and metalloids.

8
Section 1 Elements
Classifying Elements by Their Properties
Three Major Categories of Elements
9
Section 1 Elements
10
Section 2 Compounds
Bellringer
The word compound refers to something
that consists of two or more parts. How might you
make a compound using elements? How many
compounds can you think of that you use every
day. Record your answers in your science journal.
11
Section 2 Compounds
Objectives

• Explain how elements make up compounds.
• Describe the properties of compounds.
• Explain how a compound can be broken down into
  its elements.
• Give examples of common compounds.

12
Section 2 Compounds
Compounds Made of Elements

• Compound pure substance composed of two or more
  elements that are chemically combined. Elements
  combine by reacting with one another.
• Molecule particle of a compound, formed when
  atoms of two or more elements join together.

13
Section 2 Compounds
Compounds Made of Elements

• The Ratio of Elements in a Compound
• Elements join in a specific ratio according to
  their masses to form a compound.
• EX every sample of water has a 18 mass ratio of
  hydrogen and oxygen.

14
Section 2 Compounds
Properties of Compounds

• Each compound can be identified by its physical
  and chemical properties.
• Properties Compounds Versus Elements
• A compound has properties that differ from those
  of the elements that form it.
• EX sodium chloride
• sodium (soft, silvery metal, reacts
  violently w/water
• chlorine (poisonous greenish gas)
• sodium chloride (white, crystalline solid,
  safe to eat)

15
Section 2 Compounds
Breaking Down Compounds

• Compounds can be broken down into their elements
  or into simpler compounds by chemical changes.
• Methods of Breaking Down Compounds
• Sometimes, energy is needed for a chemical
  change to happen.
• 2 ways to add energy
• apply heat
• apply electric current

16
Section 2 Compounds
Compounds in Your World

• Cpds in Nature EX proteins, carbon dioxide,
  carbohydrates.
• Compounds in Industry
• Some cpds must be broken down for industrial
  use.
• Other cpds made in industry for use as
  medicines, food preservatives, synthetic fabrics.

17
Section 3 Mixtures
Bellringer
When you add sugar to coffee, tea, iced tea,
or lemonade, the sugar disappears. What do you
think happens to the sugar? Does the same thing
happen to salt when you add it to soup? Does
temperature, acidity, or color matter? Why or why
not? Record your answers in your science journal.
18
Section 3 Mixtures
Objectives

• Describe three properties of mixtures.
• Describe four methods of separating parts of a
  mixture.
• Analyze a solution in terms of its solute and
  solvent.
• Explain how concentration affects a solution.
• Describe the particles in a suspension.
• Explain how a colloid differs from a solution
  and a suspension.

19
Section 3 Mixtures
Properties of Mixtures

• mixture combination of two or more substances
  that are NOT chemically combined.
• No Chemical Changes in a Mixture
• No chemical changes happen when a mixture is
  made.
• Each substance has the same chemical makeup it
  had before the mixture was formed.

20
Section 3 Mixtures
Properties of Mixtures, ctd

• Separating Mixtures Through Physical Methods
  Mixtures can be separated by using physical
  changes. Physical changes do not change the
  identities of the substances.
• The next slide shows some common ways to separate
  mixtures by using physical changes.

21
Section 3 Mixtures
22
Section 3 Mixtures
Properties of Mixtures, ctd

• The Ratio of Components in a Mixture
• The components of a mixture do NOT need to be
  mixed in a definite ratio.
• EX granite is mixture of three minerals.
• Different ratios of the minerals give granite
  different colors, but the mixture is always
  called granite.

23
Section 3 Mixtures
Solutions

• solution a mixture that appears to be a single
  substance.
• dissolving process in which particles of
  substances separate and spread evenly throughout
  a mixture
• solute the substance that is dissolved.
• solvent the substance in which the solute is
  dissolved.

24
Section 3 Mixtures
Solutions, ctd

• Examples of Solutions
• Liquid solutions soft drinks, gasoline, and tap
  water.
• Gaseous solutions air.
• Solid solutions steel, metal alloys such as
  brass Alloys solid solutions of metals or
  nonmetals dissolved in metals.

25
Section 3 Mixtures
Solutions, ctd

• Particles in Solutions ? are so small that they
  never settle out they also cannot be removed by
  filtering.
• The particles in solutions are so small they
  dont even scatter light.

26
Section 3 Mixtures
Concentrations of Solutions

• concentration measure of the amount of solute
  dissolved in a solvent
• Concentrated or Dilute?
• Solutions can be described as being concentrated
  or dilute.
• But these two terms DO NOT tell the amount of
  solute that is dissolved.
• The next slide shows how to calculate
  concentration.

27
Section 3 Mixtures
Concentrations of Solutions, ctd

• Solubility ability of a solute to dissolve in a
  solvent at a certain temperature.
• The solubility of most solids in water increases
  with temperature.

28
Section 3 Mixtures
Concentrations of Solutions, ctd

• Dissolving Gases in Liquids
• Gases become LESS soluble in liquids as
  temperature increases.
• Dissolving Solids Faster in Liquids
• Three ways to make a solute dissolve faster
• mixing the solution
• heating the solution
• crushing the solute into smaller particles
  (increase surface area).

29
Section 3 Mixtures
Suspensions

• suspension mixture in which particles of a
  material are dispersed throughout a liquid or a
  gas but are large enough that they settle out.
• The particles in a suspension are large enough
  to scatter or block light.
• A suspension can be separated by passing it
  through a filter.

30
Section 3 Mixtures
Colloids

• colloid mixture in which the particles are
  dispersed throughout but are not heavy enough to
  settle out.
• Particles in a colloid are large enough to
  scatter light.
• A colloid cannot be separated by passing it
  through a filter.