Chapter 4
Formation of Compounds
4.1 The Variety of Compounds
4.2 How Elements Form
Compounds
4.1 The Variety of
Compounds
Objectives
• Distinguish the properties of compounds from
•
•
those of elements of which they are composed.
Compare and contrast the properties of sodium
chloride, water and carbon dioxide.
Analyze evidence to conclude the differences
exist in the ways compounds form.
Salt: A Familiar Compound
• Chemical Name: Sodium Chloride
• Formula: NaCl
• Very abundant in nature
– Large, solid, underground deposits
– Dissolved in the oceans
• Salt can be obtained by mining the solid
deposits or evaporating the seawater
Sodium Chloride Uses
• Food enhancer
• Essential nutrient in living things
• Used to melt ice
Physical Properties of NaCl
• White solid at room temperature
• Crystalline
• Brittle
• Melting point: 800°C
• Dissolves easily in water
• Salt water is an excellent conductor of
electricity
Chemical Properties of NaCl
• Does not react readily with other
substances.
• Does not degrade quickly
• No special handling procedures
Properties of Sodium
• Shiny
• Silvery-white
• Soft
• Solid metal
• Melting point: 98°C
• Stored under oil b/c it reacts with oxygen
and water vapor in the air
Properties of Sodium
• One of the most reactive of the common
elements
• Free element sodium is never found in the
environment
• Always combined with another element
Properties of Chlorine
• Pale green
• Poisonous gas
• Choking odor
• Kills living cells
• Slightly soluble in water
• Excellent disinfectant for water supplies
and pools
Properties of Chlorine
• Nonmetal, halogen
• Gas must be cooled to -34°C before it
turns to a liquid
• Among the most reactive of elements
• Handled with extreme care
Salt Formation
Formation of Sodium Chloride
• Two extremely reactive and unstable
elements combine to form a stable, safe
substance.
+

Review
1. What are two physical properties of
Sodium Chloride?
2. What is a chemical property of Sodium
Chloride?
3. What are two physical properties of
Sodium?
4. What are two physical properties of
Chlorine?
4.1 The Variety of Compounds
(Continued)
Carbon Dioxide: A Gas to Exhale
• Formula: CO2
• Colorless gas
• We exhale carbon dioxide as a result of
respiration
• Plants use carbon dioxide and release
oxygen during photosynthesis
Physical Properties of CO2
• Colorless
• Odorless
• Tasteless
• Gas
• When cooled to -80°C, the gas changes
directly to a white solid
Physical Properties of CO2
• Soluble in water
• Weak conductor of electricity
• “Dry Ice”-does not melt to a liquid
Chemical Properties of CO2
• Relatively stable
• Used in fire extinguishers-does not
support burning
• Photosynthesis-most significant chemical
reaction using CO2.
The Properties of Carbon
•
•
•
•
•
•
•
Nonmetal
Black, brittle solid
Fairly unreactive at room temperature
At higher temps will react with many elements
Burns well: Charcoal is 90% carbon
Forms a huge variety of compounds
Organic chemistry?
The Properties of Oxygen
• Nonmetal
• Colorless
• Odorless
• Tasteless Gas
• 21% of the air we breathe
• Oxygen supports burning
The Properties of Oxygen
• Becomes a liquid when cooled to -183°C
• Slightly soluble in water
• More reactive than carbon
– Rusting
• Combines with many elements
• Most abundant element in Earth’s crust
Earth’s Crust
Water, Water Everywhere
• Formal Chemical name: Dihydrogen
monoxide
• Formula: H2O
• Covers 70% of the Earth
• Approx. 70% of the mass of the
average human body
Physical Properties of Water
• Three states: Solid, Liquid, Gas
• Boiling Point: 100°C
• Freezing Point: 0°C
• Pure water does not conduct electricity
• Excellent solvent “universal solvent”
• Vital in the transport of dissolved
materials
Water
Chemical Properties of Water
• Stable
• Does not react with many other
substances
• Medium in which many chemical reactions
occur (human body)
• Starting material for photosynthesis
Properties of Hydrogen
• Lightest element
• Most abundant element in the universe
• Nonmetal
• Reactive element
• Odorless
• Colorless
• tasteless
Properties of Hydrogen
• Seldom found as a free element
• React vigorously with many elements,
including oxygen forming water
• Becomes a liquid at -253°C
• Does not conduct electricity
• Only slightly soluble in water
Using Clues to Make a Case
• Elements combine to form compounds
with different properties
• Elements do not always combine in the
same way or all compounds would have
similar properties
• We will examine how elements combine in
the Section 4.2
Review
• What are some properties of Carbon
Dioxide?
• What are
• What are
• What are
• What are
some
some
some
some
properties
properties
properties
properties
of
of
of
of
Carbon?
Oxygen?
Water?
Hydrogen?