chapter 5 - structure and properties of material Flashcards
define element
an element is a pure substance
that cannot be broken down into
two or more simpler substances
by chemical processes or
electricity.
define a compound
A compound is a pure substance that
contains two or more elements
chemically combined.
define a mixture
A mixture contains two or more substances
without chemical reaction between these
substances.
name some elements that exists as diatomic molecules
H2, N2, O2
what are some properties of an element?
• has fixed melting and boiling
points.
• separation: It cannot be
broken down into simpler
substances.
• properties: it has its unique
physical and chemical
properties.
• composition: An element has
a fixed composition by mass.
what are some properties of compounds?
• has a fixed melting and boiling points.
• separation: It can only be broken
down into its elements or simpler
compounds by chemical processes
(such as thermal decomposition and
electrolysis)
• properties: Its physical and chemical
properties are different from the
elements it is made up of.
• composition: The elements in a
compound are always combined in a
fixed mass ratio.
• energy changes: A chemical reaction
takes place when a compound is
formed and usually there is an energy
change. The reactants get hot or cold.
what are some properties of a mixture?
melts and boils over a range of temperature.
• separation: The components of a mixture
can be separated by physical processes
such as magnetic separation, filtration,
distillation or chromatography.
• properties: The chemical properties of a
mixture are the same as those of its
components.
• composition: The components of a mixture
can be mixed in any ratio.
• energy change: No chemical reaction
takes place when a mixture is formed and
usually there is little or no heat change.
name 3 example of elements
any elements on the periodic table (magnesium, sulfur etc)
name the 2 types of compounds
ionic compounds (sodium chloride etc) and covalent compounds (ammonia, water etc)
name 3 types of mixtures
• mixture of compounds & elements: air
• mixture of compounds:
crude oil
seawater – (consist of water and salt)
• mixture of elements:
brass alloy (zinc & copper)
steel alloy (iron & carbon)
name the structure of an ionic compound
giant crystal lattice structure
name the structure of a simple covalent substance
simple molecular structure
name the types of bonding of an ionic compound
• formed between metal and non-metal
• strong electrostatic forces of attraction
between cations and anions (ionic bond).
• examples: NaCl
name the types of bonding of a simple covalent substance
• formed between non-metals
• strong covalent bonds between the atoms within molecules.
• weak intermolecular forces of attraction (between molecules)
• example: hydrogen chloride
state the melting and boiling points of an ionic compound (high/low)
high melting and boiling points
why does an ionic compound have high melting and boiling points?
as large amount of energy is required to overcome the
strong electrostatic forces of attraction between
the positively charge ions and negatively charge ions.
state the melting and boiling point of simple covalent substance (high/low)
low melting and boiling points
why does simple covalent substance have low melting and boiling points?
as smaller amount of energy is required to overcome the weak
intermolecular forces of attraction.
ionic compound conducts electricity in solid state. true or false?
false. it does not conduct electricity in solid state.
why does ionic compounds not conduct electricity in a solid state?
ions are held at fixed positions by strong ionic bonds. no free moving ions to conduct electricity.
ionic compound only conducts electricity in molten state. true or false?
false. it conducts electricity in molten or aqueous state.
simple covalent substance conducts electricity in liquid state. true or false?
false. it does not conduct electricity in all states.
simple covalent substance conducts electricity in liquid state. true or false?
false. it does not conduct electricity in all states.
why does simple covalent substance not conduct electricity in all states?
covalent compounds exist as molecules. no free moving ions to
conduct electricity.
why can ionic compound conduct electricity in molten or aqueous state?
giant crystal lattice structure breaks down. ions are able to move freely in the structure.
what is the solubility of ionic compounds?
they are mostly soluble in water and mostly insoluble in organic solvent.
state the solubility of simple covalent substance
they are mostly insoluble in water and mostly soluble in organic solvent
