chapter 5 - structure and properties of material

Question 1

define element

Answer 1

an element is a pure substance
that cannot be broken down into
two or more simpler substances
by chemical processes or
electricity.

Question 2

define a compound

Answer 2

A compound is a pure substance that
contains two or more elements
chemically combined.

Question 3

define a mixture

Answer 3

A mixture contains two or more substances
without chemical reaction between these
substances.

Question 4

name some elements that exists as diatomic molecules

Answer 4

H2, N2, O2

Question 5

what are some properties of an element?

Answer 5

• 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.

Question 6

what are some properties of compounds?

Answer 6

• 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.

Question 7

what are some properties of a mixture?

Answer 7

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.

Question 8

name 3 example of elements

Answer 8

any elements on the periodic table (magnesium, sulfur etc)

Question 9

name the 2 types of compounds

Answer 9

ionic compounds (sodium chloride etc) and covalent compounds (ammonia, water etc)

Question 10

name 3 types of mixtures

Answer 10

• 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)

Question 11

name the structure of an ionic compound

Answer 11

giant crystal lattice structure

Question 12

name the structure of a simple covalent substance

Answer 12

simple molecular structure

Question 13

name the types of bonding of an ionic compound

Answer 13

• formed between metal and non-metal
• strong electrostatic forces of attraction
between cations and anions (ionic bond).
• examples: NaCl

Question 14

name the types of bonding of a simple covalent substance

Answer 14

• formed between non-metals
• strong covalent bonds between the atoms within molecules.
• weak intermolecular forces of attraction (between molecules)
• example: hydrogen chloride

Question 15

state the melting and boiling points of an ionic compound (high/low)

Answer 15

high melting and boiling points

Question 16

why does an ionic compound have high melting and boiling points?

Answer 16

as large amount of energy is required to overcome the
strong electrostatic forces of attraction between
the positively charge ions and negatively charge ions.

Question 17

state the melting and boiling point of simple covalent substance (high/low)

Answer 17

low melting and boiling points

Question 18

why does simple covalent substance have low melting and boiling points?

Answer 18

as smaller amount of energy is required to overcome the weak
intermolecular forces of attraction.

Question 19

ionic compound conducts electricity in solid state. true or false?

Answer 19

false. it does not conduct electricity in solid state.

Question 20

why does ionic compounds not conduct electricity in a solid state?

Answer 20

ions are held at fixed positions by strong ionic bonds. no free moving ions to conduct electricity.

Question 21

ionic compound only conducts electricity in molten state. true or false?

Answer 21

false. it conducts electricity in molten or aqueous state.

Question 22

simple covalent substance conducts electricity in liquid state. true or false?

Answer 22

false. it does not conduct electricity in all states.

Question 23

simple covalent substance conducts electricity in liquid state. true or false?

Answer 23

false. it does not conduct electricity in all states.

Question 24

why does simple covalent substance not conduct electricity in all states?

Answer 24

covalent compounds exist as molecules. no free moving ions to
conduct electricity.

Question 25

why can ionic compound conduct electricity in molten or aqueous state?

Answer 25

giant crystal lattice structure breaks down. ions are able to move freely in the structure.

Question 26

what is the solubility of ionic compounds?

Answer 26

they are mostly soluble in water and mostly insoluble in organic solvent.

Question 27

state the solubility of simple covalent substance

Answer 27

they are mostly insoluble in water and mostly soluble in organic solvent