What is the best method to classify a chemical substance?
classifiers
conductivity
conductive when dissolved in water = ionic compound
not conductive = non metal
chemical compounds
metals
malleable
have luster when sanded
ductile
non-metals
dull
ionic compounds
type of substance
shape
regular
ionic compounds are brittle, break in regular shapes (i.e. sodium chloride)
metals are malleable and ductile, can be found in strips/wires
irregular
metals are malleable, but likely found in clusters/irregular chunks
usually brittle
usually can dissolve in water
high melting point
organic
inorganic
form
solid
liquid
gas
mixture
classification
element
metals
metallic bonding
compounds
non metals
covalent bonding
non metal + metal
ionic bonding
mixture
contents
no fixed shape, reforms to fit container
fixed shape
ability to be stretched out into wires
ability to be reshaped through force
high boiling point
ionic bonds are built when atoms share transfer electrons - if a negatively charged atom is displaced and slides close to another negatively charged atom, it produces a force that pushes them apart
conductive when dry
conductive when dry = metal
deconstruct
what is a chemical substance?
covalent bonds
a chemical substance is any compound or element that has a consistent composition and structure
how do you classify a chemical substance?
methods for classification
depending on the bond, a chemical substance's properties can vary due to the type of bond
conductivity
use a conductivity probe to test for electrical conductivity
melting and boiling point
hardness and malleability
if not electrically conductive when dry, submerge in water
solubility
submerge in water
if the substance dissolves, it is water soluble
test for conductivity again
good heat conductors
conductivity is a factor that can determine the substance's compound form
exposing the substance to heat
if the substance breaks easily, it is brittle
if the substance does not break but dents, it is malleable
if the substance is a liquid, it can be placed in a beaker and held above
use a board and hammer to lightly hammer the substance (IF SOLID)
chemical substances can be identified and classified through a series of tests which confirm different properties of specific categories
for example, running a conductivity test when the substance is dry/dissolved in water would determine whether it is a metal (conductive when dry) or an ionic compound (conductive when dissolved in water)
a physical blend of 2 or more substances that can exist within themselves
brittle
poor conductors
high ionisation energy and electronegativity
luster
does the substance appear shiny without sanding?
when sanded, does the substance appear shiny?
can the substance be described as dull?
the appearance of the substance in terms of luster can assist in determining the chemical bond of the substance
expected outcomes/dependent variables
variables to consider
environment
is the environment that all the experiments are conducted in consistent?
what variables affect the consistency?
temperature
lighting (sun, heat, direct light, colour of light)
controlled variables
using the results gathered, it should become easier to assume the type of bond that occurs within the structure of the substance
the assumption SHOULD BE MADE using correct scientific evaluation and knowledge
i.e. putting together the different results from a test, and knowing it is an ionic bond because of the properties that the substance displayed.
consistent amount of water/heat applied etc. when conducting tests
temperature of bunsen burner
amount of the substance used
how will each method be proved effective?
time taken to conduct the method
reliability of the results
difficulty of which the results can be gathered
because different types of bonding can display the same properties and characteristics, how will the observations provide a clear difference between these types of bonds?