Support
activities – Concept review
MW4
P
answer
key
Concept
review: chemical
change,
conservation of matter,
decomposition and synthesis,
dissolution, oxidation,
photosynthesis and respiration,
physical change,
precipitation
hysical and chemical changes
conservation of matter,
decomposition and synthesis,
dissolution, oxidation,
photosynthesis and respiration,
physical change,
precipitation
1. Complete
the sentences,
using the
words in
the box
below. You
may not
need some
words, and
you may
use others
more than
once.
-
• always• atoms• chemical• chlorophyll• colour• combustion• element• energy• gas• matter• molecule(s)• nature• often• oxygen• solid• solute• solvent• substance(s)• sugars• water
nature
substance
nature
a) A
physical change
is a
transformation
that changes
neither the
________________________
nor the
characteristic
properties of
matter. No
new
________________________
is produced.
substances
colour
b) A
chemical change
is a
transformation
that changes
the
________________________
and
characteristic
properties of
matter. New
________________________
are produced.
The following
signs indicate
that a
chemical change
has occurred:
– There
is a
change in
________________________.
energy
– There
is a
change in
temperature.
gas
– A
large amount
of
________________________
is released
or absorbed.
solid
– A
________________________
is emitted.
– A
________________________
is formed
when two
liquids are
mixed together.
– The
change is
usually
irreversible.
matter
always
matter
c) According
to the
law of
conservation of
matter, in
all changes,
whether physical
or chemical,
the amount
of
_______________________
________________________
remains
the same.
The
mass of
________________________
does not
change.
solute
solvent
d) Dissolution
is the
process of
preparing a
solution by
mixing a
________________________
in
a
________________________.
chemical
oxygen
oxygen
e) Oxidation
is a
________________________
change involving
________________________
or a
substance with
properties
similar to
those of
________________________.
molecule
atoms
molecules
atoms
f) Synthesis
is the
formation of
a complex
____________________
from
____________________
or simpler
molecules.
Decomposition is
the
transformation of
complex
________________________
into simpler
molecules or
into
________________________.
sugars
water
chlorophyll
combustion
g) Photosynthesis
is the
process by
which producers
use solar
energy to
make their
food
(________________________)
from carbon
dioxide and
________________________.
This process
takes place
in cells
that contain
________________________.
Cellular
respiration is
the opposite
reaction to
photosynthesis.
It is
the process
by which
living cells
produce energy
through the
________________________
of complex
nutrients.
solid
h) Precipitation
is the
formation of
an insoluble,
or only
slightly soluble,
____________________
substance, called
a precipitate.
Precipitation may
occur when
two solutions
are combined.
2.
Are the
following
phenomena
physical or
chemical changes?
Check the
appropriate
column.
-
Physical changeChemical changea)A burning forest
b)Snow melting in the spring
c)The moulding of plastic
d)Photosynthesis in plants
3.
Various signs
indicate that
a chemical
change has
occurred or
is occurring.
What signs
could you
observe in
each of
the following
chemical changes?
Change
in colour and irreversible change
a) Rust
appears on
an object.
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Formation
of a solid and irreversible change
b) When
you mix
vinegar with
milk, a
white solid
forms.
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- WChange in temperature, release of a large amount of energy and emission of a gashen you recharge a car battery, an explosive gas (hydrogen) is formed, and the battery becomes hot.
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4
. The
following are
steps you
might take
in lab
procedures. Check
the actions
that produce
a chemical
change.
-
a) You distill alcohol. b) You melt ice. c) You burn wooden splints. d) You mix a blue liquid with a yellow liquid, and the mixture turns green. e) You mix two liquids, and a precipitate forms. f) You mix two liquids, and the mixture gives off a large amount of heat.
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