Unit 1.0

Question 1

Difference between physical and chemical properties

Answer 1

Physical property can be
* observed or measured without forming a new substance(colour,density)
VS
* chemical properties describes how a substance reacts with another substance when forming a new substance ( combustibility, iron
rusting, glucose and yeast
fermenting, TNT exploding)

Question 2

Chemical property

Answer 2

• the ability of a substance to react with
  another substance and form one or more new
  substances
• are exhibited during a chemical reaction

Question 3

what are examples of Chemical Properties:

Answer 3

• reactivity with other substances
• combustibility
• stability
• toxicity

Question 4

Reactivity with
Water

Answer 4

➢ Calcium carbide
(a compound)
combines with
water to form
acetylene gas
(C2H2
)

➢ CaC2 + H2O
→ C2H2 +
Ca(OH)2

Cavers use acetylene gas as a
light source.

Question 5

Reactivity with
Oxygen

Answer 5

➢Aluminum metal reacts
with oxygen to
produce
aluminum oxide
➢ Al + O2 →
Al2O3

Aluminum oxide protects these grain storage bins from coroding

Question 6

Reactivity with acids

Answer 6

➢ Baking soda
(sodium
bicarbonate) reacts
with vinegar to
produce carbon
dioxide gas (CO2
).

➢ NaHCO3 +
CH3COOH →
CO2 + H2O +
Na2CO3

In baking, carbon dioxide gas makes the dough rise

Question 7

reactivity with another pure substance

Answer 7

➢ Sodium and chlorine
(two highly reactive
elements) combine to
form sodium chloride
(salt).
➢ Na + Cl2 → NaCl

Knowing how pure substances react help chemists to create
new products.

Question 8

Chemical Properties of Common Gases

Answer 8

• hydrogen gas (H2)
• Water vapour** (H2O)**
• Carbon dioxide** (CO2) **
• oxygen gas (O2)

Question 9

how to test to see if you can prouduce hydrogen gas (H2)

Answer 9

bring a flaming splint close to the top of a slanted test tube
containing the gas. Hydrogen gas will ignite and burn rapidly down
the test tube, producing a “whoop” or “pop” sound.

Question 10

how to test to see if Water vapour (H2O) is produced

Answer 10

with a piece of cobalt chloride paper. The blue paper will turn pink in the presence of water.

Question 11

how to test and see if oxygen gas (O2) is being produced

Answer 11

involves bringing a glowing splint (one
that is no longer flaming) into the slanted test tub. If oxygen gas is
present, the splint will re-ignite.

Question 12

Combustiblity

Answer 12

• the ability of a
  substance to burn in
  air
• e.g. propane (C3H8
  ) is

combustible and
reacts with oxygen
(O2
) in air to release a
large amount of heat

* C3H8 (g) + 5 O2 (g) ⎯→
3 CO2 (g) + 4 H2O(l
H = -2220 kJ

Question 13

Stability

Answer 13

• the ability of a substance to
  remain unchanged
• how easily the substance breaks
  down or decomposes
• more stable substances take
  longer to decompose
• for a chemical to be useful, it
  must have enough stability to
  exist long enough to carry out its
  required function

Question 14

Toxicity

Answer 14

• the ability of a substance to cause harmful
  effects in plants and animals
• almost all chemicals are poisonous at high
  enough concentrations
• e.g. you need oxygen to breathe, but too
  much will kill you

Question 15

facts about toxicity

Answer 15

• toxicity is reported as a LD50 value
  – the dose required to kill 50% of the exposed
  population
• e.g. only 0.000 000 001 g/kg body mass of
  Clostridium tetani is needed to kill a person!

Question 16

2 types of toxicity

Answer 16

• acute toxicity
  – severe and sudden toxicity
  – Eg. Iron (Fe) - Iron overdose has been one of the
  leading causes of poisoning deaths in children
  younger than 6 years.
• chronic toxicity
  – long-developing toxicity due to prolonged exposure
  over time
  – Eg. Lead (Pb) - there is a wide range of neurological
  effects associated with lead exposure, some of which
  may likely be irreversible.

Question 17

acute toxicity

Answer 17

– severe and sudden toxicity
– Eg. Iron (Fe) - Iron overdose has been one of the
leading causes of poisoning deaths in children
younger than 6 years.

Question 18

chronic toxicity

Answer 18

– long-developing toxicity due to prolonged exposure
over time
– Eg. Lead (Pb) - there is a wide range of neurological
effects associated with lead exposure, some of which
may likely be irreversible.

Question 19

2 chemical properties that are linked

Answer 19

stability and toxicity

Question 20

Stability and toxicity

Answer 20

• stability and toxicity are often linked
• e.g. DDT is stable, thus it does not easily break
  down and thus bioaccumulates (stability) and
  biomagnifies (toxicity).

Question 21

Physical Properties

Answer 21

– Can be observed without changing a substance
into another substance.
* Boiling point, density, mass, volume, etc.

Question 22

Chemical properties

Answer 22

– Can only be observed when a substance is
changed into another substance.
* Flammability, corrosiveness, reactivity with acid,
etc.

Question 23

Evidences of chemical change

Answer 23

• gas formation
• precipation formation
• odour change
• energy production

Question 24

Gas formation

Answer 24

• usually observed as bubbles

Question 25

Precipitate formation

Answer 25

an insoluble solid formed during a reaction

Question 26

Odour change

Answer 26

a new smell being produced

Question 27

Energy production

Answer 27

the production of light or heat by a reaction

Question 28

what are the 2 types of changes

Answer 28

physical and chemical changes

Question 29

physical changes

Answer 29

These are changes in matter that do not change the composition of a substance. | * Changes of state, temperature, volume, etc.

Question 30

Chemical changes

Answer 30

Chemical changes result in new substances. | * Combustion, oxidation, decomposition, etc.