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THE PHYSICAL AND CHEMICAL PROPERTIES OF TWO METALS
Purpose: To observe, identify and compare the physical and chemical properties of magnesium and copper.
Pre-Lab:
/9 K/U
/4I
/10 C
1) What kind of evidence should you look for when determining whether you were observing a physical or a chemical
property? Be specific in your description of what general types of observations you would look for during an experiment
(5 K/U)
Physical property: Traditionally, metals have certain characteristic physical properties: they are usually shiny (they have metallic luster), have a high
density, are ductile and malleable, usually have a high melting point, are usually hard, are usually a solid at room temperature and conduct electricity, heat
and sound well.
Chemical property: Most metals are chemically reactive, reacting with oxygen in the air to form oxides over changing timescales (for example iron rusts
over years and potassium burns in seconds). The alkali metals react quickest followed by the alkaline earth metals, found in the leftmost two groups of the
periodic table.
2) Propose two additional experiments you could use to test the chemical properties of the two metals. What would you
expect to observe? (2 I)
Summary of the Reaction of Metals with Air, Water and Acids
3) Propose two additional experiments you could use to test the physical properties of the two metals. (2I)
a) density of the 2 metals
b) melting point
c) electrical conductivity
4) Identify the reactants and the products (if any) for the reaction with each metal in step # 6 of the procedure. Write a
chemical equation for each reaction with subscripts for each element or compound (solid, liquid or gas) (4 K/U))
Metal(s) + Oxygen(g)
The equations for the reactions are
2 Mg(s ) + O2(g ) --> 2 MgO(s ) but some magnesium nitride is also formed
3 Mg(s ) + N2(g ) --> Mg3N2(s )
5) Draw a flow chart and create a data table for this experiment. (5 C)
Steps
1
2
3
Mg(s)
Mg(s)
Mg(s)
+ 3mL H20
2 drops phenol.
heat with oxygen
Save product
+ 1mL of HCl (aq)
+ 1mL of HNO3 (aq)
Record observations
Record observations
4
Shake 20s
Record observations
Product + 3mL water
Steps
1
2
3
Cu(s)
Cu(s)
Cu(s)
+ 3mL H20
2 drops phenol.
heat with oxygen
Save product
+ 1mL of HCl (aq)
+ 1mL of HNO3 (aq)
Record observations
Record observations
4
Shake 20s
Record observations
Product + 3mL water
Mg(s)
2 drops phenol.
Shake 20s
Record observations
Cu(s)
2 drops phenol.
Shake 20s
Record observations
6) In your lab notebook, create a data table for this experiment. (5 C)
Apparatus:
crucible tongs
Test tubes (8)
10 mL graduated cylinder steel wool
heating pad
magnesium ribbon
nitric acid 6M
Bunsen burner
test tube holder
copper wire
phenolphthalein solution
hydrochloric acid 6 M
CAUTION: Be very careful with both acids. They are corrosive and fairly concentrated
Procedure:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Record all observations in a table you create in the observation section.
Attempt to bend a piece of magnesium ribbon. Record your observations in the table
Identify four other physical properties of magnesium ribbon. Record your observations.
Clean four pieces of magnesium ribbon, approximately 1 cm in length, with steel wool (do this on top of a piece of paper
rather than directly on the lab bench)
Place one of the magnesium pieces in approximately 3 mL of distilled water in a test tube and then add two drops of
phenolphthalein and shake the test tube for 20 seconds. Record your observations before and after adding the
phenolphthalein.
Light the Bunsen burner and place the wire gauze next to the burner. Take the another piece of magnesium and hold one end
of it with crucible tongs and place the other end in a blue Bunsen burner flame until you see a reaction. Hold the magnesium
over the gauze once the reaction has started. Save the product. Record your observations.
Place the product from #6 in a test tube containing 3 mL of water. Add two drops of phenolphthalein and shake the tube for
20s. Record all of your observations.
Add a 1 cm piece of magnesium to approximately 1 mL of hydrochloric acid in a test tube. Record your observations.
Add a 1 cm piece of magnesium to approximately 1 mL of nitric acid in a test tube.
Repeat steps 1 – 9 using copper wire instead of magnesium ribbon.
Data table: (create your observation table – your table should highlight the comparison of the metals and you should organize your
information as clearly and simply as possible)
Metal
Physical
characteristics
Magnesium
they are usually shiny
(they have metallic luster),
have a high density, are
ductile and malleable,
usually have a high
melting point, are usually
hard, are usually a solid at
room temperature and
conduct electricity, heat
and sound well.
Mg(s )
Reaction with
Reaction
Reaction with Acid
water and
with air
phenolphthalein
Pink colour
2 Mg(s ) +
2HCl + Mg --> H2 +
O2(g ) --> 2
MgCl2
MgO(s )
but some
magnesium
nitride is also
formed
they are usually shiny
(they have metallic luster),
have a high density, are
ductile and malleable,
usually have a high
melting point, are usually
hard, are usually a solid at
room temperature and
conduct electricity, heat
and sound well.
Pink colour
copper +
oxygen ------->
copper oxide
Strongly
electropositive
metals, such as
magnesium react with
nitric acid as with
other acids, reducing
the hydrogen ion.
Mg + 2 H+ → Mg2+
+ H2
3 Mg(s ) +
N2(g ) -->
Mg3N2(s )
Copper
Reaction with Base
2HCl + Cu -> CuCl2
+ H2
Copper(II)chloride is
green
With less electropositve
metals the products
depend on temperature
and the acid
concentration. For
example, copper reacts
with dilute nitric acid at
ambient temperatures
with a 3:8 stoichiometry.
3 Cu + 8 HNO3 → 3
Cu2+ + 2 NO + 4
H2O + 6 NO3The nitric oxide
produced may react
with atmospheric
oxygen to give
nitrogen dioxide.
With more
concentrated nitric
acid, nitrogen
dioxide is produced
directly in a reaction
with 1:4
stoichiometry.
Cu + 4 H+ + 2 NO3−
→ Cu2+ + 2 NO2 + 2
H2O
Discussion Questions:
1. What are two similarities and two differences in both the physical properties and chemical properties of
magnesium and copper? (4 A)
Metals
Magnesium and
Copper
Physical Differences:
Magnesium is not a good
conductor of electricity
but copper is a great
conductor of electricity
and that is why they use
it in cables.
Chemical Differences:
- Magnesium is more
reactive than copper
Physical Similarities
Copper and Magnesium
are both shiny and
malleable
Chemical Similarities
Magnesium and copper
both react when heated
with air to produce
oxides
2.
Why have we known about the existence of copper since the beginning of recorded history whereas
magnesium was only identified as an element in 1755? (2 A)
Because we have used copper for utensils and have been able to observe how the environment (air, water and acids,
time) have turned it green.
Errors:
(this is yours to write) these should be errors which occurred do to experimental design or equipment. If errors in your
experiment occurred because of bad lab technique you should repeat that part of the experiment.
1)
2)
3)
4)
5)
Conclusion:
Observation and recording errors
Not waiting to see the oxide with the copper
Not waiting to observe the indicator turn pink
Not shaking and waiting to record the results
Using a base instead of an acid with the phenol indicator will cause it not to turn pink, but it will turn clear.
(this is yours to write – your conclusion should be short, clear and should directly relate to the purpose)
1) Magnesium reacts quickly with air to from oxide. Magnesium reacts with water to from hydrogen gas and oxide. Magnesium
reacts with acids to form hydrogen gas and salt solution.
2) Copper reacts slowly when heated to from an oxide layer. Copper is a bigger atom and therefore not as reactive with water and
acids as magnesium.
Safety in the Lab
* Standard lab safety procedures including goggles, gloves, lab coat.
- you will be working with strong acids
- be extremely careful.
- avoid inhaling any gases.
- Immediately notify your
- Instructor of any spills or breakage.
Marking Scheme for Lab:
18 marks Application (5 completed data table, 6 analysis, 2 error analysis , 2 conclusion, 3 lab performance)
TOTAL
/18