Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Related Concepts
Fairness &
development
Breathing Hot and Cold
Thermochemistry
Unit 4
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
ATL: Social skills
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Lesson 6
Electrolysis of
Copper(II) Sulfate
Solution
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills
Learning objectives:
•Predict the products of electrolysis of aqueous electrolytes, using inert
electrodes,
•Write half-equations for reactions occurring at the anode and cathode of
voltaic cells.
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Starter Activity:
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills
In this practical, students carry out the
electrolysis of copper(II) sulfate
solution.
Watch the video on
the link below:
https://www.nagwa.co
m/en/videos/45016850
4980/
The outcomes of the experiment
provide the opportunity to introduce a
discussion about electroplating and the
industrial electrolytic refining of
copper
Take notes!
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills
Risk assessment:
Hazardous
Chemicals or
equipment
Nature of Hazard
Copper(II) sulfate
solution,
CuSO4(aq)
Control Measures to reduce risks
- Wear eye protection.
- Wash their hands at the end of all practical work.
- At the suggested concentrations, the copper(II) sulfate solution is LOW
HAZARD. If the concentrations are increased, the solutions must be
labelled with the correct hazard warnings. Copper(II) sulfate solution is
HARMFUL if concentration is equal to or greater than 1 M.
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Background Information:
Electrolysis is a type of process where an electric current is passed
through a liquid or a solution containing ions, which causes the
substances inside to decompose.
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills
Apparatus:
Chemicals:
•Eye protection
•Beaker, 250 cm3
•Graphite electrodes, about 5 mm
diameter, x2
•Retort stand and clamp to hold
electrodes
•DC power supply, 6 volt
•Light bulb, small, 6 volt, 5 watt
•Leads and crocodile clips
•Aqueous copper(II) sulfate,
about 0.5 M, 200 cm3
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
•Copper strips x2 (optional;
these can be used in place of
the graphite rods as an
extension to the basic
experiment)
•Small pieces of emery paper
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Method:
• Set up the cell as shown in the picture below.
• Watch for any activity on each of the electrodes.
• Write down your observations.
The cathodes can be cleaned using emery paper.
• Repeat two more times
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills
Observations:
- You will see a deposit of copper forming on the cathode. This will often be powdery and
uneven.
- You should explain that, if the current used is much lower, then the solid coating is shiny,
impermeable and very difficult to rub off; this process forms the basis of electroplating.
- Bubbles of gas (oxygen) are formed at the anode.
- Cathode reaction: Cu2+(aq) + 2e- → Cu(s)
- Anode reaction: 2H2O(l) → O2(g) + 4H+(aq) + 4e-
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills
Observations:
- With carbon (graphite) electrodes, the oxygen usually reacts with the anode to
form CO2.
- If copper is used for the electrodes, the copper anode dissolves. The reaction is the
reverse of the cathode reaction.
- The results of this experiment can lead to a discussion about electroplating and
the electrolytic refining of copper.
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Related Concepts
Fairness &
development
Extension:
After doing the electrolysis as described above, the electrodes can be interchanged.
Students can then see the copper disappearing from the surface of the copper-coated
anode:
Cu(s) → Cu2+(aq) + 2eThis leads to a discussion as to why, during electrolytic refining:
1. the anode consists of an unrefined sample of the metal;
2. the cathode is made of pure copper or a support metal such as stainless steel.
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
ATL: Social skills
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Related Concepts
Fairness &
development
Practice:
Question 1:
What products are formed from the electrolysis of dilute sodium chloride solution?
A. Sodium is produced at the cathode and chlorine at the anode.
B. Sodium is produced at the cathode and oxygen at the anode.
C. Hydrogen is produced at the cathode and chlorine at the anode.
D. Oxygen is produced at the cathode and hydrogen at the anode.
E. Hydrogen is produced at the cathode and oxygen at the anode.
Question 2:
What equation shows the reaction at the cathode during the electrolysis of potassium chloride solution using
inert electrodes?
A. 2H+ + 2e-  H2
B. 4OH-  2H2O + O2 + 4e–
C. 2Cl-  Cl2 + 2eD. 2H+  H2 +2eE. K+  K+e–
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
ATL: Social skills
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Related Concepts
Fairness &
development
Practice:
Question 3:
What equation shows the reaction at the anode during the electrolysis of copper sulfate solution using inert electrodes?
A.
SO42-  SO2 +O2 +2e-
B.
Cu2+  Cu + 2e-
C.
SO2 +O2 +2e-  SO42-
D.
4OH-  2H2O+O2 +4e–
E.
2H++2e-  H2
Question 4:
Which three products are formed during the electrolysis of aqueous rubidium bromide?
A. Rubidium, bromine, and water
B. Hydrogen, bromine, and rubidium hydroxide
C. Hydrogen, bromine, and water
D. Rubidium, bromine, and rubidium hydroxide
E. Hydrogen, bromide, and rubidium hydroxide
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
ATL: Social skills
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Concept
Change
Practice:
Question 5:
What gas or gases are produced during the electrolysis of sulfuric acid using inert electrodes?
A- Hydrogen
B- Oxygen
D- Hydrogen and oxygen
C- Hydrogen and sulfur dioxide
E- Hydrogen, oxygen, and sulfur dioxide
Question 6:
What ions are present in an aqueous solution of strontium chloride?
A.
Sr2+, H+, Cl–, OH–
B.
Sr2+, Cl–, OH–
C.
Sr2+, H+, Cl–
D.
Sr2+, Cl–
E.
H+, OH–
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Related Concepts
Fairness &
development
ATL: Social skills
Grade 9 Unit 3
Breathing hot
and cold
Global Context:Energy,
Environment
Statement of Inquiry: Development is often the result of human capability to change
energy in an environmentally clean way
Practice:
Question 7:
What products are formed from the electrolysis of concentrated sodium chloride?
A.
Hydrogen is produced at the cathode and oxygen at the anode.
B.
Sodium is produced at the cathode and oxygen at the anode.
C.
Oxygen is produced at the cathode and hydrogen at the anode.
D.
Sodium is produced at the cathode and chlorine at the anode.
E.
Hydrogen is produced at the cathode and chlorine at the anode.
Question 8:
What name is given to the blue aqueous ionic compound in this experimental setup?
A. Electrolyzer
B. Electrode
C. Electrolytic
D. Electrolysis
E. Electrolyte
Learrner Profile:
Applications:
In this lesson you will strive to be thinkers and collaborators
How can this be applied to familiar and unfamiliar situations?
Concept
Change
Related Concepts
Fairness &
development
ATL: Social skills