8
Learning
SCIENCE
15- Chemical Effects of Electric Current: Worksheet-15.1
Name:
l
Date:
Choose the most appropriate option.
1. The chemical reaction that takes place during electrolysis depends on
i. The strength of current passing through the circuit
ii. The concentration of the metal ion in the solution
iii. The duration of passing current through the solution
a. i only
b. i and ii only
c. ii and iii only
d. i, ii and iii
2. Which of the following statements is not correct?
a. In a salt solution, negative and positive ions from the constituent atoms carry electricity
b. In solids, the movement of electrons in a particular direction constitutes current
c. Cations carry negative change towards the cathode while anions carry positive change
towards the anode.
d. Tap water contains traces of salt and hence conducts electricity
3. A light emitting diode
i. is used to detect electric current ii. glows even when a weak current flows through it
iii. glows because of the heating effect of current iv. glows because of the magnetic effect of current
a. i, ii, iii and iv
b. i, ii and iii only c. i and ii only
d. ii and iii only
4. Tins cans used for storing food are made by electroplating
a. zinc on tin
b. tin on iron
c. chromium on tin
d. copper on tin
5. The figure shows electrolytic refining of copper. What are X, Y and Z?
X YZ
a. Copper sulphate
solution
Impure
Pure
copperCopper
b.Sulphuric
acid Copper
sulphate
Pure
copper
c. Copper sulphate
solution Pure
copper
Impure
copper
d.Sulphuric
acid
Impure
Pure
coppercopper
cathode (–)
anode (+)
Z
Y
X
Learning
SCIENCE
l
Match the following:
l
8
Column I
Column II
Column III
1. Zinc plating
a. cutlery
i. reduces contact resistance
2. Chromium plating
b. iron bridges
ii. gives a shiny look
3. Gold plating
c. taps
iii. gives a precious look at low cost
4. Silver plating
d. electronic parts
iv. prevents corrosion
Correct the false statements.
1. The electrode connected to the positive terminal of a battery is called cathode while that
connected to the negative terminal is called anode.
2. Alcohol does not conduct electricity because the molecules do not dissociate to form free atoms.
3. When a copper rod donates electrons to hydrogen ions, it loses positive charge.
4. In an atom, electrons revolve around the protons.
5. Tin is plated on car and cycle parts, bicycle handle bars, wheel rims, etc. to give them a shiny
look.
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Learning
SCIENCE
8
15- Chemical Effects of Electric Current: Worksheet-15.2
Name:
l
l
l
Date:
Name the following:
1. Negative ion …………………….. .
2. Positive ion …………………. .
3. Two ionic compounds ……………………. ………………… .
4. Two non-ionic compounds …………………… ……………… .
5. Groups of atoms that have charge on them ……………….. .
6. Two metals used for electroplating ………………… ………………… .
7. Two products obtained on electrolysis of sodium chloride solution ………………… .
…………………… .
8. Two metals purified by electrolysis ………………… …………………. .
9. A substance which gets dissociated into ions in molten state or in a solution and conducts
electricity ……………….
10.Particles carrying charges in an ionic solution ………………. …………….
Fill in the blanks.
1. ………………… is done to improve the appearance of metals and for protection against
corrosion.
2. The rods or plates that are partially immersed in the solution during electrolysis are called
…………… .
3. When electric current is passed through water, hydrogen gas is evolved at the ………… and
oxygen gas is evolved at the ………………… .
4. …………………. are formed when an atom or a group of atoms become charged by losing or
gaining one or more electrons.
5. Electroplating an iron statue with copper can be done by taking …………… as the electrolyte.
Think and answer the following questions.
1. A pencil sharpened from both sides can be used as an electrode. Explain.
2. Why is the metal to be coated on an object made the anode?
3. When a few drops of acid are added to distilled water it starts to conduct electricity. Why?
4. Solid sodium chloride does not conduct electricity but it does so when it is dissolved in water. Explain.
5. Copper is a good conductor of electricity but it is not an electrolyte. Explain.
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