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Essential Chemistry for IGCSE - Chemical Changes (Section 1)

1
What is the key feature that distinguishes a chemical change from a physical change?
Answer
(C)
Formation of new substances.
2
In a simple electrochemical cell, the electrode with the more positive reduction potential will act as the:
Answer
(B)
Cathode and be reduced
3
Which of the following are key features of fuel cells?
Answer
A
B
4
What do all batteries have in common?
Answer
(B)
They all have a positive and negative terminal.
5
Which of the following are fuels?
Answer
A
B
C
6
What component is essential for any electrochemical cell to function?
Answer
(C)
A potential difference
7
What does the sign of ΔH (enthalpy change) indicate?
Answer
(C)
Whether the reaction is endothermic or exothermic
8
Which aspects are advantages of using fuel cells?
Answer
A
B
D
9
What is a fuel cell?
Answer
(B)
A device that converts chemical energy directly into electrical energy.
10
Which of the following are forms of fuel that can be used in a fuel cell?
Answer
A
D
11
What happens to electrons in a fuel cell?
Answer
(C)
They flow from the anode to the cathode through an external circuit.
12
Which of the following best describes the products of a fuel cell using hydrogen and oxygen?
Answer
(A)
Water and electricity
13
What is the main difference between a physical change and a chemical change?
Answer
(A)
Physical changes involve a change in state only, while chemical changes involve the formation of new substances.
14
What type of reaction is represented by the following equation: 2H₂ + O₂ -> 2H₂O + energy?
Answer
(B)
Exothermic
15
Which type of reaction involves the breaking and forming of bonds?
Answer
(D)
Chemical
16
What are the main components of a simple electrochemical cell?
Answer
A
B
17
What is the function of the electrolyte in an electrochemical cell?
Answer
(B)
To conduct electricity by allowing the flow of ions.
18
In a hydrogen fuel cell, what is produced at the anode?
Answer
(C)
Electrons
19
Which type of reaction is characterized by the absorption of energy from the surroundings?
Answer
(B)
Endothermic
20
What is the role of the platinum in a hydrogen fuel cell?
Answer
(C)
To catalyze the reactions.
21
What is the purpose of a catalyst in a chemical reaction?
Answer
(C)
To lower the activation energy of the reaction.
22
Which of the following is an example of a physical change?
Answer
(C)
Melting ice
23
Which of the following statements best describes an endothermic reaction?
Answer
(C)
It absorbs energy from the surroundings.
24
Which of the following statements is true about the reactivity series?
Answer
(D)
The reactivity series helps predict whether a metal will displace another metal.
25
What is the main function of a catalyst?
Answer
(C)
To speed up the reaction by lowering the activation energy
26
Which statement accurately describes the energy levels in an endothermic reaction?
Answer
(A)
The products have more energy than the reactants.
27
What is the role of the external circuit in a fuel cell?
Answer
(B)
To allow the flow of electrons, generating electricity.
28
What is the significance of the negative sign for an energy change (ΔH) in a chemical reaction?
Answer
(B)
The reaction is exothermic.
29
Which of the following is true regarding endothermic reactions?
Answer
C
D
30
In a simple electrochemical cell, what is the role of the metal electrodes?
Answer
(B)
To allow electron flow and be the site of reactions.
31
What type of energy is directly converted into electricity in a fuel cell?
Answer
(B)
Chemical energy
32
Which type of reaction is the burning of a fuel in oxygen?
Answer
(D)
Exothermic
33
What is a common byproduct of a hydrogen fuel cell?
Answer
(B)
Water
34
In an electrochemical cell, where does reduction occur?
Answer
(B)
At the cathode
35
What is the function of the electrolyte in a fuel cell?
Answer
(C)
To allow the flow of ions between electrodes.
36
What is the role of the platinum electrode in a hydrogen fuel cell?
Answer
(C)
To catalyze the oxidation of hydrogen and reduction of oxygen.
37
Which of the following is an example of a fuel that can be used in a fuel cell?
Answer
(B)
Ethanol
38
What is the function of the anode in a fuel cell?
Answer
(A)
To oxidize the fuel.
39
What is the purpose of the salt bridge in an electrochemical cell?
Answer
(B)
To maintain electrical neutrality in the half-cells.
40
Which of the following correctly represents a chemical reaction?
Answer
B
C
41
Which of the following is an example of an exothermic reaction?
Answer
(C)
Burning wood
42
What is the role of hydrogen gas in a fuel cell?
Answer
(B)
It donates electrons.
43
Which type of reaction is often characterized by an increase in temperature?
Answer
(B)
Exothermic
44
Which process involves the formation of a new substance?
Answer
(C)
Chemical change
45
Which of the following correctly represents an exothermic reaction?
Answer
(B)
Reactants -> Products + Heat
46
What is the general rule of thumb concerning the reactivity series of metals?
Answer
(B)
The higher the metal is on the reactivity series the greater its tendency to release electrons.
47
What is the source of electricity in a hydrogen fuel cell?
Answer
(C)
The flow of electrons through an external circuit.
48
In a fuel cell, where does the reduction of oxygen occur?
Answer
(B)
Cathode
49
What is the primary purpose of a catalyst?
Answer
(C)
To speed up the reaction rate.
50
Which of the following is NOT a characteristic of an exothermic reaction?
Answer
(D)
The reaction absorbs heat from the surroundings.