Answer Key_Simulation Test
To download the question paper: here
Showing posts with label Chemical Energetics. Show all posts
Showing posts with label Chemical Energetics. Show all posts
Thursday, 19 February 2026
Monday, 27 November 2023
IGCSE Chemical Energetics Essay (with the answer key)
1. Iodine reacts with chlorine to form dark brown iodine
monochloride.
I2 + Cl2 → 2ICl
(a) Calculate the overall energy change for the reaction between iodine and chlorine using the bond energy values shown.
(a) Calculate the overall energy change for the reaction between iodine and chlorine using the bond energy values shown.
Show your working. [3]
(b) Draw a labelled energy level diagram for the reaction between iodine and chlorine using the information in (a). [2]
[Total: 5]
2. Look this reaction.
The reaction is exothermic.
S(g) + 2F2(g) --> SF4(g)
(a) Complete the energy level diagram for this reaction. Include an arrow which clearly shows the energy change during the reaction.
(b) During the reaction the amount of energy given out is 780 kJ / mol.
The F–F bond energy is 160 kJ / mol.
Use this information to determine the bond energy, in kJ / mol, of one S–F bond in SF4.
.................................. kJ / mol [3]
[Total: 6]
DOWNLOAD THE ANSWER KEY: [here]
IGCSE CHEMICAL ENERGETICS MCQ PRACTICE (with the answer key)
1 The energy level diagram for the reaction between sodium hydrogen carbonate and dilute hydrochloric acid is shown.
B The products are at a lower energy level than the reactants.
C The reaction is endothermic.
D The temperature increases during the reaction.
3. The energy level diagram shows the energy of the reactants and products in a chemical reaction.
Which row correctly describes the energy change and the type of reaction shown?
4. Which reaction is endothermic?
A acid neutralising alkali causing a temperature increase
B adding magnesium to hydrochloric acid
C calcium carbonate decomposing when heated
D combustion of fossil fuels
The mixture was stirred and the temperature recorded every 10 seconds. The results are shown on the graph:
6. Which row correctly describes whether the reaction is exothermic or endothermic?
7 A metal reacts with an aqueous solution.
The graph shows the temperature before,
during and after
the reaction.
8. The diagrams show four chemical reactions.
Which reaction is endothermic?
1 When limestone, CaCO3, is heated it decomposes into lime, CaO.
2 Water is slowly dripped onto the cooled lime. The lime appears to expand and steam is
produced. Slaked lime, Ca(OH)2, is formed.
Which row shows the correct description of each of the chemical reactions?
10. Which statements about exothermic and endothermic reactions are correct?
1 During an exothermic reaction, heat is given out.
2 The temperature of an endothermic reaction goes up because heat is taken in.
3 Burning methane in the air is an exothermic reaction.
A 1, 2 B 1 and 2 only C 1 and 3 only D 2 and 3 only
11. What occurs when a fuel burns?
12. Some reactions are endothermic.
How does the temperature and energy change in an endothermic reaction?
13. Two chemical processes are described below.
● In the combustion of methane, energy is ......1...... .
● In the electrolysis of molten lead(II) bromide, energy is ......2...... .
Which words correctly complete gaps 1 and 2?
A reaction occurs and the temperature change is measured. Which statement is correct?
A If the reaction is endothermic, the temperature decreases and energy is taken in.
B If the reaction is endothermic, the temperature increases and energy is given out.
C If the reaction is exothermic, the temperature decreases and energy is given out.
D If the reaction is exothermic, the temperature increases and energy is taken in.
15. When anhydrous copper(II) sulfate is added to water a solution is formed and heat is given out
Which row correctly shows the temperature change and the type of reaction taking place?
The ammonium nitrate can be recovered by evaporating the water added. Which explains these observations?
A The ammonium nitrate dissolves in the water and the process is endothermic.
B The ammonium nitrate reacts with the water and the process is endothermic.
C The ammonium nitrate dissolves in the water and the process is exothermic.
D The ammonium nitrate reacts with the water and the process is exothermic.
What would show that the process was exothermic?
A A blue solution is formed.
B The beaker feels cooler.
C The beaker feels warmer.
D The powder dissolves in the water.
18. The diagrams show the difference in energies of the reactants and products in two types of reaction.
20. A diagram for the
energy change during an exothermic reaction is shown
For which reactions would this be an appropriate diagram?
1 CH4 + 2O2 → CO2 + 2H2O
2 2H2 + O2 → 2H2O
3 C + O2 → CO2
A none of them
B 1 and 2 only
C 2 and 3 only
D all of them
21. The diagram shows the reaction between zinc oxide and dilute hydrochloric acid.
Which diagram and which type of energy change apply to a fuel burning in air?
19. The diagram shows a match.
By striking the match, a chemical reaction takes place. Which statements about the chemical reaction are correct?
19. The diagram shows a match.
By striking the match, a chemical reaction takes place. Which statements about the chemical reaction are correct?
For which reactions would this be an appropriate diagram?
1 CH4 + 2O2 → CO2 + 2H2O
2 2H2 + O2 → 2H2O
3 C + O2 → CO2
A none of them
B 1 and 2 only
C 2 and 3 only
D all of them
21. The diagram shows the reaction between zinc oxide and dilute hydrochloric acid.
Which terms describe the reaction?
A Acetylene and oxygen react exothermically.
B Acetylene is saturated.
C Oxygen and steel react endothermically.
D Oxygen is a gaseous fuel.
23. Which fuel needs oxygen in order to produce heat energy and which type of reaction
produces the energy?
methane + oxygen → carbon dioxide + water
sodium + water → sodium hydroxide + hydrogen
magnesium + hydrochloric acid → magnesium chloride + hydrogen
Which word correctly describes all of these reactions?
A combustion
B endothermic
C exothermic
D neutralisation
25. Which is an endothermic process?
A
burning hydrogen
B
distilling petroleum
C
reacting potassium with water
D
using petrol
in a motor car engine
26. The diagrams show some pieces
of laboratory equipment.
Which equipment is needed to find out whether dissolving salt in water is an endothermic process?
A 1 only B 1 and 3 C 2 and 3 D 3 only
27. Clouds are formed when water vapour evaporates from the sea.
What is the energy change and what name is given to the type of change when water evaporates?
28. Which process is not exothermic?
Which words describe this reaction?
A decomposition
and endothermic
B decomposition and exothermic
C neutralisation and endothermic
D neutralisation and exothermic
30. Which diagram shows a process in which an endothermic change is taking place?
DOWNLOAD ANSWER KEY: [click here]
Wednesday, 25 October 2023
IGCSE Chemistry – Chemical Energetics Worksheet
IGCSE Chemistry – Chemical Energetics
Name :
Class/# :
Day, Date :
Question 1: Multiple Choice
- When a chemical reaction absorbs heat from the surroundings, it is called: A) Endothermic B) Exothermic C) Isothermic D) Thermogenic
Question 2: Fill in the Blanks 2. In an exothermic reaction, the surroundings __________ heat and the temperature of the surroundings __________.
Question 3: Short Answer 3. Explain the difference between endothermic and exothermic reactions, providing an example for each.
Question 4: Calculation 4. Calculate the energy change when 2 moles of methane (CH₄) are burned completely in oxygen according to the following equation: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) ΔH = -890 kJ/mol
Question 5: Application 5. Consider a reaction where 50.0 g of sodium hydroxide (NaOH) is dissolved in 200 mL of water, and the temperature of the solution increases from 25°C to 40°C. Calculate the energy change for this process. (Assume the density of water is 1 g/mL and specific heat capacity of water is 4.18 J/g°C)
Question 6: Diagram Analysis 6. Study the energy profile diagram below and answer the questions. (Insert a simple energy profile diagram with reactants and products labeled, along with activation energy.)
a) Identify the reactants and products. b) Label the activation energy on the diagram. c) Determine whether the reaction is endothermic or exothermic. d) Explain what the activation energy represents in a chemical reaction.
Question 7: Research and Analysis 7. Research an industrial process that involves an exothermic reaction. Explain the process, the reaction involved, and why the reaction being exothermic is beneficial for the industry.
Question 8: Critical Thinking 8. Discuss why it is important for scientists and engineers to understand the concept of energy changes in chemical reactions, especially in fields such as environmental science and pharmaceuticals.
Friday, 20 October 2023
IGCSE Chemistry: Chemical Energetics, worksheet
Heat Exchange in Reactions
- When a chemical reaction occurs, it involves the transfer of energy into and out of reaction mixtures.
- The terms used to describe this are the system (what happens in the chemical reaction) and the surroundings (anything other than the chemicals reacting)
- The energy within the system comes from the chemical bonds themselves which could be considered as tiny stores of chemical energy.
- The energy transferred is in the form of heat energy, although sometimes other types of energy are produced such as light or sound.
- When a chemical reaction occurs, it involves the transfer of energy into and out of reaction mixtures.
- The terms used to describe this are the system (what happens in the chemical reaction) and the surroundings (anything other than the chemicals reacting)
- The energy within the system comes from the chemical bonds themselves which could be considered as tiny stores of chemical energy.
- The energy transferred is in the form of heat energy, although sometimes other types of energy are produced such as light or sound.
Exothermic Reactions
- In exothermic reactions energy is transferred to the surroundings so the temperature of the surroundings increases.
- This energy is transferred from the chemical energy store of the chemical system to the surroundings and so the energy of the system falls - this means that the energy change is negative
- The overall transfer is from the system to the surroundings.
- Combustion, oxidation, and neutralisation reactions are typical exothermic reactions.
- Hand warmers used in the wintertime are based on the release of heat from an exothermic reaction.
- Self-heating cans of food and drinks such as coffee and hot chocolate also use exothermic reactions in the bases of the containers.
- In exothermic reactions energy is transferred to the surroundings so the temperature of the surroundings increases.
- This energy is transferred from the chemical energy store of the chemical system to the surroundings and so the energy of the system falls - this means that the energy change is negative
- The overall transfer is from the system to the surroundings.
- Combustion, oxidation, and neutralisation reactions are typical exothermic reactions.
- Hand warmers used in the wintertime are based on the release of heat from an exothermic reaction.
- Self-heating cans of food and drinks such as coffee and hot chocolate also use exothermic reactions in the bases of the containers.
Exothermic reactions: Heat is released.
- 1) Combustion: The burning of carbon-containing compounds uses oxygen, from air, and produces carbon dioxide, water, and lots of heat.
- 2) Rain: Condensation of water vapor into rain releasing energy in the form of heat is an example of an exothermic process.
- 1) Combustion: The burning of carbon-containing compounds uses oxygen, from air, and produces carbon dioxide, water, and lots of heat.
- 2) Rain: Condensation of water vapor into rain releasing energy in the form of heat is an example of an exothermic process.
Endothermic Reactions
- In endothermic reactions energy is taken in from the surroundings so the temperature of the surroundings decreases
- This energy is transferred to the chemical energy store of the chemical system and so the energy of the system increases - this means the energy change is positive.
- The overall transfer is from the surroundings to the system.
- These types of reactions are much less common than the exothermic reactions.
- Electrolysis, thermal decomposition reactions and the first stages of photosynthesis are typical endothermic reactions.
- Sports injury treatments often use cold packs based on endothermic reactions to take heat away from a recently injured area to prevent swelling.
- In endothermic reactions energy is taken in from the surroundings so the temperature of the surroundings decreases
- This energy is transferred to the chemical energy store of the chemical system and so the energy of the system increases - this means the energy change is positive.
- The overall transfer is from the surroundings to the system.
- These types of reactions are much less common than the exothermic reactions.
- Electrolysis, thermal decomposition reactions and the first stages of photosynthesis are typical endothermic reactions.
- Sports injury treatments often use cold packs based on endothermic reactions to take heat away from a recently injured area to prevent swelling.
Endothermic reactions: Heat is absorbed.
- 1) Photosynthesis: Plants absorb heat energy from sunlight to convert carbon dioxide and water into glucose and oxygen.
- 2) Cooking an egg: Heat energy is absorbed from the pan to cook the egg.
- 1) Photosynthesis: Plants absorb heat energy from sunlight to convert carbon dioxide and water into glucose and oxygen.
- 2) Cooking an egg: Heat energy is absorbed from the pan to cook the egg.
Energy Level Diagrams
- Energy level diagrams (sometimes called reaction pathway diagrams or reaction profiles) are graphical representations of the relative energies of the reactants and products in chemical reactions.
- The energy of the reactants and products are displayed on the y-axis and the reaction pathway (a bit like time) is shown on the x-axis.
- The difference in height between the energy of reactants and products represents the overall energy change of a reaction.
- This is usually a sketch but can be drawn to scale if data is provided.
- Arrows on the diagrams indicate whether the reaction is exothermic (overall reaction arrow is downwards pointing, showing that the system has lost energy) or endothermic (overall reaction arrow is upwards pointing, showing that the system has gained energy)
- The initial increase in energy represents the activation energy (Ea), which is the minimum energy that colliding particles must have in order to react.
- The greater the initial rise, the more energy that is required to get the reaction going e.g. more heat needed.
EXERCISE WORKSHEET
- Energy level diagrams (sometimes called reaction pathway diagrams or reaction profiles) are graphical representations of the relative energies of the reactants and products in chemical reactions.
- The energy of the reactants and products are displayed on the y-axis and the reaction pathway (a bit like time) is shown on the x-axis.
- The difference in height between the energy of reactants and products represents the overall energy change of a reaction.
- This is usually a sketch but can be drawn to scale if data is provided.
- Arrows on the diagrams indicate whether the reaction is exothermic (overall reaction arrow is downwards pointing, showing that the system has lost energy) or endothermic (overall reaction arrow is upwards pointing, showing that the system has gained energy)
- The initial increase in energy represents the activation energy (Ea), which is the minimum energy that colliding particles must have in order to react.
- The greater the initial rise, the more energy that is required to get the reaction going e.g. more heat needed.
EXERCISE WORKSHEET
