Chapter 1 : Fuels

Question 1

What is a fuel?

Answer 1

A substance that undergoes a chemical reaction (burning in air) to produce energy.

Question 2

Differentiate between renewable and non-renewable fuels.

Answer 2

Non-renewable fuels are fossil fuels (e.g., coal, natural gas, petrol), carbon-based, and finite. Renewable fuels, like biofuels, can be replenished within a human’s lifespan.

Question 3

Explain the formation of black coal.

Answer 3

Dead animals and plants form peat, which undergoes heat and pressure over millions of years to become brown coal. Further heat and pressure result in black coal with higher energy content.

Question 4

What is the primary component of natural gas, and how is it extracted?

Answer 4

Natural gas is predominantly methane (CH4). It is extracted through fracking, an environmentally harmful process, and is adsorbed onto the surface of coal deposits.

Question 5

How is petrol (petrochemical fuel) produced from crude oil?

Answer 5

Crude oil undergoes fractional distillation to separate hydrocarbons. Petrol, a mixture of small hydrocarbons, is obtained with an energy content of around 44-46 MJ/kg.

Question 6

What are the common types of biofuels, and how is bioethanol produced?

Answer 6

Common biofuels include biogas, biodiesel, and bioethanol. Bioethanol is produced by fermenting sugar, followed by distillation.

Question 7

Define enthalpy and explain its role in chemical reactions.

Answer 7

Enthalpy is the total energy stored in a substance. In chemical reactions, it is released when bonds break and absorbed when new bonds form.

Question 8

What are endothermic and exothermic reactions?

Answer 8

Endothermic reactions absorb energy (ΔH > 0), while exothermic reactions release energy (ΔH < 0).

Question 9

Provide an example of an exothermic reaction involving the combustion of a fuel.

Answer 9

Example - Combustion of methane: CH4(g) + 2O2(g) → 2H2O(g) + CO2(g) with ΔH = -55.6 kJ mol-1.

Question 10

Explain the concept of limiting reactants in a chemical reaction.

Answer 10

A limiting reactant is completely used up, while an excess reactant is leftover. The limiting reactant determines the amount of product formed.

Question 11

What is the role of activation energy in a chemical reaction?

Answer 11

Activation energy (Ea) is the energy required to break bonds in reactants and initiate a reaction.

Question 12

Describe the process of aerobic respiration and its significance.

Answer 12

Aerobic respiration occurs with sufficient oxygen, oxidizing glucose to produce CO2 and H2O. It is vital for energy production in living organisms.

Question 13

How does fermentation relate to anaerobic respiration in plants?

Answer 13

Fermentation is anaerobic respiration in plants, breaking down sugars into ethanol and CO2, used in processes like bread-making and beer brewing.

Question 14

What is the chemical equation for photosynthesis, and what does it produce?

Answer 14

The chemical equation for photosynthesis is: 6CO2(g) + 6H2O(l) → C6H12O6(aq) + 6O2(g). It produces glucose and oxygen.

Question 15

Describe the process of cellular respiration.

Answer 15

Cellular respiration is the exothermic reaction where glucose is oxidized in the presence of oxygen to produce carbon dioxide and water: C6H12O6(aq) + 6O2(g) → 6CO2(g) + 6H2O(l).

Question 16

Explain the difference between aerobic and anaerobic respiration.

Answer 16

Aerobic respiration occurs with oxygen and produces more energy, while anaerobic respiration occurs without oxygen, producing less energy and sometimes lactic acid in animals.

Question 17

What is the energy content of carbohydrates, proteins, and fats?

Answer 17

Carbohydrates have an energy content of 16 kJ g-1, proteins have 17 kJ g-1, and fats have 37 kJ g-1.

Question 18

What is the energy content of petrol, and how is it calculated?

Answer 18

Petrol has an energy content of around 44-46 MJ/kg. The energy content in mixtures can be calculated by dividing the heat of combustion per mole by the molar mass.

Question 19

Define limiting and excess reactants. Provide an example.

Answer 19

A limiting reactant is completely used up, while an excess reactant is leftover. Example: In the reaction 2CH3OH(g) + 3O2(g) → 2CO2(g) + 4H2O(g), the limiting reactant determines the amount of product formed.

Question 20

Explain the significance of energy profiles in chemical reactions.

Answer 20

Energy profiles summarize energy changes in a reaction, including activation energy (Ea) and enthalpy change (ΔH), providing insights into reaction mechanisms.

Question 21

What is the role of minerals, vitamins, and water in food?

Answer 21

Minerals and vitamins have specialized roles in cellular processes, and water acts as a solvent and transport agent. They contribute to overall health.

Question 22

Describe the breakdown of fats during metabolism and provide an example.

Answer 22

Fats are broken down in an exothermic reaction. Example: Linoleic acid breakdown - C17H31COOH + 25O2 → 18CO2 + 16H2O, releasing energy.

Question 23

What is the primary function of carbohydrates in the body?

Answer 23

Carbohydrates serve as a major energy source for the body, providing fuel for various metabolic processes and activities.

Question 24

Name three types of carbohydrates and provide examples.

Answer 24

Three types of carbohydrates are monosaccharides (e.g., glucose), disaccharides (e.g., sucrose), and polysaccharides (e.g., starch).

Question 25

Explain the process of hydrolysis as it relates to carbohydrates.

Answer 25

Hydrolysis is the breakdown of carbohydrates into simpler compounds through the addition of water. For example, disaccharides can be hydrolyzed into monosaccharides.

Question 26

What is the role of proteins in the body?

Answer 26

Proteins play crucial roles in growth, tissue repair, enzymatic reactions, and serving as an energy source when needed.

Question 27

: How are proteins broken down during digestion, and where does this process occur?

Answer 27

Proteins are broken down into amino acids through the process of hydrolysis. Digestion primarily occurs in the stomach and small intestine, facilitated by enzymes.

Question 28

Provide examples of protein-rich foods and their importance in the diet.

Answer 28

Provide examples of protein-rich foods and their importance in the diet.

Question 29

What is the function of lipids in the body?

Answer 29

Lipids serve as energy storage, insulation, and cushioning for organs. They also play a role in cell membrane structure and certain biological processes.

Question 30

Differentiate between saturated and unsaturated fats. Provide examples of each.

Answer 30

Saturated fats have no double bonds and are solid at room temperature (e.g., butter). Unsaturated fats have double bonds and are typically liquid (e.g., olive oil).

Question 31

Explain the breakdown of triglycerides during metabolism.

Answer 31

Triglycerides undergo hydrolysis during metabolism, breaking into glycerol and fatty acids. These components can then be further metabolized for energy.