Case Study:

In many countries, automobile companies are testing hydrogen-powered cars as an alternative to petrol and diesel vehicles. Hydrogen is considered a clean fuel because when it burns, it mainly produces water vapour instead of harmful smoke. Scientists also know that hydrogen has a very high calorific value, nearly 150 kJ/g, which is much higher than petrol. This means hydrogen can release a large amount of energy from a small mass of fuel.

While hydrogen is a fascinating frontier, it is part of a much larger shift in how we generate power. To understand the broader landscape, you should explore why renewable energy is important and how it compares to our current reliance on fossil fuels vs renewable sources.

However, despite these advantages, petrol cars cannot instantly switch to hydrogen fuel everywhere. One major problem is storage. Hydrogen gas is highly inflammable and occupies large space, so it must be stored either at very high pressure or at extremely low temperatures. This requires specially designed fuel tanks and safety systems.

Another challenge is infrastructure. Most cities already have thousands of petrol pumps, but hydrogen filling stations are very limited and expensive to build. In addition, producing hydrogen fuel on a large scale often requires electricity or natural gas, which may increase cost and energy consumption.

The logistical hurdles of hydrogen are similar to those faced by other large-scale systems. If you're interested in the engineering side, take a look at how a thermal power plant works or the high-stakes science behind nuclear energy. For a more localised look at energy, you can also see how biogas and hydroelectric power plants work.

During a transport survey in a metro city, engineers observed that a hydrogen-powered bus travelled about 480 km using 5 kg of hydrogen, while a petrol bus required nearly 40 litres of petrol for a similar distance. Even though hydrogen showed better energy efficiency and cleaner exhaust, the total operating cost remained higher because of storage technology and fuel supply issues.

This situation shows that a good source of energy is not judged only by high energy output, but also by safety, availability, cost, storage, and ease of transportation.

 Before you dive into these specific questions,  it’s a good idea to brush up on your core concepts. You can practice with this Physics worksheet or test your exam readiness with an unsolved practice paper. If you get stuck, we also have a solved practice paper available to guide you through the ideal answers.

CASE-BASED QUESTIONS

 MCQ 

Q1. Why is hydrogen considered a better fuel than petrol in terms of energy output?
A. It is cheaper to produce
B. It has a higher calorific value
C. It is available everywhere
D. It burns at low temperature

Q2. Which practical problem mainly prevents immediate large-scale use of hydrogen vehicles?
A. Hydrogen produces poisonous gases
B. Hydrogen cannot burn in engines
C. Storage and transport of hydrogen are difficult
D. Hydrogen has low efficiency

 Assertion - Reason 

Q3. Assertion (A): Hydrogen is called a clean fuel.
Reason (R): Burning hydrogen mainly produces water vapour.
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true, but R is false.
D. A is false, but R is true.

 Application-Based 

Q4. A company wants to replace diesel buses with hydrogen buses in a hilly area. Suggest one advantage and one major challenge they may face.

Q5. A student says, “If hydrogen gives more energy than petrol, all vehicles should immediately use hydrogen.” Using the case study, explain why this statement is incomplete.

 Data/Logic-Based 

Q6. A hydrogen bus uses 5 kg of hydrogen to travel 480 km. Another petrol bus uses 40 litres of petrol for the same distance.
Based on the data, which conclusion is most reasonable?
A. Petrol has greater energy efficiency than hydrogen
B. Hydrogen can provide more energy with less fuel quantity
C. Petrol and hydrogen release exactly the same energy
D. Hydrogen vehicles do not require advanced technology

ANSWER KEY WITH EXPLANATION

A1. B. It has a higher calorific value
Explanation: Hydrogen releases more heat energy per unit mass than petrol. According to NCERT, fuels with higher calorific value are considered efficient energy sources.

A2. C. Storage and transport of hydrogen are difficult
Explanation: Hydrogen is highly inflammable and occupies a large volume. Safe storage under high pressure or low temperature makes its large-scale use difficult.

A3. A. Both A and R are true, and R is the correct explanation of A. 
Explanation: Hydrogen combustion mainly forms water vapour, so it causes very little air pollution. Hence, hydrogen is considered a clean fuel.

A4. Advantage: Hydrogen buses can provide high energy efficiency with less pollution.
Challenge: Safe storage and transport of hydrogen in hilly regions may be difficult and costly.

A5. The statement ignores practical challenges like storage, transportation, fuel station availability, and high infrastructure costs. A good fuel must also be safe, affordable, and easily available.

A6. B. Hydrogen can provide more energy with less fuel quantity
Explanation: The bus travelled a similar distance using a much smaller quantity of hydrogen, showing its high calorific value and better energy efficiency.

HOTS EXTENSION QUESTIONS

Q1. If scientists develop a new lightweight material that can safely store hydrogen at normal pressure, how might this change the future of public transport systems?

Q2. Hydrogen fuel is clean during use, but producing hydrogen may require electricity from coal-based power plants. Should hydrogen still be called an eco-friendly fuel? Justify your answer logically.