What Is Energy? — Reading Comprehension

Energy flows through every system on Earth, from the food we eat to the electricity that powers our homes. When a runner sprints down the track, a phone vibrates, or sunlight warms the ground, energy is at work. Scientists define energy as the ability to do work or cause change. This means that energy allows objects to move, temperatures to rise, and matter to change forms. Understanding energy is essential for explaining how our world functions and how we can use resources efficiently.

How Energy Works in Systems

Energy does not appear from nowhere, nor does it disappear when used. According to the law of conservation of energy, energy cannot be created or destroyed; it can only be transformed from one form to another. For example, when you eat food, your body changes the chemical energy in food into kinetic energy for movement and thermal energy (heat) to maintain body temperature. Similarly, a battery stores potential energy and transforms it into electrical energy when powering a device. In every transformation, the total amount of energy stays the same, but its form changes.

Scientists measure energy in units called joules. For instance, lifting a small apple about one meter requires about one joule of energy. This measurement helps us compare different forms and amounts of energy in scientific investigations.

Energy Transformations in Daily Life

Energy transformations occur constantly in our environment. Plants use sunlight, which is radiant energy, to make food through photosynthesis. The food stores chemical energy that animals use to move, think, and grow. When you ride a bike, your muscles convert this chemical energy into kinetic energy as you pedal, and some energy is released as heat due to friction. In a flashlight, chemical energy stored in batteries changes to electrical energy and then to light energy.

Not all energy transformations are 100% efficient. Some energy is always released as heat, which often spreads into the environment. For example, only about 20-25% of the energy in food is used for movement; the rest is lost as heat. Understanding these processes helps scientists design more efficient machines and ways to save energy.

Broader Implications and Scientific Principles

The study of energy is connected to many scientific principles and real-world challenges. By understanding energy transformations, engineers can improve technologies, such as making cars that use less fuel or solar panels that convert more sunlight into electricity. The idea that energy cannot be created or destroyed is central to all physical sciences and helps us predict how systems will behave.

From maintaining our health to powering cities, energy is the foundation of modern life. By measuring, transforming, and conserving energy, we can make our world more sustainable and efficient for future generations.

Interesting Fact: The total energy in the universe has remained constant since the beginning of time—every transformation follows the same rules, from stars to smartphones!

What is the scientific definition of energy?

Which unit do scientists use to measure energy?

According to the law of conservation of energy, what happens to energy in a closed system?

Which of the following is an example of chemical energy being transformed into kinetic energy?

What is always produced during energy transformations, such as when you ride a bike?

What does the passage state about the total energy in the universe?

Which process allows plants to store sunlight as chemical energy?

True or False: When energy changes form, all of it is used efficiently with no loss.

True or False: Potential energy is the energy of motion.

Why is understanding energy transformations important for building better machines?