The question of how much air is inside an apple connects to fundamental principles of biology and physics. The apple’s internal structure is complex, directly influencing its physical characteristics, such as texture and interaction with water. Understanding the volume of air requires looking into the microscopic architecture of its flesh. This internal composition is the reason behind one of the apple’s most recognizable physical properties.
The Specific Volume of Air
The portion of an apple’s total volume occupied by air is substantial. Across most common varieties, approximately 25% of the apple is composed of air. This significant air content makes apples relatively light for their size compared to other produce. This high volume of gaseous space is a defining characteristic of the apple’s makeup.
How Apples Store Air Internally
The air within the apple is not stored in a single large pocket but is distributed throughout the flesh in a complex microscopic network. This air resides within the parenchyma tissue, which forms the bulk of the fruit we eat. This tissue is made up of millions of individual plant cells that are not tightly cemented together. Instead, extensive gaps exist between the walls of these cells, known as intercellular spaces.
These intercellular spaces create a continuous, interconnected system of tiny air channels that permeate the apple’s structure. The gas filling these channels is similar to the air we breathe, composed primarily of nitrogen and oxygen, alongside carbon dioxide produced by the fruit’s natural respiration process. This biological design allows for gas exchange, which is necessary for the cells to remain alive and metabolically active after harvest. This internal gaseous volume directly contributes to the fruit’s characteristic crispness and texture when bitten.
Why Apples Float
The high volume of air within the apple directly explains its tendency to float when placed in water. Whether an object sinks or floats is determined by its density, which is a measure of its mass relative to its volume. Water has a density of approximately 1 gram per cubic centimeter (g/cm³). Any object with a density less than this value will float, while anything denser will sink.
Since about a quarter of the apple’s total volume is air, which has negligible mass, the overall density of the fruit is significantly reduced. The average density of an apple is around 0.8 g/cm³. Because this figure is less than the density of water, the water exerts an upward buoyant force greater than the apple’s downward gravitational force, causing it to remain on the surface.