Search the Properties of Matter site Properties of Matter glossary Photos, illustrations and streaming media on the Properties of Matter site Properties of Matter table of contents Properties of Matter home page Link to NSRC home page

Reading Selection, Lesson 3

Why Did the Titanic Float?

Click here for audio and Spanish translation

The New York Herald front page reports the sinking of the Titanic.
This newspaper article reported on the disastrous maiden voyage of the Titanic. Why was this voyage a disaster? What role did density play in the tragedy?
On April 10, 1912, the luxury liner Titanic left England for New York and sailed straight into the annals of history. Why is the name Titanic so well known? At that time, she was considered the safest ship ever built; some people even considered her unsinkable. The Titanic became famous when she struck an iceberg and sank on her first voyage. About 1500 people drowned or froze to death in the ice-cold Atlantic water.

People often ask, “Why did the Titanic sink?” Perhaps a better question would be, “Why did the ship float?” She was, after all, made mainly from iron and steel. Her anchors alone weighed 28 metric tons. (That’s almost 62,000 pounds!) Steel has a density about eight times that of water, so you would expect a ship made of steel to sink.

The bow of the Titanic seen under water.
The Titanic now lies under 12,500 feet of water. It was made mainly from steel, which is denser than water. How did it manage to float at all?

However, if you were to look at a plan of the Titanic, you would discover that most of her volume was occupied by air. Air has a density of about one-thousandth that of water. Therefore, the average density of the ship was less than the density of water. That’s why she floated.

Iceberg with plane flying in front of it.
Icebergs float in water. What does this tell us about their density?

Why did she sink? When the Titanic hit the iceberg, water rushed into the ship’s hull and displaced the air. The average density of the water and the steel ship was greater than the density of water. The result of this change? The Titanic sank to the bottom of the Atlantic.

QUESTIONS

Unfortunately, life vests, or personal flotation devices (PFDs), were not enough to save the lives of many of the Titanic’s passengers. However, they save hundreds of lives every year.
1. If you were designing a PFD, what factors would you need to take into account?

2. Draw a diagram of a PFD of your own design. Label it, explaining the role of each of its parts, and be sure to include the word “density” somewhere in your explanation.

Information about the STC/MS curriculum Link to NSRC home page NSRC contact information NSRC copyright and permissions information Smithsonian Institution privacy policy Properties of Matter site map