The diagram shows an iceberg floating in seawater beside a research boat. The ice has density 920 kg/m3. Seawater has density 1030 kg/m3. Most of the iceber...
Question 1 Report
The diagram shows an iceberg floating in seawater beside a research boat. The ice has density 920 kg/m3. Seawater has density 1030 kg/m3. Most of the iceberg is below the water surface.
(a) State why the iceberg floats. [2]
(b) Explain why only part of the iceberg is above the water surface. [3]
(c) Calculate the mass of an iceberg with volume 250 m3. [2]
(d) State whether the iceberg would float higher or lower in fresh water. [1]
(e) Explain your answer to part (d). [3]
(f) Give one danger caused by the part of the iceberg below water. [2]
Answer Details
(a) Ice has lower density than seawater. [1] It floats when the upthrust from the seawater balances its weight. [1]
(b) The iceberg displaces seawater. [1] As more of it is submerged, the volume of displaced water, and therefore the upthrust, increases. [1] It settles when upthrust equals its weight, so only enough ice is submerged to provide that upthrust. [1]
(c) \[m=\rho V=920\text{ kg/m}^3\times250\text{ m}^3=230\,000\text{ kg}\]
Correct formula [1]; mass = 230 000 kg. [1]
(d) The iceberg would float lower, with more of its volume submerged, in fresh water. [1]
(e) Fresh water has lower density than seawater. [1] Each cubic metre of fresh water displaced provides a smaller upthrust. [1] Therefore more of the iceberg must be submerged for the upthrust to balance its unchanged weight. [1]
(f) The underwater part can be difficult for boats to see [1] and may damage or sink a vessel in a collision. [1]
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