5.11 Atmospheric pressure
9 exam questions worth 20 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Approximately how big is atmospheric pressure at sea level?
Choose one answer.
Correct Not quite: the answer is 100 000 Pa
Mark scheme
C: 100 000 Pa
Model answer
100 000 Pa (C).
Describe how the atmospheric pressure changes as you climb up a mountain.
Mark scheme
it decreases / gets lower
Model answer
The atmospheric pressure decreases.
Explain what causes atmospheric pressure.
Mark scheme
air molecules are moving randomly / colliding with surfaces (1); each collision exerts a force (1); the pressure is the force per unit area, from a very large number of collisions / the weight of air above (1)
Model answer
Air molecules move randomly and collide with surfaces. Each collision exerts a force, and the very large number of collisions gives a force per unit area, which is the pressure.
Explain why the atmospheric pressure is lower at the top of a mountain than at sea level.
Mark scheme
there is less air above (so less weight pressing down) (1); the air is less dense, so there are fewer collisions with a surface each second (1)
Model answer
There is less air above, so less weight pressing down. The air is also less dense, so fewer molecules collide with a surface each second.
The atmospheric pressure on a flat roof of area 20 m² is 100 kPa. Calculate the force of the atmosphere on the roof.
Mark scheme
100 kPa = 100 000 Pa (1); F = p A = 100 000 × 20 (1); 2 000 000 N (1)
Model answer
F = p A = 100 000 × 20 = 2 000 000 N.
The atmosphere exerts a very large force on a window, but the window does not break. Explain why.
Mark scheme
there is an equal pressure on the other side of the window (1); so the forces are balanced / the resultant force is zero (1)
Model answer
The air inside the room exerts an equal pressure on the other side of the window, so the forces are balanced.
A sealed bag of crisps is taken up a mountain and the bag swells. Explain why.
Mark scheme
the atmospheric pressure outside the bag decreases (1); the pressure of the air inside the bag stays the same (1); so there is a resultant outward force and the bag expands (1)
Model answer
The pressure outside the bag drops as the height increases, but the pressure inside the bag stays the same. The bag expands because of the resultant outward force.
Use the graph to estimate the atmospheric pressure at a height of 10 km and describe how it compares with the pressure at sea level.
Mark scheme
about 26 kPa (1); about a quarter of the pressure at sea level (1)
Model answer
About 26 kPa, which is about a quarter of the pressure at sea level.
Explain how drinking through a straw depends on atmospheric pressure.
Mark scheme
sucking reduces the air pressure inside the straw (1); atmospheric pressure on the surface of the drink is greater than the pressure inside the straw (1); so the drink is pushed up the straw by the atmospheric pressure (1)
Model answer
Sucking reduces the pressure inside the straw. The atmospheric pressure pushing down on the surface of the drink is then greater than the pressure in the straw, which pushes the drink up the straw.
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