CIE Chemistry Paper-1: Specimen Questions 21 - 22 of 99
Question number: 21
The diagrams show the arrangement of particles in three different physical states of substance X.
Which statement about the physical states of substance X is correct?
Particles in state 1 vibrate about fixed positions.
State 1 changes to state 2 by diffusion.
The substance in state 3 has a fixed volume.
State 2 changes directly to state 3 by condensation.
The molecules in a solid are in fixed positions and are close together. Although the molecules can still vibrate, they cannot move from one part of the solid to another part. As a result, a solid does not easily change its shape or its volume.
Question number: 22
A test-tube has damp iron wool and is inverted in water. After 3 days, the water level inside the test-tube rise. Explain cause of rise.
Iron wool has been reduced.
The temperature of the water has risen.
Iron oxide has been formed.
Oxygen has been formed.
Air is composed of Nitrogen - about 78%, Oxygen
about 21%, Argon about 1 % and other gasses. These gasses compose 100 % of the air so they exert 100 % of the pressure. IN the test tube, at the beginning, there was the same pressure inside the test tube as outside. As the steel wool started to rust, the oxygen was taken out of the air, therefore the pressure was reduced. Over time, the pressure was reduced by the percentage of oxygen removed…. about 21%. As the pressure drops, the
pressure on the outside of the test tube pushes the water level up inside the test tube. The iron in the steel wool became an iron oxide.