Changes in the state of matter
SUBLIMATION ⇒
(a) The boxes list changes that may happen in a laboratory and the names of some changes.
Draw one straight line from each change to its correct name.
(b) A student has two solids, X and Y.
One of these solids is a pure substance and the other is a mixture.
Describe how the student could identify which solid is pure and which is a mixture by measuring a physical property of each solid.
Answer. Highlight the space below to reveal the answers.
(a) ice turns into water → melting
solid carbon dioxide turns directly into a gas → sublimation
a solute is stirred into a solvent → dissolving
(b) a description including
M1 measure the melting point
M2 if fixed/sharp melting point the substance is pure
M3 if melts over range of temperatures the substance is a mixture
This question is about states of matter.
(a) The box gives words relating to changes of state.
Complete the table by giving the correct word from the box for each
change of state
(b) When ammonia gas and hydrogen chloride gas mix, they react together
to form a white solid called ammonium chloride.
The equation for the reaction is
NH3 (g) + HCl (g) → NH4Cl (s)
A teacher soaks a piece of cotton wool in concentrated ammonia
solution and another piece of cotton wool in concentrated
hydrochloric acid.
The teacher places the two pieces of cotton wool at opposite
ends of a glass tube at the same time.
After several minutes, a white ring of solid ammonium chloride forms.
(i) State the name given to the spreading out of gas particles.
(ii) State how the diagram shows that the particles of ammonia gas are
travelling at higher speeds than the particles of hydrogen chloride gas.
(iii) Gas particles travel at high speeds.
Give a reason why the white ring of ammonium chloride takes
several minutes to form.
(iv) Concentrated ammonia solution and concentrated hydrochloric acid
are corrosive.
Give one safety precaution the teacher should take.
Answer. Highlight the space below to reveal the answers.
(a) solid to liquid melting
solid to gas sublimation
liquid to solid freezing
(b) (i) diffusion
(ii) Any one from:
ammonia travels further (in the same time)
the ammonium chloride / (white) ring / solid forms
further away from the ammonia
the ammonium chloride / (white) ring / solid forms
closer to the hydrochloric acid
(iii) Any one from:
gas particles move in random directions
gas particles collide with air particles / each other
gas particles collide with the wall of the tube
Any one from:
(iv) eye protection / wear safety glasses / goggles
wear gloves
apron / lab coat
