Specification References

Teacher activity

Changing state

Specification references:  P3.1.1 Density of materials (part)  P3.1.2 Changes of state  WS 1.1, 1.2

Aims In this activity, students will observe a model of the particles in solids, liquids and gases, and then use their understanding of this model to answer a set of related questions.

Learning outcomes After completing this activity, students should be able to:  describe the properties of solids, liquids and gases  describe the arrangement of the particles in a solid, liquid and gas  explain the behaviour of a material in terms of the arrangement of particles within it  state that a material’s stored energy changes when its temperature is increased  describe the forces acting between the particles in a solid, liquid and gas  name the changes of state  describe the changes in the behaviour and the energy of the particles in a material during changes of state  explain why the density of a material changes during a change of state, using a particle model.

Teacher notes  The Student sheet is designed for students to attempt after they have been shown a model of the atoms in the three states of matter, which can be done using small balls or marbles in a tray. Clips of similar demonstrations can be found on the Web, for example at http://viewpure.com/YZ-52iBKSsM?ref=bkmk. Interactive animations of particles in different states of matter can be found at http://www.harcourtschool.com/activity/states_of_matter/ (simple) or https://phet.colorado.edu/en/simulation/states-of-matter (more detailed).  Note that the phrase ‘kinetic theory’ is not explicitly used in the AQA specifications, but various specification statements relating to particles in solids, liquids and gases amount to a basic knowledge and understanding of kinetic theory.

Teacher activity

Answers 1 1 mark per underlined label – see diagram below. (8 marks)

2 1 mark per underlined point in table below.

State Property Explanation in terms of particles Has a fixed shape, and Particles are strongly attracted to each other Solid cannot be poured. and cannot move from place to place. Difficult to compress. Particles are very close together. Can be poured / has no fixed shape / takes Particles are not held in a fixed arrangement. Liquid shape of (lower part of) container. Difficult to compress. Particles are very close together. Particles are far apart (relative to their size) / Easy to compress. are much farther apart than in solids and Gas liquids. Much lower density than Particles are far apart / there is more empty liquids or solids. space than in solids and liquids. (5 marks) 3 Any two of: no change in atoms/molecules present; no chemical reaction happens; substance is still made of identical (water) molecules; when particles brought back together, original liquid (water) is reformed. (2 marks) 4 Any two of: same type of atoms; and same number of atoms present; no atoms created or destroyed. (2 marks)

Teacher activity

5 a Gas (1 mark) b Solid and liquid (1 mark) c Liquid and gas(1 mark) d Solid and liquid. (1 mark) 6 Any two similarities and two differences between demonstration and kinetic theory (answers will depend on exact nature of demonstration), such as: model particles are in contact with each other in solid and liquid states; model particles are farther apart in gas state; model particles have kinetic energy; but: model particles not attracted to each other in solid and liquid states; model particles do not vibrate in solid state; model particles not far enough apart, relative to their size, in gas state. (4 marks)

Student follow-up answers 1 Particles shown as circles with equal or similar sizes; and for solid: particles in contact; in regular arrangement; for liquid: particles in contact; in irregular arrangement; for gas: particles far apart; in irregular arrangement. (7 marks) 2 a An atom (of copper). (1 mark) b A molecule (with one oxygen atom bonded to two hydrogen atoms). (1 mark) 3 An (invisible) fluid; that cannot be created or destroyed.(2 marks) 4 Kinetic energy of particles. (Strictly speaking, this is only referred to as ‘heat’ while it is being transferred from one object or place to another, otherwise it is part of what is described as ‘internal energy’, which students will learn about in the next lesson.) (1 mark) 5 Caloric fluid is transferred to the object. (1 mark) 6 Average kinetic energy of particles increases. (1 mark) 7 Caloric fluid repels itself (and therefore tends to spread out). (1 mark) 8 Particles pass on kinetic energy (to neighbours); by collisions. (2 marks)

Extension 9 Can rub hands for any length of time, seemingly creating endless amounts of caloric fluid (1); this caloric fluid does not seem to come from surroundings, since they do not get cooler when hands are rubbed; or other suitable argument (1). (2 marks) 10 Any three of: moving hands have kinetic energy; which is transferred to individual particles in hand / converted to heat energy; so average kinetic energy of hand particles increases; which means temperature of hand rises. (3 marks) 11 Less mass in given volume (or, same mass spread out over larger volume). (1 mark) 12 Any three of: in all three states, particle kinetic energy increases when substance is heated; which tends to make particles move farther apart; but in solids and liquids, forces between particles are significant; and stop particles from moving much farther apart; whereas forces between particles in gases are insignificant. (3 marks)

Teacher activity

Technician notes

Equipment, for teacher demonstration  Plastic tray  Identical small balls to use as model atoms/molecules