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2.5 - Classification of Particles – Questions

Q1. (a) Name the only stable .

______(1)

(b) (i) When aluminium-25( Al) decays to magnesium-25 (Mg-25) an (νe) and another are also emitted.

Complete the equation to show the changes that occur.

(2)

(ii) Name the exchange particle responsible for the decay.

______(1) (Total 4 marks)

Q2. More than 200 subatomic particles have been discovered so far. However, most are not fundamental and are composed of other particles including .

It has been shown that a can be made to change into a and that and are made of quarks.

(a) Name one process in which a proton changes to a neutron.

______

______(1)

(b) Name the particle interaction involved in this process.

______

______(1)

(c) Write down an equation for the process you stated in part (a) and show that the baryon number and number are conserved in this process.

baryon number ______

______

______

Page 1 of 18 lepton number ______

______

______(2)

(d) The strange was used to explain the existence of particles whose tracks had been seen in experiments in the early 1950s. These were unexplained at that time and were referred to as ‘strange particles’. One of these particles was later named the K+ .

State the quark composition of a K+ kaon.

______

______(1)

(e) A K+ kaon decays into a π+ particle and a π° particle.

Explain one property which is conserved and one property which is not conserved in this decay.

conserved ______

______

not conserved ______(2) (Total 7 marks)

Q3. (a) Complete the table comparing some of the properties of the positive , π+, and the proton.

Name π+ Proton

Relative +1

Baryon number

Quark

composition

(5)

(b) When a positive pion interacts with a proton, a kaon can be produced, along with another , as shown in this equation

Circle the type of interaction shown in this equation.

Page 2 of 18 Electromagnetic Gravitational Strong Nuclear Weak Nuclear

(1)

(c) Deduce the relative charge, baryon number and of particle X.

(3)

(d) Particle X can decay to produce a neutron and positive pion as shown in this equation

Circle the type of interaction shown in this equation.

Electromagnetic Gravitational Strong Nuclear Weak Nuclear

(1)

(e) Explain your answer.

______

______

______

______(2)

(f) The neutron and positive pion will then decay. The positive pion can decay into a and an .

Write down the equation for the decay of the neutron.

(2)

(g) Explain why no further decays occur.

______

______

______

______(2) (Total 16 marks)

Page 3 of 18 Q4. (a) , and are affected by particle interactions.

Write an account of these interactions. Your account should:

• include the names of the interactions • identify the groups of particles that are affected by the interaction • identify the exchange particles involved in the interaction • give examples of two of the interactions you mention.

The quality of your written communication will be assessed in your answer.

______

______

______

______

______

______

______

______

______

______(6)

(b) Draw a labelled diagram that represents a particle interaction. (3) (Total 9 marks)

Q5. The diagram below represents the decay of a particle X into a particle Y and two other particles.

The quark structure of particles X and Y are shown in the diagram.

(a) Deduce the name of particle X.

Page 4 of 18 ______(1)

(b) State the type of interaction that occurs in this decay.

______(1)

(c) State the class of particles to which the W − belongs.

______(1)

(d) Show clearly how charge and baryon number are conserved in this interaction.

You should include reference to all the particles, including the quarks, in your answer.

______

______

______

______

______(2)

(e) Name the only stable baryon.

______(1)

(f) A is an unstable particle.

State the names of the particles that are produced when a muon decays.

______(1) (Total 7 marks)

Q6. (a) Complete the following equation for beta minus (β−) decay of

strontium-90 ( Sr) into an of yttrium (Y).

(3)

(b) During β− decay of a nucleus both the composition and the quark composition change. State the change in quark composition.

Page 5 of 18 ______(1)

(c) A positive kaon consists of an and an antistrange quark . This kaon decays by strong and weak interactions into three . Two of the pions have quark compositions of . The third pion has a different quark composition.

(i) Name the unique family of particles to which the kaon and pions belong.

______(1)

(ii) Tick the box corresponding to the charge of the third pion.

positive negative neutral

(1)

(iii) Positive have unusually long lifetimes. Give a reason why you would expect this to be the case.

______

______(1)

(iv) Name the exchange particles which are involved in the strong and weak interactions of the kaon.

______

______(1) (Total 8 marks)

Q7. Leptons, mesons and baryons are three classes of sub-atomic particles.

(a) Some classes of particles are fundamental; others are not. Circle the correct category for each of these three classes.

Leptons fundamental/not fundamental Mesons fundamental/not fundamental Baryons fundamental/not fundamental (1)

(b) Name the class of particles of which the proton is a member.

______(1)

(c) By referring to the charges on up and down quarks, explain how the proton has a charge of + 1e.

Page 6 of 18 ______

______(2) (Total 4 marks)

Q8. (a) Give the name of a particle that is a .

______(1)

(b) Pions are mesons.

Give a possible quark structure for a pion.

______(1) (Total 2 marks)

Q9. (a) (i) Give an example of an exchange particle other than a W+ or W– particle, and state the fundamental force involved when it is produced.

exchange particle ______

fundamental force ______

(ii) State what roles exchange particles can play in an interaction.

______

______

______(4)

(b) From the following ,

p e+ μ– π0

identify all the examples of

(i) , ______

(ii) leptons, ______

(iii) , ______

(iv) charged particles. ______(4) (Total 8 marks)

Page 7 of 18 Q10. (a) (i) Name two baryons.

______(2)

(ii) State the quark structure of the pion .

______(1)

(b) (i) The K+ kaon is a strange particle. Give one characteristic of a strange particle that makes it different from a particle that is not strange.

______

______(1)

(ii) One of the following equations represent a possible decay of the K+ kaon. K+ → π+ + π0

K+→ μ+ +

State, with a reason, which one of these decays is not possible.

______

______(2)

(c) Another strange particle, X, decays in the following way: X → π– + p

(i) State what interaction is involved in this decay.

______(1)

(ii) Show that X must be a neutral particle.

______

______(1)

(iii) Deduce whether X is a , baryon or lepton, explaining how you arrive at your answer.

______

Page 8 of 18 ______

______

______(2)

(iv) Which particle in this interaction is the most stable?

______(1) (Total 11 marks)

Q11. Mesons that contain a strange (or antistrange) quark are known as K-mesons or kaons. Mesons are a sub-group of a larger group of particles.

(a) (i) State the name of this larger group of particles.

______(1)

(ii) Determine the charge on a kaon with a quark structure of us̄ .

______(1)

(b) A proposed decay for this kaon is

(i) Apply the law of conservation of strangeness to the proposed decay.

______

______

______(1)

(ii) Comment on whether or not this decay is possible.

______

______

______(1) (Total 4 marks)

Q12. Leptons, mesons and baryons are three classes of sub-atomic particles.

(a) Some classes of particles are fundamental; others are not. Circle the correct

Page 9 of 18 category for each of these three classes.

leptons fundamental/not fundamental

mesons fundamental/not fundamental

baryons fundamental/not fundamental

(1)

(b) Name the class of particles of which the proton is a member.

______(1)

(c) By referring to the charges on up and down quarks explain how the proton has a charge of +1e.

______

______

______(2) (Total 4 marks)

Q13. (a) Name two hadrons.

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______

(b) Name two leptons which are also antiparticles.

______

______

(c) State a possible quark structure of the pion π0. A table of the properties of quarks is given in the Data booklet.

______

(d) A K– kaon is a strange particle. State one characteristic of a strange particle.

______

______(Total 4 marks)

Q14. (a) A particle is made up from an anti-up quark and a .

Page 10 of 18 (i) Name the classification of particles that has this type of structure.

______(1)

(ii) Find the charge on the particle.

(1)

(iii) State the baryon number of the particle.

(1)

(b) A suggested decay for the positive muon (µ+) is

+ + µ → e + ve

Showing your reasoning clearly, deduce whether this decay satisfies the conservation rules that relate to baryon number, lepton number and charge.

Baryon number ______

Lepton number ______

Charge ______(3) (Total 6 marks)

Q15. (a) State the quark substructure of a neutron.

______(2)

(b) Circle the terms below that can be used to describe a neutron.

baryon fundamental particle hadron lepton meson (2) (Total 4 marks)

Q16. The list of sub-atomic particles below contains particles that are either hadrons or leptons:

electron neutron pi-meson proton

(a) Complete the table below by adding the names of the particles to the correct box.

Hadrons

Leptons

(4)

Page 11 of 18 (b) Underline the names of the particles that are baryons. (2) (Total 6 marks)

Q17.

Neutrons were discovered when beryllium, Be, was bombarded with alpha particles.

An knocked a neutron out of a beryllium nucleus producing a nucleus, C.

(a) Write down the equation that describes this reaction.

______(2)

(b) (i) Describe the quark substructure of a neutron.

______

______(1)

(ii) Describe how the quark substructure of a meson differs from that of a baryon such as a neutron.

______(1) (Total 4 marks)

Q18. State the differences in quark structure between a meson and a baryon.

______

______

______

______(Total 2 marks)

Q19. (a) (i) How do hadrons differ from all other subatomic particles?

______

______

(ii) Give the quark composition of the following particles.

neutron ______

Page 12 of 18 neutral pion ______

______

(iii) Classify the following as either leptons, baryons or mesons.

kaon ______

muon ______(5)

(b) Which is the most stable baryon?

______(1)

(c) This table may be useful in answering the questions which follow.

baryon lepton particle strangeness number number

π − 0 0 0

p 1 0 0

p̄ −1 0 0

e− 0 1 0

e+ 0 −1 0

v̄ e 0 −1 0

The particle X, which is a strange particle, decays in the following way:

X → π − + p

(i) State whether X is a meson, a baryon or a lepton.

______

(ii) Use conservation laws to decide whether each of the following decays of the π − is possible. Give a reason for your answer.

− + (A) π → e + νe

Is this decay possible? ______

reason ______

(B) π − → p̄ + e− + e+

Is this decay possible? ______

reason ______

Page 13 of 18 (5) (Total 11 marks)

Q20. (a) State whether or not each of the following properties of a baryon is conserved when it decays by the weak interaction.

charge ______

baryon number ______

strangeness ______(2)

(b) State, with a reason, whether or not each of the following particle reactions is possible.

(i) p + π– → K– + π+

______

______

______

(ii) p + → n = e+

______

______

______(4) (Total 6 marks)

Q21. (a) Quarks may be combined together in a number of ways to form sub-groups of hadrons. Name two of these sub-groups and for each, state its quark composition.

sub-group 1 ______

______

sub-group 2 ______

______(3)

(b) A free neutron is an unstable particle.

(i) Complete the following to give an equation that represents the decay of a neutron.

n →

Page 14 of 18 (ii) Describe the change that occurs to the quark structure when a neutron decays.

______

______

______

______

______(4) (Total 7 marks)

Q22. Some subatomic particles are classified as hadrons.

(a) What distinguishes a hadron from other subatomic particles?

______

______(1)

(b) Hadrons fall into two subgroups. Name each subgroup and describe the general structure of each.

subgroup 1 ______

______

subgroup 2 ______

______(3)

(c) The following equation represents an event in which a positive muon collides with a neutron to produce a proton and an antineutrino.

n + μ+ p + .

Show that this equation obeys the conservation laws of charge, lepton number and baryon number.

______

______

______(3) (Total 7 marks)

Q23.

Page 15 of 18 The equation

+ p n + β + ve

represents the emission of a positron from a proton.

(a) Energy and momentum are conserved in this emission. What other quantities are conserved in this emission?

______

______

______

______(3)

(b) Draw the that corresponds to the positron emission represented in the equation.

(4)

(c) Complete the following table using ticks and crosses .

particle fundamental meson baryon lepton particle

p

n

β+

ve

(4) (Total 11 marks)

Q24. (a) The table gives information about some fundamental particles.

Complete the table by filling in the missing information.

Page 16 of 18 particle quark charge strangeness baryon structure number

uud 0

Sigma + uus + 1

ud̄ 0 0

(7)

(b) Each of the particles in the table has an antiparticle.

(i) Give one example of a baryon particle and its corresponding antiparticle.

particle ______

antiparticle ______(1)

(ii) State the quark structure of an antibaryon.

______(1)

(iii) Give one property of an antiparticle that is the same for its corresponding particle and one property that is different.

Same ______

______

Different ______

______(2) (Total 11 marks)

Q25. Which line correctly classifies the particle shown?

Quark Particle Category combination

A neutron baryon ū d

B neutron meson udd

C proton baryon uud

D positive pion meson ū d (Total 1 mark)

Page 17 of 18 Q26. What of the following is a hadron of zero charge?

A neutrino

B

C proton

D neutron (Total 1 mark)

Q27. 7 What are the numbers of hadrons, baryons and mesons in an of 3Li?

hadrons baryons mesons

A 7 3 3

B 7 4 4

C 7 7 0

D 10 7 0 (Total 1 mark)

Q28. Which of the following is not true?

A Each meson consists of a single quark and a single antiquark.

B Each baryon consists of three quarks.

C The magnitude of the charge on every quark is

A particle consisting of a single quark has not been D observed.

(Total 1 mark)

Page 18 of 18