Physics P1

1. Physics P1 Matter

2. P1.1: The particle model P1.1 The particle model

3. P1.1a The development of atomic theory Objective • To be able to describe how and why the atomic model has changed over time Can you guess what this is? Now? Now?

4. What is an Atom? • The word atom comes from the Greek word ‘atomos’ which means ‘indivisible’ (can’t be divided into smaller parts). • Democritus, a Greek philosopher thought that if you kept cutting something eventually you would get down to a solid ball (an atom) whichcould no longer be cut. • A very popular Greek philosopher, Aristotle, disagreed with Democritus and so Democritus’ idea was forgotten.

5. … 2000 years later • A school teacher and a scientist at the University of Manchesterperformed many experiments to study how elements join together to form new substances. • He discovered that: • All substances are made up of atoms which are small particles that cannot be created, divided, or destroyed. • Atoms of the same element are exactly alike and atoms of different elements are different. • Atoms join with other atoms to form different substances

6. Is there anything smaller than an atom? • J.J. Thomson (1856-1940)discovered that atoms are made of smaller negatively-charged particles called electrons. • So he said there were negative electrons, in a ‘soup’ of positive charge. This was called the plum pudding model.  J. J. Thomson 1904

7. Was it right? • Ernest Rutherford, a student of J.J. Thomson, disagreed with the “Plum Pudding Model”. • So he did an experiment to investigate the structure of positive and negative charges in the atom.

8. THE experiment • He worked alongside Hans Geiger and Ernest Marsden in 1909, at the University of Manchester, and what they saw was astonishing. • “It was almost as incredible as if you fired a 40cm bullet at a piece of tissue paper and it came back and hit you.”

9. Further development • Niels Bohr in the 1920s realised that electrons orbited the nucleus in certain ways. • James Chadwick in 1932 discovered that there were also neutrons present in the nucleus of the atom.

10. Activity • Create a timeline showing the development of atomic theory through the ages.

11. Quiz • Which Greek philosopher is accredited with coining the term "atom"? • Which scientist proposed the Plum Pudding model? • Who discovered the existence of the electron? • Who discovered that the nucleus was made of positively charged particles? • How did the 3 scientists discover the nucleus had a positive charge?

12. P1.1B Atomic Structure Objectives • To be able to recall the properties of the different parts of the atom. • To be able to describe the structure of the atom. Name the 3 particles that make up the atom.

13. Labelling the atom

14. Activity – label the parts of the atom - - Electron Proton - + - + + + + + - + Nucleus Neutron - - -

15. The central part of an atom. Composed of protons and neutrons. Contains most of an atom's mass. Overall positive charge. WHAT IS THE NUCLEUS?

16. Positively charged particle. Charge = +1 Relative Mass = 1 Found within an atomic nucleus. WHAT IS A PROTON?

17. Uncharged particle. Charge = 0 Relative Mass = 1 Found within an atomic nucleus. WHAT IS A NEUTRON?

18. Negatively charged particle. Charge = -1 Relative Mass = 0.0005 ≈ 0 Located in shells that surround an atom's nucleus. WHAT IS AN ELECTRON?

19. Mass and electrical charge There are two properties of protons, neutrons and electrons that are especially important: • mass • electrical charge. Particle Mass Charge proton 1 +1 neutron 1 0 electron almost 0 -1 The atoms of an element contain equal numbers of protons and electrons and so have no overall charge.

20. Properties of the particles of the atom

21. How many protons? The atoms of any particular element always contain the same number of protons. For example: • hydrogen atoms always contain 1 proton • carbon atoms always contain 6 protons • magnesium atoms always contain 12 protons. The number of protons in an atom is known as the atomic numberor proton number. It is the smaller of the two numbers shown in most periodic tables.

22. What is the atomic number? What are the atomic numbers of these elements? 11 sodium 26 iron 50 tin 9 fluorine

23. What is mass number? Electrons have a mass of almost zero, which means that the mass of each atom results almost entirely from the number of protons and neutrons in the nucleus. The sum of the protons and neutrons in an atom’s nucleus is the mass number. It is the larger of the two numbers shown in most periodic tables. Atoms Protons Neutrons Mass number hydrogen 1 0 1 lithium 3 4 7 aluminium 13 14 27

24. Neutrons Atoms Mass number Atomic number helium fluorine strontium zirconium uranium How many neutrons? number of neutrons = mass number - number of protons = mass number - atomic number How many neutrons are there in these atoms? 4 2 2 19 9 10 88 38 50 91 40 51 238 92 146

25. Atoms Protons Neutrons Electrons helium copper iodine How many electrons? Atoms have no overall electrical charge and are neutral. This means atoms must have an equal number of positive protons and negative electrons. The number of electrons is therefore the same as the atomic number. 2 2 2 29 35 29 53 74 53 Atomic number is the number of protons rather than the number of electrons, because atoms can lose or gain electrons but do not normally lose or gain protons.

26. What are the missing numbers?

27. P1.1c - Relative sizes • The atom is of the order 10-10m= 0.000000001m • The diameter of a pinhead is 100,000 times smaller than the diameter of a stadium. • Likewise the diameter of the nucleus of an atom is 100,000 times smaller than the diameter of an atom

28. Quiz • Name the particle, in the atom, with a positive charge. • Name the particle, in the atom, with the smallest mass. • Name the particle, in the atom, with a neutral charge. • How many times larger, is the radius of the atom, than the radius of the nucleus?

29. Objective Density • To be able to work out a material’s density. These two objects are the same volume, so why is one heavier?

30. What is density? Density is the amount of mass in a volume. It tells us how tightly matter is packed together. What is Density? How do objects float? How do substances float?

31. Copy the equation into your book Mass (g) Density = Volume (cm3)

32. How do we work out density?

33. The volume of a cuboid

34. Demonstrate

36. Density 2 Objective • To be able to work out a material’s density, using the displacement of water to find an object’s volume.

37. Demonstrate • Measure the mass and volume of each object and calculate their density. • The volume of the object is the same as the volume of water it displaces from the Eureka can.

38. Density Questions

39. Density calculations – Exam Questions

42. density - states of matter Objective • To understand that mass is conserved during evaporation and condensation. True/False • The density of water is 5g/cm3 • A material with a high density feels heavier than something of the same size with a low density. • Density is how much mass there is in 1cm3 of a material. • You can calculate density if you know a material’s mass. • The units of density are g/cm3. • Density = volume mass

43. Consolidate TRUE OR FALSE?

44. The density of water is 5g/cm3 • FALSE! • It is 1g/cm3

45. A material with a high density feels heavier than something of the same size with a low density. • TRUE!

46. Density is how much mass there is in 1cm3 of a material. • TRUE!

47. You can calculate density if you know a material’s mass. • FALSE! • You need to know it’s volume too.

48. The units of density are g/cm3. • TRUE!

49. Density = volume mass • FALSE! • Density = mass • volume

50. Solids, Liquids and Gases - Density Solid Liquid Gas When substances change state mass is conserved.