1. 1 Atomic Theory Click the links below to access the activities: - Activity 1Activity 1 - Activity 2Activity 2 - Activity 3Activity 3 - Extension activityExtension activity - Activity 4Activity 4

2. 2 Activity 1: Conservation of mass ?

3. 3 If a piece of magnesium is burnt, will there be a gain or a loss in mass? Video 1 Video 2

4. 4 Your tasks… Task 2 Compare the mass of sodium hydroxide (NaOH) solution and copper(II) sulphate (CuSO 4 ) solution with the mass of the mixture where we can see some precipitate of Cu(OH) 2. Task 2 Compare the mass of sodium hydroxide (NaOH) solution and copper(II) sulphate (CuSO 4 ) solution with the mass of the mixture where we can see some precipitate of Cu(OH) 2. Task 1 Measure the mass of 500 cm 3 of your favourite drink. Then compare your body mass before and after drinking it. Task 1 Measure the mass of 500 cm 3 of your favourite drink. Then compare your body mass before and after drinking it. Task 3 Dissolve 5 g table salt in 100 cm 3 of water. Compare the masses of solute, solvent and the resulting solution Task 3 Dissolve 5 g table salt in 100 cm 3 of water. Compare the masses of solute, solvent and the resulting solution

5. 5 What can you conclude from the above data?

6. 6 The Law of Conservation of Mass ‘In a chemical reaction, the mass of the products is equal to the mass of the reactants.’ ‘Matter can neither be created nor destroyed in any physical or chemical change.’

7. 7 People had no idea why the law was always true.

8. 8 Activity 2: The Law of Definite Proportions End of 1700s Some chemists tried to mix different elements to see how they reacted with each other.

9. 9 Look at the results of the following reactions: carbon + oxygen  carbon dioxide carbon + oxygen  carbon monoxide copper + oxygen  copper(II) oxide

10. 10 What can you conclude from the data above?

11. 11 The Law of Definite Proportions Nobody could explain why elements behaved like this. ‘A given chemical compound always contains the same proportions by mass of its constituent elements.’ Proposed by Joseph Louis Proust in 1797

12. 12 Activity 3: Atomic theory All matter is composed of very small discrete particles. For elements, the particles are called atoms and they are indivisible and indestructible in chemical reactions.

13. 13 What is a law? What is a theory?

14. 14 What is a law? What is a theory? Theories are the explanations of those relationships Laws are descriptions of relationships among phenomena in nature Ideal Gas Law PV = nRT Kinetic Theory

15. 15 Law and Theory Kinetic Theory explains these behaviours i.e. the Ideal Gas Law. The Ideal Gas Law describes the behaviours of ideal gases. Kinetic model

16. 16 Another example Explained by the “particle theory of light” Law of Reflection Incident light rayReflected light ray Normal θiθi θrθr Steel Ball Rebound Light Reflection Mirror Many light particles in a light ray

17. 17 Hypothesis Theory Law Hierarchical relationship?

18. 18 A theory will not turn into a law or vice versa. Scientific theories and laws are different kinds of knowledge.

19. 19 Extension Atomic Theory All matter is composed of very small discrete particles. For elements, the particles are called atoms and are indivisible and indestructible in chemical reactions. Each atom of a given element has the same mass. (ii) All atoms of a given element are identical. (iii) The masses of atoms of different elements are different. A chemical compound is formed from its elements by the combination of the different atoms in a fixed ratio for that compound. Comment on Dalton’s Atomic Theory!

20. 20 For elements, the particles are called atoms and are indivisible and indestructible in chemical reactions. Each atom of a given element has the same mass. 12 C 13 C isotopes

21. 21 “An atom is made of electrons, protons and neutrons.” Has this statement been revised? Try to look up websites to answer this question!

22. 22 Scientific knowledge is subject to change

23. 23 Activity 4: Assessment (a) The mass of an iron atom in a hammer is greater than the mass of an iron atom in a nail. (b) When you change a piece of solid copper into the liquid state, the mass of each copper atom decreases. Question 1 (c) When you heat a silver ring, it expands. This is because the silver atoms become bigger.

24. 24 What would be left if all the atoms are removed? Question 2

25. 25 (a) What will be the difference in masses of the iron, compared to the rusted iron? Question 3

26. 26 (b) Draw a picture to show what a piece of rusted iron would look like if you could see the atoms.

27. 27 Before rusting After rusting

28. 28 Compare the mass of the setup before and after CuSO 4 crystals have grown. Explain your answer. Question 4 CuSO 4 solution in a closed system. After a few days, crystals have grown. crystals

29. 29 Question 5 Compare the masses of 355cm 3 Diet Coke tm and 355cm 3 regular Coke tm after pouring them out of the cans. Discuss whether this is related to the Law of Conservation of Mass or not.