Matter is anything that takes up space and has mass. All matter is made of atoms

1. Matter is anything that takes up space and has mass. • All matter is made of atoms • Atoms are the building blocks of matter, sort of how bricks are the building blocks of houses. • What is an atom? • Atom: the smallest unit of matter that retains the identity of the substance

2. Three Laws Supporting the existence of Atoms • Law of definite proportions – states that a chemical compound always contains the same elements in exactly the same proportions by weight or mass • Law of multiple proportions – states that when two elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other is in the ratio of small whole numbers • Law of conservation of mass – states that mass cannot be created or destroyed in ordinary chemical and physical changes

3. Dalton’s Theory • All matter is composed of extremely small particles called atoms, which cannot be subdivided, created, or destroyed. • Atoms of a given element are identical in their physical and chemical properties. • Atoms of different elements differ in their physical and chemical properties. • Atoms of different elements combine in simple, whole-number ratios to form compounds. • In chemical reactions, atoms are combined, separated, or rearranged but never created, destroyed, or changed.

4. Discovery of the Subatomic Particles • Electrons – Discovered using Cathode Rays by English Physicist J.J. Thomson. • Nucleus – Discovered by Ernest Rutherford using Gold-foil experiment

5. Atomic Structure • Atoms are composed of 2 regions: • Nucleus: the center of the atom that contains the mass of the atom • Electron cloud: region that surrounds the nucleus that contains most of the space in the atom Nucleus Electron Cloud

6. What’s in the Nucleus? • The nucleus contains 2 of the 3 subatomic particles: • Protons: positively charged subatomic particles • Neutrons: neutrally charged subatomic particles

7. What’s in the Electron Cloud? • The 3rd subatomic particle resides outside of the nucleus in the electron cloud • Electron: the subatomic particle with a negative charge and relatively no mass

8. How do these particles interact? • Protons and neutrons live compacted in the tiny positively charged nucleus accounting for most of the mass of the atom • The negatively charged electrons are small and have a relatively small mass but occupy a large volume of space outside the nucleus

9. How do the subatomic particles balance each other? In an atom: • The protons = the electrons • If 20 protons are present in an atom then 20 electrons are there to balance the overall charge of the atom—atoms are neutral • The neutrons have no charge; therefore they do not have to equal the number of protons or electrons

10. Periodic Table Atomic Number: Number of protons and it is also the number of electrons in an atom of an element. 8 O Element’s Symbol:An abbreviation for the element. Oxygen Elements Name 15.999 Atomic Mass/Weight: Number of protons + neutrons.

11. How do we know the number of subatomic particles in an atom? • Atomic number: this number indicates the number of protons in an atom • Ex: Hydrogen’s atomic number is 1 • So hydrogen has 1 proton • Ex: Carbon’s atomic number is 6 • So carbon has 6 protons **The number of protons identifies the atom. Ex. 2 protons = He, 29 protons = Cu

12. Learning Check State the number of protons in each. • A nitrogen atom • 5 protons • 7 protons • 14 protons • A sulfur atom • 32 protons • 16 protons • 6 protons

13. How do we know the number of subatomic particles in an atom? • Mass number: the number of protons and neutrons in the nucleus • Ex: hydrogen can have a mass of 3. Since it has 1 proton it must have 2 neutrons • # of neutrons = mass # - atomic #

14. Determining the number of protons and neutrons Li has a mass number of 7 and an atomic number of 3 • Protons = 3 (same as atomic #) • Neutrons= 7-3 = 4 (mass # - atomic #) • Ne has a mass number of 20 and an atomic number of 10 • Protons = • Neutrons =

15. What about the electrons? • The electrons are equal to the number of protons • So e- = p = atomic # • Ex: He has a mass # of 4 and an atomic # of 2 • p+ = 2 • no = 2 • e- =2

16. Determine the number of subatomic particles in the following: • Cl has a mass # of 35 and an atomic # of 17 • p+ = no = e- = • K has a mass # of 39 and an atomic # of 19 • P+ = no = e- =

17. An atom refresher • An atom has three parts: • Proton = positive • Neutron = no charge • Electron = negative • The proton & neutron are found in the center of the atom, a place called the nucleus. • The electrons orbit the nucleus. Picture from http://education.jlab.org/qa/atom_model_03.gif

20. States of Matter • The Kinetic Theory 1. All matter is composed of small particles (atoms, molecules, or ions). 2. They are in constant, random motion. 3. They constantly collide with each other and with the walls of their container.

21. Particle Properties Volume Shape Energy Phase Proximity definite little close definite Solid moderate indefinite definite close Liquid indefinite far apart a lot indefinite Gas

22. What is a Physical Change? • A physical change alters the form of a substance, but does not change it to another substance. Example: Making Orange Juice

23. What is a Chemical Change? • When a substance undergoes a chemical change, it is changed into a different substance with different properties. Example: Baking a Cake

24. 5 Signs of a Chemical Change • Color Change • Precipitation Precipitation – the solid that forms from a solution during a chemical reaction. It looks like a cloudy solid in an otherwise clear solution.

25. 5 Signs of a Chemical Change • Gas Production • Temperature Change • Changes in Characteristic Properties (odor, light given off)

26. Chemical or Physical Change? • Cutting paper? • Physical

27. Chemical or Physical Change? • Ice melting? • Physical

28. Chemical or Physical Change? • Toast burning? • Chemical

29. Chemical or Physical Change? • Rocket fuel burning? • Chemical

30. Chemical or Physical Change? • Sawing wood? • Physical

31. Chemical or Physical Change? • Metal rusting? • Chemical

32. Chemical or Physical Change? • Disappearing puddle? • Physical

33. Chemical or Physical Change? • Candle burning? • Chemical

34. Chemical or Physical Change? • Dry ice? • Physical

35. Physical or Chemical Property? • Ability of gun powder and fire to explode. Chemical Property

36. Physical or Chemical Property? Physical Property • The color of a sunset.

37. Physical or Chemical Property? • The ability of a nail to rust. Chemical Property

38. Physical or Chemical Property? • The shape of a leaf. Physical Property

39. Physical or Chemical Property? • The ability of wood to burn. Chemical Property

40. Physical or Chemical Property? • The hardness of a diamond. Physical Property

41. Physical or Chemical Property? • The volume of your coke. Physical Property

42. Physical or Chemical Property? • The mass of two camels. Physical Property

43. Physical or Chemical Change? • Water evaporates from the ocean.

44. Physical or Chemical Change? • The yolk of an egg, which contains sulfur, causes tarnish to form on silver.

45. Physical or Chemical Change? • The ice on a lake melts to become water in the lake.

46. Physical or Chemical Change? • Charcoal in a fire turns to ash after several hours.

47. Physical or Chemical Change? • A pencil is sharpened in a pencil sharpener, leaving behind shavings.

48. Physical or Chemical Change? • A battery makes electricity to turn on a flashlight.

49. Physical or Chemical Change? • A bicycle rusts when left in the rain.

50. Physical or Chemical Change? • A shirt is accidentally torn in the washing machine.