People have long asked, "What is the world made of?" and "What holds it together?"

1. The Atomic Theory People have long asked, "What is the world made of?" and "What holds it together?"

2. The World in Ancient Thought A. Through out the history of the human civilization, people have been curious about what makes up objects. Ancient thinkers thought everything was made up of four elements – earth, fire, air, and water.

3. The World in Ancient Thought B. Even the great Greek philosopher, Aristotle, believed that earth, air, water, and fire made up all objects. C. The Chinese system of object arrangement, Feng Shui, is based on a system of five elements – fire, water, wood, metal, and earth.

4. I. Thinking About the Atom • The current thinking about what makes up all objects is the atom. Instead of four elements that make up all objects, we have identified 109. Ideas about the atom represent all our understanding about the smallest particles of matter. • The ideas about the atom have varied greatly over time, and it is quite possible that today’s model of the atom will change as new information becomes available.

5. II. Early Atomic Theory • As early as 400 BC, Greek philosophers proposed the atomic theory. • The Greek philosopher, Democritus, proposed that all matter is composed of tiny particles, called atoms. • The word atom, from the root word atomos, or indivisible, was used by Democritus to describe the tiny particles of matter.

6. II. Early Atomic Theory D. Democritus’ model describes atoms as small particles that differ in size and shape, that combine in different ways, and are constantly in motion.

7. III. Atomic Theory and Experiments • Many centuries later, the English chemist and physicist John Daltonwas one of the first scientists to set out to gather evidence for the idea of the atom.

8. III. Atomic Theory and Experiments B. In 1808, John Dalton published a detailed atomic theory: • Each element is composed of extremely small particles called atoms. • All atoms of a given element are identical. • Atoms of different elements have different properties, including mass and chemical reactivity. • Atoms are not changed by chemical reactions, they are rearranged into different compounds.

9. III. Atomic Theory and Experiments C. Dalton experimented with different gasses. His careful experiments measurements gave him repeatable evidence that matter is made up of atoms. D. Dalton thought atoms were tiny, hard spheres.

10. III. Atomic Theory and Experiments E . Dalton’s atomic theory laid the groundwork for later atomic models, and over time, his original theory has been expanded and updated.

11. IV. Identifying the Electron • English physicist Joseph John Thomsonconducted experiments with cathode ray tubes (early versions of neon lights) to determine if atoms contained smaller parts.

12. IV. Identifying the Electron B. Thomson, in 1903, identified the electron. Thomson new that atoms were electrically neutral, so he proposed that the atom was a positive sphere with negative electrons embedded in it like blueberries in a muffin.

13. V. Discovering the Nucleus • In 1911, English physicist Ernest Rutherfordused high-speed, lightweight atoms called alpha particles to bombard very thin pieced of gold foil. • Most of the alpha particles passed through the foil and hit a screen behind it. But surprisingly, some of them bounced back! Rutherford concluded that some parts of the foil had greater density.

14. V. Discovering the Nucleus C. Rutherford hypothesized that an atom must be made up of mostly empty space, allowing most of the alpha particles to pass thorough the foil. In the center of the atom, he suggested, was a tiny core called a nucleus.

15. V. Discovering the Nucleus

16. VI. Determining Where Electrons are Located • Danish physicist Niels Bohr used information about the nature of the emission of light by heated objects to update Rutherford’s model. • Bohr described electrons as moving around the nucleus in fixed orbits that have a set amount of energy. Bohr’s model of electron orbits is still used today in many analysis of the atom.

17. C. This is a Bohr Model – there are 18 protons and 22 neutrons in the nucleus. The first three energy levels are full of electrons. This is Argon.

18. VII. Discovering Neutrons A. In 1932, James Chadwick, an English physicist working in Rutherford's lab, discovered the neutron.

19. VIII. The Quantum Physics Atomic Model • Austrian physicist Erwin Schrodingerdeveloped a mathematical description of electrons around the nucleus that is called the quantum model of the atom. • This model is also called the electron cloud model, and is currently the accepted model of the atom today.

20. VIII. The Quantum Physics Atomic Model Quantum physics model

21. MATTER

22. Questions one and two • (1) What is matter? • (2) Give examples of matter:

23. I. What is Matter? A. What is matter? Matter is sometimes easier to describe than to define. B. Your book, your desk, your lunch, the air you breathe and the water you drink are all made of matter

24. Question 3 • (3) What are some characteristics of matter?

25. I. What is Matter? C. Matter is a term used to describe anything that has mass and takes up space. D. Different types of matter have different characteristics, such as boiling and melting temperatures, hardness, and elasticity.

26. Composition of Matter

27. (4) What can matter be classified on? • (5) What is the fundamental unit of matter?

28. (6) What is a compound? • (7) Give one example of a compound?

29. II. Elements and Compounds • Matter can be classified based on its properties. • The fundamental unit of matter is the element. An element is a type of matter that contains only one type of atom. An element is a substance that cannot be changed into simpler substances under normal lab conditions. Examples of elements are hydrogen, oxygen, and nitrogen.

30. II. Elements and Compounds C. A compound is a substance containing two or more elements that can be separated into simpler substances only by chemical reactions. Some examples of compounds are salt (NaCl) and water (H2O) D. If you break down a compound into the elements that make up a compound, the elements are nothing like the compound.

31. II. Elements and Compounds E. For example, you can break down the compound NaCl, or salt, into sodium and chlorine. After breaking apart salt, you would have sodium – which is a soft, yellow metal that can cause an explosion if dropped in water. You would also have chlorine, which is a yellowish, poisonous gas.

32. II. Elements and Compounds F. So to summarize elements and compounds: 1. Elements contain 1 type of atom 2. Compounds contain two or more different types of atoms (two or more elements) 3. Elements can not be broken down into simpler substances using normal lab procedures. 4. Compounds can be broken down into elements using chemical reactions.

33. Types Of Matter

34. (8) What is a mixture? • (9) Name two kinds of mixture

35. III. Mixtures • A mixture is a physical blend of two or more substances. Examples of mixtures include soda, trail mix, or milk and cereal. • There are two types of mixtures – homogeneous mixtures and heterogeneous mixtures.

36. Substance • type of matter with a fixed composition that cannot be separated by physical means Element • substance made up of atoms with same identity  • Examples: gold, helium, aluminum Compound • atoms of two or more elements combined • Examples: water (H2O), carbon dioxide (CO2)

37. Mixture materials made of two or more substances that can separated by physical means Heterogeneous mixture in which different materials can be easily distinguished • Examples: Pizza, Fruit salad Granite

38. Homogeneous mixture in which two or more substances are Uniformly spread out • Examples: Vinegar, Salt water

39. (10) Give an example of an homogeneous mixture: • (11) Give an example of an heterogeneous mixture

40. III. Mixtures C. Homogeneous mixture is a mixture that contains more than one type of matter and is the SAME throughout. D. Examples of homogeneous mixtures include soda, air, and chocolate ice cream

41. III. Mixtures E. A heterogeneous mixture is a mixture that contains more than one type of matter and is NOT THE SAME throughout the mixture. F. Examples of heterogeneous mixtures are chicken soup, a bowl of cereal, and rocky road ice cream.

42. (12) Why do scientists and medical researchers try to isolate mixtures?

43. IV. Separating Mixtures A. Separating mixtures into compounds and elements is a very important part of scientific work. Medical researchers try to isolate the compounds in plants that may help heal diseases. Forensic scientists try to match evidence from the scene of a crime with substances found with a suspect.

44. IV. Separating Mixtures B. Separating mixtures is not always an easy task. Mixtures can be separated physically or chemically.

45. Solution • homogeneous mixture of particles so small that they cannot even be seen with a microscope and will never settle to the bottom of their container. Examples: Vinegar, Soda (unopened), and Hydrogen Peroxide.

46. Suspension • heterogeneous mixture containing a liquid in which visible particles settle. Examples: Italian dressing, muddy pond water, chocolate milk. * HINT: If it needs shaking to mix, then it’s a suspension

47. Colloid • type of mixture with particles that are larger than those in solution, but still too light to settle out. Examples: Milk (Water & Fat) Fog (Water & Air), Cool Whip  # Detecting colloids is sometimes difficult so shining a beam of light at colloid will make the light scatter – this scattering of light by a colloid is called the Tyndall Effect.

48. States of Matter

49. (17) Name three states of matter:

50. VI. States of Matter • On earth, elements and compounds are usually found as solids, liquids, or gasses. These are called states of matter. • Each element or compound can exist in each of the three states of matter, and each substance has a characteristic temperature and pressure at which it will undergo a change of state.