Classifying Matter

1. Classifying Matter

2. 4.01 – States of Matter • Anything with mass that takes up space (volume) is matter. • Exists in 4 states • Solid • Liquid • Gas • Plasma

3. 4.01 – States of Matter • Solid: • The particles of a solid are in a tight, fixed position. Since the particles in solids are not free to move around they vibrate just a little. Solids have a set volume and a set shape.

4. 4.01 – States of Matter • Liquid: • The particles of a liquid are close together, but they are not in a neat arrangement like in a solid. They have enough space to slide past each other. Liquids have a set volume but no set shape.

5. 4.01 – States of Matter • Gas: • The particles of a gas have a lot of space between them. They move fast and in no order. The volume of gas also increases as temperature increases. Gasses have no set volume and no set shape.

6. 4.01 – States of Matter • Plasma: • Contains particles that are positively and negatively charged. Atoms begin to lose electrons, creating charged particles that move freely. Plasma, like a gas, has no set volume or shape and can be found in stars, Plasma TVs, and neon signs.

7. 4.01 – States of Matter • Kinetic Theory of Matter • All matter is composed of tiny particles • These particles are in constant, random motion • The particles collide with each other and with the walls of any container in which they are held • The amount of energy that the particles lose from these collisions is negligible.

8. 4.01 – States of Matter • Kinetic Molecular Theory • Explains why matter changes states • Matter changes states due to gain or loss of energy • Explains why a particular state behaves as it does • Objects expand when heated • Explains why the temperature of a substance increases as you heat it • Temperature of an object is a measure of the average kinetic theory of a substance

9. 4.01 – States of Matter • Heating Curves • A graph of temperature vs. time for heating a substance

10. 4.02 – Classifying Matter • Pure Substances • Elements – • Element and atom are not the same • Periodic Table of Elements • Compounds – • Made from combined elements

12. 4.02 – Classifying Matter

13. 4.02 – Classifying Matter Bromine (Br2) and Oxygen (O2) exist naturally as molecules. Each molecule consists of two atoms bonded together. Even though it is made of molecules it is still an element because it contains only one type of atom.

14. 4.02 – Classifying Matter Element or Compound?? H20 Copper (Cu) C6H12O6 NaCl Oxygen (O2) Sodium (Na)

15. 4.02 – Classifying Matter Mixtures- Heterogeneous Mixtures – Homogeneous Mixtures- Solutions-

16. 4.02 – Classifying Matter Classify the following as an element, compound, or mixture. If mixture, make sure to label homogenous or heterogeneous. 1) soda 4) Nitrogen (N) 2) water (H20) 5) NH4 3) gravel 6) a taco

17. 4.03 – Properties of Matter • Physical properties • Physical properties are characteristics of a substance that can be measured without changing the identity of the substance. • Appearance (for example, color or shape) • Odor • Melting point and boiling point • Density • Hardness • Ductility and Malleability (ability to change shape) • Solubility • Electrical and thermal conductivity • Magnetism

18. 4.03 – Properties of Matter • Chemical properties • characteristics of a substance that describe the ways it can react to form new materials. • Chemical properties cannot be measured or studied without changing the composition of the substance. • Flammability and other tendencies to react with oxygen • Reaction with acids and bases • Reaction with water • Decomposition caused by light or heat • Tendency to corrode

19. 4.03 – Properties of Matter • Physical Changes • Physical changes are changes that do not result in the formation of a new substance. • The substance is still the same because chemical bonds have not been broken or formed, and so the atoms of the molecules are still connected in the same way.

20. 4.03 – Properties of Matter • Chemical Changes • referred to as chemical reactions. • always produce new substances with properties that are typically very different from those of the reactants. • some clues that can indicate a chemical change has occurred. • visible flames • color change • bubbling or fizzing • smoke • heat or light given off • formation of a substance in a different state (for example, a solid from two liquids) • Of these observations, seeing flames is the only sign that always indicates a chemical change. All of the others can sometimes be the result of a physical change.

22. 4.03 – Properties of Matter • Law of Conservation of Mass • Mass cannot be created or destroyed • To put the law another way, the amount of matter before the change equals the amount of matter after the change.

23. 4.03 – Properties of Matter • The law of conservation of mass is also true for physical changes. An ice cube has the same mass as the water produced when it melts. • In other cases, conservation of mass is less obvious. If we think about it, we can usually explain cases in which the law of conservation of mass seems to have been violated.

24. 4.04 – Atomic Theory Democritus (400 B.C.) • Proposed that matter was composed of tiny indivisible particles • Not based on experimental data • Greek: atomos

25. 4.04 – Atomic Theory Alchemy (next 2000 years) • Mixture of science and mysticism. • Lab procedures were developed, but alchemists did not perform controlled experiments like true scientists.

26. 4.04 – Atomic Theory John Dalton (1807) • British Schoolteacher • based his theory on others’ experimental data • Billiard Ball Model • atom is a uniform, solid sphere

27. 4.04 – Atomic Theory John Dalton Dalton’s Four Postulates 1. Elements are composed of small indivisible particles called atoms. 2. Atoms of the same element are identical. Atoms of different elements are different. 3. Atoms of different elements combine together in simple proportions to create a compound. 4. In a chemical reaction, atoms are rearranged, but not changed.

28. 4.04 – Atomic Theory J. J. Thomson (1903) • Cathode Ray Tube Experiments • beam of negative particles • Discovered Electrons • negative particles within the atom • Plum-pudding Model

29. 4.04 – Atomic Theory J. J. Thomson (1903) Plum-pudding Model • positive sphere (pudding) with negative electrons (plums) dispersed throughout

30. 4.04 – Atomic Theory Ernest Rutherford (1911) • Gold Foil Experiment • Discovered the nucleus • dense, positive charge in the center of the atom • Nuclear Model

31. 4.04 – Atomic Theory Ernest Rutherford (1911) • Nuclear Model • dense, positive nucleus surrounded by negative electrons

32. 4.04 – Atomic Theory Niels Bohr (1913) • Bright-Line Spectrum • tried to explain presence of specific colors in hydrogen’s spectrum • Energy Levels • electrons can only exist in specific energy states • Planetary Model

33. 4.04 – Atomic Theory Niels Bohr (1913) • Planetary Model • electrons move in circular orbits within specific energy levels Bright-line spectrum

34. 4.04 – Atomic Theory Erwin Schrödinger (1926) • Quantum mechanics • electrons can only exist in specified energy states • Electron cloud model • orbital: region around the nucleus where e- are likely to be found

35. 4.04 – Atomic Theory Erwin Schrödinger (1926) Electron Cloud Model (orbital) • dots represent probability of finding an e-not actual electrons

36. 4.04 – Atomic Theory James Chadwick (1932) • Discovered neutrons • neutral particles in the nucleus of an atom • Joliot-Curie Experiments • based his theory on their experimental evidence

37. 4.04 – Atomic Theory James Chadwick (1932) Neutron Model • revision of Rutherford’s Nuclear Model

38. 4.05 – Properties of Atoms An atom refresher • 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.

39. 4.05 – Properties of Atoms 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

40. 4.05 – Properties of Atoms What are elements? • Elements are the alphabet to the language of molecules. • To make molecules, you must have elements. • Elements are made of atoms. While the atoms may have different weights and organization, they are all built in the same way.

41. 4.05 – Properties of Atoms

42. 4.05 – Properties of Atoms More about Elements.. • Elements are the building blocks of all matter. • The periodic table is a list of all of the elements that can build matter. It’s a little like the alphabet of chemistry. • The periodic table tells us several things…

43. 4.05 – Properties of Atoms 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 Atomic Mass/Weight: Number of protons + neutrons. 16

44. 4.05 – Properties of Atoms Atom Models • There are two models of the atoms we will be using in class. • Bohr Model • Lewis Dot Structure

45. 4.05 – Properties of Atoms Bohr Model • The Bohr Model shows all of the particles in the atom. • In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N. • In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. - + + -

46. 4.05 – Properties of Atoms Electrons have special rules…. • You can’t just shove all of the electrons into the first orbit of an electron. • Electrons live in something called shells or energy levels. • Only so many can be in any certain shell.

47. 4.05 – Properties of Atoms Nucleus 1st shell 2nd shell 3rd shell Adapted from http://www.sciencespot.net/Media/atomsfam.pdf

48. 4.05 – Properties of Atoms Electrons have special rules…. • You can’t just shove all of the electrons into the first orbit of an electron. • Electrons live in something called shells or energy levels. • Only so many can be in any certain shell. • The electrons in the outer most shell of any element are called valance electrons.

49. So let’s try it…. 3 Li Lithium 7

50. So let’s try it…. Protons = 3 3 Li Lithium 7 - + + + - - Electrons = 3 2 in the 1st shell, 1 in the 2nd shell Neutrons = 4 (7-3=4)