Atoms, elements, and reactions

1. Atoms, elements, and reactions

2. What is matter? • Matter is anything that has mass, occupies space, and can be converted into energy • Matter has 2 types of properties: Physical and Chemical

3. Physical properties of matter • Can be observed with the 5 senses • Can be determined without destroying the object • Examples: color, shape, mass, length, odor , density, solubility, taste, melting point, hardness, boiling point, luster, texture

4. Chemical properties of matter • These indicate how a substance reacts with something else. • The original substance is fundamentallychanged while observing a chemical property • Examples: rusting (oxidation), flammability, reactions with other substances such as acids or bases, combustibility

5. Work it… • Physical and Chemical properties practice

6. Elements

7. What are elements? • Elements are PURE substances • They cannot be broken down into more simple substances • They cannot be made by combining other substances

8. Atoms and elements • If you could look at the atoms in a chemical element, you would see that they are all the same type: Identically built Identical parts Identical number of parts

9. Element symbols Elements are organized and presented in a the periodic table Each element on the periodic table has its own box which includes: • Its symbol (a capital letter alone or a capital letter and a lower case number combo) • Element name • Atomic number • Atomic mass

10. Atomic number Element symbol Element name Atomic weight

11. Element/Periodic table activity Safari Videos: “Using the Periodic Table” (25 min.) “Atomic Structure and the Periodic Table” (24 min.) or…If I can access it… Video: “Hunting the Elements” by Nova on PBS http://www.pbs.org/wgbh/nova/physics/hunting-elements.html Worksheets: --Parts of the Periodic Table Activity --Getting to Know the Periodic Table

12. Question • How can only 92 naturally occurring chemical elements form millions of different types of materials? COMPOUNDS!

13. What are compounds? • The substance that is formed when two or more elements chemically combine in a chemical reaction • The new substance formed has different properties from the original elements Example of a compound = H2O (water) Water is made of two gases, hydrogen and oxygen but is a liquid with its own properties

14. What are compounds? • Compounds always have the same ratio of elements…water will ALWAYS have two hydrogen atoms and one oxygen atom

15. Compound When you have chemical reaction, it is like making a cake. Your elements are the ingredients and the compound is the cake. You cannot unmake the cake. It has turned into another substance! Safari Video: “Properties of Compounds” (26 minutes)

16. atomic theory How the theory developed into what we think today

17. Theories in science change • As new information is discovered, scientific theories can change • Our theory about the atom has changed over time • Even though no one has actually seen the atom up close, we are still able to make new discoveries

18. What is an atom? • An atom is the smallest particle that an element can be divided into and still BE that element • Structure of the Atom Worksheet

19. When did the atomic theory start? • The term “atom” actually comes from the Greek word “atomos”, which means not able to be divided • Early theories developed during the ancient Greek times

20. Democritus (460-370 BC) An ancient Greek philosopher He concluded that there was a limit to how far you could divide matter. You would eventually end up with a piece of matter that could not be cut. He proposed that atoms: • Are small, hard particles • They are made of a single material that is formed into different shapes and sizes • They are always moving • They form different materials by joining together

21. John dalton (1776-1844) • A British chemist and school teacher who rethought the ideas of Democritus Dalton’s Ideas: • All substances are made up of atoms • Atoms of the same element are exactly alike and atoms of different atoms are different • Atoms join with other atoms to form different substances

22. J.J. Thomson(1856-1940) • Thomson did experiments with cathode ray tubes and discovered negatively charged particles called electrons • Thomson did not know how the electrons were arranged…he believed they were mixed throughout the atom • He proposed that the atom was a sphere of positively charged material with negatively charged electrons spread throughout like plum pudding (or like a chocolate chip cookie) –which is why his theory is referred to as the Plum Pudding Model

23. Earnest rutherford(1871-1937) He was awarded the Nobel Prize for Chemistry for his discovery of alpha particles, positively charged particles emitted from radioactive elements He studied J.J. Thompson but did not agree with the plum pudding model Rutherford’s Gold Foil Experiment: http://micro.magnet.fsu.edu/electromag/java/rutherford Rutherford’s Atomic Theory: 1. Much of an atom is empty space with most matter of an atom found in a very small, dense part of the atom called the nucleus 2. Like charges repel so the nucleus must be positive and the negatively charged electrons much surround the nucleus at a distance

24. The bohr model of the atom • Bohr proposed that electrons move in paths at certain distances around the nucleus • Electrons can jump from a path on one level to a path on another level http://www.colorado.edu/physics/2000/quantumzone/bohr.html

25. Modern atomic theory Electrons travel in regions called the electronic cloud You cannot predict exactly where an electron will be found in the cloud http://www.fearofphysics.com/Atom/atom3.html

26. Modern atomic theory Energy Levels The energy that an electron has is based on its location around the nucleus Electrons that are closer to the nucleus have less energy than those that are farther away

27. Work it…. • Development of Atomic Theory Fill In.

28. Work it! • Atoms Webquest

29. Chemical Reactions

30. See a reaction in “action” • Elephant toothpaste

31. What is a Reaction? When elements combine or rearrange to form a NEW substance, they are said to REACT. This process is called a chemical reaction.

32. How do we make substance react in a chemical reaction? • Sometimes just mixing!…example: mix hydrogen peroxide and blood then bubbles of carbon dioxide automatically form! Plastic Milk Lab • Heating…example: just mixing sulfur (a powdery non-metal) with the metal iron only results in a mixture but when heated, a new substance is formed--Iron Sulfide! Magnesium?? • Mixing with water…example: when dried citric acid and sodium bicarbonate are dissolved in water, they react to fizz (Alka-Seltzer)

33. Mixtures • Mixtures are formed when substances are simple stirred together and NO new substance is formed. • When we mix sugar and water it seems like it disappears but we can still separate the water and sugar through evaporation…both the water and sugar still exist • When we mix iron filings and sand you may not be able to tell which part is sand and which part is iron filings but we can separate the mixture using a magnet to attract the iron filings. SEPARATING A MIXTURE activity

34. Kinds of mixtures • Homogeneous: a mixture that is uniformly dispersed (the solute is dissolved in the solvent evenly throughout the mixture) (Homo = same) • Heterogeneous: a mixture in which the solute is not evenly distributed throughout the mixture (Hetero = different)

35. How is a chemical reaction different from a mixture?

36. Dissolving To dissolve something means to break up substances into individual atoms or molecules Example: sugar or salt can be dissolved in water with stirring When substance is completely dissolved in another substance the mixture is called a solution The substance that is dissolved is called the solute The substance which the dissolving is INTO is called the solvent

37. Dissolving (Water) Solvent Solution Solute

38. Are Solutions always a solid dissolved in liquid??? NOPE!!! You can make a solution out of any combination of liquid, solid, or gas! Examples: • alcohol in water (liquid in liquid) • iodine vapor in air (liquid in gas) • the air we breath is a solution of various gases (nitrogen, oxygen, etc.)

39. How can we show a chemical reaction in writing? A chemical equation is a statement that uses symbols, chemical formulas, and numbers to stand for a chemical reaction Example: HCl + NaOHNaCl + H2O (reactants) (products) Reactants are the chemicals added together and the products are the chemicals you end up with!

40. Review Chemical Reactions/mixtures • Any change in which substances turn into other substances is called___________________ • A combination of substances in which no reaction takes place __________________ • When sugar is dissolved in water the water is the: A) solute B)solvent C)solution

41. Balancing equations can be Tricky!!!!! The amount of ingredients you start out with as reactants in a chemical equation is the amount you have to end up with. Now the ingredients may be arranged differently but the amount of the substances must stay equal the amount you began with H + O + O H2O The above equation starts out with one hydrogen and two oxygens…the product is water but it still ends up with one hydrogen atoms and two oxygen atoms

42. The Law of the conservation of matter This law states that matter cannot be created or destroyed in any chemical change

43. Balancing equations In order to follow the Law of Conservation we have to make the two sides of a reaction come out even (balanced) you can use numbers called coefficients before the formulas

44. Balancing Example Example: H2+ O2 H2O (this equation is NOT balanced because we started out with two hydrogens and two oxygens but ended up with two hydrogen but only one oxygen) But if we add coefficents… 2H2+ O22H2O NOW we start out with two sets of two hydrogen (2x2=4 hydrogen) and two oxygen. Then we end up with two sets of H2O (2x2=4 hydrogen…2x1=2 oxygen)

45. Review Balancing 2Na + Cl2 2NaCl Look at the above chemical equation to answer the following questions: • What are the reactants? • What are the products? • Is the equation balanced? Why or why not?

46. GROUP ACTIVITY: Try to balance these equations using coefficients... You have just a few minutes! Why didn’t anyone tell me it was so easy to balance equations???!!! [1] Na + Cl2NaCl [2] CH4 + O2 CO2 + H2O [3] Li + HNO3  LiNO3 + H2 [4] Al + O2 Al2O3

47. How did you get on?? Here are the answers: [1] 2 Na + Cl22 NaCl [2] CH4 + 2 O2 CO2 + 2 H2O [3] 2 Li + 2 HNO3 2 LiNO3 + H2 [4] 4 Al + 3 O22 Al2O3

48. Balancing equations practice • Balancing Equations practice worksheet

49. Synthesis and decomposition reactions The word synthesis means “to combine parts” If something decomposes, it breaks down.

50. Synthesis In asynthesis reaction two or more substances combine to form a compound Example: iron (Fe) and sulfur (S) combine to make the compound Iron sulfide (FeS)