Chemistry

1. Chemistry Chapters 1 and 16

2. 2 types of chemical rxns: • exothermic- energy is released in the rxn • exo- out • takes place without help

3. endothermic- energy is absorbed in rxn • endo- in • have to have energy in order to occur

4. Chemistry • the study of the composition of substances and the changes they undergo • energy is involved in accomplishing these changes

5. Which of these items is a chemical?

6. all of those substances are chemicals • chemical- substance that has a definite composition • water- H2O • sucrose- C12H22O11 • hematite- Fe2O3

7. Branches of Chemistry • 2 major: 1. inorganic- concerns substances that are usually without carbon 2. organic- study of substances containing carbon subst from living things

8. Types of research: 1. basic research- carried out for the sake of increasing knowledge chance discoveries can occur and have changed our lives!

9. 2. applied research- carried out to solve problems depletion of ozone layers by CFCs led scientists to develop new refrigerants

10. technological development- production and use of products that improve our quality of life

11. Matter • Which of the following could be called matter?

12. Matter • anything that has a volume and a mass • mass- measure of the amount of matter use a balance to measure • volume- amount of space a 3D object takes up

13. many forms of matter • fundamental building blocks of matter: • atoms and molecules What’s the difference?

15. atom- smallest unit of an element that maintains the chemical identity of that element • molecule- smallest unit of a diatomic element or a compound that retains all the properties of that subst • elements generally make up molecules

17. these particles make up elements and compounds • What’s the difference? • elements- pure subst that CANNOT be broken down into simpler, stable subst; made of 1 kind of atom

18. compound- subst that can be broken down into simpler, stable subst • usu made from 2 or more kinds of atoms

20. Properties of Matter • used to distinguish between subst and to separate them • help to reveal unknown subst • ALL matter has many properties by which it can be grouped • properties are either intensive or extensive

21. Intensive Properties • do NOT depend on the amount of matter examined • same for a 0.5g sample as 500kg sample • ex: melting point, boiling point, density, conduction of electricity

22. Extensive Properties • DO depend on the amount of matter present • there will be a difference in a 0.5g sample and a 500kg sample • ex: volume, mass, amount of energy in sample

23. properties can also be grouped into 2 general categories: 1. physical properties- characteristic that can be observed or measured without changing the identity of the substance ex: color, density, hardness, melting point, boiling point

24. 2. Chemical properties- prop that matter exhibits as it undergoes changes that transform it into different subst easiest to see as matter reacts to form new subst ex: reactivity with oxygen, flammability

25. Matter frequently goes thru changes2 types of changes: 1. physical chg- a change in a subst that does NOT involve a chg in the identity of the subst ex: melting, boiling, grinding, tearing, cutting

26. 2. chemical changes- aka chemical reactions- a chg in which the subst is converted into different subst ex: rusting, tarnishing, burning

27. some phy chg are part of an important class of chgs called change of state • phy chg of a subst from one state to another • 4 main states of matter: • STATES OF MATTER FOLDABLE

29. 2. chemical changes- aka chemical reactions- a chg in which the subst is converted into different subst ex: rusting, tarnishing, burning

30. Chemical Rxn magnesium plus oxygen yields magnesium oxide Mg + O2 MgO parts of chemrxn: 1. reactants- the substances that react in the chemrxn arrow points AWAY FROM reactants

31. 2. products- the subst that are formed by the chem chg arrow ALWAYS POINTS TO products 3. arrow stands for yields ex: p. 10 fig.7

32. Energy • ALL changes (physical OR chemical) will involve energy • can be different forms, like heat and light • boundaries between phy and chemchgs are not always very clear • in any chg, the total amount of energy involved DOES NOT change • the Law of conservation of energy

33. Classification of Matter • tremendous variety of forms of matter • can be categorized into 2 groups: 1. pure substance- composition is same thruout • can be elements or compounds 2. mixture- contains more than 1 subst; can vary in composition and properties

34. Pure Substances • every sample has a fixed composition • H2O (by mass, 88.8% O and 11.2% H) • every sample has exactly the same characteristic properties • properties can be used to identify the subst • either elements or compounds

35. Mixtures • blend of 2 or more kinds of matter, each retaining its own identity and properties • usu physically combined and can be separated • properties of mixture are a combination of the properties of subst that make it up • 2 types of mixtures:

36. 1. homogeneous mixtures • homo- same • looks the same thru-out • uniform in composition • aka- solutions • may be solids, liquids, gases

37. 2 parts to a soln: • solvent- part that does the dissolving usu water aka- the universal solvent 2. solute- part that is dissolved

38. 2. heterogeneous mixture • hetero- different • may look different • composed of more than one phase • separated by boundaries called interfaces

39. Elements • substances composed of only one kind of atom • ALWAYS have the same composition • ex: gold, mercury, hydrogen

40. Compounds • substances composed of more than one kind of atom always arranged in definite ratios • ex: copper II sulfate, CuSO4 • sucrose, C12H22O11

41. In chemical changes: • one or more subst are used up • 1 or more new subst are formed • energy is absorbed or released

42. Evidence of chemical changes: • color change • formation of precipitate (ppt)

43. gas bubbling • energy changes- heat, light

44. 2 types of chemical rxns: • exothermic- energy is released in the rxn • exo- out • tend to take place without help

45. endothermic rxn- energy is absorbed in the rxn • endo- inside • have to have input of energy to occur

46. Physical Changes • occur with NO changes in the composition • can be: • chgs of state • cutting/breaking • dissolving • distillation • fractional crystallization

47. Energy • phy and chemchgs ( ) always accompanied by energy changes • energy changes occur betw sys and surroundings • energy transfer as a result of temp difference is HEAT • can measure energy chg using units called Joules (J)

48. older unit used is calorie • 1 cal = 4.184 J • food calorie is a larger unit • 1 CAL = 1 000 cal • convert betw units

50. Thermochemistry • study of the transfer of heat energy that accompany chemrxns and physical chg • temp- is a measure of the average kinetic energy of the particles in a sample of matter • greater KE, higher temp, hotter it feels