Matter and Measurement

1. Matter and Measurement Chapter 1 CHE 101 – Intro to Chemistry Sleevi

2. What is Chemistry? • The study of matter, its properties and the changes it undergoes

3. What is Matter? • Anything that has mass and takes up space • mass • the measure of the amount of matter in an object • volume • the amount of space occupied by matter

4. Why Study Chemistry?

5. How we study chemistry

6. Models • Physical or mathematical representations that help us understand concepts. • Symbols • Ball and stick models • Graphs

7. Models of Matter • States of Matter • Solid • Liquid • Gas

8. States of Matter Solid: • has a definite volume • maintains its shape regardless of its container • has particles that lie close together in three-dimensional array • not compressible

9. Statesof Matter Liquid: • has definite volume • takes the shape of its container • has particles that are close together but can move past one another • not compressible

10. Statesof Matter Gas: • has no definite shape or volume • expands to fill the volume • assumes the shape of any container • has particles that are very far apart and move around randomly • compressible

11. Pure substance • constant composition • fixed set of properties • cannot be physically separated into simpler substances

12. Types of Substances • Element • Compound

13. Type of Substances • Element: • made up of only one kind of atom • monoatomic (e.g. gold, lead, aluminum), • diatomic (e.g., O2, F2, N2, etc.), • triatomic (e.g., O3) • polyatomic (e.g., C as graphite or buckyball C60) • cannot be chemically subdivided into simpler substances

14. Elements C60

15. Type of Substances • Compound: • made up of heteroatomic molecules or individual ions of two or more kinds • CO2, H2O • NaCl, CuSO4 • can be chemically subdivided into simpler substances

16. Compounds CO2 H2O NaCl

17. Particles of Substances Atom: • smallest particle of an element that retains the properties of that element, • fundamental unit of which elements are composed, • cannot be separated by ordinary means.

18. Particles of Substances Atoms

19. Particles of Substances • Molecule: • a bonded collection of two or more atoms of the same element or different elements • a representative particle of a molecular compound • can be separated by chemical means

20. Particles of Substances Molecules

21. Particles of Substances • Ion: • a charged particle in an ionic compound or in solution

22. Particles of Substances • Formula Unit: • a bonded collection of two or more ions that represents the lowest whole number ratio of the ions in the crystal lattice • a representative particle of an ionic compound • can be separated by chemical means

23. Particles of SubstancesCrystal Lattices and Formula Units Formula Unit https://www.askiitians.com/iit-jee-Solid-State/crystal-lattices-and-unit-cells.html

24. Particles of SubstancesCrystal Lattices and Formula Units Formula Unit Formula Unit

25. Particles of SubstancesCrystal Lattices and Formula Units Formula Unit

26. Properties and Changes • Physical property • Quality or condition of a substance that can be observed or measured without changing the substance’s composition

27. Examples of Physical Properties

28. Properties and Changes • Chemical property • Ability of a substance to form different substances

29. Examples of Chemical Properties

30. Practice Lecture problem #1 (see next slide)

31. Physical or Chemical Property? • The boiling point of a certain alcohol is 78 oC • Diamonds are very hard • Sugar ferments to form alcohol • A metal wire conducts an electric current • Iron rusts

32. Properties and Changes • Physical change: • A change in the physical form of a substance but not its chemical composition • Chemical bonds are NOT broken or formed

33. Physical Change

34. Properties and Changes • Chemical change: • Change of a substance into another substance through the reorganization of the atoms by breaking or making of chemical bonds • Properties of the new substance are different

35. Chemical Change

36. Indicators of Chemical Change • Unexpected color change • Formation of a precipitate • Evolution of a gas • Change in energy (heat, light, explosion)

37. Differentiating Physical & Chemical Changes • Physical change • Does not alter composition • May alter appearance • The process of the change can be described in terms of physical properties • Reversible by another physical change

38. Differentiating Physical & Chemical Changes • Physical change • Key words • Bend, break, crush (malleability, brittleness, hardness, etc.) • Dissolve (solubility) • Boil, melt, evaporate, condense (change in state)

39. Differentiating Physical & Chemical Changes • Chemical change • Composition of substance does change • May alter appearance • The process of the change can be described in terms of a chemical reaction • Key words • React, burn, bubble, fizz, give off, precipitate, explode, emit, flame

40. Differentiating Physical & Chemical Changes • Chemical change • Reactants • Starting materials in a reaction • Products • Substances formed in the reaction Physical properties of reactants are DIFFERENT from physical properties of products

41. Practice Lecture problem #2 (see next slide)

42. Physical or Chemical Change? • A shirt is scorched by a hot iron • A silver tea set gets black with tarnish over time • Dry ice sublimes • Oven cleaner converts grease to a soapy material • A damp towel dries

43. How Physical & Chemical Properties are Used • Identification • Reactivity • Separation of mixtures • Safe storage and handling practices

44. Mixture • Combination of two or more substances that are not chemically combined • Components of mixture can be separated by physical means • Composition of a mixture is variable

45. Types of Mixtures • Homogeneous Mixture • Heterogeneous Mixture

46. Types of Mixtures • Homogeneous Mixture: • completely uniform in composition • components not distinguishable • a solution • can be made up in different concentrations, each is uniform

47. Types of Mixtures • Heterogeneous Mixture • not uniform in composition • components typically readily distinguishable • different properties in different parts of the mixture

48. Matter Substance Definite Composition Mixture of Substances Variable Composition Homogeneous Mixture Heterogeneous Mixture Element Compound Composed of 2 or more elements (Water, Sodium Chloride) Simplest form, under ordinary conditions (Iron, Helium, Mercury, Carbon) Uniform throughout; solution (air, tap water, salt solution) Non-uniform; distinct phases (vegetable soup, concrete) Physically Separable: Chemically Separable: Mixtures are separated by a variety of techniques based on the properties of the substances in the mixture. Compounds can be separated into elements by chemical reactions

49. Practice Lecture problem #3 (see next slides)

50. Classification of Matter a. A piece of hard white blackboard chalk is heated strongly in a flame, the mass of the piece of chalk will decrease, and eventually the chalk will crumble into a fine white powder. Does this suggest that chalk is composed of an element or compound? Explain.