UNIT 1: Properties of Matter & Change Section 1: Properties of Matter Section 2: Significant Figures Section 3: Changes in Matter Section 4: Types of

Transcription

1 UNIT 1: Properties of Matter & Change Section 1: Properties of Matter Section 2: Significant Figures Section 3: Changes in Matter Section 4: Types of Chemical Change Section 5: Balancing Chemical Equations

2 UNIT 1 Synapsis In our first unit we will begin our exploration of matter by reviewing some of the properties of matter and how they can be classified. Since properties of matter are very often measurable, how to express precision in measurements using significant figures will be the focus of the 2 nd part of the unit. From there we will look at the various ways that matter can change. In the last two parts of the unit we will narrow our focus to chemical change and look broadly at a few of the most common categories of chemical change. Finally, we will look at how the law of conservation of matter is observed during chemical changes.

3 Section 1: Properties of Matter This section of the Unit is covered on pages in your textbook

4 Section 1: Properties of Matter / Objectives After this lesson I can distinguish between intrinsic and extrinsic properties of matter give examples of intrinsic and extrinsic properties of matter distinguish between physical and chemical properties give examples of physical and chemical properties of matter. explain how intrinsic properties of matter can be used to identify substances (lab 1) identify substances based on their density (Lab 1)

5 Matter Review Matter is anything that has mass and takes up space. Mass is one way to measure how much matter we have. All matter is made of atoms, and we will look at atoms in depth in our second unit. A Substance is a type of matter with unique properties. Substances can be mixtures or pure substances. We will focus on pure substances for must of this coarse and anytime you see or hear the word substance you can assume it s a pure substance.

6 Properties of Matter The unique properties of a substance can be classified in several ways. Here are a couple of the ways we classify matter: Physical state (a.k.a. phase) Intrinsic properties Extrinsic properties Physical properties Chemical Properties Physical state or the phase of matter you are familiar with (solid, liquid, gas) Extrinsic properties are things about a substance that depends on the amount of substance you have. Intrinsic properties are things about a substance that do NOT depend on the amount of substance you have. They are essentially part of that substance s identity. They are what make it, it! For example water being a liquid at room temperature or clear when it is pure are the same regardless if you have a lot or little amount of water. On a side note, intrinsic is sometimes referred to as intensive, and extrinsic is sometimes referred to as extensive.

7 Examples of Intrinsic & Extrinsic Properties Extrinsic Properties Mass Volume Shape Intrinsic Properties Density Melting and Boiling Point Appearance (color, luster, order, smell) Hardness Reactivity

8 Video Time!!! Chem Academy Video: Intensive and Extensive Properties

9 Physical & Chemical Properties The reactivity of a substance is a noteworthy intrinsic property because the reactivity of a substance can also be referred to as it s chemical properties. Chemical properties deal only with the how, why, and what of a substance reacting. Chemical Properties include things like: Flammability Corrosiveness Toxicity In short, all chemical properties are intrinsic properties, but not all intrinsic properties are chemical properties. Physical properties, on the other hand, are basically everything else. This includes extrinsic properties, physical state, and all the intrinsic properties of a substance that are unrelated to it reacting to form a new substance.

10 Video Time!!! Chem Academy Video: Physical vs Chemical Properties Explained

11 Section 1 Additional Resources & Links The Organic Chemistry Tutor Video: Physical vs. Chemical Properties explained, examples

12 Section 2: Significant Figures This section of the Unit is covered on pages in your textbook

13 Section 2: Significant Figures / Objectives After this lesson I can explain the importance of significant figures. identify the zeros in a measurement that are significant and zeros that are not (all non-zeros are always significant). perform multiplication and division problems using significant figures. calculate density.

14 Significant Figures Significant figures are what scientists, researchers, and engineers use to keep it real. In other words, it is what we use to represent the level of precision in our measurements and calculations. You don t want to represent a higher level of precision than you really have. For example, the density of an object is equal to it s mass divided by it s volume: D = m / V Suppose you put a metal nail on an electronic balance and it gives you a mass g. Then you place it in a graduated cylinder and get a volume of ml. You put those into your calculator and you get: g/ml If you were to publish a paper you have to round off to 4 digits because that s the highest level of precision your electronic balance and graduated cylinder gives you. So you would say the density of your object is g/ml. Saying it has a density implies you have a higher level of precision than you really do. If you were to say in a paper the density of your object is you are arguable making a fraudulent claim.

15 Video Time!!! Tyler Dewitt s Video: Why Use Significant Figures

16 Significant Figures Knowing how to identify the sig figs in a measurement is not always as simple as what your scale reads. Furthermore, the measurement might have been taken by someone else. If this is the case they must record the measurement in a way that other scientist like yourself might understand. See below:

17 Significant Figures Examples Measurement Significant Figures g 3 sig figs 10,000 ml 1 sig figs 10,000. ml 5 sig figs 104,000 m 3 sig figs in. 6 sig figs 4,809 ft 4 sig figs kg 5 sig figs mg 4 sig figs kg 1 sig figs 103,900 m 4 sig figs 123,000 L 3 sig figs 120,000,001 g 9 sig figs

18 Practice Problems: Significant Figures Directions: Determine the number of Significant Figures in the following numbers 1) grams 2) 3,900 L 3) mg 4).0200 g 5) m 6) ml 7) sec 8) 100. meters 9) km 10) 10 kg 11).1005 g 12) ml 13).004 g 14) 900,000,000 lbs.

19 Significant Figures in Multiplication & Division As mentioned on a previous slide, the rules for significant figures when two or more numbers are multiplied or divided is simple: The answer contains no more significant figures than the least number of significant figures used in the operation. We will not worry about significant figures for problems involving addition and subtraction in this class.

20 Significant Figures in Multiplication & Division Examples 3.45 g / ml = =.0767 g/ml (rounds to 3 sig figs) kg / L = = kg/l (rounds to 5 sig figs) g 334 J/g = J = 4010 J (rounds to 3 sig figs) 400 kg / 12 L = kg / L = 30 kg/l (rounds to 1 sig fig) g / ml = = g/ml (rounds to 4 sig figs) 10,003 g 2,210 J/g = 22,106,630 J = 22,100,000 J (rounds to 3 sig figs)

21 Practice Problems: Significant Figures in Multiplication & Division Directions: Solve the following problems and record your answer with the correct number of sig figs 1) grams /.005 ml 2) 23.7 g 3.8 J/g 3) g / 3.74 ml 4) g.25 J/g 5) g / 0.42 ml 6) J/g.010 g 7) 6.47 g 64.5 J/g 8) 4,278 g / L

22 Section 2 Additional Resources & Links Bozeman Science Video on Significant Figures Tyler Dewitt s Video: Why Use Significant Figures Tyler Dewitt s Video: Significant Figures and Zeros Tyler Dewitt s Video: Significant Figures Practice Problems Tyler Dewitt s Video: Significant Figures Practice Problems with multiplication and division. Khan Academy Video on Significant Figures

23 Section 3: Changes in Matter This part of the Unit is covered on pages in your textbook

24 Section 3: Changes in Matter / Objectives After this lesson I can distinguish physical and phase change. label the parts of a chemical equation. define phase, nuclear, and chemical change. identify equations that represent phase, nuclear, or chemical change.

25 Physical, Chemical, & Nuclear Change Physical change is when the form of a substance changes, but the chemical composition does not change. Most us are familiar with phase change which is when a substance changes physical state like melting or condensing. A phase change is a physical change, but physical changes can also include something much more simple like cutting a substance in half or grinding it up into a powder. In chemical change, a substance changes into another substance. In this type of change, atoms get rearranged and bonded to different atoms. The old substances are called the reactants and the new substances are called the products. Finally there is nuclear change. In a nuclear change, the atoms themselves change. That is to say, atoms turn into different atoms.

26 Phase Change Model Image Credit: :

27 Chemical Change Model Image Credit:

28 Nuclear Change Model Image Credit: Wikipedia

29 Chemical Equations One of the most important models in chemistry are chemical equations. Chemical equations provide information about the reactants and the products. Here are a few chemical equations for chemical reactions you might be familiar with: Octane or gasoline reacts with air: 2 C 8 H 18 (l) + 25 O 2 (g) 16 CO 2 (g) + 18 H 2 O(l) A plant uses photosynthesis to turn carbon dioxide and water into oxygen and sugar: 6 CO 2 (g) + 6 H 2 O(l) C 6 H 12 O 6 (s) + 6 O 2 (g) A piece of Iron rusts: 4 Fe(s) + 3 O 2 (g) 2 Fe 2 O 3 (s) Note that the same elements are in the products and reactants, they are just combined in different ways. On the next slide, all of the parts of a chemical equation are identified and labeled.

30 Parts of a Chemical Equation

31 Nuclear Changes are Also Modeled Using a Chemical Equation Even though they are called chemical equations they are useful in modeling nuclear changes as well. As mentioned on the previous slide, in a nuclear change, the atoms themselves change. Here are some examples of nuclear changes you might be familiar with. A Uranium atom splits apart like when an atomic bond detonates: 1 n U 92 Kr Ba n Hydrogen atoms are fused into helium atoms inside the sun: 2 H + 3 H 4 He + 1 n Radon atoms in air radioactively decay: 222 Rn 4 He Po Note that in nuclear change equations, the atoms in the products and reactants are different.

32 Phase Changes can be modeled with chemical equations too Phase changes can also be modeled using chemical equations. These equations are incredibly simple: Some examples you are hopefully familiar with: Ice Melting H 2 O(s) H 2 O(l) Condensation: H 2 O(g) H 2 O(l) Note that the product and reactant are the same substance, it s just in a different physical state.

33 Practice Problems: Identifying Change Equations Directions: Label each equation as representing a chemical, nuclear, or phase change 1) C 5 H 12 (l) + 8 O 2 (g) 5 CO 2 (g) + 6 H 2 O(g) 2) H 2 O(l) H 2 O(s) 3) 2 Ca(s) + O 2 (g) 2 CaO(s) 4) NiC 10 H 10 (s) NiC 10 H 10 (g) 5) 256 Fm 140 Xe Pd n 6) H 2 CO 3 (aq) H 2 O(l) + CO 2 (g) 7) 60 Ti 60 V + β 8) 2 N 2 O 5 4 NO 2 + O 2 9) Pb(NO 3 ) 2 (aq) + 2 KI(l) PbI 2 (s) + 2 KNO 3 (aq) 10) 3 H + 3 H 4 He + 1 n 11) C 2 H 6 O(g) C 2 H 6 O(l)

34 Section 3 Additional Resources & Links Some Random Teacher s Video: Parts of a Chemical Equation

35 Section 4: Types of Chemical Change This part of the Unit is covered on pages in your textbook

36 Section 4: Types of Chemical Change / Objectives After this lesson I can Define combustion reactions, single replacement reactions, double replacement reactions, synthesis reactions, and decomposition reactions. Identify a chemical equation as representing a combustion reaction, single replacement reaction, double replacement reaction synthesis reaction, or decomposition reaction.

37 #1: Synthesis Reactions (a.k.a. combination reactions) In a synthesis reaction, two or more elements or compounds combine to form a larger, more complex compound. Sample Chemical Equations: 3 H 2 + N 2 2 NH 3 2 H 2 + O 2 2 H 2 O Mg + O 2 MgO CaO + H 2 O Ca(OH) 2 Generic Chemical Equation: A + B C How to identify: There should only be 1 product in the equation.

38 #2: Decomposition Reactions In a decomposition reaction, A compound breaks down into two or more elements or compounds. This often occurs through heating but not always. In decomposition equations the arrow actually means breaks down to produce or decomposes to produce. Sample Chemical Equations: 2 H 2 O 2 2 H 2 O + O 2 CuCO 3 (s) CuO(s) + CO 2 (g) C 3 H 5 (NO 3 ) 3 (l) 6 N 2 (g) + 12 CO 2 (g) + 10 H 2 O(g) + O 2 (g) Generic Chemical Equation: A B + C How to identify: There will only be 1 reactant in the equation

39 #3: Single Replacement Reactions In a single replacement reaction two elements replace one another. In most cases, the substances are a pure metal and a compound that is dissolved in water. Sample Chemical Equations: 2 Al(s) + 3 CuCl 2 (aq) 3 Cu(s) + 2 AlCl 3 (aq) Fe(s) + CuSO 4 (aq) Cu(s) + FeSO 4 (aq) Fe(s) + Pb(NO 3 ) 2 (aq) Pb(s) + Fe(NO 3 ) 2 (aq) Generic Chemical Equation: A + BC B + AC How to identify: Look for a pure element and a compound in the reactants. In the products the pure element should have switched places with one of the elements in the compound.

40 #4: Double Replacement Reactions In a double replacement reaction, two metals switch places. This almost always occurs when both reactants are in dissolved in water but not always. Sample Chemical Equations (Solid Precipitation) 3 CaCl 2 (aq) + 2 Na 3 PO 4 (aq) 6 NaCl(aq) + Ca 3 (PO 4 ) 2 (s) 2 NaOH(aq) + CuBr 2 (aq) Cu(OH) 2 (s) + 2 NaBr(aq) Li 2 CO 3 (aq) + Mg(NO 3 ) 2 (aq) MgCO 3 (s) + 2 LiNO 3 (aq) HCl(g) + NaOH(aq) H 2 O + NaCl(aq) Generic Chemical Equation AB + CD CB + AD How to identify?: Look for two compounds in the reactants. The products should contain two compounds as well but two elements should have switched places.

41 #5: Combustion Reactions As you might have already realized, combustion reactions are when carbon compounds burn or explode. With one notable exception, which is the combustion of hydrogen gas, this produces carbon dioxide and water. Combustion reactions produce light and heat and occasionally you will see heat written as a product. Sample Chemical Equations: CH O 2 CO H 2 O 2 C 8 H O 2 16 CO H 2 O 2 C 2 H 6 O + 7 O 2 4 CO H 2 O Generic Chemical Equation: Organic Compound + O 2 CO 2 + H 2 O How to identify: Look for Carbon Dioxide and Water in the products. Oxygen should be a reactant.

42 Other Types of Reactions Not all reactions fit neatly into the five classifications listed previously. Here are some examples of those equations: Cu 2 S + 12 HNO 3 Cu(NO 3 ) 2 + CuSO NO H 2 O 2 K 2 MnF SbF 5 4 KSbF MnF 3 + F 2 It s not in our objectives that your able to place every single chemical reaction into a specific category, just that you are able to clearly identify the five mentioned on the previous slides. There are also reactions that are in a gray area between two different classifications. Hydrogen gas, for example, will explode and produce nothing but water: 2 H 2 + O 2 2 H 2 O This could be classified as combination. Even though carbon dioxide is not a product, it could also be classified as combustion because it produces a flame, has water as a product, and oxygen gas as a reactant.

43 Identifying Types of Chemical Reactions Summary Combustion: Look for Carbon Dioxide and Water in the products. Oxygen should be a reactant. Single Replacement: Look for a pure element and a compound in the reactants. In the products the pure element should have switched places with one of the elements in the compound. Double Replacement: Look for two compounds in the reactants. The products should contain two compounds as well but two elements should have switched places. Decomposition: Look for 1 reactant and 2 or more Products Synthesis/Combination: Look for 1 product

44 Section 4 Additional Resources & Links Tyler Dewitt s Video on Types of Chemical Reactions

45 Section 5: Balancing Chemical Equations This part of the Unit is covered on pages in your textbook

46 Section 5: Balancing Chemical Equations / Objectives After this lesson I can recite the law of conservation of mass and explain what it means. balance a chemical equation.

47 The Law of Conservation of Mass The law of conservation of mass states that in any type of change, matter cannot be created or destroyed. Another way of saying this is that the total amount of matter in the universe is constant. One of the things this means is that chemical equations must be balanced. A balanced chemical equation has the same number of atoms going into and out of the equation. The reactants are the substances to the left of the arrow in a chemical equation, & the products are the substances to the right of the arrow. If an equation is presented in it s unbalanced form, it can be balanced by inserting coefficients in front of the chemical formulas. If a chemical formula does not have a coefficient in front of it, the coefficient is 1. The coefficients technically represent the number of moles (A concept we will learn about in UNIT 4) but thinking of them as just the number of molecules makes things easier. When balancing, you must NEVER alter the chemical formulas. You can only change or add coefficients in front of the chemical formulas.

48 Video Time!!! TedED Video: The Law of Conservation of Mass

49 Examples of a Chemical Equation in it s Unbalanced and Balanced Forms (#1)

50 Examples of a Chemical Equation in it s Unbalanced and Balanced Forms (#2)

51 Examples of a Chemical Equation in it s Unbalanced and Balanced Forms (#3)

52 Examples of a Chemical Equation in it s Unbalanced and Balanced Forms (#4)

53 Examples of a Chemical Equation in it s Unbalanced and Balanced Forms (#5)

54 Balancing Equations Tips 1) Balance elements that appear twice on one side of the equation last. So if Oxygen is in two of the reactants and/or two of the products, save it for last. (This is a lot of equations so as a general rule leave oxygen for last) 2) Only whole numbers are allowed, but if you end up with half a number, you can get yourself out of that situation by doubling ALL the coefficients in the equation. (if you end up with.25 you can get yourself out of that situation by quadrupling all coefficients) 3) Take your time. Balancing is a skill that takes practice but with enough patience an answer will be found.

55 Section 5 Additional Resources & Links WikiHow on balancing chemical equations. Khan Academy Video: Balancing Chemical Equations. Tyler Dewitt s Video: Introduction to Balancing Chemical Equations Tyler Dewitt s Video: Balancing Chemical Equations Practice Problems