Matter and Energy. 1.1 Matter and Its Classification. : same composition throughout, & from sample to sample. Pure Substances

Transcription

1 Matter and Energy Matter and Its Classification : anything that occupies space & has mass Forms of energy are NOT matter. Heat & light do not occupy space & have no mass. We classify matter to better understand Pure substances Mixtures Matter anything that occupies space and has mass Pure Substances have uniform chemical composition throughout and from sample to sample Mixtures are composed of two or more pure substances and may or may not have Copy right Mc Graw-Hill Educ ation. Permis sion required for reproduction uniform 1-2 dis play composition. 1.1 Matter and Its Classification : same composition throughout, & from sample to sample. can be further classified as either elements or compounds. Elements Pure Substances Compounds : a substance that cannot be broken down into simpler substances even by chemical reaction Are separated further into metals, nonmetals & metalloids : a substance composed of 2 or more elements combined in definite proportions 1-3 1

2 1.1 Matter and Its Classification Pure Substances Elements Compounds Metals Nonmetals 1-4 : Classification of Matter Identify the metals. Explain the characteristics you considered in making your decision. Figure 1.4 Phosphorus Copper Bromine Nickel Lead Gold Carbon Aluminum Sulfur 1-5 Tin 1.1 Matter and Its Classification : an element having the following properties: Lustrious Malleable and ductile Conductor of heat and electricity Usually a solid at room temperature (except mercury) : an element having the following properties: Dull Brittle Insulator of heat and electricity May be a solid, liquid or gas at room temperature : an element having properties of both metals and nonmetals 1-6 2

3 1.1 Matter and Its Classification : the smallest unit of an element that retains the chemical properties of that element. Matter is composed of atoms Matter and Its Classification a pure substance composed of 2 or more elements (atoms) combined chemically in definite proportions. A compound has properties that are different from those of its component elements. A compound can be separated into their elements by chemica means Matter and Its Classification Water, H 2 O, is a compound that can be broken down by electrolysis (a chemical process) to its elements H 2 and O 2. H 2 O 2 H 2 O 1-9 3

4 1.1 Matter and Its Classification Pure sand is the compound silicon dioxide, SiO 2. What does the formula tell us about the combination of elements in this compound? 1-10 Activity: Elements and Compounds Identify each of the following as an element or compound. 1. He 2. H 2 O 3. sodium chloride 4. copper Matter and Its Classification Matter anything that occupies space and has mass Pure Substances have uniform (the same) chemical composition throughout and from sample to sample Mixtures are composed of two or more pure substances, either elements or compounds. Elements Compounds Homogeneous Heterogeneous Metals Metalloids Nonmetals

5 1.1 Matter and Its Classification : two or more elements or compounds. Mixtures can be separated by physical processes. Example: salt & water Salt water can be separated into salt and water by the process of evaporation, which is a physical process Matter and Its Classification Mixtures can be further classified as homogeneous and heterogeneous. : the same composition throughout. : do not have uniform composition throughout. : Classify each of the following mixtures as homogeneous or heterogeneous: 1. Salt water 2. Lake water 3. Tap water 4. Air 5. Brass (an alloy of Cu and Zn) 6. Potting soil Cake mix 1.1 Matter and Its Classification Figure

6 Representations of Matter Macroscopic we can see with our eyes Molecular level a theoretical magnification to a level that shows atoms Symbolic shorthand using element symbols He 1-16 Representations of Matter : Does this image represent atoms or molecules? Is this an element, compound, or mixture? 1-17 : Classification Classify each of the following as an element, compound or mixture:

7 1.1 Matter and Its Classification Physical & Chemical Changes & Properties of Matter : a characteristic that we can observe. : is a process that changes the properties of a substance. : a characteristic that we can observe without changing the composition of a substance. Color qualitative properties Odor Mass quantitative properties Density : a process in which no new substances are produced. Change in physical state Physical & Chemical Changes & Properties of Matter : A characteristic that can only be observed when a substance is converted into one or more other substances Pennies will tarnish Gasoline is flammable : a process where one or more substances are converted into one or more new substances (chemical reaction) Pennies tarnishing Burning gasoline Evidence of a chemical change: bubbling a permanent color change a sudden change in temperature

8 Is Boiling Water a Chemical or Physical Change? 1-22 : Physical & Chemical Changes Do the following images represent a chemical or physical change 1-23 : Physical & Chemical Changes Do the following images represent a chemical or physical change Classify each of the following as a physical or chemical change: 1. Evaporation of water 2. Burning of natural gas 3. Melting a metal 4. Converting H 2 and O 2 to H 2 O

9 More Physical Properties: Mass : measures the quantity of matter common units are grams (g) Prefixes make it easier to refer to large or small masses Prefixes Mass measurements giga- G Gg = 10 9 g mega- M Mg = 10 6 g nano- n ng = 10 9 g pico- p pg = g 1-25 More Physical Properties: Volume : amount of space a substance occupies Volume of a solid can be calculated by measuring the sides of a cube or rectangular side, then multiplying them Volume = length width height Common units are centimeters cubed (cm 3 ), sometimes called cubic centimeters More Physical Properties: Volume Volumes of liquids are usually measured in units of milliliters (ml). 1 ml = 1 cm 3 exactly How many ml in 1 L?

10 Convert 25.0 ml to L. : Volume Unit Conversions Convert 25.0 ml to quarts (1 L = qt) 1-28 More Physical Properties: Density : the ratio of the mass to its volume D = $%&& '()*$+, $- or,.$/ for (s) & (l), for (g) - Figure More Physical Properties: Density The density of a substance is the ratio of its mass to volume: mass Density = volume : If the mass of the cube is 11.2 grams, what is its density? 2.0 centimeters

11 : Density Compare the density of the Dead Sea water and of the person. Which has the higher density? How can you tell? 1-31 : Density The cube of gold has a greater mass than that of aluminum. Which cube has the greater density? 1-32 : Density Given that these samples of metals have the same mass, which has the greater density? Gold Aluminum

12 : Density Which is more dense, regular soda or diet soda? How can you tell? 1-34 : Density What is less dense, liquid water or ice? How can you tell? 1-35 More Physical Properties: Temperature : a measure of how hot or cold something i relative to some standard is measured with a thermometer Scientific units are degrees Celsius, C & kelvins, K

13 1.3 Energy and Energy Changes : the capacity to do work or to transfer heat Two main forms of energy are: : the energy of motion : energy possessed by an object because of its position Other energies are forms of kinetic and potential energy (chemical, mechanical, electrical, heat, etc.) When chemical or physical changes occur, energy changes also occur. Some processes release energy (exothermic) and some require an energy input (endothermic) Energy and Energy Changes When hydrogen burns with oxygen, energy in the form of heat and light is released. This process is Energy and Energy Changes Electricity is used to decompose water into its elements. This process is

14 Kinetic and Potential Energy Figure : Kinetic Energy Which pair of molecules has more kinetic energy? Figure from p Scientific Inquiry : an approach to asking questions and seeking answers that employs a variety of tools, techniques, and strategies The method generally includes: - observations - hypotheses - laws - theories Observations include: - experimentation - collection of data A hypothesis is a tentative explanation for the properties or behavior of matter that accounts for a set of observations and can be tested. - Often equations : predict outcomes under certain circumstance : explain why observations, hypotheses, or laws apply 1-42 under many Copy right different Mc Graw-Hill Educircumstances. ation. Permis sion required for reproduction or dis play. 14

15 Math Toolbox Scientific Notation A number written in scientific notation is expressed as: C 10 n where: - C is the coefficient, 1 and <10, - n is the exponent, a ± integer C is obtained by moving the decimal point to immediate right of the leftmost nonzero digit in the number n is equal to the number of places moved to obtain C - If the decimal point is 3245 Left moved to the left, then Right n is positive. - If the decimal point is moved to the right, then n is negative. 3,245,000,000 Left Right Left Permis 2.45 sion required reproduction Neither or dis play Copy right Mc Graw-Hill Educ ation. for. : Scientific Notation Convert the values shown in decimal form to scientific notation. 9,000,000, ,800, Math Toolbox Scientific Notation You can simplify calculations with exponents: Multiplication add exponents ( )( ) = ( ) 10 6+( 3) = Division subtract exponents ( )/( ) = (4.0/2.0) 10 ( 2) 3 = Raising the exponent to a power multiply exponents ( ) 2 = (3.0) =

16 : Scientific Notation Multiplication and Division of Exponents 1) ( )( ) = 2) ( ) / ( ) = 3) ( ) 4 = 1-46 Math Toolbox 1.2 Significant Figures : the numbers in a calculation that represent the uncertainty of the measurements used in the calculation. All non-zero digits are significant. 435 g 3 SF s Zeroes: zeroes are 405 g 3 SF s 40.5 g 3 SF s zeroes are 5.00 g 3 SF s 500 g 1 SF zeroes are NEVER significant g 3 SF s g 3 SF s there is a decimal 1-47 : Significant Figures Determine the number of significant figures in each of the following values

17 Math Toolbox 1.2 Significant Figures Your final answer must reflect the number of SF s in the least accurate (most uncertain) measurement. The least accurate measurement is determined differently depending on the mathematical operation you are performing. Count SF s in each value Use the LEAST number of SF s for the final answer cm x cm x 0.12 cm = = cm 3 : Perform the following calculation and express the final answer to the correct number of significant figures: x = 1-49 Math Toolbox 1.2 Significant Figures Determine the uncertainty of each value in the calculation Use the largest uncertainty for the final answer cm 0.12 cm cm 0.01 cm cm 0.1 cm cm 0.1 cm : Perform the following calculations and express the final answer to the correct number of significant figures: = = 1-50 Math Toolbox 1.2 Significant Figures The appropriate rules must be applied at each step of the calculation. =>.@A B=>.@= = = =>.@C : Perform the following calculations and express the final answer to the correct number of significant figures: I=J.K L MA@.K = 2. K.@ I.>J + >.ANI =.@K =

18 : Significant Figures Calculate the following to the correct number of significant figures: x 10 > = 2. J.J T K@ UV I T K@ WX = C.CJ T K@ YZ IJ.CM LJJ.=> 3. = A>.K=CJ 1-52 Math Toolbox 1.3 Dimensional Analysis 1. Decide what the problem is asking for. : 2. Decide what the relationships is between the information given and the desired quantity. 3. Set up the problem logically, using the relationships decided upon in step Check the answer to make sure it makes sense, both in magnitude and units : Dimensional Analysis 1. How many inches are in 2 kilometers? 2. What is the volume in cubic centimeters of a 14 lb block of gold? 3. Dan regularly runs a 5-minute mile. How fast is Dan running in feet per second?