Introduction. Matter and Measurement

Transcription

1 Introduction Matter and Measurement

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6 Gases Forms of Matter No definite volume or shape. Volume depends on temperature and pressure. Very compressible. Less dense than the liquid form Experience flow Very large spaces between the particles. High energy form of matter.

7 Forms of Matter Plasma is a high temperature physical state of matter in which atoms lose their electrons and become ionized. The sun is a good example of a plasma as is a fluorescent bulb. Bose-Einstein Condensate(BEC) Newest form of matter Occurs at very low temperatures Easiest to make with Group IA elements Called fuzzy matter

8 State Changes When one form of matter changes into another form of matter, a state,or phase, change occurs. Solid to liquid Liquid to gas Solid to gas Liquid to solid Gas to liquid Gas to solid

9 Properties of Matter There are chemical and physical properties of matter. Chemical properties are those which cause a substance to change its features into something else. A new substance is formed when a chemical property is observed. A chemical change occurs in which one or more substances are converted into something new. There are several evidences that a chemical change has occurred. They may include large energy change, evolution of gas, change in color, formation of a precipitate, odor change and difficulty of reversal. In a chemical reaction the starting substances are called reactants while the ending substances are called products.

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11 Classification of Matter Pure Substances Uniform composition Definite composition Homogeneous Identical properties Cannot be separated and maintain its identity Mixtures Physical combination(blend) of two or more substances Separable by physical means Variable composition Components retain their properties

12 Homogeneous Also called a solution Physical combinations Kinds of Mixtures Uniform throughout a given sample Components uniformly distributed Composition may vary from sample to sample Separable by physical means Heterogeneous Physical combinations Nonuniform within a sample Components are distinguishable Separable by physical means

13 Elements Kinds of Substances All samples are identical. Approximately 120 Approximately 90 are naturally occurring May be metal, metalloid, or nonmetal Exist as solids, liquids, or gases Compounds All samples are identical. Chemical combinations Cannot be physically separated and keep identity. New properties that are different from component properties Definite composition Homogeneous Can be broken into elements by a chemical change.

14 Elements Elements are summarized on the Periodic Table. They are represented by symbols of 1, 2, or 3 letters. The vertical columns are groups or families whose members have similar properties. The horizontal rows or periods have members whose properties change regularly as one moves from left to right. All elements may be classified as representative (Gps 1-2 and 13-18) or transition (Gps 3-12). The lanthanides and actinides are transition elements.

15 Metallic Elements Conduct heat and electricity. Are malleable. Are ductile. Have luster. Are solids, except for mercury which is a liquid. Have high tensile strength. Are found on the left side of the Periodic Table.

16 Nonmetallic Elements Do not conduct well. Are brittle. Are dull in color. May be gases or solids, except bromine which is a liquid. Are found on the right side of the Periodic Table.

17 Elemental Abundance The most abundant element in the Earth s crust is oxygen. (Si, Al, Fe, Ca) The most abundant metal in the Earth s crust is aluminum. The most abundant element in our atmosphere is nitrogen. (O 2, Ar) The most abundant element in our universe is hydrogen. The most abundant element in the human body is oxygen.(c, H 2 )

18 The Importance of Measurement There are two kinds of measurement. Both provide important information. One kind of measurement is quantitative. It gives results in numerical form. It is objective because it requires an instrument. The other kind of measurement is qualititative. It gives results in a descriptive form. It is subjective because it depends on the bias of the observer.

19 Lavoisier: The Founder of Modern Chemistry Lived in the mid 1700 s His work overthrew the phlogiston theory of burning. Mercury experiments were carefully measured to help disprove that theory.

20 Accuracy vs. Precision Closeness to a true value Dependent upon the quality of the measuring device. Only one measurement. Closeness of a set of values Not related to accurate value Dependent upon the skill of the person making the measurement.

21 Significant Figures in Measurements These are digits which may be read from an instrument plus one digit which is estimated. Check each instrument before using it to determine how many figures may be read from it. Then estimate one more figure. The use of these lends reliability and consistency to measurements.

22 What digits are significant? All nonzero digits are significant. All captive zeroes are significant. All beginning zeroes are NOT significant. All zeroes to the right of a nonzero digit and a decimal point are significant. Ending zeroes in numbers without a decimal may or may not be significant. The final significant zero may be noted with a bar over it.

23 What about calculations? When adding or subtracting, the answer may have only as many DECIMAL PLACES as the least precise number in the operation. When multiplying or dividing, the answer may have only as many SIGNIFICANT DIGITS as the least precise number in the operation.

24 Comparing and Contrasting measurement systems The English system has no standard of comparison. The English system has no easy conversion from a small unit to a larger unit measuring the same quantity. The metric and SI systems have standards. The metric system is based on Pt-Ir objects whereas the SI is based on physical phenomena. The metric/si conversions are based on powers of 10.

25 Comparing and Contrasting measurement systems The English system is not widely used. The English system has no base unit for a quantity. The English system uses commas. The metric/si systems are widely used and are the foundation of scientific measurement. The metric/si systems use base units. The SI system uses spaces.

26 Comparing and Contrasting the measurement systems The English system uses o F for temperature. The English system uses fractions. The metric system uses o C for temperature whereas the SI system uses K for temperature. The metric/si system uses decimals.

27 The SI System There are seven fundamental units: meter, kilogram, second, Ampere, candela, mole, and kelvin. All other units are derived from these. The meter is based on the distance light travels in a vacuum in 1/3x10 8 ths of a second. The second is based on the number of disintegrations from a cesium-133 atom.

28 Metric Prefixes yotta 1.00E+24 yocto 1.00E-24 zetta 1.00E+21 zepto 1.00E-21 exa 1.00E+18 atto 1.00E-18 peta 1.00E+15 femto 1.00E-15 tera 1.00E+12 pico 1.00E-12 giga 1.00E+09 nano 1.00E-09 mega 1.00E+06 micro 1.00E-06 kilo 1.00E+03 milli 1.00E-03 hecto 1.00E+02 centi 1.00E-02 deka 1.00E+01 deci 1.00E-01

29 Instruments and Methods Length is measured with a meter stick or metric ruler. Mass is measured with a triple beam balance. Volume is measured in 3 different ways depending upon the substance to be measured.

30 Measuring Volume Liquids are measured with a graduated cylinder, never with a beaker or a flask. Regular solids are measured to find dimensions and then volume formulas are used. Irregular solids are measured by displacement.

31 Random Details One liter is equal to 1 decimeter cubed. One gram of water is equal to 1 centimeter cubed at 4 o C. Approximately 20 drops of water is 1 ml. A kilogram of water is the mass of 1 liter. Density is mass divided by volume. Specific gravity is a comparison of the density of a substance to the density of a reference material. It has no units.

32 Random Details Temperature is the degree of hotness or coldness of an object. Heat transfer occurs when two objects differ in temperature. Heat energy flows from a warm object to a cooler one. Temperature is measured in degrees and heat is measured in calories or joules.

33 Specific Heat Capacity Specific heat capacity is defined as the quantity of heat required to change the temperature of an object by 1 degree Celsius. The formula for calculating heat required is Q = m C (t 2 - t 1 ), where Q is heat, m is mass, C is specific heat, and t is temperature.