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INTRODUCTION: MATTER AND MEASUREMENT Chapter 1

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Classifications of Matter Solid rigid, definite volume and shape. Liquid relatively incompressible fluid, definite volume, takes shape of container. Gas easily compressible fluid, no fixed volume or shape.

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The three forms of matter - solid, liquid and gas - are referred to as the states of matter.

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Pure Substances and Mixtures puresubstance A pure substance is a kind of matter that cannot be separated into other kinds of matter by any physical process. A mixture is a material that can be separated by physical means into two or more substances. A mixture is a material that can be separated by physical means into two or more substances.

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Get two types of mixtures: –A homogeneous mixture is a mixture that is uniform in its properties throughout given samples. –A heterogeneous mixture is a mixture that consists of physicallly distinct parts, each with different properties. Note : A phase is one of several homogeneous materials present in the portion of matter under study.

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Separation of Mixtures Examples to separate heterogeneous mixtures: - Magnetic - Filtration Examples to separate homogeneous mixtures: - Distillation - Chromatography

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Basic Distillation Setup

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Separation of Mixtures by Paper Chromatography

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Separation of Mixtures by Column Chromatography

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Elements and Compounds Laviosier defined an element as a substance that cannot be decomposed by any chemical reaction into simpler substances.

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compound. A compound is a substance composed of two or more elements chemically combined.

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A physical change is a change in the form of matter but not in its chemical identity. Example: A physical change is a change in the form of matter but not in its chemical identity. Example: - Dissolution of salt. - Distillation chemical change A chemical change or chemical reaction is a change in which one or more kinds of matter are transformed into a new kind of matter or several new kinds of matter. Example: - The rusting of iron. Physical and Chemical Changes

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Intensive vs Extensive Properties Extensive property: is dependent on the amount of substance in a system. Extensive property: is dependent on the amount of substance in a system. eg. mass, volume etc. Intensive property: is NOT dependent on the amount of substance in a system. Intensive property: is NOT dependent on the amount of substance in a system. eg. density, temperature, pressure etc.

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In flow-diagram form:

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Physical Measurements Chemists characterise and identify substances by their particular properties. To determine many of these properties requires physical measurements. In a modern chemical laboratory, measurements often are complex, but many experiments begin with simple measurements of mass, volume, time, and so forth.

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Units of Measurement Any measurement consists of three interlinked concepts: a measured number a unit a measure of the uncertainty If you repeat a particular measurement, you usually do not obtain precisely the same result, because each measurement is subject to experimental error.

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The Length of a Steel Rod

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SI Base units and SI Prefixes The International System or SI was adopted in 1960 and is a particular choice of metric units. The International System or SI was adopted in 1960 and is a particular choice of metric units. There are seven base units from which all other units can be derived. There are seven base units from which all other units can be derived. In SI a larger or a smaller unit for a physical quantity is indicated by a SI prefix. In SI a larger or a smaller unit for a physical quantity is indicated by a SI prefix.

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SI Base Units

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SI Prefixes

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Length, Mass and Time Self study

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Temperature

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Converting from one temperature scale to another

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Example: In winter the average low temperature of interior Alaska is –30°F. What is the temperature in degree Celsius? And in Kelvin?

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Derived SI units

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Area Once base units have been defined for a system of measurement, then other units can be derive. Once base units have been defined for a system of measurement, then other units can be derive. SI unit of area = (SI unit of length) x (SI unit of length)

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Volume Volume is defined as length cubed and has the SI unit of cubic meter (m 3 ). 1 L = 1 dm 3 and 1 mL = 1 cm 3

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Density The density of an object is its mass per unit volume. d = m v Suppose an object has a mass of 15.0 g and a volume of 10.0 cm 3

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Which is more dense?

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Calculating the Density of a Substance Alternate Example Oil of wintergreen is a colourless liquid used as a flavouring. A 28.1 g sample of oil of wintergreen has a volume of 23.7 ml. What is the density of wintergreen?

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Using Density to relate Mass and Volume A sample of gasoline has a density of 0.718 g/mL. What is the volume of 454 g of gasoline? d = m v Alternate Example

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The advantages of this are: The advantages of this are: –The correct units for the answer follow automatically. –Errors are more easily identified. eg. when the final units are nonsense Dimensional analysis the method of calculation in which one carries along the units for quantities Dimensional Analysis

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Example Calculate the volume, V, of a cube, given s, the length of one of its sides. V = s 3, if s = 5.00 cm NO guesswork in the final units

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Converting Between Units. What is 5 liters in terms of cm 3 ? We know: 1 mL = 1 cm 3

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Converting Units: Metric Unit to Metric Unit Alternate Example A sample of sodium metal is burned in chlorine gas, producing 573 mg of sodium chloride. How many grams is this? How many kilograms? 573 mg

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An experiment calls for 54.3 mL of ethanol. What is the volume in cubic meters? Converting Units: Metric Volume to Metric Volume

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Number of Significant Figures Number of significant figures number of digits reported for the value of a measured or calculated quantity, indicating the precision of the value. Scientific notation is the representation of a number in the form: A x 10 n A x 10 n eg. 3x10 -8 m

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Sig. Fig. Rules! All digits are significant except zeros at the beginning of the number and possibly terminal zeros. eg. 0.0023159000 All digits are significant except zeros at the beginning of the number and possibly terminal zeros. eg. 0.0023159000 Terminal zeros ending at the right of the decimal point are significant. eg. 0.2540 Terminal zeros ending at the right of the decimal point are significant. eg. 0.2540 Terminal zeros in a number without an explicit decimal point or may not be significant. Terminal zeros in a number without an explicit decimal point or may not be significant.

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Determine the number of sig. fig.’s in the following: 27.53 cm 39.240 cm 102.0 g 0.00021 kg 0.06080 L 0.0002 L

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Sig. Fig.’s in Calculations Multiplication and division: Multiplication and division: –result must have as many sig. fig.’s as there are in the measurement with the least number of sig. fig.’s. Addition and Subtraction: Addition and Subtraction: –result must have same number of decimal places as there are in the measurement with the least number of decimal places.

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Suppose you have a substance believed to be cis- platin and, in an effort to establish its identity, you measure its solubility. You find that 0.0634 g of the substance dissolves in 25.31 g of water. The amount dissolving in 100.0 g is : 100.0 g of water x 0.0634 g cis-platin 25.31 g of water Example:

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In performing the calculation 100.0 X 0.0634 ÷ 25.31, the calculator display shows 0.2504938. We would report the answer as because the factor has the least number of significant figures

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Exact Numbers & Rounding An exact number is a number that arises when you count items or sometimes when you define a unit. An exact number is a number that arises when you count items or sometimes when you define a unit. The conventions of significant figures do NOT apply to exact number. The conventions of significant figures do NOT apply to exact number. eg. suppose you want the total mass of 9 coins when each coin has a mass of 3.0 grams. The calculation is: Rounding is the procedure of dropping nonsignificant digits in a calculation and adjusting the last digit reported. Rounding is the procedure of dropping nonsignificant digits in a calculation and adjusting the last digit reported.

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Example Perform the following calculations, rounding the answers to the correct number of sig. fig.’s. 5.8914 1.289 x 7.28

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One more Example 92.34 x (0.456 - 0.421) =

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