General Chemistry I CHEM 110 Instructor: Professor Huyen Nguyen www.mychemistryprof.com/index-NYiT.php Email: hnguye13@NYiT.edu huyen126@aol.com http://www.stjohns.edu/academics/university-course-offerings?field_course_school_tid=501&field_course_level_tid=428&field_course_term_tid=6126&field_course_campuses_tid=17

Chapter 1 (Short) Introduction: Matter, Energy, and Measurement Lecture Presentation Chapter 1 (Short) Introduction: Matter, Energy, and Measurement James F. Kirby Quinnipiac University Hamden, CT

Chemistry Chemistry is the study of matter, its properties, and the changes it undergoes. Matter And Measurement Matter And Measurement

Matter Matter is anything that has mass and takes up space. The three states of matter are solid. liquid. gas.

Classification of Matter

Elements .

Compound A compound is made of atoms from two or more different elements Chemical formula of water: H2O The formula shows that in one water molecule there are two H atoms and one O atom joined by strong forces called chemical bonds.

Physical and Chemical Properties Physical properties can be observed without changing a substance into another substance. Chemical properties can only be observed when a substance is changed into another substance.

Types of Properties Intensive properties are independent of the amount of the substance that is present. Examples include density, boiling point, or color. These are important for identifying a substance. Extensive properties depend upon the amount of the substance present. Examples include mass, volume, or energy.

Types of Changes Physical changes are changes in matter that do not change the composition of a substance. Ex: fusion, solidification, vaporization, sublimation Chemical changes result in new substances. Ex.: decomposition of water by electricity. 2 H2O → 2 H2 + O2

Measurements Measurement of a quantity is made by comparison with a standard (called unit) Result of a measurement = number x unit The International System (SI) is used almost exclusively for scientific work.

SI Units of Measurement

Metric System Prefixes

Mass,Length and Volume Mass is a measure of the amount of material. SI unit for mass is the kilogram (kg). The metric system unit is the gram (g). Length is a measure of distance. The meter is the base unit. Volume has unit m3 (m × m × m) A milliliter (1mL) is a cube 1 centimeter (cm) long on each side. 1L = 103 mL = 1000cm3 1m3 = 102cm ×102cm×102cm =106cm3 = 103L

Temperature

Temperature The linear equation relating Celsius and Fahrenheit temperatures is of the form: The linear equation relating Celsius and kelvin temperatures is of the form: Temperature in kelvin is proportional to the average kinetic energy of molecules .

Energy Energy is the capacity to do work or transfer heat. Kinetic Energy = ½mv 2 . Unit of energy is joule, KE possessed by 2 kg object moving at speed of 1 m/s. Potential energy=stored energy, due to attractions & repulsions Work is the energy transferred when a force exerted on an object causes a displacement of that object. Heat is the amount of energy transferred between objects caused by a temperature difference

Density Density of a substance is its mass per unit of volume. Density = mass/ volume ; D = m / V The most common units are g/mL or g/cm3. Substances with high density ( lead, mercury, uranium) have a much larger amount of matter in a given volume than do substances with low density ( lithium, aluminum)

Accuracy & Precision Uncertainty of a measurement depends on many factors, one of which is the instrument used. The accuracy of a measurement is it closeness to the true value. Accuracy is associated with systematic error. The precision of measurements indicates the degree of reproducibility of several measurements of the same quantity. Precision reflects the random error.

Significant Figures We use the convention that the uncertainty in the last digit on the right is + 1. The number of significant figures is the number of digits that are known accurately plus the first uncertain digit. Significant figures do not apply to exact numbers. Numbers fixed by definition are exact. Counting numbers are exact.

Significant Figures All nonzero digits are significant. Zeroes between nonzero digits are significant. Zeroes at the beginning of a number are never significant. Zeroes at the end of a number are significant if it contains a decimal point.

Significant Figures in Calculations When addition or subtraction is performed, answers are rounded to the least significant decimal place. When multiplication or division is performed, answers are rounded to the same number of digits as the measurement with the fewest number of significant figures. Know the number of appropriate digits throughout, but round off at the end only!

Information required = information given x conversion factor Dimensional Analysis Many chemical problems involving quantities that are directly proportional can be solved by a method called dimensional analysis. When two quantities are directly proportional, we can find conversion factors to calculate the value of one property from the value of the other property. y = m x Information required = information given x conversion factor

Dimensional Analysis Dimensional analysis is used to change units. To change from meter to inches: conversion factors 1m = 100 cm 1 in = 2.54 cm We use the conversion factor which allows us to change units (puts the units we have in the denominator to cancel).