Chemistry Lecture Presentation - Introduction PDF

Lecture Presentation Chapter 1 Introduction: Matter, Energy, and Measurement James F. Kirb...

Lecture Presentation Chapter 1 Introduction: Matter, Energy, and Measurement James F. Kirby Quinnipiac University Hamden, CT © 2022 Pearson Education Ltd.  Chemistry Chemistry is the study of matter, its properties, and the changes it undergoes. It is central to our fundamental understanding of many science- related fields. Matter And Measurement © 2022 Pearson Education Ltd.  Matter Matter is anything that has mass and takes up space. Matter And Measurement © 2022 Pearson Education Ltd.  Methods of Classification State of Matter Composition of Matter Matter And Measurement © 2022 Pearson Education Ltd.  States of Matter The three states of matter are 1) solid. 2) liquid. 3) gas. In this figure, those states are ice, liquid water, and water vapor. Matter And Measurement © 2022 Pearson Education Ltd.  Classification of Matter Based on Composition If you follow this scheme, you can determine how to classify any type of matter. – Homogeneous mixture – Heterogeneous mixture – Element – Compound Matter And Measurement © 2022 Pearson Education Ltd.  Classification of Matter—Substances A substance has distinct properties and a composition that does not vary from sample to sample. The two types of substances are elements and compounds. – An element is a substance which can not be decomposed to simpler substances. – A compound is a substance which can be decomposed to simpler substances because it is made up of more than one element. Matter And Measurement © 2022 Pearson Education Ltd.  Classification of Matter Based on Composition Atoms are the building blocks of matter. Each element is made of a unique kind of atom, but can be made of more than one atom of that kind. Note: Balls of different colors are A compound is made used to represent atoms of different of atoms from two or elements. Attached balls represent connections between atoms that more different are seen in nature. These groups of elements. Matter atoms are called molecules. And Measurement © 2022 Pearson Education Ltd.  Elements and Composition There are currently 118 named elements. Only five elements make up 90% of the Earth’s crust by mass. Only three elements make up 90% of the human body by mass! Note the importance of Matter oxygen! And Measurement © 2022 Pearson Education Ltd.  Representing Elements Chemists usually represent elements as symbols. Symbols are one or two letters; the first is always capitalized. Some elements are based on Latin, Greek, or other foreign language names. Matter And Measurement © 2022 Pearson Education Ltd.  Compounds and Composition Compounds have a definite composition. That means that the relative number of atoms of each element in the compound is the same in any sample. This is The Law of Constant Composition (or The Law of Definite Matter Proportions). And Measurement © 2022 Pearson Education Ltd.  Classification of Matter—Mixtures Mixtures exhibit the properties of the substances that make them. Mixtures can vary in composition throughout a sample (heterogeneous) or can have the same composition throughout the sample (homogeneous). A homogeneous mixture is also called a solution. Matter And Measurement © 2022 Pearson Education Ltd.  Two Types of Properties Physical properties Chemical properties Matter And Measurement © 2022 Pearson Education Ltd.  Physical Properties Physical properties can be observed without changing a substance into another substance. – Some examples include color, odor, density, melting point, boiling point, and hardness. Matter And Measurement © 2022 Pearson Education Ltd.  Chemical Properties Chemical properties can only be observed when a substance is changed into another substance. – One common chemical property is flammability, or the ability to burn in oxygen. Matter And Measurement © 2022 Pearson Education Ltd.  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. Matter And Measurement © 2022 Pearson Education Ltd.  Types of Changes Physical changes are changes in matter that do not change the composition of a substance. – Examples include changes of state, temperature, and volume. Chemical changes result in new substances. – Examples include combustion, oxidation, and decomposition. Matter And Measurement © 2022 Pearson Education Ltd.  Changes in State of Matter Converting between the three states of matter is a physical change. When ice melts or water evaporates, there are still 2 H atoms and 1 O atom in each molecule. Matter And Measurement © 2022 Pearson Education Ltd.  Chemical Reactions (Chemical Change) In the course of a chemical reaction, the reacting substances are converted to new substances. Here, the copper penny reacts with nitric acid; it gives a blue solution of copper(II) nitrate and a brown gas called nitrogen dioxide. NOTE: Physical properties, like color, often helps us Matter SEE that chemical change has occurred. And Measurement © 2022 Pearson Education Ltd.  Separating Mixtures Mixtures can be separated based on physical properties of the components of the mixture. Some methods used are – filtration – distillation – chromatography Matter And Measurement © 2022 Pearson Education Ltd.  Filtration In filtration, solid substances are separated from liquids and solutions. Matter And Measurement © 2022 Pearson Education Ltd.  Distillation Distillation uses differences in the boiling points of substances to separate a homogeneous mixture into its components. Matter And Measurement © 2022 Pearson Education Ltd.  Chromatography This technique separates substances on the basis of differences in the ability of substances to adhere to the solid surface, in this case, dyes to paper. Matter And Measurement © 2022 Pearson Education Ltd.  Energy Energy is the capacity to do work or transfer heat. Work is the energy transferred when a force exerted on an object causes a displacement of that object. Heat is the energy used to cause the temperature of an object to increase. Force is any push or pull Matter And on an object. Measurement © 2022 Pearson Education Ltd.  Two Fundamental Forms of Energy Kinetic energy is the energy of motion. – Its magnitude depends on the object’s mass and its velocity: KE = ½ m v2 Potential energy of an object depends on its relative Matter And position compared to other objects. Measurement © 2022 Pearson Education Ltd.  Numbers and Chemistry Numbers play a major role in chemistry. Many topics are quantitative (have a numerical value). Concepts of numbers in science – Units of measurement – Quantities that are measured and calculated – Uncertainty in measurement – Significant figures – Dimensional analysis Matter And Measurement © 2022 Pearson Education Ltd.  Units of Measurements—SI Units Système International d’Unités (“The International System of Units”) A different base unit is used for each quantity. Matter And Measurement © 2022 Pearson Education Ltd.  Units of Measurement—Metric System The base units used in the metric system – Mass: gram (g) – Length: meter (m) – Time: second (s or sec) – Temperature: degrees Celsius (°C) or Kelvins (K) – Amount of a substance: mole (mol) – Volume: cubic centimeter (cc or cm3) or liter (l) Matter And Measurement © 2022 Pearson Education Ltd.  Units of Measurement— Metric System Prefixes Prefixes convert the base units into units that are appropriate for common usage or appropriate measure (as seen with mL on the can in the last slide). Matter And Measurement © 2022 Pearson Education Ltd.  Mass and Length These are basic units we measure in science. Mass is a measure of the amount of material in an object. SI uses the kilogram as the base unit. The metric system uses the gram as the base unit. Length is a measure of distance. The meter is the base unit. Matter And Measurement © 2022 Pearson Education Ltd.  Volume Note that volume is not a base unit for SI; it is a derived unit from length (m × m × m = m3). The most commonly used metric units for volume are the liter (L) and the milliliter (mL). – A liter is a cube 1 decimeter (dm) long on each side. – A milliliter is a cube 1 centimeter (cm) long on each side, also called 1 cubic centimeter (cm × cm × cm = cm3). Matter And Measurement © 2022 Pearson Education Ltd.  Glassware for Measuring Volume Matter And Measurement © 2022 Pearson Education Ltd.  Temperature In general usage, temperature is considered the “hotness and coldness” of an object that determines the direction of heat flow. Heat flows spontaneously from an object with a higher temperature to an object with a lower temperature. Matter And Measurement © 2022 Pearson Education Ltd.  Temperature In scientific measurements, the Celsius and Kelvin scales are most often used. The Celsius scale is based on the properties of water. – 0 °C is the freezing point of water. – 100 °C is the boiling point of water. The Kelvin is the SI unit of temperature. – It is based on the properties of gases. – There are no negative Kelvin temperatures. – The lowest possible temperature is called absolute zero (0 K). K = °C + 273.15 Matter And Measurement © 2022 Pearson Education Ltd.  Temperature The Fahrenheit scale is not used in scientific measurements, but you hear about it in weather reports! The equations below allow for conversion between the Fahrenheit and Celsius scales: – °F = 9/5(°C) + 32 – °C = 5/9(°F − 32) Matter And Measurement © 2022 Pearson Education Ltd.  Energy The unit of energy: Joule (J). It is a derived unit: – KE = ½ m v2 – If the object is 2 kg, and it moves at 1 m/s, it will posses 1 J of kinetic energy: – 1J = ½ (2 kg) (1 m/s)2 OR: 1 J ≡ 1 kg · m2/s2 The kJ is commonly used for chemical change. Historically, the calorie was used: 1 cal = 4.184 J This calorie is NOT the nutritional Calorie. That one is a kcal. 1 nutritional Calorie = 1 Cal = 1000 cal Matter And Measurement © 2022 Pearson Education Ltd.  Density Density is a physical property of a substance. It has units that are derived from the units for mass and volume. The most common units are g/mL or g/cm3. D = m/V Matter And Measurement © 2022 Pearson Education Ltd.  Numbers Encountered in Science Exact numbers are counted or given by definition. For example, there are 12 eggs in 1 dozen. Inexact (or measured) numbers depend on how they were determined. Scientific instruments have limitations (equipment errors) and individuals can read some instrumentation differently (human errors). Matter And Measurement © 2022 Pearson Education Ltd.  Uncertainty in Measurements Different measuring devices have different uses and different degrees of accuracy. All measured numbers have some degree of inaccuracy. The last digit measured is considered reliable, but NOT exact. Matter And Measurement © 2022 Pearson Education Ltd.  Accuracy versus Precision Precision is a measure of how closely individual measurements agree with one another. Accuracy refers to how closely individual measurements agree with the correct, or “true,” value. Experimentally, we often take several measurements and determine a standard Matter And deviation. Measurement © 2022 Pearson Education Ltd.  Significant Figures All digits of a measured quantity, including the uncertain ones, are called significant figures. When rounding calculated numbers, we pay attention to significant figures so we do not overstate the accuracy of our answers. Matter And Measurement © 2022 Pearson Education Ltd.  Significant Figures 1. All nonzero digits are significant. 2. Zeroes between nonzero digits are significant. 3. Zeroes at the beginning of a number are never significant. 4. Zeroes at the end of a number are significant if it contains a decimal point. Problem: whole numbers ending in zeroes. Matter And Measurement © 2022 Pearson Education Ltd.  Significant Figures in Calculations The least certain measurement limits the number of significant figures in the answer. 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! Matter And Measurement © 2022 Pearson Education Ltd.  Dimensional Analysis Dimensional analysis is used to change units. We apply conversion factors (e.g., 1 in = 2.54 cm), which are equalities. We can set up a ratio of comparison for the equality: 1 in./2.54 cm or 2.54 cm/1 in. We use the ratio which allows us to change units (puts the units we have in the denominator to cancel). We can use multiple conversions, as long as each one is an equality. Matter And Measurement © 2022 Pearson Education Ltd.