1: Module 1 - Matter and Measurement

Last updated
Save as PDF

Page ID: 423563

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

1.1: Chemicals Compose Ordinary Things
Chemistry is the branch of science dealing with the structure, composition, properties, and the reactive characteristics of matter. Matter is anything that has mass and occupies space. Thus, chemistry is the study of literally everything around us—the liquids that we drink, the gases we breathe, the composition of everything from the plastic case on your phone to the earth beneath your feet. Moreover, chemistry is the study of the transformation of matter.
1.2: The Scope of Chemistry
Chemistry is the study of matter and the ways in which different forms of matter combine with each other. You study chemistry because it helps you to understand the world around you. Everything you touch or taste or smell is a chemical, and the interactions of these chemicals with each other define our universe. Chemistry forms the fundamental basis for biology and medicine.
1.3: What is Matter?
Matter is anything that has mass and volume (takes up space). For most common objects that we deal with every day, it is fairly simple to demonstrate that they have mass and take up space. You might be able to imagine, however, the difficulty for people several hundred years ago to demonstrate that air has mass and volume. Air (and all other gases) are invisible to the eye, have very small masses compared to equal amounts of solids and liquids, and are quite easy to compress (change volume).
1.4: Classifying Matter According to Its State—Solid, Liquid, and Gas
Three states of matter exist—solid, liquid, and gas. Solids have a definite shape and volume. Liquids have a definite volume, but take the shape of the container. Gases have no definite shape or volume.
1.5: Classifying Matter According to Its State—Solid, Liquid, and Gas
Three states of matter exist—solid, liquid, and gas. Solids have a definite shape and volume. Liquids have a definite volume, but take the shape of the container. Gases have no definite shape or volume.
1.6: Classifying Matter According to Its Composition
One useful way of organizing our understanding of matter is to think of a hierarchy that extends down from the most general and complex, to the simplest and most fundamental. Matter can be classified into two broad categories: pure substances and mixtures. A pure substance is a form of matter that has a consistent composition and properties that are constant throughout the sample. A material composed of two or more substances is a mixture.
1.7: Differences in Matter- Physical and Chemical Properties
A physical property is a characteristic of a substance that can be observed or measured without changing the identity of the substance. Physical properties include color, density, hardness, melting points, and boiling points. A chemical property describes the ability of a substance to undergo a specific chemical change.
1.8: Changes in Matter - Physical and Chemical Changes
Change is happening all around us all of the time. Just as chemists have classified elements and compounds, they have also classified types of changes. Changes are either classified as physical or chemical changes. Chemists learn a lot about the nature of matter by studying the changes that matter can undergo. Chemists make a distinction between two different types of changes that they study—physical changes and chemical changes.
1.9: Conservation of Mass - There is No New Matter
The law of conservation of mass states that matter can not be created or destroyed in a chemical reaction. So the mass of the product equals the mass of the reactant. The reactant is the chemical interaction of two or more elements to make a new substance, and the product is the substance that is formed as the result of a chemical reaction. Matter and its corresponding mass may not be able to be created or destroyed, but can change forms to other substances like liquids, gases, and solids.
1.10: Compounds Display Constant Composition
A compound is a substance that contains two or more elements chemically combined in a fixed proportion. The elements carbon and hydrogen combine to form many different compounds. One of the simplest is called methane, in which there are always four times as many hydrogen particles as carbon particles. Methane is a pure substance because it always has the same composition. However, it is not an element because it can be broken down into simpler substances—carbon and hydrogen.
1.11: Chemical Formulas - How to Represent Compounds
A chemical formula is an expression that shows the elements in a compound and the relative proportions of those elements. A molecular formula is a chemical formula of a molecular compound that shows the kinds and numbers of atoms present in a molecule of the compound. An empirical formula is a formula that shows the elements in a compound in their lowest whole-number ratio.
1.12: Energy
When we speak of using energy, we are really referring to transferring energy from one place to another. Although energy is used in many kinds of different situations, all of these uses rely on energy being transferred in one of two ways—energy can be transferred as heat or as work.
1.13: Energy and Chemical and Physical Change
Phase changes involve changes in energy. All chemical reactions involve changes in energy. This may be a change in heat, electricity, light, or other forms of energy. Reactions that absorb energy are endothermic. Reactions that release energy are exothermic.
1.14: Taking Measurements
Chemists measure the properties of matter and express these measurements as quantities. A quantity is an amount of something and consists of a number and a unit. The number tells us how many (or how much), and the unit tells us what the scale of measurement is. For example, when a distance is reported as “5 kilometers,” we know that the quantity has been expressed in units of kilometers and that the number of kilometers is 5.
1.15: Scientific Notation - Writing Large and Small Numbers
Chemists often work with numbers that are exceedingly large or small. For example, entering the mass in grams of a hydrogen atom into a calculator requires a display with at least 24 decimal places. A system called scientific notation avoids much of the tedium and awkwardness of manipulating numbers with large or small magnitudes.
1.16: Significant Figures - Writing Numbers to Reflect Precision
Uncertainty exists in all measurements. The degree of uncertainty is affected in part by the quality of the measuring tool. Significant figures give an indication of the certainty of a measurement. Rules allow decisions to be made about how many digits to use in any given situation.
1.17: Significant Figures in Calculations
To round a number, first decide how many significant figures the number should have. Once you know that, round to that many digits, starting from the left. If the number immediately to the right of the last significant digit is less than 5, it is dropped and the value of the last significant digit remains the same. If the number immediately to the right of the last significant digit is greater than or equal to 5, the last significant digit is increased by 1.
1.18: The Basic Units of Measurement
Metric prefixes derive from Latin or Greek terms. The prefixes are used to make the units manageable. The SI system is based on multiples of ten. There are seven basic units in the SI system. Five of these units are commonly used in chemistry.
1.19: Problem Solving and Unit Conversions
During your studies of chemistry (and physics also), you will note that mathematical equations are used in a number of different applications. Many of these equations have a number of different variables with which you will need to work. Note also that these equations will often require the use of measurements with their units. Algebra skills become very important here!
1.20: Solving Multi-step Conversion Problems
Sometimes you will have to perform more than one conversion to obtain the desired unit.
1.21: Units Raised to a Power
Conversion factors for area and volume can also be produced by the dimensional analysis method. Remember that if a quantity is raised to a power of 10, both the number and the unit must be raised to the same power of 10.
1.22: Density
Density is a physical property found by dividing the mass of an object by its volume. Regardless of the sample size, density is always constant.