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Topic 1 Topic 1 Topic 1: Chemistry and Matter Table of Contents Basic Concepts Additional Concepts

Chemistry is the science that investigates and explains the structure and properties of matter. Composition, Structure, and Behavior Chemistry and Matter: Basic Concepts Matter is the stuff that’s all around you: the metal and plastic of a telephone, the paper and ink of a book, the glass and liquid of a bottle of soda, the air you breathe, and the materials that make up your body. A more formal definition of matter is anything that takes up space and has mass. Topic 1 Topic 1

Mass is the measure of the amount of matter that an object contains. Composition, Structure, and Behavior The structure of matter refers to its composition—what matter is made of—as well as how matter is organized. The properties of matter describe the characteristics and behavior of matter, including the changes that matter undergoes. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts

Matter that is large enough to be seen is called macroscopic, so all of your observations in chemistry, and everywhere else, start from this perspective. Macroscopic View of Matter You may get hints of the actual structure from a macroscopic view. You must go to a submicroscopic perspective to understand how the hidden structure of matter influences its behavior. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts

The submicroscopic view gives you a glimpse into the world of atoms. Submicroscopic View of Matter It is a world so small that you cannot see it even with the most powerful microscope, hence the term submicroscopic. We will study the atomic structure of matter in later chapters. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts

Pure substance or a mixture? Topic 1 Topic 1 Chemistry and Matter: Basic Concepts A substance is matter, either an element or compound, with the same fixed composition and properties. A sample of matter is either pure—made up of only one kind of matter— or it is a mixture of different kinds of matter.

A mixture is a combination of two or more substances in which the basic identity of each substance is not changed. Unlike pure substances, mixtures do not have specific compositions. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture?

A physical change is a change in matter that does not involve a change in the chemical identity of individual substances. Examples of physical changes include: boiling, freezing, melting, evaporating, dissolving, and crystallizing. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture?

Physical properties are characteristics that a sample of matter exhibits without any change in its identity. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture?

Examples of the physical properties of a chunk of matter include its: solubility, melting point, boiling point, color, density, electrical conductivity, and physical state (solid, liquid, or gas). Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture?

A heterogeneous mixture is one with different compositions, depending upon where you look. The components of the mixture exist as distinct regions, often called phases. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture?

Homogeneous mixtures are the same throughout. Another name for a homogeneous mixture is solution. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture? Some solutions are gases. Air, for example, is a homogeneous mixture of several gases. Some solutions are solid. Liquid solutions do not have to contain water.

Alloys are solid solutions that contain different metals and sometimes nonmetallic substances. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture?

When you dissolve sugar in water, sugar is the solute—the substance being dissolved. The substance that dissolves the solute, in this case water, is the solvent. When the solvent is water, the solution is called an aqueous solution. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture?

Many of the solutions you encounter are aqueous solutions, for example, soda, tea, contact-lens cleaner, and other clear cleaning liquids. In addition, most of the processes of life occur in aqueous solutions. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture?

Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Pure substance or a mixture?

Scientific Methods A scientific method is a systematic approach to answer a question or study a situation. Topic 1 Topic 1 Chemistry and Matter: Additional Concepts It is both an organized way for scientists to do research and a way for scientists to verify the work of other scientists.

Scientific Methods A typical scientific method includes: making observations, forming a hypothesis, performing an experiment, and arriving at a conclusion. Topic 1 Topic 1 Chemistry and Matter: Additional Concepts

Scientific Methods Often, a scientist will begin with qualitative data—information that describes color, odor, shape, or some other physical characteristic that relates to the five senses. Chemists also use numerical quantitative data. Topic 1 Topic 1 Chemistry and Matter: Additional Concepts A hypothesis is a possible explanation for what has been observed. An experiment is a set of controlled observations that test a hypothesis.

Scientific Methods The variable that is changed in an experiment is called the independent variable. The variable that you watch to see how it changes as a result of your changes to the independent variable is called the dependent variable. Topic 1 Topic 1 Chemistry and Matter: Additional Concepts

Scientific Methods Many experiments also include a control, which is a standard for comparison. A conclusion is a judgment based on the data obtained in the experiment. If data support a hypothesis, the hypothesis is tentatively affirmed. Hypotheses are never proven; they are always subject to additional research. Topic 1 Topic 1 Chemistry and Matter: Additional Concepts

Scientific Methods Over time, data from many experiments can be used to form a visual, verbal, and/or mathematical explanation—called a model—of the phenomenon being studied. Topic 1 Topic 1 Chemistry and Matter: Additional Concepts A theory is an explanation that has been supported by many experiments. Theories are always subject to new experimental data and are modified to include new data.

Scientific Methods A scientific law describes a relationship in nature that is supported by many experiments and for which no exception has been found. Topic 1 Topic 1 Chemistry and Matter: Additional Concepts

Additional Assessment Questions Identify the dependent variable and the independent variable in the following experiments. Question 1 Topic 1 Topic 1

A student tests the ability of a given chemical to dissolve in water at three different temperatures. independent variable: temperature; dependent variable: ability to dissolve in water Answer 1a Question 1a Topic 1 Topic 1 Additional Assessment Questions

A farmer compares how his crops grow with and without phosphorous fertilizers. independent variable: presence of phosphorous fertilizer; dependent variable: crop growth Answer 1b Question 1b Topic 1 Topic 1 Additional Assessment Questions