Chapter 1: Matter and Change

1. Chapter 1: Matter and Change Chemistry 1-2 Mr. Chumbley

2. Section 1: Chemistry is a Physical Science

3. What is Chemistry? • For most of human history, the natural sciences were divided into two broad categories: • Biological Sciences • Physical Sciences • However, those divisions began to break down as knowledge increased • Chemistry is the study of the composition, structure, and properties of matter, the processes that matter undergoes, and the energy changes that accompany these processes

4. Branches of Chemistry • As the understanding of matter and its processes increased, different branches of chemistry arose to better describe specific types of chemicals and processes • A chemical is any substance that has a definite composition

5. Chemistry Applications • Basic chemical research is conducted for the purpose of expanding knowledge • Applied chemical research is conducted for the purpose of solving a specific problem • Technological development involves the production and use of products to improve the quality of life

6. Homework • Read: • Chapter 1, Sections 2: Matter and Its Properties • Stop once you get to “Main Idea: Matter can be a pure substance or a mixture.”

7. Section 2: Matter and its Properties

8. What is Matter? • It is much easier to identify that things are made up of matter than it is to define matter • By looking at the same properties for all matter there are two universal commonalities: • Things made of matter take up space (have volume) • Things made of matter have mass • Mass is a measure of the amount of matter • Using these universal characteristics we can define matter • Matter is anything that has mass and takes up space

9. Atoms are the building blocks of Matter • While matter exists in many different forms, the most fundamental form is the atom • An atom is the smallest unit of an element that maintains the chemical identity of that element • An element is a pure substance that cannot be broken down into simpler, stable substances and is made of one type of atom

10. Atoms are the Building Blocks of Matter • When atoms of different elements chemically combine, molecules of a compound are formed • A compound is a substance that can be broken down into simple stable substances, but is made from the atoms of two or more elements that are chemically bonded • The smallest unit of a compound is a molecule

11. All Substances Have Characteristic Properties • The specific characteristics of a substance, either element or compound, are considered its properties • Properties can be used to identify individual substances, or an entire group of substances • Properties can be one of two types • Extensive properties depend on the amount of matter present • mass • volume • total energy • Intensive properties do not depend on the amount of matter present • melting point • boiling point • density • conductivity

12. Physical Properties • Properties of substances are often used as identifying characteristics • Physical properties are characteristics that can be observed or measured without changing the identity of the substance • Examples:

13. Physical Changes • The physical properties of a substance are can change, even if the substance does not • A physical change is a change in a substance that does not involve a change in the identity of the substance • Examples:

14. States of Matter • Matter exists in states of matter that are physical properties • When a substance undergoes a change of state, it is a physical change from one state to another • While the substance has some new and different physical properties, the chemical identity has not changed

15. States of Matter • As a substance changes from solid to liquid to gas, the atoms or molecules become less organized and have increasing ability to move away from each other • A fourth state of matter, plasma, is a high-temperature physical state of matter in which atoms lose most of their electrons

16. Chemical Properties • In any situation where a substance could change its identity, chemical properties can be observed • Chemical properties relate to a substances ability to undergo changes that transform it into a different substance • Examples:

17. Chemical Changes • A chemical change (or chemical reaction) is a change in which one or more substances are converted into different substances • The reactants are the substances that react in a chemical change • The products are the substances that are formed by the chemical change

18. Signs of a Chemical Change • Production of an odor • Change in temperature • Change in color • Formation of bubbles • Formation of a solid • Emission of light

19. Energy and Changes in Matter • In both physical and chemical changes, energy is involved • Many different types of energy can be involved • The law of conservation of energy says that energy can be absorbed or released, but it is never created nor destroyed

20. Homework • Read: • Chapter 1, Sections 2: Matter and Its Properties • Start at “Main Idea: Matter can be a pure substance or a mixture.” • Finish at the end of Section 2 • Answer #1-5 of the Formative Assessment on p. 14

21. Matter Can be a Pure Substance or a Mixture • The variety of forms in which matter can exist is enormous • Two major classifications of matter are whether or not it is a pure substance or a mixture • Regardless of whether a sample is a pure substance or a mixture, it can be described and classified in terms of its properties

22. Pure substances • A pure substance is any form of matter that has a fixed, or definite, composition • Pure substances have two defining characteristics: • Every sample of a given pure substance has exactly the same characteristic properties. • Every sample of a pure substance has exactly the same composition.

23. Mixtures • A mixture is a blend of two or more kinds of matter each of which retains its own identity and properties • Another way of describing a mixture is that the matter combines physically, but not chemically • Since mixtures do not have a defined composition, the amount of different substances within a sample of a mixture must be specified

24. Mixtures • Mixtures can be described by the uniformity of their compostion • Homogeneous mixtures (or solutions) are mixtures that are uniform in composition • Heterogeneous mixtures are mixtures that are not uniform in composition

25. Mixtures • One of the most important characteristics of a mixture is that it can be physically separated • Examples of physical separation: • Filtration • Vaporization • Settling • Centrifuge separation • Chromatography

26. Laboratory Chemicals and Purity • Typically, we treat chemicals used in the laboratory is if they were pure • Chemicals do have impurity, and depending on the standards and grade desired or used • The level of purity is important to know since the level of impurities can affect results