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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.

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Presentation on theme: "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."— Presentation transcript:

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2 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?

3 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?

4 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?

5 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?

6 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 be liquid or contain water.

7 When you dissolve sugar in water, sugar is the solutethe 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?

8 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?

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

10 Two Types of Substances One type of pure substance can be broken down into simpler substances. This type of substance is called a compound. Another type of substance cannot be broken down into simpler substances. Such a substance is called an element. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts All the substances of the universe are either elements, compounds formed from elements, or mixtures of elements and compounds.

11 Two Types of Substances Of the known elements, only about 90 occur naturally on Earth. The remainder are synthesized, usually in barely detectable amounts, in high-energy nuclear experiments. Less than half of the 90 naturally occurring elements are abundant enough to play a significant role in the chemistry of everyday stuff. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts

12 Compounds Are More Than One Element A more complete definition is that a compound is a chemical combination of two or more different elements joined together in a fixed proportion with a unique set of chemical and physical properties. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts More than 10 million compounds are known and the number keeps growing.

13 Compounds Are More Than One Element Topic 1 Topic 1 Chemistry and Matter: Basic Concepts Some new compounds are discovered and isolated from natural chemical sources such as plants and colonies of bacteria and are synthesized in laboratories for many different uses.

14 Compounds Are More Than One Element The properties of the compound are different from the properties of the elements that compose the compound. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts silver + bromine = silver bromide

15 Compounds Are More Than One Element A formula is a combination of the chemical symbols that show what elements make up a compound and the number of atoms of each element. CompoundFormula CaffeineC 8 H 10 N 4 O 2 Topic 1 Topic 1 Chemistry and Matter: Basic Concepts

16 Compounds Are More Than One Element Formulas provide a shorthand way of describing a submicroscopic view of a compound. You probably already use formulas like H 2 O and CO 2 as a way of talking about water and carbon dioxide. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts

17 Organizing the Elements The periodic table organizes elements in a way that provides a wealth of chemical informationmuch more than is evident to you now. It shows the chemical symbols for the elements. Their symbols usually correspond to their names in Latin. Topic 1 Topic 1 Chemistry and Matter: Basic Concepts

18 Periodic Table of the Elements MODERN PERIODIC TABLE Arranged in order of increasing atomic number Rows are called periods Columns are called groups or families Periodic Law – elements arranged in increasing atomic number have a periodic pattern in their physical and chemical properties. Elements with similar properties are in the same group.

19 Basic Assessment Questions Question 1 Identify each of the following as either a compound or a mixture. A. sand B. water C. juice Topic 1 Topic 1

20 Basic Assessment Questions Answers A. sand B. water C. juice mixture compound mixture Topic 1 Topic 1

21 Basic Assessment Questions Classify each of the following as an intensive or extensive physical property. Question 2 A. density B. mass C. color D. melting point E. volume Topic 1 Topic 1

22 Basic Assessment Questions Answers A. density B. mass C. color D. melting point intensive property extensive property intensive property Topic 1 Topic 1 E. volume extensive property


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