1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Composition of Matter Chapter 2 Matter Matter is anything that occupies space and has mass. Mass is the quantity of matter an object has.

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Composition of Matter Chapter 2 Elements and Atoms Elements are made of a single kind of atom and cannot be broken down by chemical means into simpler substances. Atoms are composed of protons, neutrons, and electrons.

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Composition of Matter Chapter 2 Elements and Atoms, continued The Nucleus –Protons and neutrons make up the nucleus of the atom.

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Composition of Matter Chapter 2 Elements and Atoms, continued Electrons –Electrons move about the nucleus in orbitals. –An orbital is a three- dimensional region around a nucleus that indicates the probable location of an electron.

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Composition of Matter Chapter 2 Elements and Atoms, continued Isotopes –Atoms of the same element that have a different number of neutrons are called isotopes.

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Composition of Matter Chapter 2 Compounds Compounds consist of atoms of two or more elements that are joined by chemical bonds in a fixed proportion.

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Composition of Matter Chapter 2 Compounds, continued Covalent Bonds –A covalent bond is formed when two atoms share electrons.

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Composition of Matter Chapter 2 Compounds, continued Ionic Bonds –An ionic bond is formed when one atom gives up an electron to another. The positive ion is then attracted to a negative ion to form the ionic bond.

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Ionic Bonding Section 1 Composition of Matter

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Polarity Water is considered to be a polar molecule due to an uneven distribution of charge. The electrons in a water molecule are shared unevenly between hydrogen and oxygen.

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Polarity, continued Solubility of Water –The polarity of water makes it effective at dissolving other polar substances such as sugars, ionic compounds, and some proteins.

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Hydrogen Bonding A hydrogen bond is the force of attraction between a hydrogen molecule with a partial positive charge and another atom or molecule with a partial or full negative charge.

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Hydrogen Bonding, continued Cohesion and Adhesion –Cohesion is an attractive force that holds molecules of a single substance together, such as water molecules. –Adhesion is the attractive force between two particles of different substances, such as water molecules and glass molecules.

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Hydrogen Bonding, continued Temperature Moderation –Water has the ability to absorb a relatively large amount of energy as heat and the ability to cool surfaces through evaporation.

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Hydrogen Bonding, continued Density of Ice –Solid water is less dense than liquid water due to the shape of the water molecule and hydrogen bonding.

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Solutions A solution consists of a solute dissolved in a solvent.

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Acids and Bases Ionization of Water –Water ionizes into hydronium ions (H 3 O + ) and hydroxide ions (OH – ).

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Acids and Bases, continued Acids –Acidic solutions contain more hydronium ions than hydroxide ions.

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Acids and Bases, continued Bases –Basic solutions contain more hydroxide ions than hydronium ions.

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Acids and Bases, continued pH –Scientists have developed a scale for comparing the relative concentrations of hydronium ions and hydroxide ions in a solution. This scale is called the pH scale, and it ranges from 0 to 14.

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 The pH Scale

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Acids and Bases, continued Buffers –Buffers are chemicals that neutralize the effects of adding small amounts of either an acid or a base to a solution.