CH. 2 Chemistry of life Section 1 Nature of matter

1. CH. 2 Chemistry of life Section 1 Nature of matter Atoms • Atom- is the smallest unit of matter that cannot be broken down by chemical means. • Atoms consist of 3 kinds of particles: electrons, protons and neutrons.

2. CH. 2 Chemistry of life Section 1 Nature of matter Electron, protons, and Neutrons • Electrons have a negative charge (-), and are located outside the nucleus in the electron cloud. • Protons have a positive charge (+), and are located in the nucleus or core of an atom. • Neutrons have no charge, located in the nucleus or core of an atom.

3. CH. 2 Chemistry of life Section 1 Nature of matter Electrons, Protons, and Neutrons • Because electrons have a negative chare the electron cloud of an atom is always negative • Because protons are positive and neutrons are neutral the nucleus of an atom is always positive. • Because electrons and protons are oppositely charged they attract one another.

4. CH. 2 Chemistry of life Section 1 Nature of matter Elements • Element- a pure substance made of only one kind of atom. • There are more than 100 known elements, and each is represented by a one, two, or three letter symbol. Ex. Hydrogen (H) Carbon (C). • Elements differ in the number of protons their atoms contain.

5. CH. 2 Chemistry of life Section 1 Nature of matter Chemical Bonding • Atoms can join with other atoms to form stable substances. • A force that joins atoms is called a chemical bond. • compound-a substance made of the joined atoms of two or more different elements.

6. CH. 2 Chemistry of life Section 1 Nature of matter Covalent Bonds • Molecule-smallest unit of a substance that keeps all of the properties of that substance; it can consist of one atom or two or more atoms bonded together. • Covalent bonds form when two or more atoms share electrons to form a molecule. • A moleculesuch as the water molecule shown below, is a group of atoms held together by covalent bonds.

7. CH. 2 Chemistry of life Section 1 Nature of matter CovalentBonds • The arrangement of their electrons determines how atoms bond together. • An atom becomes stable when its outer electron level is full. If the outer electron level is not full, an atom will react readily with atoms that can provide electrons to fill its outer level.

8. CH. 2 Chemistry of life Section 1 Nature of matter Ionic Bonds • Sometimes atoms or molecules gain or lose electrons. • Ion-An atom or molecule that has gained or lost one or more electrons. • Ionshave an electrical charge because they contain an unequal number of electrons and protons. Ions of opposite charge may interact to form an ionic bond.

9. Ch. 2 Chemistry of life Section 2 Water and solutions

10. CH. 2 Chemistry of lifeSection 2 Water and solutions Water in living things • 70 % of your body is made up of water. • 2/3 of molecules in your body are water molecules.

11. CH. 2 Chemistry of lifeSection 2 Water and solutions Storage of Energy • Many organisms release excess heat through water evaporation. • In organisms, this ability to control temperature enables cells to maintain a constant internal temperature when the external temperature changes. • In this way, water helps cells maintain homeostasis.

12. CH. 2 Chemistry of lifeSection 2 Water and solutions Cohesion and Adhesion • Cohesion-is an attraction between substances of the same kind. • Because of cohesion, water and other liquids form thin films and drops. • Molecules at the surface of water are linked together by hydrogen bonds like a crowd of people linked by holding hands. This attraction between water molecules causes a condition known as surface tension.

13. CH. 2 Chemistry of lifeSection 2 Water and solutions Cohesion and Adhesion • Adhesion-is an attraction between different substances. Aqueous Solutions • Solution-a mixture in which one or more substances are evenly distributed in another substance. • Substances can dissolve in water, they can more easily move within and between cells.

14. CH. 2 Chemistry of lifeSection 2 Water and solutions Polarity • The polarity of water enables many substances to dissolve in water. • When ionic compounds dissolve in water ions become surrounded by polar water molecules. • The resulting solution is a mixture of water molecules and ions. • Nonpolar molecules do not dissolve well in water.

15. CH. 2 Chemistry of lifeSection 2 Water and solutions Acids and Bases • Acids-compounds that from hydrogen ions when dissolved in water. • When an acid is added to water, the concentration of hydrogen ions in the solution is increased above that of pure water. • Bases-compounds that reduce the concentration of hydrogen ions in a solution. • The pH scale measures the concentration of hydrogen ions in a solution.

16. Chapter 2 Chemistry of life Section 3 Chemistry of cells

17. CH. 2 Chemistry of lifeSection 3 Chemistry of cells Carbon Compounds • Four principal classes of organic compounds are found in living things: Carbohydrates, lipids, proteins, and nucleic acids. • Without these compounds cells could not function.

18. CH. 2 Chemistry of lifeSection 3 Chemistry of cells Carbohydrates