Biology 1 of 40
2-1 The Nature of Matter 2 of 40
2-1 The Nature of Matter Atoms Atoms The study of chemistry begins with the basic unit of matter, the atom. 3 of 40
2-1 The Nature of Matter Atoms Placed side by side, 100 million atoms would make a row only about 1 centimeter long. Atoms contain subatomic particles that are even smaller. 4 of 40
2-1 The Nature of Matter Atoms The subatomic particles that make up atoms are protons neutrons electrons 5 of 40
2-1 The Nature of Matter Atoms The subatomic particles in a helium atom. 6 of 40
2-1 The Nature of Matter Elements and Isotopes Elements and Isotopes A chemical element is a pure substance that consists entirely of one type of atom. C stands for carbon. Na stands for sodium. 7 of 40
2-1 The Nature of Matter Elements and Isotopes The number of protons in an atom of an element is the element's atomic number. Commonly found in living organisms: 8 of 40
Isotopes 2-1 The Nature of Matter Elements and Isotopes Atoms of the same element that differ in the number of neutrons they contain are known as isotopes. 9 of 40
2-1 The Nature of Matter Elements and Isotopes Because they have the same number of electrons, all isotopes of an element have the same chemical properties. 10 of 40
2-1 The Nature of Matter Elements and Isotopes Isotopes of Carbon 6 electrons 6 protons 8 neutrons 11 of 40
2-1 The Nature of Matter Elements and Isotopes Radioactive Isotopes Some isotopes are radioactive, meaning that their nuclei are unstable and break down at a constant rate over time 12 of 40
2-1 The Nature of Matter Elements and Isotopes Radioactive isotopes can be used: to determine the ages of rocks and fossils. to treat cancer. to kill bacteria that cause food to spoil. as labels or tracers to follow the movement of substances within an organism. 13 of 40
2-1 The Nature of Matter Chemical Compounds Chemical Compounds A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions. 14 of 40
2-1 The Nature of Matter Chemical Compounds Chemical Formula Water Table Salt Hydrochloric Acid Glucose 15 of 40
2-1 The Nature of Matter Chemical Bonds Chemical Bonds The atoms in compounds are held together by chemical bonds. The electrons that are available to form bonds are called valence electrons. 16 of 40
2-1 The Nature of Matter Chemical Bonds The main types of chemical bonds are: ionic bonds covalent bonds 17 of 40
Ionic Bonds 2-1 The Nature of Matter Chemical Bonds An ionic bond is formed when one or more electrons are transferred from one atom to another. These positively and negatively charged atoms are known as ions. 18 of 40
2-1 The Nature of Matter Chemical Bonds Sodium atom (Na) Sodium ion (Na+) Sodium ion (Cl - ) Sodium atom (Cl) Protons +11 Electrons - 11 10 Charge +10 Protons +17 Electrons - 17 18 Charge -10 19 of 40
2-1 The Nature of Matter Chemical Bonds Covalent Bonds Sometimes electrons are shared by atoms instead of being transferred. 20 of 40
2-1 The Nature of Matter Chemical Bonds A covalent bond forms when electrons are shared between atoms. single covalent bond double bond triple bond 21 of 40
2-1 The Nature of Matter Chemical Bonds The structure that results when atoms are joined together by covalent bonds is called a molecule. 22 of 40
2-1 The Nature of Matter Chemical Bonds Van der Waals Forces When molecules are close together, a slight attraction can develop between the oppositely charged regions of nearby molecules. van der Waals forces 23 of 40
2-1 Continue to: - or - Click to Launch: 24 of 40
2-1 The particles that move around the nucleus of an atom are called a. neutrons. b. protons. c. electrons. d. isotopes. 25 of 40
2-1 The atomic number of a carbon atom is 6. How many neutrons does the isotope carbon-14 have? a. 6 b. 8 c. 12 d. 14 26 of 40
2-1 Which of the following statements about the three isotopes of carbon is true? a. They are all radioactive. b. They have different numbers of electrons. c. They have the same chemical properties but differ in atomic mass. d. They have the same number of protons and neutrons. 27 of 40
2-1 A chemical compound consists of a. Electrons mixed with neutrons. b. two or more elements combined in a definite proportion. c. two or more protons combined in any proportion. d. at least three elements combined by ionic or covalent bonds. 28 of 40
2-1 Van der Waals forces are the result of a. unequal sharing of electrons. b. ionic bonds. c. the bonding of different isotopes. d. the chemical combination of sodium and chlorine. 29 of 40
END OF SECTION
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2-2 Properties of Water 32 of 40
The Water Molecule A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms. 33 of 40
The Water Molecule Water Molecule 34 of 40
The Water Molecule Hydrogen Bonds Because of their partial positive and negative charges, polar molecules can attract each other. 35 of 40
The Water Molecule Cohesion is an attraction between molecules of the same substance. Because of hydrogen bonding, water is extremely cohesive. 36 of 40
The Water Molecule Adhesion is an attraction between molecules of different substances. 37 of 40
Solutions and Suspensions Solutions and Suspensions A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined. 38 of 40
Solutions and Suspensions Two types of mixtures can be made with water solutions suspensions 39 of 40
Solutions and Suspensions Solutions All the components of a solution are evenly distributed throughout the solution. solute the substance that is dissolved. solvent the substance in which the solute dissolves. 40 of 40
Solutions and Suspensions When a crystal of table salt is placed in warm water, sodium and chloride ions are attracted to the polar water molecules. Cl - Cl - Na + Na + Wate r Wate r 41 of 40
Solutions and Suspensions Suspensions Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out easily. 42 of 40
Acids, Bases, and ph Acids, Bases, and ph A water molecule is neutral, but can react to form hydrogen and hydroxide ions. H 2 O H + + OH - 43 of 40
Acids, Bases, and ph The ph scale Chemists devised a measurement system called the ph scale to indicate the concentration of H + ions in solution. The ph scale ranges from 0 to 14. 44 of 40
Acids, Bases, and ph At a ph of 7, the concentration of H + ions and OH - ions is equal. The ph Scale Sea water Human blood Pure water Milk Normal rainfall 45 of 40
Acids, Bases, and ph Acids An acid is any compound that forms hydrogen (H + ) ions in solution. 46 of 40
Acids, Bases, and ph Bases A base is a compound that produces hydroxide ions (OH - ) ions in a solution. 47 of 40
Acids, Bases, and ph Buffers The ph of the fluids within most cells in the human body must generally be kept between 6.5 and 7.5. Controlling ph is important for maintaining homeostasis. 48 of 40
2-2 49 of 40
2-2 A molecule in which the charges are unevenly distributed is called a polar molecule. cohesive molecule. hydrogen molecule. covalent molecule. 50 of 40
2-2 A dissolved substance is called a solvent. solution. solute. Suspension. 51 of 40
2-2 A compound that produces hydroxide ions in solution is called a(an) base. buffer. acid. salt. 52 of 40
2-2 Hydrogen bonds between water molecules result from adhesion between water molecules. magnetic attractions between water molecules. uneven electron distribution in each water molecule. ionic bonds in the water molecule. 53 of 40
2-2 On a ph scale, a value of 2 means that the solution has equal concentrations of H + and OH - ions. the same concentration of H + ions as pure water. higher concentration of H + than in pure water. lower concentration of H + than in pure water. 54 of 40
END OF SECTION