Chapter 3 Chemistry of Life
Content Objectives Write these down! I will be able to identify: The make-up of matter. Why atoms form bonds. Some important interactions between substances in living things.
Chapter 3 Section 1: Matter & Substance Key Vocabulary Terms Adapted from Holt Biology 2008
Atom The smallest unit of matter that cannot be broken down by chemical means. The smallest unit of an element that maintains the chemical properties of that element. Adapted from Holt Biology 2008
Atom The smallest unit of matter that cannot be broken down by chemical means. The smallest unit of an element that maintains the chemical properties of that element. Adapted from Holt Biology 2008
Element A substance that cannot be separated or broken down into simpler substances by chemical means. A substance made up of atoms that have the same number of protons. Adapted from Holt Biology 2008
Valence Electron An electron that is found in the outermost shell of an atom and that determines the atom's chemical properties. Adapted from Holt Biology 2008
Compound A substance made up of atoms of two or more different elements joined by chemical bonds. Adapted from Holt Biology 2008
Molecule A group of atoms that are held together by chemical forces (covalent bonds); a molecule is the smallest unit of matter that can exist by itself and retain all of a substance's chemical properties. Adapted from Holt Biology 2008
Ion An atom, radical, or molecule that has gained or lost one or more electrons and has a negative or positive charge. Adapted from Holt Biology 2008
Mass A quantity representing the amount of matter in a particle or object. The standard unit of mass in the International System (SI ) is the gram ( k ). Adapted from Holt Biology 2008
Protons A subatomic particle with a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom along with neutrons. Adapted from Holt Biology 2008
Electrons A subatomic particle carrying a negative electric charge which has no known components or substructure. Adapted from Holt Biology 2008
Neutrons A subatomic particle with no net electric charge and a mass slightly larger than that of a proton. Except for Hydrogen the nuclei of atoms consist of protons & neutrons. Adapted from Holt Biology 2008
Polar Molecules with partial charges on opposite ends are said to be polar. The water molecule is polar. Adapted from Holt Biology 2008
Chapter 3 Section 1: Matter & Substance Supplementary Words Adapted from Holt Biology 2008
Electron Cloud The region of an atom in which the electrons move around the nucleus. Adapted from Holt Biology 2008
Isotopes Variants of atoms of an element which have a different number of neutrons. Adapted from Holt Biology 2008
Valence Shell The outermost shell of an atom. Adapted from Holt Biology 2008
An attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction. Chemical Bond Adapted from Holt Biology 2008
Covalent Bond A form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. Adapted from Holt Biology 2008
Ionic Bond A type of chemical bond formed through an electrostatic attraction between two oppositely charged ions. Adapted from Holt Biology 2008
Polarity Equally bonding electrons are shared between atoms causing a condition where the molecule has opposing physical properties at different points, or slight electric charges at opposite poles. Adapted from Holt Biology 2008
Solubility In general, solubility is an ability of a substance to dissolve. In the process of dissolving, the substance which is being dissolved is called a solute and the substance in which the solute is dissolved is called a solvent. A mixture of solute and solvent is called a solution. Adapted from Holt Biology 2008
The attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond. Hydrogen Bond Adapted from Holt Biology 2008
Chapter 3 Section 1: Matter & Substance Notes Adapted from Holt Biology 2008
Section 1: Matter and Substances Preview Matter Atoms Chemical Bonds Polarity
Matter Matter is anything that has mass and takes up space. All living and non-living things are made of matter.
Atoms An atom is the smallest unit of matter that cannot be broken down by chemical means.
The nucleus of an atom is made up of positively charged protons and uncharged neutrons. Atoms, continued
Negatively charged electrons have very little mass and move around the nucleus in a large region called the electron cloud. Atoms, continued
Atoms, continued Elements An element is a substance made up of atoms that have the same number of protons.
Atoms, continued Elements For example, each atom of the element carbon has six protons.
Atoms, continued Elements Atoms of an element may have different numbers of neutrons. These atoms are called isotopes of elements.
Think, Share, Write #1 What is a neuron?
Think, Share, Write #1 What is a proton? A proton is a positively charged particle that is part of the nucleus of an atom.
Chemical Bonds Electrons in the outermost level, or shell, are called valence electrons.
Chemical Bonds When atoms combine, a force called a chemical bond holds them together.
Chemical Bonds, continued Atoms become stable when they have eight electrons in the valence shell.
Chemical Bonds, continued When atoms of different elements combine, a compound forms. A compound is a substance made of the bonded atoms of two or more elements.
YOUR TURN With a partner, read the Chapter 3 Section 1 Active Reading Matter and Substances 1 st - Take turns reading the questions aloud to each other, alternating questions. 2 nd - Take turns reading the selection aloud to each other, alternating sentences or paragraphs. Adapted from Holt Biology 2008
YOUR TURN As you read discuss the content. Reread and discuss each question. Write down the best answer to the question using full descriptive sentences. Be prepared to share with the class. 2 Adapted from Holt Biology 2008 Adapted from Holt Biology 2008
Chemical Bonds, continued Covalent Bonding Occurs when atoms bond by sharing valence electrons and form a covalent bond.
Chemical Bonds, continued Covalent Bonding A molecule is a group of atoms held together by chemical bonds.
Chemical Bonds, continued Covalent Bonding A water molecule, H2O, forms when an oxygen atom forms covalent bonds with two hydrogen atoms.
Think, Share, Write #2 What is a chemical bond?
Think, Share, Write #2 What is a chemical bond? A chemical bond is the attractive force that holds atoms or ions together.
Ionic Bonding An ion is an atom or group of atoms that has an electric charge because it has gained or lost electrons. (to become stable) Chemical Bonds, continued
Ionic Bonding The attractive force between oppositely charged ions is an ionic bond. Chemical Bonds, continued
Ionic Bonding in Salt
Polarity In some covalent bonds one end (pole) of the molecule has a partial negative charge (-), while the opposite end has a partial positive (+) charge.
Polarity Molecules with partial charges on opposite ends are said to be polar.
Polarity, continued Solubility The partially charged ends of polar molecules attract opposite charges. Water molecules are polar.
Polarity, continued Solubility Because of this behavior, polar molecules can dissolve other polar molecules and ionic compounds. For example, water can dissolve sugar and salt.
Polarity, continued Solubility Nonpolar substances, such as oil, grease, and wax, do not dissolve well in water.
Ionic Compounds in Water
Hydrogen Bond When bonded to an oxygen, nitrogen, or fluorine atom, a hydrogen atom has a partial charge nearly as great as a proton s charge. Polarity, continued
Hydrogen Bond A hydrogen bond, is stronger than attractions between other molecules, but not as strong as covalent bonds. Polarity, continued
Polarity, continued Hydrogen bonding plays an important role in many of the molecules that make up living things.
Hydrogen Bonding
Think, Share, Write #3 Why does salt dissolve in water?
Think, Share, Write #3 Why does salt dissolve in water? Salt dissolves in water because the partial positive charge of the H atoms in water molecules (H 2 O) attracts the negatively charged chloride ions in salt crystals (NaCl). The partially negative charge of the O atom of water molecules attracts the positively charged sodium ions in salt crystals.