biology module 6

• Chemistry is the study of matter, its composition, and properties
• Matter is anything that has mass and takes up space
• Atoms are the building blocks of matter
• An atom is made up of neutrons, protons, and electrons
• Neutrons and protons are located at the center of the atom in the nucleus
• Protons are positively charged particles, neutrons have no charge, and electrons are negatively charged particles found outside the nucleus
• Atoms contain an equal number of protons and electrons, resulting in an overall charge of zero
• Elements are pure substances that cannot be broken down into other substances by physical or chemical means
• There are over 100 known elements, 92 of which occur naturally
• Isotopes are atoms of the same element with different numbers of neutrons
• Radioactive isotopes can decay, giving off radiation, and have practical applications in various fields
• Compounds are pure substances formed when two or more different elements combine
• Compounds have unique characteristics, including being formed in fixed ratios, being chemically and physically different from the elements that make them up, and being able to be broken down by chemical means
• Water is classified as a compound because it is formed when two or more substances combine, and the force that holds the substances together is called a chemical bond
• Chemical bonds store energy when formed and provide energy when broken
• There are two main types of chemical bonds: ionic bonds and covalent bonds
• Ionic bonds:

  • Atoms become ions by losing or gaining electrons to become stable
  • An ionic bond is an electrical attraction between oppositely charged ions
  • Substances formed by ionic bonds are called ionic compounds
• Covalent bonds:

  • Atoms share electrons in their outer energy levels to form covalent bonds
  • Compounds with covalent bonds are called molecules
  • Covalent bonds can be single, double, or triple depending on the number of shared electron pairs
• Most compounds in living organisms have covalent bonds holding them together
• Elements are pure substances made up of only one kind of atom
• Isotopes are forms of the same element that have a different number of neutrons
• Elements can form covalent and ionic bonds
• Chemical reactions involve the reorganization of atoms or groups of atoms in substances into different substances
• Chemical bonds are broken and formed during chemical reactions
• Rust is a compound called iron oxide formed when oxygen in the air reacts with iron
• Clues that a chemical reaction has occurred include the production of heat or light, and the formation of a new gas, liquid, or solid
• Physical changes alter a substance's appearance but not its composition
• Chemical equations express each component of a reaction with reactants on the left side of the arrow and products on the right side
• Balanced chemical equations must show an equal number of atoms for each element on both sides
• Matter cannot be created or destroyed in chemical reactions, following the law of conservation of mass
• Activation energy is the minimum energy needed for reactants to form products in a chemical reaction
• Catalysts lower the activation energy needed to start a chemical reaction
• Enzymes are biological catalysts that lower the activation energy of biochemical reactions
• Enzymes are specific to one reaction and are essential for many life processes
• Factors such as temperature and pH affect enzyme activity
• Enzyme activity decreases as temperature or pH moves away from optimal levels
• Inhibitors can reduce or completely block enzyme activity
• Polarity is the property of having two opposite poles or ends
• Molecules with unequal distribution of charges are called polar molecules
• Water is a polar molecule with a slightly negative end and two slightly positive ends