1st Quarter Reviewer in Physical Science PDF

1st Quarter Reviewer in Physical Science Important Terms: Stellar nucleosynthesis It is the process by which elements are formed within stars. CNO Cycle a method where the main-sequence stars hotter than 15 million K could facilitate the production of helium once carb...

1st Quarter Reviewer in Physical Science Important Terms: Stellar nucleosynthesis It is the process by which elements are formed within stars. CNO Cycle a method where the main-sequence stars hotter than 15 million K could facilitate the production of helium once carbon was present from alpha processes. Miscibility It is the ability of two liquids to mix in all proportions. Solubility It refers to the ability of a solute to dissolve in a certain amount of solvent. Electronegativity tendency of an atom to attract shared electrons when forming chemical bond. Molecule a group of two or more atoms held together by chemical bond. Polarity it refers to the distribution of electric charge around atoms, chemical groups, or molecules. Synthesis of Elements The invention of the device called cyclotron paved the way for transmuting one element into another artificially. Transuranic elements are synthetic elements with atomic numbers higher than that of Uranium (Z = 92). Superheavy elements are elements with atomic numbers beyond 103. These are produced by bombarding heavy nuclear targets with accelerated heavy projectiles. Polarity of Molecules Polar covalent bonds occur when electron pairs are unequally shared. The difference in electronegativity between atoms is 0.5 – 1.9 Non-polar covalent bonds occur when electron pairs are shared equally or the difference in electronegativity between atoms is less than 0.5 Ionic bonds the difference in electronegativity between atoms is 2.0 above Properties of Liquids 1. Surface tension is a phenomenon between liquids and gases. It causes objects that usually sink due to their higher density to swim. 2. Viscosity the resistance of a liquid to flow. The greater the viscosity, the slower the liquid flows. 3. Vapor pressure a pressure exerted by molecules that have enough energy to escape the surface, as Temperature ↑, Vapor Pressure ↑, Evaporation ↑ 4. Boiling point the boiling point is the temperature at which the vapor pressure of a liquid is equal to the external pressure. The boiling point of a liquid is the temperature at which the liquid converts into a gas. The normal boiling point is the temperature at which the liquid converts to a gas when the external pressure is 1 atm. The normal boiling point of water is 100oC. 5. Molar heat of vaporization (ΔHvap) the molar heat of vaporization (ΔHvap) is the energy required to vaporize 1 mole of a liquid at a given temperature. H is the symbol for enthalpy, which means heat content at a given standard condition. Molar heats of vaporization and boiling points of selected substances INTERMOLECULAR FORCES Intermolecular forces are forces that form between molecules, atoms, or ions. Intramolecular forces are forces that hold molecules together. They are forces within a molecule. Four main types of Intermolecular forces: 1. ION-ION INTERACTION Exists between oppositely charged ions. It occurs between ionic compounds. Most ion-ion interaction is strong and compounds which have them have high melting and boiling points. Ions of like charges repel while opposite charges attract. 2. DIPOLE-DIPOLE INTERACTION Occurs between polar molecules. Polar molecules are also referred to as “dipoles” due to their two poles. This is due to the partial positive pole and the partial negative pole of the molecule. Average dipole-dipole interaction is relatively weak, around 4kJ/ mol. 2. DIPOLE-DIPOLE INTERACTION Occurs between polar molecules. Polar molecules are also referred to as “dipoles” due to their two poles. This is due to the partial positive pole and the partial negative pole of the molecule. Average dipole-dipole interaction is relatively weak, around 4kJ/ mol. 3. HYDROGEN BONDING Is a very strong dipole-dipole interaction. Hydrogen bond occurs in polar molecules containing H and any one of the highly electronegative elements, in particular F, O, N. Hydrogen tends to be strongly positive due to the strong tendencies of F, O, or N to attract the electron towards it. 4. DISPERSION FORCES also known as LONDON FORCES in honor of Fritz London. Van der Waals forces were named after him to pay tribute to his great contribution on the study of liquids and gases. Dispersion Forces or London Forces is present in all molecules. It is the only force present in nonpolar molecules. It is very weak and acts in very small distances. Biological Macromolecules Carbohydrate  The word carbohydrate may be broken down to carbon and hydrate  Carbohydrates can be seen as hydrates of carbon  Carbohydrates are the primary energy source of the human body  Another term for carbohydrate is saccharide  Derived from the Latin word “saccharum” referring to sugar a common carbohydrate Simple sugars Monosaccharide (one saccharide) 1. Glucose  Used in dextrose,  blood sugar; the form utilized by the human body 2. Galactose  Found in milk and milk products 3. Fructose  Found in fruits and honey  The above monosaccharides all have the same chemical formula of C6H12O6 Difference in its properties  Galactose (163-169oC) has a higher melting point than glucose (148-155oC).  Glucose is sweeter than galactose. Disaccharide (two saccharides) 1. Maltose  Glucose + Glucose  Found in malt 2. Sucrose  Glucose + Fructose  Found in regular table sugar, sugarcane, and sugar beet 3. Lactose  Glucose + Galactose  Found in milk and milk products Complex sugars Polysaccharide (many saccharides) 1. Starch / Amylose  Composed of 250 - 400 glucose molecules connected via α-1-4-glycosidic bond  Storage form of glucose in plants Polysaccharide (many saccharides) 2. Amylopectin  Like amylose but has more branches attached via α-1-6 glycosidic bond  Storage form of glucose in plants 3. Glycogen  Composed of more glucose, more highly branched  Storage form of glucose in animals, stored in the liver and muscles 4. Cellulose  Composed of glucose units connected via β-1-4 glycosidic bond, linear chain arranged in a parallel manner  Structural material in plants cell wall in wood, wood fiber  Cannot be digested by humans Proteins  Proteins are composed of amino acids in the similar way that carbohydrates are composed of saccharides.  The word protein came from the Greek term proteios meaning first.  Proteins are composed of four elements, namely, carbon, hydrogen, oxygen and nitrogen  Sulfur and other metals are sometimes also found in proteins  An amino acid is a molecule that has an amine and a carboxyl group.  There are 20 amino acids.  The combination of many amino acids creates protein.  Amino acids are joined together with a peptide bond.  Proteins are also called polypeptides.  Protein can acquire many configurations. Common examples are α-helix and β-pleated sheets. Examples of proteins and their structure and functions are: 1. Keratin is a structural protein found in hair, skin, and nails. It is a highly cross-linked protein containing α-helix and β-pleated sheets. Sheep’s wool is made largely of keratin. 2. Fibroin / Silk protein Fibroin is found in silk. Silk has a smooth and soft texture. It is one of the strongest natural fibers that have high resistance to deformation. It is also a good insulation. Silk is primarily composed of β-pleated sheets. The long polypeptide chain doubles back on its own running parallel connected together by H-bonds. 3. Collagen is a major insoluble fibrous protein found in connective tissues such as tendons, ligaments, skin, cartilage and the cornea of the eye. It comprises as much as 30% of proteins in animals. Its strength is attributed to its triple helix structure comprising of α-helices braided together. When several triple helices combine, they form the fibrils that make up connective tissues. Enzymes function to catalyze chemical reactions. They either speed up a reaction, lower the needed energy for a reaction to take place, or bind substances to their specific partners. Enzymes themselves are very specific as can be seen in their shape. Examples of Enzymes Myoglobin is a polypeptide that stores oxygen in muscles. It is a globular protein comprised of 153 amino acids in a single polypeptide chain. It contains a heme group which has an iron (II) ion at its center. This is where the oxygen is stored. Hemoglobin is a globular protein that carries oxygen from the lungs to the bloodstream. It is composed of four sub-units, each containing a heme group that enables it to transport four oxygen molecules at a time. Lipids  The word lipid comes from the Greek word lipos which means fat.  Lipids are a family of biomolecules having varied structures. They are grouped together simply because of their hydrophobicic property (water-fearing). They are soluble in non-polar solvents such as ether, acetone, and benzene.  Lipids can be classified into four categories: 1. Wax 2. Triglycerides 3. Phospholipids 4. Steroids Fatty acids Fatty acids are long-chain carboxylic acids that are insoluble in water. Fatty acids can be saturated or unsaturated. Saturated fatty acids contain single bonds in its hydro-carbon chain whereas unsaturated fatty acids contain double bonds. Triglyceride Fat and oil are the most common examples of lipids. They are under triglycerides because they are composed of glycerol and three fatty acids. Phospholipids contains glycerol, two fatty acids, and a phosphate group. Unlike other lipids, phospholipids have a polar and non-polar end. This property allows it to transport molecules in the bloodstream. It is also a major component in the cell membrane. The two parts of a phospholipid 1. Hydrophilic head (phosphate group) 2. Hydrophobic tail (fatty acid group) Nucleic Acid play an essential role in the storage, transfer, and expression of genetic information. Nucleic acid was discovered by a twenty-four year-old Swiss physician named Friedrich Miescher in 1868. He was puzzled that an unknown substance in white blood cells did not look a lot like carbohydrates, proteins, or lipids. He was able to isolate the substance from the nucleus and initially called it nuclein.  He eventually was able to break down nuclein into protein and nucleic acids. He found out that nucleic acids contain carbon, hydrogen, oxygen, nitrogen, and phosphorus. Nucleic acids are also known as polynucleotides. The most common examples of nucleic acids are 1. DNA (deoxyribonucleic acid) 2. RNA (ribonucleic acid) Three parts of nucleotide 1. Nitrogenous base 2. Five-carbon carbohydrate or sugar 3. Phosphate group The nitrogenous bases of DNA and RNA are: DNA’s : Adenine (A), Guanine (G), Cytosine (C), and Thymine (T) RNA’s : Adenine (A), Guanine (G), Cytosine (C), and Uracil (U) DNA has a different sugar group than RNA. DNA has deoxyribose while RNA has ribose. The sequence of the base pairs in one’s DNA is unique for every organism (except for identical twins). The DNA and the cell containing it determine the kind of protein that will be synthesized. The different proteins are then responsible for the processes that carbohydrates, lipids, proteins, and other substances in the body undertake.