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Matter refers to anything that has got mass and can occupy space. There are three states of matter, namely solid, liquid, and gas. Matter consists of numerous particles held together by forces of attraction, such as the intermolecular forces. The forces of attraction in the solid state extremely strong and, thus, hold particles closely together in fixed positions. However, the particles in a solid state can undergo vigorous vibrations in their fixed positions. Therefore, solids have definite shape and volume.
The forces of attraction in liquids are not as strong as in liquids and, therefore, the particles are not as close together as they are in solids. Therefore, particles in liquids can vibrate as well as move from one point to another. Liquids have volume and do not have definite shape, but assume the shape of the container.
The forces of attraction in gases are extremely weak and, therefore, particles are far apart from each other. Particles in gases can vibrate and move randomly from one point to another within the container. Therefore, gases do not have both volume and definite shape, but occupies the entire volume of the container, and assume the shape of the container. Unlike solids and liquids, which are not easily compressible, gases, are compressible because the particles are far apart from each other. Increase or decrease in pressure and temperature can change the state of a substance such as water between solid and gas.
Bromine has an atomic number of 35. A stable isotope of bromine has a mass number of 79 (79Br). How many neutrons and electrons does this isotope possess? Fluorine has an atomic number of 9. How many electrons does fluorine have in its valence shell? Fluoride (F-) is the anion formed from fluorine. How many protons and valence shell electrons does fluoride possess?
Atomic number of an element is the number of protons in the nuclear, which is the same as the number of electrons in the energy levels of atoms. Therefore, the number of electrons in Bromine is 35. The mass number of an atom depends on the number of protons and neutrons, which occupy the nucleus. Isotopes of elements exist because the number of neutrons differs from one atom to another. Therefore, there are 44 neutrons in the bromine with atomic number 79. The number of electrons in the valence shell of Fluorine is nine because the number of protons in the nucleus is the same as the number of electrons in the energy levels. Fluorine changes into fluoride ions by gaining one electron. The number of electrons increases by one while the number of protons remains the same, which is nine. Therefore, fluoride anions have ten electrons in their energy levels.
What is the difference between potential and kinetic energy? Describe the following types of reactions: • Synthesis reactions • Decomposition reactions • Exchange reactions.
Potential energy refers to the stored energy in objects, and it becomes available for use under right conditions, for instance, when the objects are in motion. On the other hand, kinetic energy refers to the energy that an object possesses or displays due to motion. Scientists have found kinetic energy to be absolutely relative to other stationary or moving objects while potential energy id not relative the object’s environment.
A synthesis reaction refers to the formation of a complex compound due to the combination of simple compounds. For instance, the combination of sulfur and iron is a synthesis reaction that results in the formation of iron (II) sulfide. Decomposition refers to a reaction in which complex molecules break down into simpler ones. For instance, water decomposes into oxygen and hydrogen molecules due to electrolysis. Exchange reaction refers to a chemical reaction in which two ions or atoms take the place of the other within the same molecule or in different molecules. For instance, the reaction of potassium iodide with lead (II) nitrate forms potassium nitrate and lead (II) iodide as the iodide anions exchanges with nitrate anions.
What are polar-covalent bonds? Explain how the polar-covalent bonds in water molecules allow it to act as a solvent to dissolve sodium chloride (NaCl).
Polar covalent bonds refer to the bonds between two atoms of anon-metals that have different electronegativities. The solvent property of water is the property of polar covalent bonding. Hydrogen and oxygen atoms share the bonding electrons unequally. This inequality results in the formation of partial positive charges with the ends of hydrogen and partial negative charges with the ends of oxygen. The opposite attractions cause the molecules of water to attract one another. Because of the partial charges and molecular interactions, water dissolves various solutes such as sodium chloride. The positive ends of hydrogen attract the chloride ions, and the negative ends of oxygen attract sodium ions. Water molecules surround sodium chloride ions and remove them from the sodium chloride crystal forming sodium chloride solution.
The activation energy of chemical reactions refers to the minimum quantity of energy that activates molecules or atoms to a condition that allows them to undergo physical transport or chemical transformation. Enzymes are the biological catalysts that ensure the activation energy is low in order to increase the rate of chemical reaction.
What is the difference between a solvent and a solute?
A solvent refers to a base substance in which the solute dissolves while a solute refers to a substance that dissolves into a solvent. For instance, water is a solvent and a crystal of sodium chloride is a solute.
You are asked to make a 1 molar (1M) solution of sodium bicarbonate (NaHCO3). What weight (in grams) would you add to 500ml of water to make this 1M solution? Show your working for this answer. Atomic weights: Na = 23; C = 12; O = 16; H = 1.
What is a strong acid? What is a strong base? What is a weak acid? What is a weak base?
A strong acid refers to an acid that undergoes complete ionization into a solution while a weak acid is an acid that undergoes partial ionization into solution. A strong base is a base that undergoes complete ionization into a solution while a weak base is a base that undergoes partial ionization into solution.
Is the concentration of hydrogen ions (H+) in the following fluids higher or lower than the concentration seen in distilled water (pH=7.00) •Gastric fluid •Semen •Vaginal fluid • Milk of Magnesia.
The concentration of hydrogen ions in gastric fluid is higher than the concentration seen in distilled water. Semen has a lower concentration of hydrogen ions than the concentration in distilled water while vaginal fluid has higher concentration of hydrogen ions than the concentration in distilled water. The concentration of hydrogen ions in the milk of magnesia is lower than the concentration seen in distilled water.
What is the difference between a monounsaturated fatty acid and a polyunsaturated fatty acid? What is the structure of a triglyceride?
Monounsaturated fatty acids refer to fatty acids with a single double bond along the chain of the fatty acid while polyunsaturated fatty acids are the fatty acids with two or more double bonds. The structure of triglycerides includes glycerol molecule and fatty acids.
Describe how the phosphate groups and the fatty acid tails of phospholipids are arranged in the lipid bi-layer that makes up the cell membrane.
The phospholipids occur in two layers and their fatty acid chains face each other. Phospholipids consist of polar heads and non-polar tails. The polar heads of the phospholipids face into the cell and to the outside the cell. The non-polar tails occur in between the polar heads.
Briefly, describe the structure of amino acids? Briefly, describe what a peptide bond is?
Amino acids contain a central carbon atom bonded to an r-group, hydrogen atom, amino group, and carboxyl group. The carbon chain has an amino and carboxyl groups at opposite ends. A peptide bond refers to a covalent bond that occurs between two molecules as the amino group of the first molecule reacts with the carboxyl group of the second molecule.
Briefly describe how energy can be stored in molecules of ATP? How can this energy be released?
Energy combines the Adenosine Diphosphate (ADP) with a third phosphate to form Adenosine Triphosphate (ATP) and water. Therefore, ATP stores energy due to the formation of a bond between ADP and a phosphate radical. Breaking the bond between ADP and phosphate radical releases the stored energy during combustion.
Briefly describe the difference between a, B, and y radiation rays and how far each can travel.
Alpha particles consist of helium nuclei that have two protons and two neutrons. Therefore, alpha particles have a positive charge due to protons. Beta particles consist of electrons that move extremely fast. These particles bear a negative charge because of the electrons. Gamma rays refer to an electromagnetic radiation that is neutral in nature. Alpha particles have a poor penetration power a piece of paper can block them. Beta particles penetrate better than alpha particles, but a piece of aluminum sheet can block them. Gamma rays have an extremely penetrating power and the only thing that can block the penetration is thick lead.