[GET] Chemistry Chapter 15 Test Answers
This includes advances in medicine, communication, transportation, building infrastructure, food science and agriculture, and nearly every other technical field that you can imagine. Chemistry is one branch of science. Science is the process by...
[DOWNLOAD] Chemistry Chapter 15 Test Answers | updated!
Although we divide science into different fields, there is much overlap among them. For example, some biologists and chemists work in both fields so much that their work is called biochemistry. Similarly, geology and chemistry overlap in the field...
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Elements and Compounds Any sample of matter that has the same physical and chemical properties throughout the sample is called a substance. There are two types of substances. A substance that cannot be broken down into chemically simpler components is an element. Aluminum, which is used in soda cans, is an element. A substance that can be broken down into chemically simpler components because it has more than one element is a compound. Water is a compound composed of the elements hydrogen and oxygen. Today, there are about elements in the known universe which are organized on a fundamental chart called the Periodic Table of Elements Fig.
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In contrast, scientists have identified tens of millions of different compounds to date. The smallest part of an element that maintains the identity of that element is called an atom. Atoms are extremely tiny; to make a line 1 inch long, you would need million iron atoms! Similarly, the smallest part of a compound that maintains the identity of that compound is called a molecule. Molecules are composed of atoms that are attached together and behave as a unit Fig. Scientists usually work with millions of atoms and molecules at a time. When a scientist is working Figure 1. Lower Panel To the left of the arrow is shown one atom of oxygen and two atoms of hydrogen. Each of these represent single elements. When they are combined on the righthand side, they form a single molecule of water H2O.
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Note that water is defined as a compound, because each single molecule is made up of more than one type of element, in this case, one atom of oxygen with two atoms of hydrogen. However, scientists can also describe chemical events on the level of individual atoms or molecules, which is referred to as the microscopic viewpoint. We will see examples of both macroscopic and microscopic viewpoints throughout this book Figure 1. Although we do not notice it from a macroscopic perspective, matter is composed of microscopic particles so tiny that billions of them are needed to make a speck that we can see with the naked eye.
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Chemistry 10th Class Chapter 15 Notes
A metal alloy, such as steel, is an example of a solid solution. Air, a mixture of mainly nitrogen and oxygen, is a gaseous solution. Homogeneous Mixtures. A mixture contains more than one substance. In the upper panel you see an example of a heterogeneous mixture of oil and water. The mixture is heterogeneous because you can visibly see two different components in the mixture. In the lower panel, you see an example of a homogeneous mixture, coffee. It is homogeneous because you cannot distinguish the many different components that make up a cup of coffee water; caffeine; coffee alkaloids and tannins. It looks the same throughout. If the mixture is homogeneous and is also see through or clear, it is called a solution. In our example, the coffee is a solution; however, a concentrated espresso may be very opaque and would only be homogeneous mixture, not a solution. States of Matter Another way to classify matter is to describe it as a solid, a liquid, or a gas, which was done in the examples of solutions, above.
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These three descriptions, each implying that the matter has certain physical properties, represent the three phases of matter. A solid has a definite shape and a definite volume. Liquids have a definite volume but not a definite shape; they take the shape of their containers. Gases have neither a definite shape nor a definite volume, and they expand to fill their containers. We encounter matter in each phase every day. In fact, we regularly encounter water in all three phases: ice solid , water liquid , and steam gas. We know from our experience with water that substances can change from one phase to another if the conditions are right. Typically, varying the temperature of a substance and, less commonly, the pressure exerted on it can cause a phase change or a physical process in which a substance goes from one phase to another Figure 1.
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NCERT Solutions For Class 12 Chemistry Chapter 15-Download
Phase changes have particular names depending on what phases are involved, as summarized in Table 1. Analyzing Phase Changes. Upper panel A photo of boiling water demonstrates the phase change of water from the liquid to the gaseous phase. Note that phase changes are a physical property of a molecule. The water is still chemically the same H2O in the solid, liquid, or gaseous state.
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General Chemistry II (CHEM 1412)
Lower panel Change in temperature can cause phase changes. Above is the temperature scale for the phase changes of water. If you add heat to solid ice, water will melt at 0oC and boil at oC. If you remove heat from gaseous water, it will condense into the liquid state at oC and freeze at 0oC. In summary, Figure 1. Generally, they follow a process called the scientific method. The scientific method is an organized procedure for learning answers to questions. The steps may not be as clear-cut in real life as described here, but most scientific work follows this general outline. Propose a hypothesis. A scientist generates a testable idea, or hypothesis, to try to answer a question or explain how the natural universe works. Some people use the word theory in place of hypothesis, but the word hypothesis is the proper word in science.
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For scientific applications, the word theory is a general statement that describes a large set of observations and data. A theory represents the highest level of scientific understanding, and is built from a wide array of factual knowledge or data. Test the hypothesis. A scientist evaluates the hypothesis by devising and carrying out experiments to test it. If the hypothesis passes the test, it may be a proper answer to the question. If the hypothesis does not pass the test, it may not be a good answer. Refine the hypothesis if necessary. Depending on the results of experiments, a scientist may want to modify the hypothesis and then test it again.
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Sometimes the results show the original hypothesis to be completely wrong, in which case a scientist will have to devise a new hypothesis. Not all scientific investigations are simple enough to be separated into these three discrete steps. But these steps represent the general method by which scientists learn about our natural universe.
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Identify them: They have a sour taste. They turn bromothymol blue from blue to yellow. They turn red litmus paper to blue. They have a slippery feeling. They react with active metals producing hydrogen gas. Identify them with the best answer: An acid is an electron pair acceptor. A base is a proton acceptor. A base is a substance that contains the OH group and produces OH- ions in aqueous solution. An acid is a proton donor. All but one of the following are the consequences of the leveling effect of water. Which is NOT.
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Baker, Mrs. (Science) / AP Chemistry
Polymers which melts on heating are thermosoftening as they have weak intermolecular forces between them. Thermosetting polymers do not melt on heating as they have strong cross-links between them. Thermosetting polymers have long chains cross-linked which are difficult to break so they do not melt on heating. They join together to form large structures. The yield of ammonia increases with an increase in pressure as an increase in pressure will shift the reaction to the less gas moles side. So the reaction will shift towards the right. An increase in temperature decreases the yield of ammonia as the reaction is exothermic. So an increase in temperature will shift the equilibrium to the left. We know that by increasing pressure improves the yield of ammonia and increases the rate of reaction But pressure cannot be raised any higher for economic reasons. Making a plant to withstand higher pressures costs more. Generation of higher pressures requires more energy and increased safety risk e.
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So we use moderate pressure and temperature and use a catalyst to increase the rate of both forward and reverse reactions at the same rate. No effect of iron on the yield. The catalyst helps the equilibrium to be attained faster. Reaction profile diagram of the reaction with and without the catalyst b. So iron oxide can be displaced by carbon to form iron and carbon dioxide. In the reaction above the desired product is iron. Carbon dioxide is a greenhouse gas and it causes global warming so it is important that the carbon dioxide is not released in the atmosphere.
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Chemistry Chapter 15 Test
In pure iron, the layers can slide over one another therefore the metal is malleable and ductile. In steel, iron is mixed with carbon which is of a different sizes than iron. Carbon disrupts the regular arrangement of the layers so they can no longer slide over one another. Paint acts as a barrier and prevents the reaction of iron with oxygen and water. Magnesium prevents iron by the method of sacrificial protection. We know that magnesium is more reactive than iron. So it donates electrons or is oxidized or reacts in preference to iron preventing iron from rusting. Answer Thermosoftening polymers have weak intermolecular forces between them. So low heat can overcome those forces therefore they melt at a lower temperature.
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Oxford University Press | Online Resource Centre | Chapter 15
On the other hand, thermosetting polymers have strong cross-linkages between them so they are difficult to melt. It is so-called because concrete reinforced with metal is a mixture of materials or a mixture of concrete, sand, and gravel, therefore it is a composite. Reversible reaction. Equilibrium is a condition when the rate of the forward reaction is equal to the rate of the reverse reaction. So an increase in pressure will shift the reaction to the less gas moles side according to the Le chatelliers principle so high pressure will give a high yield of ammonia. The above reaction is also exothermic. So low temperature will shift the reaction to the exothermic side increasing the yield of ammonia. So to have a high yield of ammonia, high pressure and low temperature are required. But these conditions are not economical. High pressure involves high energy cost and is expensive to set up.
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On the other hand, low temperature will make the rate of reaction too slow that it will not be economically profitable. So to have the high yield of ammonia with the high rate we use moderate temperature and pressure and to increase the rate at these conditions iron catalyst is used. Also, the unreacted gases are recycled back to increase the yield.
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NCERT Solutions For Class 12 Chemistry Chapter 15 - Polymers
Answer: c zinc Iron is coated with zinc to protect it from corrosion and formation of rust. The zinc coating will also give it a shiny appearance. Answer: A positively-charged body has a deficit of electrons. Page No Electronic current flows from positive to negative. True or false? Answer: False. Since electrons flow from a negatively charged body excess of electrons to a positively charged one deficit of electrons , electronic current will also flow from the negative to the positive charge. Page No A battery is used as a driving force in an electric circuit. Answer: True. Electromotive force is the driving force in an electric circuit, which pushes the electrons carrying the charge around the circuit. This force is created by an electric cell or a battery.
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Answer: Electrons are responsible for the flow of electric current. They flow from a negatively charge body with excess of electrons to a positively charged one with deficit of electrons. Page No Metals are conductors of electricity. Answer: Metals are conductors of electricity, as they allow electric current to flow through them. Answer: LED light is better for use in a tester for testing conductivity of liquids because it lights up even with a small amount of current. Answer: When electricity is passed through tap water, the gases hydrogen and oxygen are evolved. Page No Ions may be positively charged or negatively charged.
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Ions may be positively charged or negatively charged. Positively charged ions are called cations, while the negatively charged ions are called anions. Answer: An electric current brings about chemical changes in most conducting liquids. Page No Question 1: How will you show experimentally that an electric current can bring about a chemical change? What is this phenomenon called? Answer: When copper sulphate is dissolved in water, it breaks into positively charged ions cations and negatively charged ions anions. Cations move towards the negatively charged electrode cathode , and anions move towards the positively charged electrode anode , thereby depositing copper at the cathode.
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World Of Chemistry
This experiment shows that an electric current can bring about a chemical change and the phenomenon is called electrolysis. Page No What is electroplating? How will you carry out electroplating of copper in the laboratory? Answer: Electroplating is the process of coating a thin layer of a metal such as gold, silver, chromium, etc. This is done to protect the metal or to lend it an attractive look. For electroplating copper in the laboratory, the following steps are to be taken: Fill three-forth of a beaker with copper sulphate solution. Hammer a copper wire to flatten it; then connect it to the positive terminal of a battery. Connect a spoon to the negative terminal of the battery.
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Dip the copper wire as well as the spoon in the copper sulphate solution, and let the current pass. At the end of this experiment, you will observe a layer of copper formed over the spoon. Page No List four uses of electroplating, giving the reason for electroplating in each case. Answer: Four uses of electroplating are: Iron used to make bridges and automobiles is electroplated with zinc in order to prevent rusting. Gold or silver is electroplated on jewellery made from a cheaper metal in order to make the jewellery look attractive. Iron used to make food-storage utensils is electroplated with tin to prevent the food from getting spoiled by reacting with iron.
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Multiple Choice Questions And Answers
Chromium is a shiny metal that never corrodes and also resists scratches. It is electroplated on a cheaper metal like iron to make it corrosion and scratch-resistant. Chromium-plated iron is used for manufacturing car parts, wheel rims, taps, etc. Answer: During electroplating, copper is deposited at the cathode. Page No Expensive metals are protected by electroplating. Objects made from less expensive metals are electroplated with expensive metals, so that they look more attractive and beautiful. Answer: An LED light consumes less electrical energy than an electric bulb. Page No Mercury is a liquid and conducts electricity.
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FindTestAnswers.com
Do you think it is an electrolyte? HINT: Mercury is a metal that is a liquid at room temperature. Answer: No. Neither mercury produce ions in a solution nor in its liquid state; therefore, it cannot be used as an electrolyte. However, it has free electrons that can well-conduct electricity. Page No Question 3: Solid copper sulphate does not conduct electricity, but when it is dissolved in water, it does conduct electricity. Answer: One of the essential requirements for conducting electricity is the presence of free electrons or ions. In its solid state, the ions of copper sulphate ionic compound are immobile; therefore, it cannot conduct electricity. But when it is dissolved in water, it dissociates into copper ions and sulphate ions. These dissociated ions of copper sulphate conduct electricity. Page No Copper conducts electricity through electrons, whereas salt solution conducts electricity through ions.
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Chapter 15 - Water And Aqueous Systems - Standardized Test Prep - Page 515: 9
Do you agree? Answer: Yes, we agree that copper conducts electricity through electrons, while a salt solution conducts electricity through ions. Copper is a metal and has free electrons to conduct electricity, whereas a salt solution is an electrolytic solution. The salt ionizes into its constituent ions in the solution. These ions travel towards the oppositely charged electrodes and conduct electricity. Page No Why should you not touch electrical appliances with wet hands? Answer: Water is a good conductor of electricity. Page No Question 6: After doing Activity 5 electroplating a spoon with copper , a student interchanged the connections of the copper plate and the spoon. What do you think will happen now? Answer: If a student interchanges between the copper wire and the spoon during electroplating, the copper ions deposited on the spoon will move back to their place of origin.
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Chemistry Study Guide On Chapter 15 – Ms. O'Connor's Web Site
Page No Question 7: We should not try to put out a fire in an electrical appliance by pouring water on it. Therefore, if we pour water in order to put out a fire in an electric appliance, we may get electrocuted. So, we should not use water to put out a fire in an electric appliance. Page No Question 8: Instead of taking the trouble of electroplating metals with chromium for making car parts, taps, cycle parts, etc. Answer: Different metals have different properties and on the basis of these properties they are used. Chromium is only used for electroplating metals in order to increase their life span. Besides this, chromium is expensive. So, instead of making the whole item with chromium, a layer of chromium is only added to lend a lustrous look to the item.
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NCERT Solution For Class 12 Chemistry Chapter 15 - Polymers | AESL
Page No What is electric current? Answer: A continuous and directed flow of negative charges i. Page No How is electronic current different from conventional current? Answer: Conventional current flows from a positively charged body to a negatively charged one, while the electronic current flows from a negatively charged body to a positively charged one. This is the difference between electronic current and conventional current.
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Page No Differentiate between conductors and insulators. Answer: Conductors Insulators A conductor allows the electric current to flow through it when a potential difference is applied across its ends. An insulator does not conduct electricity unless extremely high potential difference is applied across its ends. A good conductor of electricity is generally a good conductor of heat. Insulators do not conduct heat. Conductors have free electrons on its surface. Insulators have bonded electrons on its surface. Page No What is an electrolyte? Answer: A substance which conducts electricity in its liquid state or when it is dissolved in water to break-up chemically is called an electrolyte. Most soluble salts, acids and bases are electrolytes.
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Thursday, May 27, 2021
Chemistry Chapter 15 Test Answers
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