Week 008 Course Module-How Chemical Changes Take Place PDF

Preview

Summary

HOPE IT HELPS...

Description

Catalysts

Jean Brainard, Ph.D.

Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required)

To access a customizable version of this book, as well as other interactive content, visit www.ck12.org

CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-source, collaborative, and web-based compilation model, CK-12 pioneers and promotes the creation and distribution of high-quality, adaptive online textbooks that can be mixed, modified and printed (i.e., the FlexBook® textbooks).

Copyright © 2016 CK-12 Foundation, www.ck12.org

(http://creativecommons.org/ licenses/by-nc/3.0/), as amended and updated by Creative Com mons from time to time (the “CC License”), which is incorporated herein by this reference.

The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by Complete terms can be found at http://www.ck12.org/about/ terms-of-use. federal, state, and international laws. Any form of reproduction of this book in any format or Printed: August 19, 2016 medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms. Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users AUTHOR in accordance with the Creative Commons Attribution- Jean Brainard, Ph.D. Non-Commercial 3.0 Unported (CC BY-NC 3.0) License

www.ck12.org Chapter 1. Catalysts

CHAPTER

1 Catalysts

• Define catalyst. • Explain how catalysts work. • Identify the role of catalysts in living things.

The tunnel through this mountain provides a faster route for cars to get to the other side of the mountain. If a chemical reaction were like a road to the other side of a mountain, a catalyst would be like a tunnel. What Is A Catalyst? A catalyst is a substance that increases the rate of a chemical reaction. The presence of a catalyst is one of several factors that influence the rate of chemical reactions. (Other factors include the temperature, concentration, and surface area of reactants.) A catalyst isn’t a reactant in the chemical reaction it speeds up. As a result, it isn’t changed or used up in the reaction, so it can go on to catalyze many more reactions.

Q: How is a catalyst like a tunnel through a mountain? A: Like a tunnel through a mountain, a catalyst provides a faster pathway for a chemical reaction to occur. How Catalysts Work Catalysts interact with reactants so the reaction can occur by an alternate pathway that has a lower activation energy. Activation energy is the energy needed to start a reaction. When activation energy is lower, more reactant particles have enough energy to react so the reaction goes faster. Many catalysts work like the one in the Figure 1.1. The catalyst brings the reactants together by temporarily bonding with them. This makes it easier and quicker for the reactants to react together. Q: In the Figure 1.1, look at the energy needed in the catalytic and non-catalytic pathways of the reaction. How does the amount of energy compare? How does this affect the reaction rate along each pathway? 1 www.ck12.org

FIGURE 1.1

A: The catalytic pathway of the reaction requires far less energy. Therefore, the reaction will occur faster by this pathway because more reactants will have enough energy to react. Catalysts in Living Things Chemical reactions constantly occur inside living things. Many of these reactions require catalysts so they will occur quickly enough to support life. Catalysts in living things are called enzymes. Enzymes may be extremely effective. A reaction that takes a split second to occur with an enzyme might take many years without it! More than 1000 different enzymes are necessary for human life. Many enzymes are needed for the digestion of food. An example is amylase, which is found in the mouth and small intestine. Amylase catalyzes the breakdown of starch to sugar. You can see how it affects the rate of starch digestion in the Figure 1.2.

FIGURE 1.2 2

www.ck12.org Chapter 1. Catalysts Q: If you chew a starchy food such as a soda cracker for a couple of minutes, you may notice that it starts to taste slightly sweet. Why does this happen? A: The starches in the cracker start to break down to sugars with the help of the enzyme amylase. Try this yourself and see if you can taste the reaction.

Summary • A catalyst is a substance that increases the rate of a chemical reaction. • A catalyst provides an alternate pathway for the reaction that has a lower activation energy. When activation energy is lower, more reactant particles have enough energy to react, so the reaction occurs faster. • Chemical reactions constantly occur inside living things, and many of them require catalysts to occur quickly enough to support life. Catalysts in living things are called enzymes.

Review 1. What is a catalyst? 2. How does a catalyst speed up a chemical reaction? 3. What are enzymes? Why are they important?

Explore More Watch the video showing a chemical reaction both with and without a catalyst. Then answer the questions below.

MEDIA Click image to the left or use the URL below. URL: https://www.ck12.org/flx/render/embeddedobject/82348

1. Write the chemical equation for the reaction that is demonstrated in the video. 2. What chemical is used to catalyze the reaction? 3. Describe two observations that provide evidence that the reaction has occurred after the addition of

the catalyst. Resources

3 www.ck12.org

MEDIA Click image to the left or use the URL below. URL: https://www.ck12.org/flx/render/embeddedobject/185405

MEDIA Click image to the left or use the URL below. URL: https://www.ck12.org/flx/render/embeddedobject/185443

References 1. Zachary Wilson. Activation energy difference between catalyzed and non-catalyzed reactions . CC BYNC 3.0 2. Zachary Wilson. CK-12 Foundation . CC BY-NC 3.0

4

Chemical Change Ck12 Science

Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required)

To access a customizable version of this book, as well as other interactive content, visit www.ck12.org

Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms.

Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons AttributionNon-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as CK-12 Foundation is a non-profit organization with a amended and updated by Creative Com mons from mission to reduce the cost of textbook materials for the time to time (the “CC License”), which is incorporated K-12 market both in the U.S. and worldwide. Using an herein by this reference. open-source, collaborative, and web-based compilation model, CK-12 pioneers and promotes the creation and Complete terms can be found at distribution of high-quality, adaptive online textbooks http://www.ck12.org/about/ terms-of-use. that can be mixed, modified and printed (i.e., the FlexBook® textbooks). Printed: December 19, 2016 Copyright © 2016 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by AUTHOR Ck12 Science federal, state, and international laws.

www.ck12.org Chapter 1. Chemical Change

CHAPTER

Change

Learning Objectives • Define chemical change. • Give examples of chemical changes.

1 Chemical

Do you like to cook? Cooking is a valuable skill that everyone should have. Whether it is fixing a simple grilled cheese sandwich or preparing an elaborate meal, cooking demonstrates some basic ideas in chemistry. When you bake bread, you mix some flour, sugar, yeast, and water together. After baking, this mixture has been changed to form bread, another substance that has different characteristics and qualities from the original materials. The process of baking has produced chemical changes in the ingredients that result in bread being made.

Chemical Change Most of the elements we know about do not exist freely in nature. Sodium cannot be found by itself (unless we prepare it in the laboratory) because it interacts easily with other materials. On the other hand, the element helium does not interact with other elements to any extent. We can isolate helium from natural gas during the process of drilling for oil. A chemical change produces a different materials than the ones we started with. One aspect of the science of chemistry is the study of the changes that matter undergoes. If all we had were the elements and they did nothing, life would be very boring (in fact, life would not exist since the elements are what make up our bodies and sustain 1 www.ck12.org us). But the processes of change that take place when different chemicals are combined produce all the materials that we use daily. One type of chemical change (already mentioned) is when two elements combine to form a compound. Another type involves the breakdown of a compound to produce the elements that make it up. If we pass an electric current through bauxite (aluminum oxide, the raw material for aluminum metal), we get metallic aluminum as a product.

FIGURE 1.1 Electrolytic production of aluminum.

However, the vast majority of chemical changes involve one compound being transformed into another compound. There are literally millions of possibilities when we take this approach to chemical change. New compounds can be made to produce better fabrics that are easier to clean and maintain; they can help preserve food so it doesn’t spoil as quickly; and, we can make new medicines to treat diseases all made possible by studying chemical change.

MEDIA Click image to the left or use the URL below. URL: https://www.ck12.org/flx/render/embeddedobject/191295

Summary • A chemical change produces a different materials than the ones we started with. Review 1. What is a chemical change? 2. List three types of chemical changes.

References 1. Jon Sullivan. http://commons.wikimedia.org/wiki/File:Marinated_grill_swordfish.jpeg . 2 www.ck12.org Chapter 1. Chemical Change 2. Ronny Jacques. http://commons.wikimedia.org/wiki/File:Alcan_Arvida_1943.jpg .

3

Recognizing Chemical Reactions Jean Brainard, Ph.D.

Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required)

To access a customizable version of this book, as well as other interactive content, visit www.ck12.org

Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms.

Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons AttributionNon-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as CK-12 Foundation is a non-profit organization with a amended and updated by Creative Com mons from mission to reduce the cost of textbook materials for the time to time (the “CC License”), which is incorporated K-12 market both in the U.S. and worldwide. Using an herein by this reference. open-source, collaborative, and web-based compilation model, CK-12 pioneers and promotes the creation and Complete terms can be found at distribution of high-quality, adaptive online textbooks http://www.ck12.org/about/ terms-of-use. that can be mixed, modified and printed (i.e., the FlexBook® textbooks). Printed: August 24, 2016 Copyright © 2016 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by AUTHOR federal, state, and international laws. Jean Brainard, Ph.D.

www.ck12.org Chapter 1. Recognizing Chemical Reactions

CHAPTER

1

Recognizing Chemical Reactions • Identify potential signs that a chemical reaction has occurred.

Look at the girl’s hair in the photo above. It has obviously changed color. The process in which this occurred involved chemical reactions. How do you know that chemical reactions have occurred? The change in color is the most obvious clue. What’s Your Sign? A change in color is just one of several potential signs that a chemical reaction has occurred. Other potential signs include: • Change in temperature-Heat is released or absorbed during the reaction. • Production of a gas-Gas bubbles are released during the reaction. • Production of a solid-A solid settles out of a liquid solution. The solid is called a precipitate.

MEDIA Click image to the left or use the URL below. URL: https://www.ck12.org/flx/render/embeddedobject/185317

1 www.ck12.org

Examples of Chemical Reactions Look carefully at the Figures 1.1, 1.2, and 1.3. All of the photos demonstrate chemical reactions. For each photo, identify a sign that one or more chemical reactions have taken place.

FIGURE 1.1 A burning campfire can warm you up on a cold day.

FIGURE 1.2 Dissolving an antacid tablet in water produces a fizzy drink.

FIGURE 1.3 Adding acid to milk produces solid curds of cottage cheese.

Q: Did you ever make a “volcano” by pouring vinegar over a “mountain” of baking soda? If you did, you probably saw the mixture bubble up and foam over. Did a chemical reaction occur? How do you know? A: Yes, a chemical reaction occurred. You know because the bubbles are evidence that a gas has been produced and production of a gas is a sign of a chemical reaction. 2 www.ck12.org Chapter 1. Recognizing Chemical Reactions Summary • Potential signs that chemical reactions have occurred include a change in color, change in temperature, production of a gas, and production of a solid precipitate. Review 1. How can you tell whether a change in matter is caused by a chemical reaction? 2. When water freezes, it changes to ice. Is this a chemical reaction? Why or why

not? Resources

MEDIA Click image to the left or use the URL below. URL: https://www.ck12.org/flx/render/embeddedobject/177395

References 1. CopyrightFreePhotos.HQ101.com. A burning campfire is a chemical reaction . Public Domain 2. Image copyright Mikael Damkier, 2014. Dissolving an antacid tablet is a chemical reaction . Used under license from Shutterstock.com 3. Image copyright eelnosiva, 2014. Adding acid to milk to form cottage cheese is a chemical reaction . Used under license from Shutterstock.com

3

Chemical Reaction Rate Jean Brainard, Ph.D.

Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required)

To access a customizable version of this book, as well as other interactive content, visit www.ck12.org

Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms.

Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons AttributionNon-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as CK-12 Foundation is a non-profit organization with a amended and updated by Creative Com mons from mission to reduce the cost of textbook materials for the time to time (the “CC License”), which is incorporated K-12 market both in the U.S. and worldwide. Using an herein by this reference. open-source, collaborative, and web-based compilation model, CK-12 pioneers and promotes the creation and Complete terms can be found at distribution of high-quality, adaptive online textbooks http://www.ck12.org/about/ terms-of-use. that can be mixed, modified and printed (i.e., the FlexBook® textbooks). Printed: August 25, 2016 Copyright © 2016 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by AUTHOR federal, state, and international laws. Jean Brainard, Ph.D.

www.ck12.org Chapter 1. Chemical Reaction Rate

CHAPTER

1 Chemical

Reaction Rate • Define chemical reaction rate. • Identify factors that influence the rate of chemical reactions.

Sodium reacts violently with water. That’s what is happening in the picture above. Why does sodium have such explosive reactions? It’s because the reactions occur so quickly. How Fast Does It Go? How fast a chemical reaction occurs is called the reaction rate. Several factors affect the rate of a given chemical reaction. They include the: • temperature of reactants. • concentration of reactants. • surface area of reactants. • presence of a catalyst. Temperature of Reactants When the temperature of reactants is higher, the rate of the reaction is faster. At higher temperatures, particles of reactants have more energy, so they move faster. As a result, they are more likely to bump into one another and to collide with greater force. For example, food spoils because of chemical reactions, and these reactions occur faster at higher temperatures (see the bread on the left in the Figure 1.1). This is why we store foods in the refrigerator or freezer (like the bread on the right in the Figure 1.1). The lower temperature slows the rate of spoilage. 1 www.ck12.org

FIGURE 1.1 Left image: Bread after 1 month on a warm countertop. Right image: Bread after 1 month in a cold refrigerator.

Concentration of Reactants Concentration is the number of particles of a substance in a given volume. When the concentration of reactants is higher, the reaction rate is faster. At higher concentrations, particles of reactants are crowded closer together, so they are more likely to collide and react. Did you ever see a sign like the one in the Figure 1.2? You might see it where someone is using a tank of pure oxygen for a breathing problem. Combustion, or burning, is a chemical reaction in which oxygen is a reactant. A greater concentration of oxygen in the air makes combustion more rapid if a fire starts burning.

FIGURE 1.2 Q: It is dangerous to smoke or use open flames when oxygen is in use. Can you explain why? A: Because of the higher-than-normal concentration of oxygen, the flame of a match, lighter, or cigarette could spread quickly to other materials or even cause an explosion. Surface Area of Reactants When a solid substance is involved in a chemical reaction, only the matter at the surface of the solid is exposed to other reactants. If a solid has more surface area, more of it is exposed and able to react. Therefore, increasing the 2 www.ck12.org Chapter 1. Chemical Reaction Rate surface area of solid reactants increases the reaction rate. Look at the hammer and nails pictured in the Figure 1.3. Both are made of iron and will rust when the iron combines with oxygen in the air. However, the nails have a greater sur...