Bio Unit 2 Lesson 1- Chemical Bonds

Biology Unit 2: Chemistry in Living Systems Lesson 1: Chemical Bonds and Reactions

Observations

Observe what happens when a cheeseburger is placed in hydrochloric acid for several hours.

Can You Explain It?

When the food you eat encounters the gastric juice in your stomach, chemical reactions help break down the food. Explain what you think happens to matter, such as a food, when it undergoes a chemical reaction.

Atoms, Elements, and Compounds

• Every physical thing you can think of, living or not, is made of incredibly small particles called atoms. An atom is the smallest basic unit of matter.

• An element is a substance made up of one type of atom and cannot be broken into simpler substances by ordinary chemical means.

Atoms, Elements, and CompoundsEngineering

ANALYZE Some elements occur naturally and are abundant on Earth. Other elements are very rare or synthesized in laboratories. Research the processes scientists and engineers use to synthesize or isolate rare elements. What types of elements have only been found in a laboratory? Why don't we see these elements in nature? Make an infographic detailing your findings.

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Atoms, Elements, and Compounds

• Atoms that have gained or lost electrons are known as ions.
• Positive and negative ions are attracted to one another. Ionic bonds form through this attraction.
• A molecule is two or more atoms held together by covalent bonds.
• Compounds are substances composed of atoms of two or more different elements bonded together in specific ratios.

Atoms, Elements, and Compounds

• Common compounds in living things include water (H2O) and carbon dioxide (CO2)

Model The chemical formal for carbon dioxide is CO2. According to the model of this molecule in Figure 6, what does the 2 represent?

Atoms, Elements, and Compounds

• The properties of a compound are often very different from the properties of the elements that make up the compound.

• When examining the chemical formulas for compounds, look closely at the ratios of the atoms of the elements in the compound.

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Explain Think back to the hamburger placed in the acid. Answer these questions about the matter in the hamburger.

1. How can matter be arranged? Draw a diagram to illustrate the difference between atoms, elements, and compounds.
2. How are atoms held together? Explain the differences between the two main types of bonding.
3. How do you think arrangement of matter, such as the matter in the hamburger, changes in chemical reactions?

Properties of Water

What characteristics of a water molecule make it unique. Why does the oxygen atom in a water molecule have a slight negative charge?

Properties of Water

Click on each property of water to learn more. Make sure to answer each of the question guys.

Water as a Solvent

Polar Molecules

Properties of Hydrogen Bonds

Acids & Bases

Hydrogen Bonds

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Properties of Water

Explain Construct an explanation for how hydrogen bonds between water molecules contribute to the properties important for the survival of living things. In your explanation, discuss the structure of the water molecule, and explain how this structure contributes to the unique properties of water. Finally, explain how these properties are related to the proper functioning and survival of living things.

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Chemical Reactions and Enzymes

Chemical reactions change substances into different substances by breaking chemical bonds and forming new chemical bonds, rearranging atoms in the process.

Explain: Think about the last food you ate. How do you know the chemical bonds in your food were broken?

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Chemical Reactions and Enzymes: Modeling Chemical Reactions

Products

Reactants

Analyze: Answer these questions about the chemical reaction:

1. How does the arrangement of atoms and bonds change?
2. What are the reactants and the products of the reaction?
3. How can you tell that matter is conserved in this reaction?

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Chemical Equilibrium

• Some chemical reactions go from reactants to products until all the reactants are consumed. -- The reaction can only proceed in one direction and is irreversible.
• Some chemical reactions can proceed in either direction meaning they are reversible. -- These chemical reactions go in one direction or the other depending on the concentrations of the reactants and products.
• Arrows pointing in each direction indicate a reversible chemical reaction.
• In a reversible chemical reaction, the reaction proceeds to an equilibrium point.
• The chemical reaction does not stop but continues in both directions at equal rates, so that the net concentrations of each reactant and product does not change.

Example

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Activation Energy

• All chemical reactions involve changes in energy.
• The reactants must absorb energy in order to break their chemical bonds.
• When new bonds form to make the products, energy is released.
• Some chemical reactions absorb more energy than they release, while others reactions release more energy than they absorb.
• Bond energy is the amount of energy needed to break a specific chemical bond.
• Activation energy is the amount of energy that needs to be absorbed to start, or activate, a chemical reaction.

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Endothermic and Exothermic Reaction

Endothermic Examples

• Chemical reactions may be classified by whether or not energy is absorbed or released during the reaction overall.
• When a chemical reaction releases more energy than it absorbs, it is called an exothermic reaction.
• When a chemical reaction absorbs more energy than it releases, it is called an endothermic reaction.

Exothermic Examples

Explain: In the firefly's body, chemical reactions take place that allow the firefly to give off light to attract a mate. Is this light most likely the result of endothermic or exothermic reactions?

Data Analysis

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Catalysts

• Chemical reactions in living things often need to happen quickly, but some have a high activation energy that makes this not possible.
• A catalyst is a substance that increases the rate of the reaction.
• Catalysts are neither changed nor consumed during a reaction, so they are not part of the equation.

Analyze: According to this graph, how does a catalyst increase the rate of a chemical reaction?

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Enzymes

• The catalysts used in living organisms are called enzymes.
• Enzymes, like other catalysts, lower the activation energy and increase the rate of chemical reactions.
• Enzymes are involved in almost every process in organisms, from breaking down food to building proteins.

Lock-and-Key Model

Denaturing Enzymes

Induced-Fit Model

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Enzymes

Explain Answer these questions to construct an explanation for how matter changes during chemical reactions:

• What happens in terms of atoms and bonds in chemical reactions?
• How are energy inputs and outputs related to chemical reactions?
• How do enzymes help living things carry out chemical reactions?

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Can You Explain It?

Refer to the notes in your Evidence Notebook to explain how matter, such as a hamburger, is changed in a chemical reaction. Use evidence and models to support your claim, and address the following questions:

1. How can matter be arranged, and how do we model the arrangement of matter?
2. How does matter and energy change in chemical reactions, and how can these changes be modeled?
3. How do the properties of water and the ability to modify the rates of chemical reactions enable living things to carry out functions necessary for life, such as digesting food?

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