Chemistry

Read Chapter 3, Sections 1 and 2.

Do the Directed Reading while you read.

• 3.1 Matter and Substances, pp51-54, Directed Reading, 
• 3.1 PowerPoint 
• 3.2 Water and Solutions, pp55-57, Directed Reading, 
• 3.2 PowerPoint

Atoms

Everything is made of atoms.            

• Atoms have three parts: protons (+),neutrons (no charge), and electrons (-)          
• The protons and neutrons hang out in the center of the atom which is called the nucleus.           
• The electrons move around the outside of the nucleus in the electron cloud.

There are many different kinds of atoms.

• The different atoms are called elements.           
• The different elements have different amounts of protons, neutrons, and electrons.                       
• For example, a carbon atom has 6 protons, 6 neutrons and 6 electrons, and an oxygen atom has 8 protons, 8 neutrons and 8 electrons.  

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Chemical Bonding

Atoms join together by bonds.

There are two basic kinds of bonds: ionic and covalent.           

• An ion is an atom that has gained or lost electrons. 
• If an atom loses an electron (-), the atom becomes a positively charged (+) ion.  
•  If an atom gains an electron (-), the atom becomes a negatively charged (-) ion.           
• A positive ion and a negative ion attract each other and form an ionic bond.     

Ionic Bond

Two atoms can join togethe by an ionic bond. In the diagram:

• The sodium atom (Na) loses an electron and becomes a positive ion (+).
• The chlorine atom (Cl) gains an electron and becomes a negative ion (-).
• The Na⁺ and Cl^- ions attract each other because of their opposite charges.
• This is an ionic bond.

Covalent Bond

Two atoms can join by a covalent bond.

• The covalent bond is stronger than the ionic bond.
• Atoms like to have the maximum possible number of electrons in their outer layer.
• This is called the valence shell.
• Two atoms can share electrons so that both atoms have full valence shells.
• The sharing of two electrons between two atoms creates a covalent bond.

Compounds and Molecules

When two or more different kinds of elements bond together by ionic or covalent bonds, it is called a compound.  

When two or more of the same or different elements covalently bond together, it is called a molecule.  

• Compounds and molecules include the same substances - like water (H₂O) is a compund and a molecule. 
• Salt (NaCl) is a compound, but not a molecule because it has an ionic bond.   
• Oxygen gas (O₂) is a molecule, but not a compound because it is only one kind of element.   

(It’s a little confusing…)

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Polarity

Polar molecules share electrons unequally in their covalent bonds.

• A polar molecule has a partial positive side and a partial negative side because of the unequal sharing of electrons.
• The charges are not as strong as the charges of ions.
• Water is a polar molecule.  
• The shared electrons hang out around the oxygen atom more than around the hydrogen atoms.
• So the oxygen atom is partially negative, and the hydrogen atoms are partially positive.

Polar molecules can dissolve other polar molecules or charged ions.

• For example, salt can mix into water.
• The ionic bond in salt comes apart and the ions mix with the polar water molecules. 

Polar molecules can make hydrogen bonds with other polar molecules.

• A hydrogen bond is a weak attraction between the partial charges of the molecules.
• The positive and negative parts of the molecules attract each other.
• This is not a bond between atoms; it is an attraction between molecules.

Do the 3.1 Quiz.

Do the 3.2 Quiz. 

Atom 

Ionic Bond

Covalent Bond

Water is a polar molecule

Hydrogen Bonding 

California Science Standards

Standard 1: Students know most macromolecules (polysaccharides, nucleic acids, proteins, lipids) in cells and organisms are synthesized from a small collection of simple precursors 

Standard 2: Students know proteins can differ from one another in the number and sequence of amino acids.

Standard 3: *Students know why proteins having different amino acid sequences typically have different shapes and chemical properties. 

Standard 4: Students know the general structures and functions of DNA, RNA, and protein.

Read Chapter 3, Section 3.

Do the Directed Reading while you read. 

• 3.3 Carbon Compunds, pp59-63, Directed Reading
• 3.3 PowerPoint 

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Carbon Compounds

Living things are made of cells. You are made of cells.

Cells are made of compounds that contain mostly carbon atoms.

These carbon compounds are called biomolecules.

Many carbon compounds are very large – millions of atoms.

The large compounds are made of many small molecules that are all the same.

• The small molecule is called a monomer.      
• The big molecule is called a polymer.           
• Polymers are made of many monomers.

A carbon atom makes four covalent bonds with other atoms.

Carbon compounds can have a variety of shapes: straight, branched, and rings.

The variety of shapes creates a variety of functions for carbon compounds.

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There are four groups of carbon compounds:

carbohydrates, lipids, proteins, and nucleic acids.

1. Carbohydrates are made of carbon, oxygen, and hydrogen atoms.

• The sugar molecule is a basic carbohydrate. For example, glucose C₆H₁₂O₆.
• A compound of only one sugar molecule is called a monosaccharide.
• A compound of two sugar molecules is called a disaccharide.
• A compound of many sugar molecules is called a polysaccharide.
• A polysaccharide is a polymer made of monosaccharide monomers.
• Cells use carbohydrates for energy, for building structures, and for identification.

2. Lipids are made of carbon, oxygen, and hydrogen atoms.

• Fats and oils are examples of lipids.
• They have long “tails” of carbon and hydrogen atoms.
• They are nonpolar – they have no charge – so they don’t mix with water.
• Lipids are good for storing energy, building membranes in cells, and repelling    water.

3. Proteins are polymers made of a monomer called an amino acid.

• There are 20 kinds of amino acids that bond together in many possible combinations.
• They are bonded together by a covalent bond called a peptide bond.
• Proteins have complex shapes that depend on the number and kinds of amino acids.
• There are many shapes of proteins and they have many functions.
• Proteins can be used for: structures or support, movement, communication, and helping chemical reactions in cells.
• They do most of the jobs in the cell.

4. Nucleic acids are polymers of monomers called nucleotides.

• A nucleotide has three parts: a phosphate group, a sugar, and a base.
• DNA and RNA are examples of nucleic acids.
• They are both polymers of nucleotides, but they contain different sugars.
• The sugar in DNA nucleotides is called deoxyribose.
• The sugar in RNA nucleotides is called ribose.
• Nucleic acids function is to store and transmit information.
• Information about an organism is contained in its DNA.
• The DNA is used to control cells and create the organism.
• All living things have DNA for storing and transmitting information.
• ATP is a nucleotide that is used for transferring energy inside of cells.
• It is not part of a polymer.
• Cells receive energy from food moleculesand change the energy into ATP.
• Cells release the energy in ATP when they need to do work.

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Activity: Molecular Models

Use images in the book and on the internet for reference.

Work with other groups for larger molecules.

• Build a monosaccharide, a disaccharide, and a polysaccharide molecule
• Build a fatty acid and a lipid (triglyceride)
• Build an amino acid, a dipeptide, and a polypeptide
• Build a phosphate, a deoxyribose, a base, and a nucleotide

Do the 3.3 Quiz.

Carbon Atom

Carbon compounds make a variety of shapes

Carbohydrate: glucose (a sugar)

Lipid

Protein

Nucleic Acid; DNA and RNA

California Science Standards

Standard 5: Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings.

Read Chapter 3, Section 4.

Do the Directed Reading while you read.

• 3.4 Energy and Metabolism, pp64-67, Directed Reading
• 3.4 PowerPoint

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Energy and Metabolism

• Energy exists in many forms: light, heat, electricity, motion, chemical bonds, nuclear.
• Energy can move or change matter.
• Energy can change from one form to another.

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Changing Matter

Living things are made of matter.

Matter can have physical changes and chemical changes.

• A physical change happens when the shape or state of the matter changes. The state of matter can change between solid, liquid and gas.
• A chemical change happens when the substance changes into a different substance. In a chemical reaction, the atoms of the starting molecules/compounds are rearranged to make new molecules/compounds.

• The Law of Conservation of Mass says that matter is neither created nor destroyed; it only changes forms.

• The Law of Conservation of Energy says that energy is neither created nor destroyed; it only changes forms.

                As energy changes forms, some of it changes to heat energy.

                The heat energy is usually not available for work in living things.

We often say, “Some energy is lost as heat,” but it isn’t lost, it is only unavailable and can’t be used.

Living things use chemical reactions to get energy for life.

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Chemical Reactions

In a chemical reaction, bonds between atoms area broken and new bonds are formed.

                A reactant is the starting substance in the reaction.

                A product is the ending substance of a reaction.

The bonds of the reactant(s) are broken, and the atoms are rearranged with new bonds to form the product(s).

• Photosynthesis: building a sugar molecule and oxygen gas from carbon dioxide and water:

                6 CO₂ + 6 H₂O à C₆H₁₂O₆ + 6 O₂

                Reactants: 6 CO₂ + 6 H₂O (6 molecules of each reactant)

The bonds in carbon dioxide and water are broken; the atoms bond together in a new way to make the sugar and the oxygen gas.

                Products: C₆H₁₂O₆ + 6 O₂ (one sugar molecule (glucose) and 6 oxygen molecules)

Activation energy is the amount of energy needed to start the chemical reaction.

• The activation energy makes the reactants move fast enough to hit each other and break apart.
• The reactants must hit each other in the right way to break the bonds. This is called alignment or orientation.

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Biological Reactions

In living things, the chemical reactions to make biomolecules usually have high activation energies.

• A catalyst is something that reduces the amount of activation energy for a reaction.
• A catalyst increases the speed of chemical reactions.
• An enzyme is a protein that acts as a catalyst in cells. It helps make reactions happen faster.
• Many reactions in cells would not happen without enzymes.
• An enzyme has an active site where the reactant(s) are held.
• Reactants are called substrates when enzymes act as catalysts for them.   

Enzyme catalyzed reactions

• The substrate(s) fits into the active site, which helps the alignment, and then the enzyme changes shape to help break the bonds in the substrate(s).
• New bonds form to make the product(s), and the product(s) are released from the active site.
• The enzyme can be used many times without wearing out.
• Changes in temperature and pH can affect an enzyme’s shape.
• If an enzyme’s shape changes, it won’t function properly.
• Most enzymes have specific temperatures and pH ranges for their best functioning.

All of the chemical reactions that happen in a cell or organism are called the metabolism.

• The energy needed for metabolism comes from food molecules.
• Enzymes help break down food molecules to release energy for making ATP molecules.
• The enzymes reduce the amount of energy needed for metabolism.
• This makes cells energy efficient, and very little energy is lost as heat.

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Additional Vocabulary

• equilibrium
• catalyst

Activity: Enzyme Lab

How does pH affect enzyme activity? Enzymatic Activity Lab

• Submit to Turnitin.

Do the 3.4 Quiz.

Enzymes lower the activation energy of chemical reactions

Vocabulary Review - (Answers)

Chapter Pre-Test - (Answers)

Chapter Review

• textbook pages 71-72, problems 6-9, 11-14, 21-22

Chapter Test