Elements - Hanover Area School District

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What’s the Matter?

All of the materials around you are made up of matter. You are made up of matter, as are the chair you sit on and the air you breathe.

1. Give an example of solid matter. 2. Give an example of liquid matter. 3. Give an example of gaseous matter. 4. Is all matter visible? 5. Does all matter take up space?

Section 2-1

Interest Grabber

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2–1 The Nature of Matter A. Atoms B. Elements and Isotopes

1. Isotopes 2. Radioactive Isotopes

C. Chemical Compounds D. Chemical Bonds

1. Ionic Bonds 2. Covalent Bonds 3. Van der Waals Forces

Section 2-1

Section Outline

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The Nature of Matter

• Life depends on chemistry.

• Just as an architect must understand the materials that make up a building, a scientist must understand the molecules that make up a living thing.

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• Atoms

•  The study of chemistry starts with the basic unit of matter, the atom. •  The atom was first used by the Greek philosopher Democritus which

means “unable to be cut.” •  There are three particles to the atom:

1.  Electron - negative charge –  Found in the electron cloud

2.  Proton - positive charge •  Found in the nucleus

3.  Neutron - no charge –  Found in the nucleus

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Elements

• An element is a pure substance that consists entirely of one type of atom. • There are 118 known elements. • The elements are mostly represented by one or two letters. • The first letter is always capitalized while the rest are lower case. • Examples:

Oxygen - O Carbon - C Sodium - Na

• An element is identified by the number of protons it has. • The elements can be found in the Periodic Table

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C Carbon 12.011

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An Element in the Periodic Table

Symbol

Atomic number

Element

Atomic Mass

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Isotopes

• Sometimes, atoms of an element can have a different number of neutrons. • These atoms are called isotopes. • The sum of the protons and neutrons is equal to the mass number. • The average weight of all the isotopes is equal to the atomic mass.

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Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14

6 electrons 6 protons 6 neutrons



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Figure 2-2 Isotopes of Carbon

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Radioactive Isotopes

• There are some isotopes that are radioactive. • This means their nucleus is unstable and break down at a constant rate over time. • The radiation that is given off can be dangerous, but could also be useful.

• Geologists can determine the ages of rocks and fossils by analyzing the isotopes found in them. • Some radiation can be used to treat cancer or be used as labels or “tracers” to follow the movement of substances.

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Chemical Compounds

• In nature, most elements are found combined with other elements. • Substances formed by the chemical combination of two or more elements in definite proportions are called chemical compounds. • The shorthand representation of a chemical compound is called a chemical formula. • Examples:

–  Water : made of two hydrogen and one oxygen : H2O –  Salt : one sodium and one chloride : NaCl

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Chemical Compounds

• The physical and chemical properties of compounds are very different from the elements that make them up. • Water:

–  Hydrogen and Oxygen are both gases, but water is a liquid.

• Salt: –  Sodium is a soft metal and is very explosive in water. –  Chloride is a poisonous, greenish gas that was used in

WWI.

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Chemical Bonds

•  The atoms of compounds are held together by chemical bonds.

•  Much of chemistry is trying to understand how and when these bonds form.

•  The bond formation is the responsibility of the electrons of each atom.

•  The electrons that form the bonds are called valence electrons. •  There are two types of chemical bonds:

1.  Ionic Bond 2.  Covalent Bond

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Ionic Bonds

• An ionic bond is formed when one or more electrons are transferred from one atom to another.

• In a neutral state, the number of electrons is equal to the number of protons.

• In ionic bonds, the atom that lost the electron has a positive charge and the atom that gained the electron has a negative charge.

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Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-)

Transfer of electron

Protons +11 Electrons -11 Charge 0


Protons +11 Electrons -10 Charge +1

Protons +17 Electrons -18 Charge -1

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Figure 2-3 Ionic Bonding

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Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-)

Transfer of electron



Protons +11 Electrons -10 Charge +1

Protons +17 Electrons -18 Charge -1

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Figure 2-3 Ionic Bonding

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Covalent Bond

• A covalent bond forms when the electrons of two or more atoms are shared between the atoms. • This means the electrons flow in the electron cloud of both atoms. • Types of covalent bonds:

–  Single bond: sharing of two electrons –  Double bond: sharing of four electrons –  Triple bond: sharing of six electrons

• The structure that results when atoms are joined together by covalent bonds is called a molecule.

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Figure 2-4 Covalent Bonding

Water Molecule

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Van der Waals Forces

• Because of their structures, atoms of different elements do not all have the same ability to attract electrons. • When atoms of a covalent bond share electrons, the sharing is not always equal. • If the sharing of the electrons is equal, the rapid movement of the electrons can create regions on a molecule that have tiny positive or negative charges. • When molecules are close together, a slight attraction can develop between the oppositely charged regions of the nearby molecules. • These intermolecular forces of attraction are called van der Waals forces.

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Geckos

• Geckos show a great example of van der Waals forces. • A geckos foot is covered by as many as half a million tiny hair-like projections. • Each projection is further divided into hundreds of tiny, flat-surface fibers. • This design allows a great area of the geckos’ foot to attract forces with the atoms of the surface they are walking on.

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Water, Water Everywhere

If you have ever seen a photograph of Earth from space, you know that much of the planet is covered by water. Water makes life on Earth possible. If life as we know it exists on some other planet, water must be present to support that life.

Section 2-2

Interest Grabber

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1. Working with a partner, make a list of ten things that have water in them.

2. Exchange your list for the list of another pair of students. Did your lists contain some of the same things? Did anything on the other list surprise you?

3. Did either list contain any living things?

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2–2 Properties of Water A. The Water Molecule

1. Polarity 2. Hydrogen Bonds

B. Solutions and Suspensions 1. Solutions 2. Suspensions

C. Acids, Bases, and pH 1. The pH Scale 2. Acids 3. Bases 4. Buffers

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Section Outline

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Properties of Water

• Water covers 3/4 of Earths Surface • Water is the single most abundant compound in most living things.

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The Water Molecule

• Water is a neutral molecule, but is considered to be polar. • The oxygen atom has a stronger attraction for electrons than the hydrogen. • Therefore the electrons spend more time around the oxygen atom. • This gives the oxygen atom a negative charge and the hydrogens a positive charge. • A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms

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Hydrogen Bonds

• Because the water molecule is polar, it has a positive and negative side. • The positive charge of one molecule attracts to the negative charge of another molecule. • This attraction forms a hydrogen bond. • Hydrogen bonds are weaker than ionic or covalent bonds. • These hydrogen bonds are responsible for many of water’s properties.

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Cohesion

• Cohesion is the attraction between molecules of the same substance. • Water molecules can form as many as four hydrogen bonds at the same time. • Water’s cohesion causes molecules on the surface to be drawn inward, which is why drops of water form beads on a smooth surface. • This cohesion make it possible for insects to walk across the surface of a pond or lake.

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Adhesion

• Adhesion is the attraction between molecules of different substances. • Example: Water in graduated cylinder

–  At eye level, the water tends to dip in the middle. –  This is because the adhesion between the water and the glass

molecules is stronger than the cohesion of the water molecules. • Capillary action:

–  The ability of water rise in a narrow tube against the force of gravity.

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Solution and Suspensions

•  Water is often found as part of a mixture. •  A mixture is a material composed of two or more elements or

compounds that are physically mixed together but not chemically combined.

•  Two types of mixtures that could be made with water are solutions and suspensions.

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Solution

•  The components of a solution are evenly distributed. •  A solution is made up of two components.

1.  Solute - the substance that is dissolved. 2.  Solvent - the substance in which the solute dissolves.

•  The best solvent in the world is water. •  Example: Salt water

–  When a crystal of salt is placed in water, sodium and chloride ions on the surface of the crystal are attracted to the polar water molecules.

–  Ions break away from the crystal and are surrounded by water molecules.

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Cl-

Water

Cl- Na+

Water

Na+

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Figure 2-9 NaCI Solution

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Section 2-2

Figure 2-9 NaCI Solution

Cl-

Water

Cl- Na+

Water

Na+

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Suspensions

• Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out. • The movement of the water molecules keep the small particles suspended. • This mixture of water and nondissolved material is called a suspension. • Example:

–  Blood: Blood is mostly made up of water, but contains blood cells that remain suspended as the blood travels through your body.

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Acids, Bases, and pH

• Water is a covalent molecule, but also has the ability to form into ions. • The following chemical equation demonstrates the reactions:

• Only about 1 in 550 million molecules of water react to form an ion.

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pH Scale

• Scientist developed a scale to determine the concentration of H+ ions in a solution. • It is called the pH scale and it ranges from 0 to 14. • At 7, the number of H+ ions is equal to the number of OH- ions. • Below 7, there are more H+ ions than OH- ions which means the solution is acidic. • Above 7, there are more OH- ions than H+ ions which means the solution is basic. • Each step on the pH scale represents a factor of 10.

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pH Scale

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Acids

• An acid is any compound that forms H+ ions in a solution. • Acidic solutions contain higher concentrations of H+ ions than pure water and have pH values below 7.

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Bases

• A base is a compound that produces OH- ions in solution. • Basic, or alkaline, solutions contain lower concentrations on H+ ions than pure water and have pH values above 7.

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Buffers

• A buffer is a weak acid or base that can react with strong acids or bases to prevent sharp, sudden changes in pH. • Buffers are important because the cell must remain at a pH between 6.5 and 7.5. • If the pH goes beyond this range, the chemical reactions that take place may be affected.

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Life’s Backbone

Most of the compounds that make up living things contain carbon. In fact, carbon makes up the basic structure, or “backbone,” of these compounds. Each atom of carbon has four electrons in its outer energy level, which makes it possible for each carbon atom to form four bonds with other atoms.

As a result, carbon atoms can form long chains. A huge number of different carbon compounds exist. Each compound has a different structure. For example, carbon chains can be straight or branching. Also, other kinds of atoms can be attached to the carbon chain.

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Interest Grabber

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1. On a sheet of paper, make a list of at least ten things that contain carbon.

2. Working with a partner, review your list. If you think some things on your list contain only carbon, write “only carbon” next to them.

3. If you know other elements that are in any items on your list, write those elements next to them.

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2–3 Carbon Compounds A. The Chemistry of Carbon B. Macromolecules C. Carbohydrates D. Lipids E. Nucleic Acids F. Proteins

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Section Outline

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The Chemistry of Carbon

• Organic chemistry is the study of molecules that contain the atom carbon. • The carbon atom is an extremely important element. • Carbon contains 4 valence electrons. • It has the ability to form covalent bonds with many different elements such as hydrogen, oxygen, phosphorus, sulfur, nitrogen, and even another carbon atom. • Because carbon has the ability to bond to another carbon, it can form long chains, form single, double, and triple bonds, and close upon itself for form rings.

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Methane Acetylene Butadiene Benzene Isooctane

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Figure 2-11 Carbon Compounds

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Macromolecules

•  The term macromolecule means “giant molecules.” •  Macromolecules are formed by small, organic compounds, called

monomers, joined together through the process called polymerization.

•  The final product of this process is a polymer. •  There are four groups of organic compounds found in living things:

1.  Carbohydrates 2.  Lipids 3.  Nucleic acids 4.  Proteins

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Carbohydrates

• Carbohydrates are made up of carbon, hydrogen, and oxygen in a 1:2:1 ratio. • They are used by living things as the main source of energy. • The immediate supply of energy for all cell activities comes from glucose. • Extra glucose is stored as a complex carbohydrate known as starch.

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Starch

Glucose

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Figure 2-13 A Starch

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Carbohydrates

• A single sugar molecule is called a monosaccharide. • Examples include glucose, galactose (milk), and fructose (fruit). • The large macromolecules are called polysaccharides. • In animals, it is called glycogen, animal starch. • In plants, it is called cellulose which is used to give plants its strength.

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Lipids

•  Lipids are molecules that are not soluble in water. •  They consist of fats, oils, and waxes. •  Lipids can be used to store energy. •  Some lipids are important parts of biological membranes and

waterproof coverings. •  Lipids are formed when a glycerol molecule combines with three fatty

acids. •  There are two types of lipids:

1.  Saturated - Contain maximum number of hydrogens. 2.  Unsaturated - There is at least one double bond between the

carbons.

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Lipids

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Nucleic Acids •  Nucleic acids are

macromolecules made up of hydrogen, oxygen, nitrogen, carbon, and phosphorus.

•  The monomer that make up a nucleic acid is called a nucleotide.

•  A nucleotide has three parts: 1.  5-carbon sugar 2.  Phosphate group 3.  Nitrogen base

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Nucleic Acids

• Nucleic acids store and transmit hereditary, or genetic, information. • There are two types of nucleic acids:

1. Ribonucleic Acid (RNA) 2. Deoxyribonucleic Acid (DNA)

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Proteins

• Proteins are macromolecules that are made up of nitrogen, carbon, hydrogen, and oxygen. • The monomer of a protein is called an amino acid.

–  Amino acids have a amino group (-NH2) on one end and a carboxyl group (-COOH) on the other.

• There are 20 different amino acids which make up all known proteins.

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Carbon Compounds

include

that consist of

which contain

that consist of that consist of that consist of

which contain which contain which contain

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Concept Map

Carbohydrates Lipids Nucleic acids Proteins

Sugars and starches Fats and oils Nucleotides Amino Acids

Carbon, hydrogen,

oxygen

Carbon, hydrogen,

oxygen Carbon,hydrogen, oxygen, nitrogen,

phosphorus

Carbon, hydrogen,oxygen,

nitrogen,

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General structure Alanine Serine

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Figure 2-16 Amino Acids

Amino group Carboxyl group

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Amino acids

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Figure 2-17 A Protein

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Matter and Energy

Have you ever sat around a campfire or watched flames flicker in a fireplace? The burning of wood is a chemical reaction—a process that changes one set of chemicals into another set of chemicals. A chemical reaction always involves changes in chemical bonds that join atoms in compounds. The elements or compounds that enter into a chemical reaction are called reactants. The elements or compounds produced by a chemical reaction are called products. As wood burns, molecules of cellulose are broken down and combine with oxygen to form carbon dioxide and water vapor, and energy is released.

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Interest Grabber

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1. What are the reactants when wood burns?

2. What are the products when wood burns?

3. What kinds of energy are given off when wood burns?

4. Wood doesn’t burn all by itself. What must you do to start a fire? What does this mean in terms of energy?

5. Once the fire gets started, it keeps burning. Why don’t you need to keep restarting the fire?

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2–4 Chemical Reactions and Enzymes A. Chemical Reactions B. Energy in Reactions

1. Energy Changes 2. Activation Energy

C. Enzymes D. Enzyme Action

1. The Enzyme-Substrate Complex 2. Regulation of Enzyme Activity

Section 2-4

Section Outline

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Chemical Reactions

• Chemical reaction is a process that changes, or transforms, one set of chemicals into another. • Mass and energy are conserved during chemical transformations. • The elements or compounds that enter into a chemical reaction are known as reactants. • The elements or compounds produced by a chemical reaction are products. • Chemical reactions always involve changes in the chemical bonds that join atoms in compounds.

Chapter 2 - 4

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Energy in Reactions

• Chemical reactions either release or absorb energy. • Chemical reactions that release energy often occur spontaneously. • Chemical reactions that absorb energy will not occur without a source of energy

2H2 + O2 2H2O

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Activation Energy

• In order to get a reaction to start, a certain amount of energy must be applied to the reactants. • The energy needed to start a chemical reaction is called activation energy.

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Energy-Absorbing Reaction Energy-Releasing Reaction

Products

Products

Activation energy

Activation energy

Reactants Reactants

Section 2-4

Figure 2-19 Chemical Reactions

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Energy-Absorbing Reaction Energy-Releasing Reaction

Products

Products

Activation energy

Activation energy

Reactants Reactants

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Figure 2-19 Chemical Reactions

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Enzymes

• Some reactions that are important to living things are too slow or have activation energies that are too high. • They still happen because the cell has the ability to make its own catalyst (a substance that speeds up reactions) which lower the activation energy.

• Enzymes are proteins that act as biological catalysts.

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Reaction pathway without enzyme Activation energy

without enzyme

Activation energy with enzyme Reaction pathway

with enzyme

Reactants

Products

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Effect of Enzymes

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Characteristics of Enzymes

• Enzymes are very specific to the substrate (reactants) they bind to. • Enzymes are often named by adding the suffix “-ase” to some part of the name of the substrates. • Enzymes do not change and are reusable.

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Glucose

Substrates

ATP

Substrates bind to enzyme

Substrates are converted into products

Enzyme-substrate complex

Enzyme (hexokinase)

ADP Products

Glucose-6- phosphate

Products are released

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Figure 2-21 Enzyme Action

Active site

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Glucose

Substrates

ATP




Enzyme (hexokinase)

ADP Products



Section 2-4


Active site

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Glucose

Substrates

ATP




Enzyme (hexokinase)

ADP Products



Section 2-4


Active site

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Glucose

Substrates

ATP




Enzyme (hexokinase)

ADP Products



Section 2-4


Active site

Videos

Click a hyperlink to choose a video. Atomic Structure Energy Levels and Ionic Bonding Covalent Bonding Enzymatic Reactions

Click the image to play the video segment.

Video 1

Atomic Structure


Video 2

Energy Levels and Ionic Bonding

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Video 3

Covalent Bonding


Video 4

Enzymatic Reactions

Career links on forensic scientists Interactive test

Articles on organic chemistry

For links on properties of water, go to www.SciLinks.org and enter the Web Code as follows: cbn-1022. For links on enzymes, go to www.SciLinks.org and enter the Web Code as follows: cbn-1024.

Go Online

1. Give an example of solid matter. Sample answers: books, desks, chairs

2. Give an example of liquid matter. Sample answers: water, milk

3. Give an example of gaseous matter. Sample answers: air, helium in a balloon

4. Is all matter visible? No

5. Does all matter take up space? Yes

Interest Grabber Answers


1. Working with a partner, make a list of ten things that have water in them. Possible answers: bodies of water, rain and snow, soft drinks and other beverages, juicy foods such as fruits, and so on.

2. Exchange your list for the list of another pair of students. Did your lists contain some of the same things? Did anything on the other list surprise you?

Students’ answers will likely be similar, but not exactly alike. 3. Did either list contain any living things?

Students’ lists may include plants, animals, or other living things.


1. On a sheet of paper, make a list of at least ten things that contain carbon. Students will likely know that charcoal and coal contain carbon. They may also list carbohydrates (starches and sugars), oil, gasoline, wood, or carbon dioxide.

2. Working with a partner, review your list. If you think some things on your list contain only carbon, write “only carbon” next to them.

Students will say that charcoal and coal contain only carbon. While these materials do contain small amounts of other elements, such as sulfur, they are composed mostly of carbon.

3. If you know other elements that are in any items on your list, write those elements next to them.

Students may know that many carbon compounds also contain oxygen and/or hydrogen.

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1. What are the reactants when wood burns? Reactants are oxygen and cellulose.

2. What are the products when wood burns? Products are carbon dioxide and water.

3. What kinds of energy are given off when wood burns? Light and heat are given off. Some students may also mention sound (the crackling of a fire).

4. Wood doesn’t burn all by itself. What must you do to start a fire? What does this mean in terms of energy?

To start a fire, you must light it with a match and kindling. You are giving the wood some energy in the form of heat.

5. Once the fire gets started, it keeps burning. Why don’t you need to keep restarting the fire?

Once the fire gets going, it gives off enough heat to start more of the wood burning.

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Elements - Hanover Area School District

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