Toward High School Biology

Key Question \#1: How are changes in the matter that makes up living and nonliving things similar?

Atoms are rearranged to form new molecules and substances in both living and nonliving things.

Key Question \#2: How do we know if a different substance has been made?

A new substance is made if the substance exhibits different properties than the original substance.

Science Idea \#1

Every substance has a unique set of characteristic properties, such as color, odor, density, melting point, conductivity and solubility, and how it behaves (such as in limewater and glowing splint tests). The properties of substances can be observed or measured and used to decide if two substances are the same or different.

Evidence: Oxygen gas and carbon dioxide are different substances because they have different properties. Oxygen has a melting point of -219 degrees Celsius while carbon dioxide melts at -78 degrees Celsius. The density of oxygen is 0.001 gram per cubic centimeter and the density of carbon dioxide is 0.003 gram per cubic centimeter.

Key Question \#3: As a new substance forms, what happens to the starting substances?

As more and more new substances are formed, the amount of the starting substance decreases.

Science Idea \#2

Changes during which new substances form are called chemical reactions. The correlation of increasing amounts of ending substances with decreasing amounts of the starting substances provides evidence that the new substances result from an interaction between the starting substances.

Evidence: When nylon is pulled out of hexamethylenediamine and adipic acid, the amount of nylon increases while the amount of the reactants decreases. Water and nylon are the new substances formed.

Key Question \#4: Why do the substances produced in a chemical reaction have different properties from the starting substances?

The substances produced in a chemical reaction has different properties because the atoms are rearranged. A different arrangement of atoms determines the properties of the substance.

Science Idea \#3

A molecule is made up of two or more atoms connected together in a specific arrangement.

Evidence: A carbon dioxide molecule is made of one carbon atom and two oxygen atoms. Acetic acid is made up of four hydrogen atoms, two carbon atoms, and two oxygen atoms.

Science Idea \#4

Each substance is made up of a single type of atom or molecule. The properties of a substance are determined by the type, number, and arrangement of atoms that it is made up of. Because no two substances are made up of the same arrangement of atoms, no two substances have the same set of properties.

Evidence: Carbon dioxide is composed of different atoms with a different arrangement than oxygen and water. They have different properties because they have a different arrangement of atoms.

Key Question \#5: How are the molecules of the ending substances made?

The molecules of the ending substances are made when the atoms of the molecules of the starting substances rearrange and form new bonds.

Science Idea \#5

During chemical reactions, atoms that make up molecules of the starting substances (called reactants) disconnect from one another and connect in different ways to form the molecules of the ending substances (called products). Because the arrangement of atoms in the products is different from the arrangement of atoms in the reactants, the products of a chemical reaction have different properties from the reactants.

Evidence: When iron and oxygen reacts, the atoms rearrange and form new bonds to produce rust. 4Fe+3O2 \---\> 2Fe2O2. The oxygen atoms form bonds with the iron atoms to make rust, which exhibits different properties than iron and oxygen.

Key Question \#6: How can small molecules be used to make very large molecules?

Small molecules can bond together to form very large molecules. Monomers can bond in two different places to form large polymers.

Science Idea \#6

Very large molecules called polymers can be formed by reacting small molecules (monomers) together. Because monomers can react in two places, it is possible for each monomer to react with two other monomers to form long polymer chains. Each time a monomer is added to the chain, atoms are rearranged and another molecule, typically water, is formed.

Evidence: Para-phenylenediamine and terephthaloyl chloride monomers bond together to form Kevlar polymers.

Key Question \#7: What happens to the amount of matter (mass) when new substances form during chemical reactions?

The mass is conserved because the amount of starting substances decrease and the amount of ending substances increases. Mass is conserved because no new atoms are created and no atoms are destroyed.

Key Question \#8: Why does rearranging atoms keep the total mass constant during chemical reactions?

The number of atoms does not decrease or increase during chemical reactions so the total mass is constant.

Science Idea \#7

Atoms are not created or destroyed during chemical reactions, so the total number of each type of atom remains the same. We say that atoms are conserved.

Evidence:

Science Idea \#8

The mass of a particular atom does not change, so a given number of that type of atom will always have the same total mass.

Science Idea \#9

Because the mass of a particular atom does not change and because the number of each type of atom stays the same, the total mass of the matter stays the same even though atoms are rearranged during chemical reactions. We say that mass is conserved.

Key Question \#9: If atoms and total mass are always conserved during chemical reactions, why can measured mass change when the container is opened?

Measured mass may change when containers are opened because atoms can leave the container and new atoms can enter and bond with existing atoms, lowering or increasing the measured mass.

Science Idea \#10

The measured mass of reactants and products is not always the same as the total mass. The measured mass changes if reactants or products (often gases) enter or leave the system. This is because atoms that make up reactants or products enter or leave the system.

Evidence: In a chemical reaction between baking soda and vinegar, the initial mass was 986.7 grams. After the chemical reaction, the mass was also 986.7 grams. When the container was opened, the mass decreased because molecules (carbon dioxide) exited the container into the air around the container. In a reaction between iron and oxygen, both the initial mass and the final mass was 139.03 grams. After the container was opened, the mass increased to 141.79 grams because oxygen atoms entered and formed bonds with the iron atoms to create rust.

Key Question \#10: What substances do plants need in order to grow and repair?

Plants need carbon dioxide and water in order to grow and repair. Carbon dioxide and water form glucose monomers which are used to form cellulose polymers, a carbohydrate.

Key Question \#11: Are the carbohydrates that make up different plant structures the same substance?

The carbohydrates that make up different plant structures are not the same substance because these plant structures exhibit different properties. The arrangement and number of monomers that form carbohydrate polymers differ so the properties also differ.

Science Idea \#11

Carbohydrates are the main polymers making up plant body structures. Carbohydrate polymers are molecules made of glucose monomers. Different carbohydrate polymers have different properties because they are made of different numbers and arrangements of glucose monomers.

Evidence: Plants such as carrots, potatoes, and bamboo shoots contain more carbohydrates than fats and proteins per 100 grams (8.24 grams, 17 grams, and 5.20 grams respectively). Glucose monomers form cellulose polymers which are the carbohydrates that make up plant structures. Since the properties of plants (ex. color and texture) differ, the arrangement and number of glucose monomers differs.

Key Question \#12: How can plants get the glucose monomers they need for building carbohydrate polymers?

Plants get the glucose monomers by they need by incorporating atoms from the environment around them.

Science Idea \#12

Plants use carbon dioxide and water molecules in their environment to make glucose and oxygen molecules. Atoms are rearranged and conserved during this chemical reaction.

Evidence: Glucose (C6H12O3) is a product of carbon dioxide (CO2) and water (H20). When scientists labeled the carbon atoms, they found that the carbon atoms from CO2 end up in the glucose molecules produced.

Key Question \#13: How do plants make the cellulose polymers they need to build their body structures?

Cellulose polymers are made when glucose monomers bond together. Atoms are rearranged during this chemical reaction.

Science Idea \#13

Plants use glucose monomers to make cellulose polymers and water molecules. Atoms are rearranged during this chemical reaction.

Evidence: Cellulose models show that it is constructed of glucose monomers.

Science Idea \#14

When plants grow or repair, they increase in mass. This increase in measured mass comes from the incorporation of atoms from molecules that were originally outside of the plants' bodies.

Evidence:

Key Question \#14: Where does the mass of growing plants come from?

The mass of growing plants come from the incorporation of atoms in their environment.

Key Question \#15: What substances do animals need in order to grow and repair?

Animals need protein in order to grow and repair. Proteins are made up of amino acids and a complete protein includes twenty different amino acids.

Key Question \#16: Are the proteins that animals eat exactly the same as the proteins that make up their own bodies?

The proteins that animals eat are not the exact same. The body breaks down the proteins that animals eat and rearrange them into the proteins that make up their own bodies.

Science Idea \#15:

Proteins are the main polymers making up animal body structures. Protein polymers are molecules made of amino acid monomers. Different proteins have different properties because they are made of different types, numbers, and sequences of amino acid monomers.

Evidence: In many animals such as the chicken, cow, or a human have more protein per 100 grams than carbohydrates and fat (42.3 grams, 60 grams, and 48 grams respectively).

Key Question \#17: How do animals use proteins from food to build and repair their body structures?

Proteins that from food are broken down in the body. These amino acids are rearranged to form different proteins that make up the body structure.

Science Idea \#16

The process by which proteins from food become part of animals' body structures involves chemical reactions in which the proteins from food are broken down into amino acid monomers, and these monomers are used to build different protein polymers that make up body structures. Atoms are rearranged during both the breakdown

and the building of protein polymers.

Science Idea \#17

When animals grow or repair, they increase in mass. Atoms are conserved when animals grow: The increase in measured mass comes from the incorporation of atoms from molecules that were originally outside of the animals' bodies.

Key Question \#18: How are the explanations we have been writing similar to the explanations that scientists write when they publish their work?

The explanations are similar in that they both provide evidence in order to prove the claim stated. They both include statements that are generally believed to be true because of prior evidence, or more commonly known as "Science Ideas". Models of atoms may be used if the explanation includes something that cannot be seen.

Key Question \#19: How does an understanding of chemical reactions help us understand the growth of all living things?

An understanding of chemical reactions helps us understand the growth of living things because chemical reactions cause the growth. Atoms from proteins or carbon dioxide and water rearrange to form molecules or polymers that are essential to the growth of living things.