Matter, Atoms, Chemical Bonds, Water, and Energy Flow in Biological Systems

Matter and Its Composition

Definition and Examples of Matter

Matter is defined as anything that takes up space and has mass. All physical substances, including rocks, water, air, plants, animals, and soil, are composed of matter.

• Matter is made of tiny building blocks called atoms.

• There are 118 types of atoms known to modern science, each representing a different element.

• The Periodic Table of Elements organizes all known elements and their letter symbols.

• Examples of elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N).

Atomic Structure

Components of an Atom

All atoms consist of a central nucleus containing protons and neutrons, with electrons moving in a cloud around the nucleus.

• Protons: Positively charged particles found in the nucleus.

• Neutrons: Neutral particles (no charge) also found in the nucleus.

• Electrons: Negatively charged particles that orbit the nucleus; they are much lighter than protons or neutrons.

The number of protons, neutrons, and electrons determines the identity and properties of each element.

Atomic Variability and Molecule Formation

• Atoms of different elements have different numbers of protons, neutrons, and electrons.

• These differences influence how atoms bond to form molecules and how molecules connect to build various types of matter.

Important Molecules in Biology and Environmental Science

Common Molecules and Their Chemical Formulas

Name of Molecule	Chemical Short-hand	Composition
Carbon dioxide	CO2	1 carbon, 2 oxygen atoms
Water	H2O	2 hydrogen, 1 oxygen atom
Methane	CH4	1 carbon, 4 hydrogen atoms
Molecular oxygen	O2	2 oxygen atoms
Ozone	O3	3 oxygen atoms
Molecular nitrogen	N2	2 nitrogen atoms
Nitrous oxide	N2O	2 nitrogen, 1 oxygen atom

Chemical Bonds

Types of Bonds Between Atoms

• Covalent bonds: Atoms share electrons. These bonds are very strong and stable.

• Ionic bonds: One atom donates electrons to another, creating charged ions that attract each other. These can be strong if many electrons are transferred.

• Hydrogen bonds: Weak attractions between a slightly positive hydrogen atom in one molecule and a slightly negative atom (often oxygen or nitrogen) in another. These are crucial for the properties of water.

Example: Water molecules are held together by hydrogen bonds, giving water its unique properties.

Properties of Water

Chemical and Physical Properties

• Polarity: Water is a polar molecule, meaning it has regions of partial positive and negative charge, allowing it to dissolve other polar substances.

• Hydrogen bonding: Causes water molecules to stick together (cohesion) and to other substances (adhesion).

• High heat capacity: Water can absorb and release large amounts of heat slowly, moderating Earth's climate and helping organisms regulate temperature.

Example: Water currents distribute heat in oceans; evaporation cools surfaces.

Acids, Bases, and the pH Scale

Definitions and Properties

• Acids: Substances that release H+ ions in water.

• Bases: Substances that release OH- ions in water.

• Ions: Atoms or molecules that have gained or lost electrons, resulting in a charge.

• The pH scale measures how acidic or basic a solution is, ranging from 0 (most acidic) to 14 (most basic), with 7 being neutral (pure water).

Example: Lemon juice (pH ~2) is acidic; household ammonia (pH ~11) is basic.

Energy in Biological Systems

Forms and Laws of Energy

• Energy is the capacity to do work.

• First Law of Thermodynamics: Energy cannot be created or destroyed, only converted between forms.

• Forms of energy include:

  • Radiant energy: Energy in light

  • Chemical energy: Stored in chemical bonds

  • Mechanical (kinetic) energy: Associated with movement

  • Thermal energy: Energy of random molecular motion (heat)

Energy Conversions in Nature

• Plants convert radiant energy to chemical energy via photosynthesis.

• Animals convert chemical energy to mechanical energy (movement).

• All energy conversions are not 100% efficient; some energy is always lost as heat (Second Law of Thermodynamics).

Energy Flow in Food Webs

Energy Transfer and Loss

• Energy moves through ecosystems in food webs from producers to consumers.

• At each step (trophic level), energy is lost as heat, waste, or through movement.

• The original energy from the sun is reduced at each step, with the least available for top predators.

Example: Plants (producers) capture solar energy; herbivores eat plants; carnivores eat herbivores; energy is lost at each step.

Quiz Review

Sample Questions and Answers

• Where are neutrons located in atoms? In the nucleus (center)

• Which weighs the least? Electron

• Which has a negative charge? Electron

• Give two examples of elements. Carbon, Oxygen

• Give two examples of molecules. Water, Carbon dioxide

• Describe a covalent bond. A bond where two atoms are sharing electrons.

• Describe an ionic bond. A bond where one atom donates electrons to another atom.

• List two important properties of water. Hydrogen bonds make water molecules stick together; water is polar and dissolves polar substances; water can absorb lots of heat and releases it slowly.

• What is an ion? An atom that has lost or gained an electron.

• What kind of ion does an acid release into water? H+

• What kind of ion does a base release into water? OH-

• What is an example of an acidic pH? Anything less than 7

• What is an example of a neutral pH? 7

• What is an example of an alkaline or basic pH? Anything more than 7

Additional info:

• The notes also reference the implications of energy loss in food webs for human diets and food production, highlighting the importance of understanding energy transfer efficiency in ecological and agricultural contexts.