Chemistry: Matter and Subatomic Particles

Matter and Elements

• Matter is composed of elements.
• An element is a pure substance that cannot be broken down by chemical reactions.
• A compound is formed when two or more elements combine in a fixed ratio.
• Compounds have unique properties that differ from their constituent elements.
• Trace elements, such as iron, zinc, and iodine, are essential for bodily functions.
• Each element is made up of unique atoms.
• An atom is the smallest unit of matter that still retains the properties of an element.

Subatomic Particles

• Atoms are composed of subatomic particles.
• The three main subatomic particles are neutrons, protons, and electrons.
• Neutrons have no charge, protons have a positive charge, and electrons have a negative charge.
• Neutrons and protons form the nucleus of an atom.
• Electrons orbit the nucleus in a cloud of negative charge.
• Neutrons and protons have almost identical masses, while electrons are much smaller and are often ignored when calculating atomic mass.

Atomic Number and Atomic Mass

• Elements differ in their number of subatomic particles.
• An element's atomic number is equal to the number of protons in its nucleus.
• An element's mass number is the sum of protons and neutrons in its nucleus.
• Atomic mass, the total mass of an atom, can be approximated by the mass number.

Isotopes

• All atoms of a specific element have the same number of protons but can differ in their number of neutrons.
• Isotopes are atoms of the same element that have different numbers of neutrons.

Radioactive Isotopes

• Some isotopes are stable and do not change over time, while others are unstable and radioactive.
• Radioactive isotopes decay over time, releasing energy in the form of radiation.
• Radioactive isotopes are used in medicine for diagnostics and treatment.
• Radiation can be beneficial for targeting cancer cells and stopping their spread.
• However, radiation can also damage healthy cells, potentially leading to side effects and long-term health risks.
• PET scanners utilize radioactive isotopes to monitor cancer growth and metabolism.

Chemical Bonds

• A chemical bond is a force of attraction between two atoms.
• Covalent bonds involve the sharing of electrons between two nonmetals.
  • Polar covalent bonds have unequal sharing of electrons.
  • Nonpolar covalent bonds have equal sharing of electrons.
• Ionic bonds form when electrons are transferred between a metal and a nonmetal.
• Hydrogen bonds are weak interactions that occur when a hydrogen atom bonded to a highly electronegative atom (like oxygen, nitrogen, or fluorine) interacts with another electronegative atom.

Properties of Water

• Water molecules are polar due to the uneven distribution of electrons in their polar covalent bonds.
• This polarity allows water molecules to form hydrogen bonds with each other, giving water unique properties essential for life.
• Water has:
  • High boiling point
  • High heat capacity
  • Universal solvent properties
  • High surface tension
  • Cohesive and adhesive properties

Water as a Universal Solvent

• A solution is a homogeneous mixture of substances.
• The solvent dissolves the solute.
• Water is a versatile solvent due to its polarity.
• Water dissolves polar and charged molecules, making it a universal solvent.
• Water cannot dissolve nonpolar substances like oil.

Water’s Boiling Point

• Water has a high boiling point (100°C) compared to other liquids due to the strong hydrogen bonds between water molecules.
• Breaking these bonds requires significant energy during boiling.

Water’s Surface Tension

• Surface tension is the resistance to stretching or breaking the surface of a liquid.
• Water has high surface tension due to the cohesive forces of hydrogen bonds pulling molecules together.

Water’s Heat Capacity

• Heat capacity is the amount of heat needed to raise the temperature of a substance.
• Water has a high specific heat capacity (amount of energy required to raise the temperature of 1 gram of a substance by 1°C) due to the strong hydrogen bonds.
• This high capacity allows water to absorb significant heat without drastic temperature changes, making it important for temperature regulation in living organisms.

Water’s Cohesive and Adhesive Properties

• Cohesion is the attraction between molecules of the same substance, while adhesion is the attraction between different substances.
• Hydrogen bonds contribute to water's cohesive and adhesive properties.
• Cohesion allows water molecules to stick together, while adhesion allows water to adhere to other surfaces.
• These properties are crucial for plant life, enabling water transport through plants.

Biological Macromolecules

• Most biological molecules contain carbon, making life carbon-based.
• Organic compounds are compounds containing carbon.
• Carbon can form four covalent bonds, allowing for the formation of diverse organic molecules.
• Macromolecules are large polymers formed by joining smaller organic molecules called monomers.
• The four main categories of macromolecules are:
  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic acids

Polymer Synthesis and Breakdown

• Dehydration synthesis is the process of forming polymers from monomers by removing water.
• Hydrolysis is the reverse process of breaking down polymers into monomers by adding water.

Carbohydrates

• Carbohydrates serve as fuel and building materials.
• They include sugars and polymers of sugars.
• Monosaccharides are simple sugars, the basic building blocks of carbohydrates.
• Polysaccharides are polymers of many sugars.

Types of Carbohydrates

• Monosaccharides: Short carbohydrate chains (glucose, fructose, galactose). Found in vegetables, fruits, honey, and dairy products.
• Disaccharides: Two monosaccharides linked together (sucrose, maltose, lactose). Sucrose is found in table sugar and syrup, maltose in grains and starchy vegetables, and lactose in the milk of all mammals.
• Polysaccharides: Long chains of carbohydrates (starch, glycogen, cellulose). Starch is found in plants, glycogen is found in animals, and cellulose is found in plant cell walls.