Chemistry of Life

Chemistry of Life

What is an Atom?

  • Atoms are defined as the smallest unit of matter.

  • Each atom is made up of sub-particles:

    • Electrons: Negatively charged particles that orbit around the nucleus.

    • Protons: Positively charged particles located within the nucleus.

    • Neutrons: Neutral particles that also reside within the nucleus.

What is an Element?

  • Elements are the purest possible substances, consisting of only one type of atom.

Important Concepts about Elements

Atomic Number

  • The Atomic Number indicates the number of protons and electrons in an atom.

  • It effectively identifies the type of element.

Atomic Mass

  • The Atomic Mass number represents the weight of the atom, which is primarily determined by the number of protons and neutrons.

Drawing Atoms

  • The structure is represented as:

    • In the center: Protons and Neutrons (the nucleus).

    • Surrounding rings: Electrons (orbiting the nucleus).

Compounds

  • Compounds readily combine with other elements.

  • A compound is a pure substance composed of two or more elements chemically bonded together.

Molecules

  • Molecules are defined as the simplest part of a substance that retains the properties of that substance and can exist freely.

Chemical Bonds

  • Bonds are defined as connections between atoms.

  • They are unstable and can be broken during chemical reactions where atoms rearrange to form new chemical bonds that store energy.

Types of Bonds

  1. Covalent Bonds

    • Formed when two atoms share one or more pairs of electrons.

  2. Ionic Bonds

    • Some atoms achieve stability through the loss or gain of electrons.

  3. Hydrogen Bonds

    • Weak bonds that are formed by molecules containing hydrogen.

    • Hydrogen bonds are the weakest among the three types of bonds.

Acids And Bases & pH Scale

Importance of Acidity

  • One of the critical aspects of living systems is the degree of acidity of ions.

  • Molecules formed from ionic bonds can dissociate in water, producing charged ions.

  • Some strongly charged ions can be classified as acids or bases depending on their charge.

Acids

  • Characteristics:

    • Generally have a sour taste and can be dangerous if they are strong.

  • Examples include:

    • Lemon juice

    • Vinegar

    • Soda

  • When mixed in water, acids increase the concentration of hydrogen ions (H+).

Bases

  • Characteristics:

    • Generally have a bitter taste or a slippery/soapy feel.

  • Examples include:

    • Baking soda

    • Soap

    • Bleach

  • Bases increase the concentration of hydroxide ions (OH-) when dissolved in water.

pH Scale

  • The pH scale is a logarithmic scale that allows for the comparison of the relative concentrations of hydrogen ions and hydroxide ions in a solution.

  • Scale ranges from 0 to 14:

    • Each unit change in pH indicates a tenfold difference in acidity or basicity.

    • Lower pH values indicate stronger acids, while higher pH values indicate stronger bases.

    • A pH of 7.0 is considered neutral.

Water (H2O)

  • Water is composed of 2 hydrogen atoms and 1 oxygen atom, represented as H2O.

Polarity in Water

  • Polarity: A condition in which a molecule has a distinct positive charge on one end and a negative charge on the other.

  • Water is considered a polar molecule because:

    • One end has a positive charge and the other has a negative charge.

Properties of Water

  1. Cohesion

    • The tendency of water molecules to cling to each other due to their polar nature.

  2. Adhesion

    • The attraction between water and different substances.

  3. Capillary Action

    • The ability of a liquid to flow in narrow spaces without external assistance.

Water – The Universal Solvent

  • Solvent: A liquid that has the capacity to dissolve a solid.

  • Solute: A solid substance that is dissolved.

  • Water is known as the universal solvent because it can dissolve almost any polar molecule.

  • Polar and ionic molecules are soluble in water due to the hydrogen bonds that allow water to break these molecules apart.

Surface Tension

  • Water exhibits high surface tension, defined as the intermolecular forces operating at the surface of a liquid that hold the surface intact.

Three States of Matter

  1. Liquid: Water in its liquid form.

  2. Solid: Ice (less dense than liquid water).

  3. Gas: Water vapor.

High Heat Capacity of Water

  • Water has a high heat capacity, meaning it can resist temperature changes.

  • Examples include:

    • Water bodies can maintain their temperature even overnight, showcasing this property.