Chemistry of life Flashcards
What are elements
Elements are pure substances that cannot be ordinarily broken down into simpler substances.
They are made up of individual atoms that retain the physical and chemical properties of that element.
What is atomic number and what is mass number?
Mass number is the sum of protons and neutrons of an element. Atomic number is the number of protons in an element
What are electrons?
Electrons are subatomic particles that orbit the nucleus of an atom in discreet layers. They travel at high speeds and avoid each other. The number of electrons in the outermost shell of an atom determines its chemical activity.
What are the four bonds that are essential for life to exist?
Ionic, Covalent, Hydrogen and van der Waals
Ionic bonds
electrical attractions between atoms that gain or lose valence electrons completely
Covalent bonds
Atoms share a pair of valence electrons. The orbitals that form covalent extend at discreet angles and directions giving discreet 3D forms.
Hydrogen bonds
Intermolecular force that forms a special dipole-dipole attraction when a hydrogen atom strongly bonded to an electronegative atom exists in the same vicinity of another electronegative atom with lone pairs of electrons.
They are weaker than covalent and ionic bonds.
van der Waals
forces between two non-polar molecules. (secondary bonds whilst ionic and covalent form primary bonds). Caused by constant motion.
How do hydrogen bonds between water molecules contribute to the properties
of water?
Cohesion- Hydrogen bonds cause water molecules to be exceptionally sticky to each other
Adhesion- Hydrogen bonds cause water to be sticky to other substances. ex water sticking to the leaves of a plant, your eyebrows when you sweat
Surface tension-The molecules of water at the surface are highly attracted to molecules at the bottom by their hydrogen bonds.
Ability to act as a solvent- water molecules create hydrogen bonds with molecules of other substances and thus make the substance soluble.
Acids produce what types of ions and alkaline produce what type of ion
Acids produce (positive) hydrogen ions and alkaline produce (negative) hydroxide ions
How do buffers work
Buffers help to keep pH under control, they do so by either releasing H+ or absorbing it. Most buffers are weak acids or bases or combinations of these substances that dissociate reversibly in water solutions to release or absorb H+ or OH-
How do antacids act as buffers to decrease the pH in the stomach?
They raise the pH of the stomach towards the point of neutrality
What type of bonding is present in a sodium chloride molecule? Explain the
conductivity of sodium chloride.
Ionic bonds, in its solid state it does not conduct electricity but when it melts it undergoes electrolysis which involves electric conduction because of the movement and discharge of ions
When a leaf falls on top of some water and floats, what is happening on a
molecular level that is preventing the leaf from sinking?
Water molecules are attracted to each other due to a phenomenon known as hydrogen bonding . This attraction creates a cohesive forces known as surface tension which allows water to resist external forces including gravity. Its like an invisible skin on the surface of the water that supports the weight of objects placed on it like a leaf.
