Chapter 2 The Chemical Basis Of Life Flashcards
What is an element?
A substance that cannot be broken down to other substances by ordinary chemical means
What is matter
Anything that occupies space and has mass
What are the 4 major chemical elements that make up living organisms
Oxygen (O), Hydrogen (H), Carbon (C), and Nitrogen (N)
What are trace elements?
Essential elements, but only in minute quantities.
Name the elements that account for 4% of the human body
Calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium,
Name at least 5 trace elements
Boron, chromium, cobalt, copper, Florine, iodine, iron, manganese, molybdenum, selenium, silicon, tin, vanadium, and Zinc
What is a compound
A substance containing two or more elements in a fixed ratio
Which are more common: compounds or pure elements?
Compounds
What are the three main subatomic particles and what are their charges?
Proton-positive- nucleus
Neutron-no charge- nucleus
Electron-negative- electron cloud
Atomic number is
Number of protons in an element
An atoms mass number is:
The sum of the protons and neutrons in the nucleus
The atomic mass is
The weight of the atom, approximately equal to the mass number
What is an Isotope
The different isotopes of an element have the same number of protons and electrons but a different number of neutrons. Behave the same in chemical reactions
What is a radioactive isotope and why is it radioactive?
An isotope in which the nucleus decays spontaneously, giving off particles and energy. Some isotopes with more neutrons are radioactive because the neutron stores excess energy that is released as radioactivity
Why are radioactive isotopes helpful?
They can help us when we use them for scans like a PET or MRI because our body cannot distinguish one isotope from another so we can use them as tracers.
How can radioactive isotopes be dangerous?
Radioactivity in larger quantities than given in PET’s are harmful to living organisms and potentially deadly. They damage molecules and DNA
What are electron shells?
Energy levels in which electrons occur. Highest energy she’ll in living organisms has 8 electrons in the shell. Lowest has one in the first shell
What are Chemical Bonds?
Attraction of two atoms to form a bond. 2 types: covalent and Ionic
What is an Ionic bond?
Attractions between ions of opposite charge. One atom pulls an 1+ electrons away from a neighboring atom and they form a Ionic bond, their attraction holding them together.
What is an Ion
An atom with an electric charge resulting from a gain or loss from one or more electrons
What is the scientific definition of salt
A synonym for an ionic compound.
What is a covalent bond?
Two atoms share one or more pairs of outer shell electrons. two or more atoms held together by a covalent bond form a molecule. Can form DOUBLE BONDS where they share two pairs of electrons
How many covalent bonds can an atom form
Number that can be formed is equal to the number of additional electrons needed to fill its outer shell
How are oxygen atoms bonded to the hydrogen atom in a water molecule?
Covalent bond
What is Electronegativity?
An atoms attraction for its electrons, including shared electrons
What is a polar covalent bond?
Produced by an unequal sharing of electrons in a covalent bond. One atom has a stronger pull making it partially negative and the other partially positive.
Why is water a Polar Molecule
It has an unequal distribution of charges
Are most of the strongest chemical bonds in organisms covalent or Ionic?
They are Covalent
What is a hydrogen bond?
Regions of molecule are attracted to oppositely charged regions on other molecules . Positively charged region in this bond is always a hydrogen atom.
How do hydrogen bonds make liquid water cohesive and what is the definition of Cohesion?
Cohesion- the tendency of molecules to stick together
At trillionths a of a second hydrogen bonds are breaking and forming with molecules around them and this allows water to stick together.
What is surface tension and how is it different from cohesion?
Surface tension- a measure of how easy it is to stretch or break the surface of a liquid.
It is different because surface tension is a measure of the breaking point of a liquid and cohesion is what is tested.
How are heat and temperature different?
Temperature measures the intensity of heat. Heat is the amount of energy associated with the movement of molecules and atoms in a body of matter.
How does water moderate temperature
Water holds heat because the heat energy disrupts hydrogen bonds and is absorbed as water molecules move faster.
Water cools slowly because it is releasing heat as it forms hydrogen bonds.
Why is ice less dense than liquid water?
Water molecules become more stable and from bonds with four neighbors, holding them farther away. This creates a not so compact area and so the volume of water vs. an equal volume of ice is denser.
Why is it important that ice floats?
Ice has to float because it insulates the water below it durning the cold months, allowing life to survive below the ice. It also has to float so oceans and lakes would not freeze completely, killing all life inside.
What is the difference between solute and solvent?
The substance doing the dissolving is the solvent. The substance dissolving is the solute.
What is an aqueous solution
The result when water is a solvent.
Why are some substances more acidic?
They have a higher concentration of H+ ( hydrogen ions)
Why are some substances more basic?
They have a higher concentration of OH- (hydroxide ions)
Acid
A compound that donates hydrogen ions to a solution
Base
Compound that accepts hydrogen ions and then removes them from the solution.
What is the pH scale?
Describes the acidity or alkalinity of a solution. pH stands for potential of Hydrogen.
What is a buffer?
Substances in organic molecules that resist change in pH by accepting H+ when it is in excess and donating H+ when it is depleted.
Acid precipitation is:
Defined as rain, snow, or fog, with a pH lower than 5.6.
What is a major concept of basic life chemistry?
The structure of atoms and molecules determines the way they behave.
Chemical reaction
A process leading to changes in the composition of matter.
Reactant vs products
Reactant: starting materials
Product: the result.
