Bio- Chapter 2 Flashcards
Matter
Anything that occupies space and mass
Mass
Is a measure of the amount of material in an object
Element
Is a substance that cannot be broken down into other substances by chemical reactions
What four elements make up 96% of the human body’s weight?
Oxygen, carbon, hydrogen, and nitrogen.
Trace Elements
Are required in only very small amounts, but you cannot live without them.
Compounds
Substances that contain two or more elements in a fixed ratio.
Atom
The smallest unit of matter that still retains the properties of an element.
Protons
Is a subatomic particle with a single unit of positive electrical charge
Electron
Is a subatomic particle with a single negative charge
Neutron
Is electrically neutral
Nucleus
The atoms center core
When an atom has an equal number of protons and electrons..
its net electrical charge is zero and so the atom is neutral
Atomic Number
All atoms of a particular element have the same unique number of protons.
Mass Number
The sum of the number of protons and neutrons.
Atomic Mass
listed in the periodic table as the bottom number and it is close to the mass number-the sum of its protons and neutrons-but may differ slightly because it represents an average of all the naturally occurring forms of that element.
Isotopes
Have the same numbers of protons and electrons as a standard atom of that element but different numbers of neutrons.
How many of the naturally occurring elements are used by your body? Which four are the most abundant in living cells?
25, oxygen, carbon, hydrogen, and nitrogen.
By definition, all atoms of carbon have exactly 6____, but the number of _____ varies from one isotope to another.
Protons, neutrons
Radioactive Isotope
One in which the nucleus decays spontaneously, shedding particles and energy
Only__ are directly involved in chemical reactions.
Electrons
Chemical Bonds
These interactions usually result in atoms staying close together, held by attractions.
Ions
Atoms or molecules that are electrically charged as a result of gaining or loosing electrons
Ionic Bond
The attraction between oppositely charged ions
Covalent Bond
When two atoms share one or more pairs of electrons. Covalent bonds are the strongest.
Molecule
Covalent bonds hold atoms together in this
When lithium ion(+) joins a bromide ion(-) to form lithium bromide, the resulting bond is a___ bond.
ionic
Polar Molecule
Is one with an uneven distribution of charge that creates two poles, one positive pole and one negative pole.
Hydrogen Bonds
These are the weakest attraction
Chemical Reactions
Changes in chemical composition of matter.
Reactants and Products
Starting molecules to the end product
Cohesion
The tendency of molecules of the same kind to stick together.
Evaporative Cooling
When a substance evaporates, the surface of the liquid that remains cools down.
Solution
a liquid consisting of a homogeneous mixture of two or more substances.
Solvent
Dissolving agent
Solute
Any substance that is dissolved
Aqueous Solution
When water is the solvent, this is the resulting solution
Acid
A chemical compound that releases H+ to a solution
pH Scale
A measure of the hydrogen ion concentration in a solution.
Base
A compound that accepts H+ and removes them from solution.
Why does water not spill over the cup?
Surface tension due to waters cohesion
Why does ice float?
Ice is less dense than water because the more stable hydrogen bonds lock the molecules into a spacious crystal.
Buffers
Substances that minimize changes in pH by accepting H+ when that ion is excess and donating H+ when it is depleted.
