Glossário

Physical Science Terms and Definitions

- the energy needed to remove "n" electrons from an atom.  
The second ionization energy for magnesium is the energy needed to remove two electrons from a magnesium atom.

- at -273.15 degrees Celsius or 0 kelvins, it is the lowest possible temperature in the universe. Although it cannot be achieved, measurements within fractions of a kelvin have been made. 
Particles would attain a minimum amount of energy (and motion) at absolute zero.

- is a change in velocity (speed and direction) over a measured length of time.  
The ball rolling down the hill accelerated from rest to a fast speed in a matter of seconds.

- a compound that dissociates in water to produce H+ ions.  
HCl is an Arrhenius acid because it dissociates into H+ and Cl- ions.

- a compound or ion that donates a proton (H+) in solution. 
Ammonium ions (NH4+) behave as acids since they can donate a H+ leaving ammonia (NH3).

- a group two element.  
The alkali earth metals are found in minerals within the earth's crust.

- a group one element, with the exception of hydrogen
The alkali metals are extremely reactive with water.

- an organic molecule that only contains single bonds between carbon atoms.  
The names of alkanes such as propane and hexane end in the suffix -ane.

- an organic compound that contains are least one double bond between adjacent carbon atoms. 
Compounds that are alkenes have names that end with the suffix -ene, as in ethene.

- an organic compound that contains are least one triple bond between adjacent carbon atoms. 
Compounds that are alkynes have names that end with the suffix -yne, as in ethyne.

- a helium nucleus; a radioactive particle made of two protons and two neutrons.  
Alpha particles are not able to penetrate matter easily due to their large size.

- describes a solid that does not have a crystalline structure.  
The particles in window glass or wax do not have a regular, repeating pattern so they are amorphous solids.

- a solution of unknown concentration that will be determined by reaction with the titrant in a titration. 
In a titration to determine the molarity of vinegar, the vinegar is considered to be the analyte.

- a negatively charged particle.  
Chlorine gains an electron to make an anion with a -1 charge.

- soluble in water.  
Unlike oil, sugar and salt can make aqueous solutions.

- the distance from the nucleus to the edge of the electron cloud of an atom.  
Due to the ambiguity involved in determining the edge of the electron cloud, the atomic radius is often determined by halving the distance between two contiguous atoms of the same element.

- a compound that dissociates in water to produce OH- (hydroxide) ions.  
KOH is an Arrhenius base because it dissociates into K+ and OH- ions.

- a compound or ion that donates a proton (OH-) in solution. 
Water can act as a base since it is capable of adding a proton, making the hydronium ion, H3O+.

- a positively charged particle.  
Potassium loses an electron to make an cation with a +1 charge.

- a group 16 element.  
Chalcogens have six valence electrons because their electron configurations end in s2p4.

- sometimes called the molecular formula, it tells how many atoms of each element are present in a molecule of a particular compound.  
According to the chemical formula of water, H2O, there are two hydrogen atoms and one oxygen atom in each water molecule.

- a chemical reaction where a hydrocarbon or organic compound reacts with oxygen in the presence of heat to produce either carbon dioxide, carbon monoxide, or carbon and water. 
The combustion of fuels produces water, but you cannot see it since it is a gas.

- when two elements of similar or the same electronegativty share electrons by forming a hybrid orbital.  
Carbon and hydrogen, two nonmetals, form a covalent bond to share electrons in an sp hybrid orbital.

- in electricity, it refers to a flow of charge, usually through a metallic wire or via electrolytes in aqueous solution.  
Electric current often describes the flow of electrons in a copper wire.

- is the ratio of mass to volume for a given substance.  

- the length between the start and end point of an object's path. 
When a batter hits a triple, his displacement from the batter's box after reaching third base is 90 feet.

- occurs when water molecules separate an ionic compound as it dissolves in water. The process takes place when the anion of the solute is attracted to the hydrogens in the water molecule and the cation of the solute is attracted to the oxygen in the water 
When potassium chloride dissociates in water, the potassium ion is attracted to the oxygen of the water molecule and the chloride is attracted to the hydrogens.

- the length of the path traveled by an object. 
When a batter hits a triple, his distance traveled after leaving the batter's box is 270 feet.

- a physical property typically associated with metals that refers to a substance's ability to be drawn into a wire.  
Copper is used to make wire because it is ductile.

- the negatively charged particle in an atom. Compared to the proton and neutron, the mass of an electron is negligible. The electrons occupy the electron cloud, which constitutes a majority of the atom's volume, and surrounds the nucleus. 
If a particle has no charge, then the number of protons and electrons are equal.

- in nuclear reactions, the term refers to the splitting of a nucleus (usually of large mass) into smaller nuclei, free neutrons, and energy.  

- that which causes an accleration. 
An applied force will cause a change in an object's motion; as when a cart is pushed to put it into motion.

- in nuclear reactions, the term refers to the 
joining (fusing) of small nuclei into a larger nucleus, accompanied by the release of energy. Fusion reactions are not easily reproducible on Earth due to the extreme temperatures required, yet it is the reaction that powers the sun and stars of the universe.

- the state of matter with greatest separation between particles, and thus the most entropy. They have an indefinite shape and volume.  
The particles in a gas are spread so far apart that the majority of the volume is empty space.

- in chemistry, refers to the vertical columns of the periodic table.  
There are 18 groups, or families, stretching from left to right on the periodic table.

- the time it takes for one-half of a radioactive isotope to undergo decay.  
A radioactive isotope that has a half-life of 6 hours and a mass of 10 g, will only have 2.5 g remaining after 12 hours.

- a group 17 element.  
The halogens are extremely reactive since they only need one electron to attain an octet.

- contains two or more unique substances that can be visually identified from one another. The different components can be separated easily.  
A salad is a heterogeneous mixture since the lettuce, tomatoes, and dressing are all very easy to identify as unique components.

- contains two or more unique substances than appear to be one uniform substance. It is not possible to see the different components visually.  
Solutions such as seawater are homogeneous mixtures because you differentiate between the salts and the water.

- an acid formed as a result of oxidation of amino acids in the body. 

- a particle with unequal numbers of protons and electrons.  
A sodium ion has 11 protons and 10 electrons.

- is formed when one element of low electronegativity gives electron(s) to an element of high electronegativity. They are also formed by the positive/negative attraction between polyatomic cations/metals and polyatomic anions/nonmetals.  
Since there is a large difference between the electronegativity of strontium and chlorine, strontium will give electrons to chlorine and form an ionic bond.

- refers to one of many different variations in the number of neutrons (and therefore mass) within atoms of a given element.  
Two isotopes of carbon, carbon-12 and carbon-14 both have six protons, but carbon-12 atoms have six neutrons while carbon-14 atoms have eight neutrons.

- any organic acid containing the ketone C=O (carbonyl) radical. 

- is a graphical representation of the number of valence electrons for an element.  
Lewis dot diagrams are not useful for transition elements since they use electrons outside their valence for bonding.

- the property that describes liquids that can mix with each other in any ratio.  
Rubbing alcohol and water are miscible, but oil and water are immiscible.

- the particle in an atom that has no charge. It is located in the nucleus and is the most massive subatomic particle. 
In smaller atoms, the ratio of neutrons to protons is 1:1, but in larger atoms the ratio grows to 1.5:1.

- a group 18 element.  
Noble gases are the most stable elements because they have a full valence shell.

- the particles (i.e. protons and neutrons) in the nucleus of an atom.  
A particle with 12 protons and 14 neutrons is said to have 26 nucleons.

- a natural deposit containing a mineral of an element to be extracted. 

- states that no two electrons in the same atom can have the same four quantum numbers.  
As a consequence of the Pauli exclusion principle, there can be no more than two electrons in an orbital, and they must have opposite spins.

- is a ratio of work to time.  
Bill accomplishes the same amount of work in half the time as Rob, therefore Bill's power output is twice that of Rob.

- a solid that is formed when two aqueous solutions are reacted in a double displacement reaction.  
When aqueous potassium iodide and lead(II) nitrate are mixed, the bright yellow precipitate lead(II) iodide settles to the bottom

- the positively charged particle in an atom. It is located in the nucleus with the neutron. 
The numbe of protons in an atom is unique for each element. Unlike neutrons and electrons, a change in the number of protons in a particle changes the identity of the element.

- the state of matter in which particles are most compact. Individual particles may vibrate in place, and It is impossible for particles to move around each other. Solids have a definite shape and definite volume. 
The particles in a solid are so compact that the most dense substances known are all solids.

- the material that is dissolved in a solution.  
Salt is the primary solute in seawater.

- the material that dissolves the solute in a solution.  
Water is the solvent in seawater because it is the medium that dissolves the salt.

- a type of chemical reaction in which there is only one product.  
Table salt, or sodium chloride, can be made from a synthesis reaction between sodium metal and chlorine gas.

- a reagent/solution of known concentration and volume that is used to determine the concentration of the analyte in a titration. 
In a titration to determine the molarity of vinegar, a standardized sodium hydroxide solution was used as the titrant.

- an element belonging to groups three through twelve.  
The transition elements are not as reactive as other metals, but they have the greatest density of all elements.

- are the electrons located on the highest energy level of an atom.  
Noble gases (except helium) have an octet, or eight valence electrons.

- the speed and direction of an object.  
While driving to my grandmother's house, I maintained a velocity of 45 miles per hour north.

- the amount of three dimensional space an object occupies.  
As more air is blown into a balloon, its volume increases.

- the distance between the crests of two successive waves.  
Due to their short wavelength, visible light is often measured in nanometers.

- high energy/small wavelength electromagnetic radiation that is between ultraviolet light (less energy) and gamma rays (more energy).  
Due to their short wavelengths, X-rays have the ability to penetrate matter.