Key Terms for Mid Unit Test

Question 1

Pure Substances

Answer 1

substances that are made of only one type of atom or only one type of molecule

Question 2

mixtures

Answer 2

A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties. Mixtures can be composed of solids, liquids, or gases.

Question 3

Elements

Answer 3

cannot be separated by chemical means. Only 1 type of ATOM.

Question 4

homogenous mixture/ solution

Answer 4

looks like one substance but it can be separated using physical means. Solution is common name for this.

Question 5

heterogeneous mixture

Answer 5

is a mixture that does not blend smoothly throughout and in which the individual substances remain distinct

Question 6

distillation

Answer 6

• mixture is heated until most volatile component vaporizes
• as vapour passes through a cooled tube, it condenses back into its liquid state
• depends on differences in volatility of components
• idea for separating a liquid from a soild in a HOMOGENEOUS mixture as long as their boiling points are not close (if they are, it will be hard because they will both start boiling and evaporating at the same time mixing them again)
• what is left is called distillate. usually one with lower boiling point (the one that boiled first)

Question 7

filtration

Answer 7

• mixture is poured into a funnel (or filter paper)
• liquid passes through, solid is left behind
• good for HETEROGENEOUS mixtures
• this process works because of gravity
• can be accelerated by vacuum filtration
• filtrate is the liquid that passes through the funnel paper

Question 8

centrifugation

Answer 8

• works for very small, solid particle separation
• the process of separation of insoluble materials from a liquid where normal filtration does not work well
• fill rotors (balanced) which then rotate really fast causing centrifugeal tubes to rotate horizontally and, due to force, the particles separate.
• solid ends up at bottom and lightest molecules on top

Question 9

chromatography

Answer 9

• there are many different kinds but they all have a mobile phase and a stationary phase

Question 10

Paper chromatography

Answer 10

• stationary phase is paper
• mobile phase is the liquid
• draw a line with some kind of marker and put it in beaker
• you will see the water travel up the paper causing the ink to separate
• this is due to the size of the molecules. some components have smaller atoms that travel easier through the paper while others stick to the bottom because they are bigger??
• this is used to separate colours in solutions like dyes,

Question 11

mass #

Answer 11

number of protons plus neutrons

Question 12

atomic mass

Answer 12

actual mass of that particular atom

Question 13

average atomic mass

Answer 13

all isotopes added up

Question 14

radioisotope

Answer 14

• unstable because the attractive nucleur forces among the neutrons and protons are too small to balance the repulsive forces among the protons

Question 15

carbon dating

Answer 15

• carbon 14 is radioisotope that decays once animal has died while carbon 12 amount remains the same
• carbon 14 decays and by looking at the ratio of carbon 12 to carbon 14, you can find the age

Question 16

relationship between isotopes of element and relative atomic mass

Answer 16

more isotope of certain mass, closer the relative atomic mass is to that number

Question 17

periodic law

Answer 17

• when elements are arranged by atomic number, their chemical and physical properties recur periodically

Question 18

how did periodic table change?

Answer 18

• mendeleev had to reverse order of elements to make their chemical properties match because he ordered them based on mass not atomic number
• some elements have higher mass but lower protons so they don’t follow the trend. he had to reorder them because they didn’t follow the trend but he didn’t know why

Question 19

What is excitation

Answer 19

When atoms or ions in the ground state are heated to high temperatures, some electrons may absorb enough energy to allow them to “jump” to higher energy levels. These excited state electrons are unstable and they will “fall” back to their normal positions of lower energy. As the electrons return to the ground state, the energy that was absorbed is emitted in the form of electromagnetic radiation. Some of this energy may be in the form of visible light (See the spectrum of electromagnetic radiation below).

Question 20

Distillation is idea for

Answer 20

liquid and solid

Question 21

why is flame test bad?

Answer 21

Flame test only tells you about metal ion, not about non-metal.

Question 22

Hydrogen must be what in order for hydrogen bonding to work

Answer 22

hydrogen MUST be positive for bonding to work

Question 23

dipole moment

Answer 23

center of positive charge and center of negative charge exist.

Question 24

ionic bond

Answer 24

electrostatic force of attraction between oppositely charged ions

Question 25

co-ordinate covalent bond

Answer 25

when elements that bonded and have deficient octets when brought in contact with atom/molecule with one or more lone pairs, they form more bonds to complete the octet. Both electrons are contributed by one of two atoms

Question 26

expanded octet

Answer 26

more than 8 electrons after third row (sulphur + beyond)

Question 27

resonance structure:

Answer 27

compounds have more than 1 lewis structure. Least formal charge means most time spend in that structure since it is the most stable.

Question 28

why does it need to be in gaseous, ground state.

Answer 28

because then attraction to other molecules would effect measurement. Gas= very loosely attracted to other atoms, ground state= not excited