0. Introduction

Question 1

mixture

Answer 1

• two or more substances that are not chemically combined with each other and can be separated by physical means
• the substances in a mixture retain their individual properties

Question 2

solution

Answer 2

• a special kind of mixture in which one substance dissolves in another

Question 3

element

Answer 3

• the simplest form of pure substance
• cannot be broken down into anything else by physical or chemical means

Question 4

compound

Answer 4

• pure substances that are unions of two or more elements
• can be broken into simpler substances by chemical means

Question 5

What are the two types of mixtures?

Answer 5

Heterogeneous (not the same throughout, particles large enough to be seen) and homogeneous (looks the same throughout, small particles).

Question 6

Parts of a solution:

Answer 6

• solute (the substance that is dissolved)
• solvent (the substance that dissolves)

Question 7

Types of solutions (by components):

Answer 7

• gas-gas (air - O&N)
• gas-liquid (soda water - CO2, H2O)
• solid-liquid (ocean water - salts, H2O)
• solid-solid (gold jewelry - Cu, Au (alloys - metals dissolved in metals - stainless steel, brass))

Question 8

Types of solutions (by amount of solute):

Answer 8

• saturated (contains the maximum quantity of solute that dissolves at that temp.)
• unsaturated (contains less solute than the maximum amount)
  (-oversaturated is not a solution but a heterogeneous mixture - too much solute)

Question 9

electrolytes

Answer 9

solutions of ionic compounds (salts, acids, bases) - completely or nearly completely dissolve into ions

Question 10

atom

Answer 10

the smallest particle of an element that has the properties of that element (basic building block of matter)

Question 11

methods of separation

Answer 11

• filtration
• dissolution (solvation)
• crystallization
• evaporation or distillation
• paper chromatography

Question 12

filtration

Answer 12

the mixture is poured through a paper filter or other porous material (solid-liquid)

Question 13

dissolution (solvation)

Answer 13

the mixture is added to water or an organic solvent (insoluble substance-soluble substance)

Question 14

crystallization

Answer 14

the mixture is dissolved in hot water or an organic solvent (e.g. alcohol), the solution cools down, and the crystals formed are isolated by filtration (less soluble substances-more soluble substances)

Question 15

evaporation/distillation

Answer 15

the mixture is heated up until one or more of its components vaporize(s) (solids/non-volatile liquids-volatile liquids)
- only possible if the two substances don’t have close boiling points

Question 16

paper chromatography

Answer 16

the mixture is placed on a piece of paper; one side of the paper is submerged in water or a solvent; components move along the paper (less soluble components (move slower/stay in place)-more soluble components (move faster))
- not separating, just proving that there is more than one compound present
- also gel and color chromatography

Question 17

What are states of matter?

Answer 17

Changes in physical properties of a substance.
- gaseous, liquid, solid, plasma

Question 18

physical properties

Answer 18

• electrical conductivity
• heat conductivity
• density
• melting point
• boiling point
• index of refraction
• malleability
• ductility

Question 19

physical change

Answer 19

when a substance changes state but not its chemical composition (form changes but properties stay the same)

Question 20

index of refraction

Answer 20

extent to which a given material bends light passing through it

Question 20

What are common signs of a chemical change?

Answer 20

Bubbles, change of mass…

Question 21

characteristics of chemical change

Answer 21

• reaction with acids/bases
• reaction with oxygen (combustion)
• ability to act as oxidizing/reducing agent
• reaction with other elements
• decomposition into simpler substances
• corrosion

Question 22

solids

Answer 22

• particles tightly packed
• vibrating around their fixed position
• definite shape and volume (little space between particles)
• infinite free surfaces

Question 23

liquids

Answer 23

• particles tightly packed but far enough apart to slide over one another
• indefinite shape, definite volume
• one free surface

Question 24

gases

Answer 24

• particles far apart and move freely
• indefinite shape and volume
• no free surfaces

Question 25

sublimation

Answer 25

solid to gas

Question 26

resublimation/deposition

Answer 26

gas to solid

Question 27

ideal gas particles:

Answer 27

1) random, constant, straight-line motion
2) separated by great distance, volume of particles considered negligible
3) no attractive forces between them
4) collisions might cause transfer of energy but total E of the system remains constant

Question 28

When does ideal gas differ from a real gas?

Answer 28

1) at high pressure - distance between particles smaller, volume of particles not negligible
2) at low temperatures - particles stagnant, low kinetic E, attraction forces between them present

Question 29

Why are there horizontal lines on the heating/cooling graph?

Answer 29

The temperature of the substance stays constant because the heat supplied to it is not used to raise the temperature but to break the attraction forces keeping the particles together. This results in a change of state.

Question 30

Maxwell-Boltzmann distribution curve

Answer 30

Since not all particles are surrounded by the same number of particles, not all of them have the same energy. Some particles have less E than the average and some more. Some have enough E to react (activation energy), and those particles evaporate before the substance’s boiling point is reached.

Question 31

What is the only way to change the activation energy?

Answer 31

By adding a catalyst (/enzyme).

Question 32

With higher temperature of the substance, the Maxwell-Boltzmann distribution curve…

Answer 32

…lowers and shifts to the right (bigger portion of it is behind the activation energy barrier).