GENERAL CHEMISTRY + MOLE CONCEPT

Question 1

what are the particles that make up matter?

Answer 1

• atoms
• molecules
• ions

Question 2

what is an atom?

Answer 2

the smallest part of an element that can exist on its own and take part in a chemical reaction

Question 3

what is a molecule?

Answer 3

two or more atoms chemically bonded together

Question 4

what is an ion?

Answer 4

an atom or group of atoms that carry an electric charge

Question 5

look at gases and kinetic particle theory in your book

Answer 5

only move on after you have read it

Question 6

what is diffusion?

Answer 6

the random movement of particles so that they get mixed up

Question 7

kinetic theory states that:

Answer 7

1. particles in solids, liquids, and gases behave as hard spheres
2. particles in gases and liquids move randomly in any direction
3. particles in gases do not attract each other

Question 8

why does diffusion only occur in liquids and gases and not in solid?

Answer 8

because the particles are able to move. they don’t occur in solids because particles are packed closely together

Question 9

what is an element?

Answer 9

a substance which cannot be split into 2 or more simpler substances by chemical means

Question 10

what is a compound?

Answer 10

consists of two or more identical molecules of different elements chemically bonded together

Question 11

what is a mixture?

Answer 11

a physical combination of two or more substances

Question 12

what is filtration?

Answer 12

the process of separating an undissolved solid from a solute or liquid through use of a funnel and filter paper

Question 13

what is decantation?

Answer 13

the pouring off of a liquid from an undissolved solid (usually those with heavy particles)

Question 14

what is centrifugation?

Answer 14

a process that spins test tubes at high speeds in a centrifuge and forces solids to the bottom of the tube

Question 15

what is crystallisation?

Answer 15

process that forms a crystalline solid from a solution

Question 16

what is simple distillation?

Answer 16

process of separating miscible mixtures using selective boiling and condensation points

Question 17

what is fractional distillation?

Answer 17

process of separating 2 liquids by distillation and collecting them as fractions which boil at different temperatures

Question 18

what is solvent extraction?

Answer 18

the removal of a substance from its aqueous solution by shaking it with another solvent that is more soluble than water

Question 19

what is chromatography?

Answer 19

process used to separate components of a mixture based on their molecular properties using a chromatogram

Question 20

how to calculate Rf

Answer 20

distance travelled by substance / distance travelled by solvent front

Question 21

how to test for purity

Answer 21

a) chromatography
if there is only a single spot on the chromatogram, the substance is likely to be pure
b) melting & boiling point
pure substances have a sharp melting and boiling point. if impure melting & boiling not sharp so it melts and boils over a range of temperatures

Question 22

what happens when ammonia reacts with hydrogen-chloride gas

Answer 22

• ammonia chloride is formed which is a white solid
• the white ring is formed closer to ammonia because ammonia has a lower relative molecular mass than hydrogen chloride and so diffuses much faster than the hydrogen-chloride gas

Question 23

isotopes

Answer 23

atoms of the same element with the same number of protons but different number of neutrons

Question 24

differences between physical & chemical changes

Answer 24

PHY
- no new substance is formed
- usually change is reversible
- mass of substance does not alter
CHEM
- new substance formed
- usually change is irreversible
- mass of substance alters

Question 25

OILRIG

Answer 25

oxidation is loss of electrons
reduction is gain of electrons