physical and chemical change

Question 1

indicators of physical change

Answer 1

temperature of substance increases
change in size or shape
expected colour change
conductivity of metals decreases
substance may change phase

Question 2

physical change

Answer 2

-identity of reactants and products remains unchanged
-overcoming forces

Question 3

indicators of chemical change

Answer 3

unexpected colour change
gas formed
heat released/absorbed
precipitate (solid) formed
light produced

Question 4

chemical change

Answer 4

atoms,molecules,ions rearrange themselves in new patterns and ratios
breaking bonds

Question 5

synthesis reaction

Answer 5

chemical reaction where 2 or more simple substances are combined to form a complex product
A+B—>AB

Question 6

decomposition reaction

Answer 6

one reactant produces 2 or more products
AB—>A + B

Question 7

dissolution

Answer 7

soluble solid is placed into water and breaks down into smaller particles surrounded by water molecules

Question 8

why does dissolution occur

Answer 8

because of the polar nature of water

Question 9

dissociation

Answer 9

the splitting of an ionic compound into its ions

Question 10

explain process of dissociation

Answer 10

formation of ions from ionic compounds

any ionic soluble substance

ionic salt further breaks down into anions and cations
ions separate away from each other by attraction of water molecules for them

Question 11

what is formed when ionic substances dissociate in water

Answer 11

electrolyte
aqueous solution that can conduct electricity as the ions are free to move to carry charge

Question 12

nitrates solubility

Answer 12

all soluble

Question 13

group 1 compounds solubility

Answer 13

Li+, K+, Na+, NH4+
all soluble

Question 14

Halides solubility

Answer 14

Cl-,Br-,I- most soluble

except Ag2+, Pb2+, Hg2+

Question 15

Sulphates solubility

Answer 15

SO4 2-
Ba2+, Pb2+,Ca2+

Question 16

Carbonates

Answer 16

CO3 2-
most insoluble
except Li+, K+, Na+, NH4+

Question 17

silver chloride (s) colour

Answer 17

white

Question 18

lead chloride colour (s)

Answer 18

white

Question 19

silver bromide colour (s)

Answer 19

Cream

Question 20

lead bromide (s) colour

Answer 20

pale yellow

Question 21

silver iodide (s) colour

Answer 21

pale yellow

Question 22

lead iodide (s) colour

Answer 22

bright yellow

Question 23

sulphate (s) colour

Answer 23

white

Question 24

carbonate (s) colour

Answer 24

white

Question 25

what is an ion exchange reaction

Answer 25

2 aqueous ionic solutions are mixed cations exchange respective anions AB (aq) + CD(aq) + AD + CB

Question 26

bond energy

Answer 26

energy stored in a bond energy needed to break bond energy released when bond broken

Question 27

bond distance

Answer 27

distance between atoms when they have bonded

Question 28

when a bond is broken…

Answer 28

substance less stable energy taken in Ep increases

Question 29

bond made..

Answer 29

substance more stable energy released/out Ep decreases

Question 30

how can aqueous ionic solutions undergo chemical change

Answer 30

electrolysis ion-exchange reactions

Question 31

activation energy

Answer 31

the minimum energy required to start a chemical reaction OR the energy required to form the activated complex Ein/Ea

Question 32

activated complex

Answer 32

a high energy, unstable, temporary transition state between the reactants and the products

Question 33

exothermic reactions

Answer 33

reactions which transform chemical potential energy into thermal energy Ereleased net release of thermal energy delta h<0 negative more energy released than absorbed surrrondings heated bonds of product stronger than bonds of reactants

Question 34

endothermic reaction

Answer 34

reactions which transform thermal energy into chemical potential energy Eenergy absorbed >Ereleaseed positive delta H>0 temp of surroundings decrease bonds of reactants stronger than bonds of products net absorption of thermal energy

Question 35

ion exchange formula

Answer 35

cations exchanged w respective anions AB+CD—> AD+BC

Question 36

how is reaction determined endo or exo

Answer 36

every chemical reaction has a endothermic (bond breaks) and exothermic( bonds made) component never same value-overall reaction

Question 37

catalyst

Answer 37

a substance that increases the rate of the reaction but remains unchanged at the end of the reaction

Question 38

delta H

Answer 38

heat of reaction/change in enthalpy net change of chemical potential energy of system

Question 39

temperature

Answer 39

a measure of the average kinetic energy of the particles of a substance

Question 40

melting point

Answer 40

the temperature at which a solid changes phase to a liquid

Question 41

boiling point

Answer 41

the temperature at which a liquid changes phase to a gas

Question 42

freezing point

Answer 42

the temperature at which a liquid changes phase to a solid

Question 43

ionisation

Answer 43

the reaction of a molecular substance with water to produce ions