physical and chemical change Flashcards

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1
Q

indicators of physical change

A

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

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2
Q

physical change

A

-identity of reactants and products remains unchanged
-overcoming forces

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3
Q

indicators of chemical change

A

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

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4
Q

chemical change

A

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

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5
Q

synthesis reaction

A

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

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6
Q

decomposition reaction

A

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

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7
Q

dissolution

A

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

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8
Q

why does dissolution occur

A

because of the polar nature of water

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9
Q

dissociation

A

the splitting of an ionic compound into its ions

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10
Q

explain process of dissociation

A

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

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11
Q

what is formed when ionic substances dissociate in water

A

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

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12
Q

nitrates solubility

A

all soluble

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13
Q

group 1 compounds solubility

A

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

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14
Q

Halides solubility

A

Cl-,Br-,I- most soluble

except Ag2+, Pb2+, Hg2+

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15
Q

Sulphates solubility

A

SO4 2-
Ba2+, Pb2+,Ca2+

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16
Q

Carbonates

A

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

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17
Q

silver chloride (s) colour

A

white

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18
Q

lead chloride colour (s)

A

white

19
Q

silver bromide colour (s)

A

Cream

20
Q

lead bromide (s) colour

A

pale yellow

21
Q

silver iodide (s) colour

A

pale yellow

22
Q

lead iodide (s) colour

A

bright yellow

23
Q

sulphate (s) colour

A

white

24
Q

carbonate (s) colour

A

white

25
Q

what is an ion exchange reaction

A

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

26
Q

bond energy

A

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

27
Q

bond distance

A

distance between atoms when they have bonded

28
Q

when a bond is broken…

A

substance less stable
energy taken in
Ep increases

29
Q

bond made..

A

substance more stable
energy released/out
Ep decreases

30
Q

how can aqueous ionic solutions undergo chemical change

A

electrolysis
ion-exchange reactions

31
Q

activation energy

A

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

32
Q

activated complex

A

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

33
Q

exothermic reactions

A

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

34
Q

endothermic reaction

A

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

35
Q

ion exchange formula

A

cations exchanged w respective anions

AB+CD—> AD+BC

36
Q

how is reaction determined endo or exo

A

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

37
Q

catalyst

A

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

38
Q

delta H

A

heat of reaction/change in enthalpy

net change of chemical potential energy of system

39
Q

temperature

A

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

40
Q

melting point

A

the temperature at which a solid changes phase to a liquid

41
Q

boiling point

A

the temperature at which a liquid changes phase to a gas

42
Q

freezing point

A

the temperature at which a liquid changes phase to a solid

43
Q

ionisation

A

the reaction of a molecular substance with water to produce ions