Answer:
it cannot be considered a physical change because it occur from the chemical reaction.
Explanation:
because physical change is the change of the size,volume, density,flexibility. in other words its a change in the outer appearance or change in which we can see or feel without using a tool or a machine
hope it help just my opinion
Physical: the raft needs to float, which means what you make the raft out of must be less dense than water.
The raft would need sturdiness- if the raft is frail, the water might break it
Chemical: It can not react with water and it can not be made of a completely soluable substance (something that would dissolve in it like salt)
Answer:
the engine cool to 40
at 14.07 minutes
Explanation:
Given information
T(5) = 70
= 100
C = 15
Newton's law of cooling :
T(t) = C + (
- C) 
where
T(t) = temperature at any given time
C = surrounding temperature
= initial temperature of heated object
k = cooling constant
to find the the time when the engine will be cooled down to 40
, we first need to find the cooling constant, k
when t = 5, T(5) = 70
so,
T(t) = C + (
- C) 
T(5) = 15 + (100 - 15) 
70 = 15 + (85) 
= (70 - 15) / 85
-5k = ln (55/85)
k = - ln (55/85) / 5
k = 0.087
thus, we have the eqaution
T(t) = 15 + (85) 
now we can determine the time when T(t) = 40
40 = 15 + (85) 
= (40-15)/85
-0.0087t = ln (25/85)
t = - ln (25/85)/0.087
t = 14.07 minutes