a substance dissolves.
like adding a soluble salt to water, it just dissolves, i.e dissociates homogeneously as water is able to dissociate salts (ionic compounds) into its ions. (it can also dissociate other non-ionic compounds like HCL)
the salt still remains chemically as a salt and is unchanged chemically thus it is not an indication of a chemical reaction as no chemical reaction has taken place.
the formation of a precipitate is a chemical reaction because a new substance (i.e new chemical) is formed. For example adding aqueous sodium hydroxide into an aqueous solution with CU2+ cations will form a blue precipitate (that is copper (II) hydroxide which is insoluble, hence it precipitates). Since a new chemical is formed, a chemical reaction has taken place and thus indicates a chemical reaction.
color change... im not sure but usually a color change will only occur when a new substance is formed. Like iron corrodes (i.e rust) slowly in moist air to form hydrated iron (III) oxide that is rust. (brown color).
usually adding a mixture to a mixture has little energy change, i.e little heat taken in by the reaction mixture or little heat given out by the reaction mixture. Whereas when a new substance is formed, there is usually noticeable energy change like the container gets colder or hotter (without heat being supplied of course). For example dissolving basic oxides into water releases energy ( more energy released than gained = exothermic reaction).
i think that should be the answer... hope it helped :D
Answer:
Incomplete question, check attachment for completed question
Explanation:
The force of attraction between two forces are given as
F=kQq/r²
Explanation:
Given that,
Initial speed of the sports car, u = 80 km/h = 22.22 m/s
Final speed of the runner, v = 0
Distance covered by the sports car, d = 80 km = 80000 m
Let a is the acceleration of the sports car. It can be calculated using third equation of motion as :
Value of g, 
Hence, this is required solution.
An electromagnet is a device that sends electricity through a coil of wire to produce a magnetic field. This leads to a magnet that can be controlled - turned on and off with the flip of a switch, or increased or decreased in strength. The coils are often wrapped around a regular magnet to make it stronger.
Answer:
1.when it is closest to the sun
2.when it is midway between its farthest
Explanation:
According to the law of Kepler's
T ² ∝ r³
T=Time period
r=semi major axis
We also know that time period T given as
v=Speed
So we can say that ,when r is more then the speed will be minimum and when r is low then speed will be maximum.
