A homogeneous mixture is a mixture in which the composition is uniform throughout the mixture.
A heterogeneous mixture is a mixture in which the composition is not uniform throughout the mixture.
Explanation:
Entropy means the amount of randomness present within the molecules of the body of a substance.
Relation between entropy and microstate is as follows.
S = 
where, S = entropy
= Boltzmann constant
= number of microstates
This equation only holds good when the system is neither losing or gaining energy. And, in the given situation we assume that the system is neither gaining or losing energy.
Also, let us assume that
= 1, and
= 0.833
Therefore, change in entropy will be calculated as follows.

= 
= 
= 
or, = 
Thus, we can conclude that the entropy change for a particle in the given system is
J/K particle.
Sometimes negative sometimes positive, your answer is B!
The researcher may first weight the beaker with water and then start to heat the water to a constant temperature, for example 30 °C and then start adding salt and stirring. He should add salt slowly until solid salt starts to become visible and the solution starts becoming cloudy. When this happens, he should quickly weigh the beaker. The increase in mass is the mass of salt dissolved at that temperature.
The procedure is then repeated but at an increased temperature until 5-6 temperatures have been tested.
Answer: 19.4 g/cm3
Explanation: density is the relationship between mass over volume.
So density of gold is 15.7g/0.81cm3 = 19.4 g/cm3