What happens to the mass of the substances when something dissolves?

If some solute dissolved in solvent the mass of solvent is increased.

Explanation:

Solvent is the liquid that allow some mass to dissolve in it.

Solute is the component that is dissolved in the solvent.

When some solute is dissolved in solvent the total mass of them remains the same but the individual mass changes as both are mixed.

Thus if some solute dissolved in solvent the mass of solvent is increased.

"For a projectile with no air resistance, at the peak of its path, it's velocity is equal to zero"

Explanation:

Suppose that you throw an object up. The initial vertical velocity will be positive, and the acceleration (the gravitational acceleration) will point downwards, meaning that it opposes to the initial direction of the velocity, and that decreases the velocity as the time goes by.

There will be a point where the velocity ( that was positive until now, so until now the height of the object was increasing), is equal to zero, this means that at this moment the object stops moving, and after, because we still have negative acceleration, the velocity will start become negative, and the object will fall down.

Then that point where the velocity was zero is the peak of its path, then we can conclude that:

"For a projectile with no air resistance, at the peak of its path, it's velocity is equal to zero"