The chalk particles embed themselves into the small pores on the surface.
Although a chalkboard seems smooth to the touch, it is quite rough at the microscopic level, with <em>pores</em> that reach below the surface.
When you drag chalk across the board, friction causes small particles of chalk to rub off onto the surface.
If you leave the markings for a long time, some of the chalk particles will work their way into the pores.
A brush will remove the surface particles, but <em>it will not be able to get at the particles in the pores</em>.
Answer: The beaker will not tip over when placed on the hot plate
Justification:
Since beakers have flat surface bottoms (usually and this is the condition to use them for this particular application) they can be placed safely on the hot plate without the risk that the they tip over.
Beakers are wide mouth cylindrical vessels used in laboratories to store, mix and heat liquids. Most are made of glass, in which case the glass is resistant to the flame and does not break when exposed to high temperatures or when is heated by direct contact on a hot plate.
So, their safe shape (flat bottom) that makes them stable, along with their ability to withstand high temperatures, make them suitable to heat solutions in laboratories.
Answer:
sulfur promotes oxide-reduction reactions.
Explanation:
In stagnant water, some solutes tend to precipitate. When Sulfur precipitate and touch a metal, Sulfur is being reduced and the metal is oxidated. This depends of potential redox of each element.
Since the Summer solstice is when the sun is highest in the sky and the solstice is in June, that's your answer :)
