1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Deffense [45]
2 years ago
5

Chalk markings cannot be easily rubbed off from a black board if kept for a long time.why?

Chemistry
1 answer:
snow_tiger [21]2 years ago
3 0

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>.

You might be interested in
If you start a chemical reaction with 5 atoms of hydrogen, how many hydrogen atoms will you have when it is finished? Group of a
mote1985 [20]

Answer:

5 atoms

Explanation:

According to the law of conservation of mass, "matter is neither created nor destroyed in the cause of a chemical reaction".

We finish with what we start with in a chemical reaction. Although new species might form, the number of atoms on both sides of the expression will still be maintained.

All chemical reactions obey this law of conservation.

8 0
3 years ago
Choose the phrase that best defines ecosystem service. (1 point)
Fantom [35]

Human:

✧・゚: *✧・゚:*  Answer:  *:・゚✧*:・゚✧

✅ the first one  

I WOULD APPRECIATE BRAINLIEST!

~ ₕₒₚₑ ₜₕᵢₛ ₕₑₗₚₛ! :₎ ♡

~

7 0
2 years ago
Read 2 more answers
A gas tank contains 3 gases (N2, O2, and CO2). The total pressure of the gases is 825mmHg. If Pco2 = 125mmHg and Po2= 350mmHg, w
DedPeter [7]

Answer:

350mmHg

Explanation:

Use Dalton law

Total=P gas 1+p gas 2+ P gas 3

825=P1+350+125

825=P1+475

825-475= P1

P1= 350 mm Hg

3 0
1 year ago
Which solution, solution X of pH 9.4 or solution Y of pH 7.5, is more acidic? Which solution, solution of 9.4 or solution of 7.5
zzz [600]

Answer:

Solution Y is more acidic

Explanation:

The pH value is an indicator of the concentration of hydrogen ions (H⁺) in an aqueous solution, and it is defined as:

pH= -log [H⁺]

⇒ [H^{+} ]= 10^{-pH}

Where  [H⁺] is the concentration of H⁺. A solution with a higher concentration of H⁺ is more acidic, and a solution with a lower concentration of H⁺ is less acidic or basic.

As result, <em>the lower the pH, the more the concentration of hydrogen ions ([H⁺]), and the aqueous solution is more acidic</em>.

Solution Y has a lower pH value (7.5) than solution X (9.4). So, solution Y is more acidic.

8 0
3 years ago
How many moles of potassium iodide (KI) are in 48.9 g of potassium iodide (KI) ? ____ moles
wel

Answer:

mass of kI = 74.55 Atomic mass

74.55 g ---> 1 mole

48.9 g --> ?

48.9 / 72

0.7 mole.

In one mole of kI --->

5 0
1 year ago
Other questions:
  • A liquid with a high surface tension exhibits __________.
    10·2 answers
  • What is the relationship between the period and the orbital radius? Select one: a. It is a direct relationship- As the period in
    5·1 answer
  • What are two types of vaporization
    11·2 answers
  • What is the best definition of "thinking at the margin"? *
    5·1 answer
  • If the distance between two objects is increased, the gravitational force will _____.
    12·2 answers
  • What would happen to the population of an animal if its food source were removed from the food web
    11·1 answer
  • what type of forces either interatomic or intermolecular forces prevents ice cubes from adopting the shape of their container​
    6·1 answer
  • Elements in the same __ have similar physical properties
    5·2 answers
  • The process of generating electricity from dams and nuclear power plants is very different, but some of the energy transformatio
    14·2 answers
  • Silver is a metal; it reacts with oxygen which is a non-metal to form Silver Oxide. The bond between Silver and Oxygen is called
    8·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!