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]
3 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]3 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
Are elements matter and why?
nata0808 [166]

All matter is made up of substances called elements, which have specific chemical and physical properties and cannot be broken down into other substances through ordinary chemical reactions. Gold, for instance, is an element, and so is carbon. There are 118 elements, but only 92 occur naturally.

<h3><u>P</u><u>LEASE </u><u>MARK</u><u> ME</u><u> BRAINLIEST</u><u>.</u></h3>
4 0
3 years ago
A solution of NaF is added dropwise to a solution that is 0.0144 M in Ba2+. When the concentration of F- exceeds ________ M, BaF
BARSIC [14]

Answer:

When the concentration of F- exceeds 0.0109 M, BaF2 will precipitate.

Explanation:

Ba²⁺(aq) + 2 F⁻(aq) <----> BaF₂(s)

When BaF₂ precipitates, the Ksp relation is given by

Ksp = [Ba²⁺] [F⁻]²

[Ba²⁺] = 0.0144 M

[F⁻] = ?

Ksp = (1.7 × 10⁻⁶)

1.7 × 10⁻⁶ = (0.0144) [F⁻]²

[F⁻]² = (1.7 × 10⁻⁶)/0.0144 = 0.0001180555

[F⁻] = √0.0001180555 = 0.01086 M = 0.0109 M

Hope this Helps!!!

7 0
4 years ago
What important substances do plants produce during photosynthesis?
I am Lyosha [343]
They produce oxygen and glucose.

Hope this helps :)
7 0
3 years ago
Read 2 more answers
Alcohol is poured into a beaker that contains 2% saltwater. Which are the solutes in the new solution?
Vadim26 [7]
A 2% saltwater is a dilute solution in which the solvent is water and the solute is salt. The solvent is the component of the solution which comprise a large percentage while the solute comprise the smaller part. When alcohol is added, the solute still is salt and the solvent is the mixture of water and alcohol.
4 0
4 years ago
Read 2 more answers
Kind of protists can live in groups with different individuals performing different jobs (site 1)
zlopas [31]

Answer:

The plasmodial slime molds are the kind of protist that can live in groups in which different individuals perform different jobs. Some kinds of bacterial cell walls also have other functions.

8 0
3 years ago
Other questions:
  • How many moles of aluminum oxide are produced from 0.35 moles of oxygen?
    8·1 answer
  • Consider this reaction: 3Fe2O3(s) + CO(g) → 2Fe3O4(s) + CO2(g). Which of the following would increase the rate of the reaction?
    8·2 answers
  • Tell Whether or not each equation is balanced
    15·1 answer
  • The catalytic decomposition of hydrogen peroxide yields oxygen gas and water. In an experiment, decomposition of hydrogen peroxi
    9·1 answer
  • What mineral is most likely used to make the plumbing pipe?
    14·1 answer
  • Hydrogen containing all compounds are not acts as acids. Why?
    10·1 answer
  • The bond angles marked a, b, and c in the molecule below are about __________, __________, and __________, respectively. Select
    6·1 answer
  • The rate of evaporation of water does not depend on the​
    13·2 answers
  • A 200.0 ml quantity of 0.9 M HCl was titrated with an NaOH solution to reach the equivalence point. The goal was to determine th
    12·1 answer
  • What is the average atomic mass of an element that has 3 isotopes with the data below?
    6·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!