What's the difference between chalk and halk?

Chalk

Definition:

(n.) A soft, earthy substance, of a white, grayish, or yellowish white color, consisting of calcium carbonate, and having the same composition as common limestone.
(n.) Finely prepared chalk, used as a drawing implement; also, by extension, a compound, as of clay and black lead, or the like, used in the same manner. See Crayon.
(v. t.) To rub or mark with chalk.
(v. t.) To manure with chalk, as land.
(v. t.) To make white, as with chalk; to make pale; to bleach.

Example Sentences:

(1) The young screenwriters possibly needed to have chalked up a few miles before they could deliver really workable scripts."
(2) The blue skipping rope – that’s the key to this race.” My eight-year-old daughter looked at me like I was mad … but when it came time for the year 3 skipping race, she did as she was told – and duly chalked up a glorious personal best in third place.
(3) His flicked header into the net seconds later, chalked off by an offside flag, confirmed the forward's luck was not in.
(4) Inside the first 10 minutes, Boyd hit the bar and Lukas Jutkiewicz saw a goal correctly chalked off for offside, while Danny Ings headed just wide at 2-1, and substitute Ashley Barnes struck the bar late on.
(5) France chalked up growth of 0.5%, beating economists' expectations, the best growth figures Fran ç ois Hollande has seen since he was elected president 15 months ago.
(6) 2) If the board and adjacent ones are firmly fixed, dust talc or chalk through the cracks to stop them rubbing together.
(7) The phrase chalk and cheese springs to mind, or as the French say jour et nuit – day and night.
(8) Remember the Theater People: the gal rigging lights for her community theater's production of The Chalk Garden in Brainerd, Minnesota.
(9) The house was later covered in chalk and finally became a curious white landmark.
(10) It is recommended that overall average and chalk carving be given equal emphasis in the selection process.
(11) HS2’s barrister, James Strachan QC, was listening closely, however, and addressed specific points with a lawyer’s care to make no rash promises: HS2’s noise would be less than traffic on the A413; HS2 were working with the RSPB to “mitigate” for barn owls; and, “If there’s a need for chalk grassland, that’s the sort of thing that can be put into these areas to compensate.” Wendy Gray was allowed to respond: “It’s very difficult to be reassured on an unknown quantity,” she said.
(12) According to the sonographic pattern and to the scintigraphic imaging the focal lesions were analysed as micro- or macrofollicular adenomas, autonomous adenomas, cysts and chalk.
(13) Shortly after arriving in Rome, Las Vegas and Tallinn, however, the lines of gameless resolve I had chalked across my mind were wiped clean.
(14) The economy is forecast to chalk up only 0.75% growth this year, and to contract by 1% in 2009 - which would be the first full year of contraction since 1991.
(15) Look, Newsnight is made by 13-year-olds,” he said, speaking at the Chalke Valley history festival about his new book on the first world war.
(16) A series of 75 spoilt soft lenses with opacities (mostly manifesting as discrete spots or as large areas of cloudiness, chalk-white in appearance) were subjected to histochemical, electron microscopical, electron probe x-ray microanalytical, x-ray diffraction, atomic absorption spectro-photometric, and biochemical analyses.
(17) A suspension of chalk powder was injected into the cavity of the urinary bladder of Fischer 344 rats.
(18) The reactivity of soils varies widely as geological and sedimentological conditions offer typical but different environments: gravels, chalk soil, clay, salt soils, sands, cave earths are examples of this wide variety, including atmospheric and biogenetic implications.
(19) A staircase descends steeply into a network of tunnels and cellars that lead to extraordinary old chalk pits.
(20) Photograph: Graham Turner for the Guardian But to date, the prospect of building on abandoned north Kent chalk quarries, has been so unattractive to housebuilders that they have delivered homes at the rate of just 25 a year when 1,000 a year are needed.