WATER

3. A cleaning agent used to test for water hardness. It reacts with hard water ions to form scum instead of lather.
5. A type of water hardness caused by dissolved calcium hydrogencarbonate. It can be removed by boiling the water.
7. An insoluble solid that forms and settles out of a liquid during a chemical reaction, such as scale forming from boiled hard water.
9. Water that contains only H₂O molecules, with no dissolved salts, minerals, or other substances.
11. The insoluble, sticky grey solid that forms when soap reacts with the calcium or magnesium ions in hard water.
13. A process of purifying water by heating it to create steam, then cooling the steam to collect it as pure liquid water, removing hardness ions.
15. The process of removing the minerals that cause hardness from water, making it "soft."

1. The rich foam produced when soap mixes with water and is agitated. Soft water produces a good lather.
2. The chalky, white deposit (mostly calcium carbonate) that forms inside kettles, pipes, and boilers when hard water is heated.
4. The process where a liquid turns into a vapor when heated to its boiling point. For pure water, this is 100°C at sea level.
6. A property of water caused by dissolved minerals, mainly calcium and magnesium ions, which prevents soap from lathering easily.
8. A measure of water's ability to conduct electricity. Hard water conducts electricity better than soft or pure water due to its dissolved ions.
10. A type of water hardness caused by dissolved calcium sulfate. It cannot be removed by boiling, only by chemical methods or distillation.
12. Naturally occurring inorganic substances. In water, dissolved minerals like calcium and magnesium cause hardness.
14. Electrically charged atoms or molecules. Hard water contains calcium (Ca²⁺) and magnesium (Mg²⁺) ions.