2 (a) (i) Give the name for the change of state from liquid to solid - Edexcel - GCSE Chemistry - Question 2 - 2021 - Paper 1

The two correct statements are:

• the molecules are more randomly arranged in ice than in water
• the molecules are arranged regularly in ice but not in water

This drinking water should not be described as pure water because pure water contains only water molecules, while this water contains dissolved solids such as calcium ions, sodium ions, and hydrogen carbonate ions. Thus, it is a mixture rather than a pure substance.

The information that shows the drinking water is neutral is the pH value, which is 7.

To calculate the mass of calcium ions in 250 cm³ of water, we know that there are 60 mg of calcium ions per 1000 cm³. Thus, for 250 cm³, the mass can be calculated as follows:

a ext{(mass)} = rac{60 ext{ mg}}{1000 ext{ cm}³} imes 250 ext{ cm}³ = 15 ext{ mg}

So the mass of calcium ions in 250 cm³ of drinking water is 15 mg.

Calcium is known to be a metal because it is positioned in Group 2 of the periodic table, which contains the alkaline earth metals. These elements typically exhibit metallic properties such as good conductivity, malleability, and ductility.