If liquid water is cooled below 0°C it turns into the solid, ice - Edexcel - GCSE Chemistry Combined Science - Question 1 - 2021 - Paper 1

• the molecules move faster in water than in ice ✅
• the molecules are more randomly arranged in ice than in water ❌
• the molecules start moving when water becomes ice ❌
• the molecules are arranged regularly in ice but not in water ✅
• the molecules have more energy in ice than in water ❌

This drinking water should not be described as pure water because it contains dissolved solids which include various ions such as calcium ions, sodium ions, and hydrogen carbonate ions. Pure water is defined as water that contains no other substances.

The drinking water is neutral as indicated by the pH of water, which is 7.

The mass of calcium ions in 250 cm³ of this drinking water can be calculated as follows:

First, note that the concentration of calcium ions is 60 mg per 1000 cm³. Therefore, for 250 cm³:

$\text{Mass} = \frac{60 \text{ mg}}{1000 \text{ cm}^3} \times 250 \text{ cm}^3 = 15 \text{ mg}$

Calcium is known to be a metal because it is located on the left side of the periodic table, in Group 2, where alkaline earth metals are found. These elements are characterized by their metallic properties, such as good conductivity and malleability.