# Explain how the properties of water make it an effective solvent for ionic compounds in living organisms.

> IB DP Biology Standard Level (2023 syllabus) — A1.1 Water · Explain · 4 marks

## Mark scheme (4 marks)

1. Water molecules are polar / have an uneven distribution of charge, with a partial negative charge (δ−) on the oxygen and partial positive charges (δ+) on the hydrogen atoms.
2. The partial charges on water molecules attract the oppositely charged ions of ionic compounds / the δ− oxygen is attracted to cations and the δ+ hydrogens are attracted to anions.
3. Water molecules surround individual ions, forming a hydration shell, which separates ions from the crystal lattice and keeps them in solution.
4. This allows ions (e.g. Na⁺, Cl⁻, mineral ions) to be transported in blood / cytoplasm / across membranes, supporting biochemical reactions in living organisms.

## Key terms

- [ionic compound](https://www.gradenine.co.uk/glossary/ionic-compound)
- [solvent](https://www.gradenine.co.uk/glossary/solvent)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-properties-of-water-f31ce5ad) · Published by Druglandscape Ltd.