Episode Details

So we're going to find out what 'pure' really means to a chemist, and why the juice fails the test. Then we'll see what the juice actually is, and why that turns out to be useful rather than a let-down.

The listener can now catch the word 'pure' lying. Pure means one substance, and you can check it because the substance melts sharply at one fixed temperature. Anything else is a mixture, where the parts keep their own properties, come in any amounts and can be pulled apart. That ability to pull things apart is what the next three episodes are about.

Sources:

• https://www.thenational.academy/teachers/programmes/chemistry-secondary-ks4-higher-ocr/units/states-of-matter/lessons/pure-substance
• https://www.vaia.com/en-us/textbooks/chemistry/introductory-chemistry-a-foundation-7-edition/chapter-3/problem-7-why-would-a-chemist-find-fault-with-the-phrase-pur/
• https://chem.libretexts.org/Courses/Harper_College/CHM_110:_Fundamentals_of_Chemistry/01:_The_Process_of_Science/1.07:_Classifying_Matter_According_to_Its_Composition
• https://www.science-revision.co.uk/purity%20and%20formulation.html
• https://yesdirt.com/is-orange-juice-a-pure-substance/
• http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/meltpt.html
• https://en.wikipedia.org/wiki/Freezing-point_depression
• https://www.lpi.usra.edu/education/explore/ice/background/allAboutWater/
• https://www.scientificamerican.com/article/why-do-we-put-salt-on-icy/
• https://en.wikipedia.org/wiki/Atmosphere_of_Earth
• https://en.wikipedia.org/wiki/Seawater
• https://rwu.pressbooks.pub/webboceanography/chapter/5-3-salinity-patterns/

Source: Episode 7 - Chemistry Level 8, Chapter 3: Separation techniques (1/4). Pure substances and mixtures…
Sections: 3.1, 3.2
Style: Exam prep
Length: 1046 words, 6 min target
Generated: 2026-10-25