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SingaporeChemistry

Experimental Chemistry and Separation Techniques

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do chemists identify unknown ions and gases by their characteristic reactions and tests?

Carry out and interpret qualitative analysis tests for common cations, anions and gases, describing the observations and the reagents used
A focused answer to the O-Level Chemistry outcome on qualitative analysis. Tests for common cations with sodium hydroxide and ammonia, tests for anions, and the standard gas tests, with the observations markers expect.
9 min answer →

How do chemists choose and read laboratory apparatus to measure mass, volume, time and temperature accurately?

Name common laboratory apparatus and select the correct instrument to measure mass, volume of liquids and gases, time and temperature, reading each to an appropriate precision
A focused answer to the O-Level Chemistry outcome on laboratory measurement. Choosing the right apparatus for mass, volume, time and temperature, reading scales to the correct precision, and the difference between accuracy and precision.
8 min answer →

How does paper chromatography separate and identify the coloured substances in a mixture?

Describe paper chromatography, interpret a chromatogram to determine the number and identity of components, and calculate and use the Rf value
A focused answer to the O-Level Chemistry outcome on paper chromatography. How the technique separates a mixture, reading a chromatogram for the number and identity of components, and calculating and using the Rf value.
8 min answer →

How do chemists choose the right method to separate and purify the components of a mixture?

Describe and select separation methods (filtration, crystallisation, simple and fractional distillation, use of a separating funnel) according to the properties of the substances, and test for purity using melting and boiling points
A focused answer to the O-Level Chemistry outcome on separation. Choosing filtration, crystallisation, simple and fractional distillation or a separating funnel from the properties of the mixture, and using melting and boiling points as purity tests.
9 min answer →