Purity of Substances and Formulations Flashcards

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What is a pure substance?

A single element or compound, not mixed with anything else.

How do the melting and boiling points show if a substance is pure or a mixture?

A pure substance melts and boils at one sharp temperature. A mixture changes state over a range.

What is an impurity?

A small amount of another substance mixed into the main substance.

What effect do impurities have on melting point?

They lower the melting point and make it melt over a wider range.

What effect do impurities have on boiling point?

They raise the boiling point and make it boil over a wider range.

How can you check the purity of a sample in the lab?

Measure its melting or boiling point in °C and compare with reliable data. A close, sharp match means pure.

What is a formulation?

A useful mixture made to a recipe, with exact amounts of each component.

Why are formulations made with precise amounts?

To give the product the right properties and the same performance every time.

Give three examples of everyday formulations.

Paints, medicines, and fuels.

In paint, what do the pigment, binder, solvent and additives do?

Pigment gives colour. Binder forms a film and sticks paint to the surface. Solvent thins the paint and helps it spread; it evaporates as it dries. Additives improve properties, like drying time or mould resistance.