Test: Is Matter Around Us Pure - Class 9 MCQ

A mixture does not have a fixed melting point, boiling point etc. On the other hand, compounds have a a fixed melting point, boiling point.

- The size range of particles in a colloidal solution is between 1 nm and 100 nm.
- Colloids are mixtures where one substance is dispersed evenly throughout another.
- Particles are larger than those in true solutions (less than 1 nm) but smaller than those in suspensions (greater than 1000 nm).
- This size allows colloidal particles to remain suspended, providing stability without settling.
- Examples include milk, fog, and gelatin, where particles are visible under an ultramicroscope but do not settle out.

Answer: C. Particles can be separated by filtration.

In a suspension, the solute particles are large enough to be filtered out.

Answer: C. Milk

Explanation: Milk is a colloidal solution where fat globules are dispersed in water.

Answer: A. The scattering of light by particles in a colloid.

Explanation: The Tyndall effect is observed when light is scattered by particles in a colloidal solution.

Answer: C. Water

Explanation: Water (H₂O) is a pure substance consisting of only water molecules.

1. Elements:

   • Elements are the simplest form of matter and cannot be broken down into simpler substances by any chemical means.
   • They are homogeneous and can exist in different physical states.

2. Compounds:

   • Compounds are made by a chemical combination of two or more elements and can be broken down into their constituent elements.
   • Compounds are also homogeneous but are not the simplest substances.

Therefore, The statement "They are the simplest substances and cannot be broken down further" applies only to elements.

A compound is a substance formed when two or more elements are chemically joined. Water, salt, and sugar are examples of compounds. When the elements are joined, the atoms lose their individual properties and have different properties from the elements they are composed of.

Tap water is not a pure substance because it is mixed with chemicals that purify it and if it was from the ground it has naturally occurring minerals mixed in it.