Classification of Substances: Mixtures and Pure Substances

Practice flashcards covering the classification of matter into mixtures (homogeneous and heterogeneous) and pure substances (elements and compounds), including separation methods such as evaporation, filtration, magnetic separation, heating, and electrolysis.

What is the definition of mixtures?

Substances composed of two or more materials, that are not chemically combined and their components can be separated by physical means (methods).

What are homogeneous mixtures, and what is another name for them?

Homogeneous mixtures are mixtures whose components cannot be distinguished by the naked eye, and all homogeneous mixtures are known as solutions.

How are heterogeneous mixtures defined, and what is an example?

Heterogeneous mixtures are mixtures whose components can be distinguished by the naked eye, such as a mixture of sand in water.

What is one similarity and one difference between a homogeneous mixture and a heterogeneous mixture?

Similarity: The components of both can be separated by physical methods. Difference: The components of a homogeneous mixture cannot be distinguished by the naked eye, whereas the components of a heterogeneous mixture can be distinguished by the naked eye.

What is the purpose of evaporation and condensation in separating mixtures?

It is a method used to separate the components of a homogeneous mixture composed of a liquid containing a dissolved solid substance, such as separating water from table salt.

How is filtration defined as a separation method?

A method used to separate the components of a heterogeneous mixture composed of a liquid and an insoluble solid substance, such as separating sand from water.

What is magnetic separation used for, and what is a given example?

It is a method used to separate the components of a heterogeneous mixture composed of a solid substance attracted to a magnet and another solid substance not attracted to it, such as separating iron filings from sand.

What are pure substances?

Substances whose components cannot be separated by physical methods.

What is an element?

The simplest pure form of matter that cannot be dissociated into simpler forms by either physical or chemical methods.

What is a compound?

A pure substance formed by the chemical combination of two or more elements in fixed mass ratios and its components can be separated by chemical methods.

What happens when red mercury oxide ($HgO$) is heated?

When red mercury oxide ($HgO$) is heated, it decomposes into its elements: mercury ($Hg$) and oxygen gas ($O_2$).

What apparatus is used for the electrolysis of acidified water?

A Hoffmann voltameter is used for the electrolysis of water ($H_2O$) acidified with sulphuric acid.

During the electrolysis of water, which gases are produced at the cathode and anode?

Hydrogen gas ($H_2$) is produced at the cathode ($-$) and oxygen gas ($O_2$) is produced at the anode ($+$).

Why is hydrogen classified as an element?

Because it cannot be dissociated into simpler forms by either physical or chemical methods.

Why is water classified as a compound?

Because it is formed by the chemical combination of hydrogen and oxygen elements in a fixed mass ratio.