Question

1) Sort the phrases pertaining to pure substances and mixtures as either true or false. Note: If any part of this question is answered incorrectly, a single red X will appear indicating that one or more of the phrases has been placed incorrectly.

a)pure substances cnnot be separated by physical means.

b) homogeneous mixtures have unifform properties throughout.

c) the components of homogeneous and heterogeneous mixtures cannot be separated.

d) components of a homogeneous mixture are visibly distinct.

e) heterogeneous mixtures contain more than one part, and each part has its own properties.

Answer 1

a) Pure substances cannot be separated by physical means.

TRUE

Explanation:

Pure substances are of two types

1 Elements – simplest form of pure substance. They cannot be broken into anything else by physical or chemical means.

2 Compounds – pure substances that are the combinations of two or more elements. They can be broken into simpler substances only by chemical means and not by any physical method

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b) Homogeneous mixtures have unifform properties throughout.

TRUE

Some fundamental definitions:

PHASE of a system is defined as a homogeneous( composition uniform throughout), physically distinct and mechanically separable portion of a system. The three types of phases are solid,liquid and vapor.

Each phase is separated from every other phase by a surface of separation called phase boundary.

If a system consists of a single phase we cal it a homogeneous system and if more than one phase is present the system is called a heterogeneous system

So a homogeneous mixture will be in a single phase and there will be no surface of separaton betwee the components.

Hence a homogeneous mixture wil have unifform properties throughout..

Example: A solution of NaCl in water..

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c) The components of homogeneous and heterogeneous mixtures cannot be separated.

FALSE

The components of both homogeneous and heterogeneous mixtures can be separated.by physical means

Eg: A homogeneous mixture like a solution of NaCl in water can be separated by evaporation of the solvent water.

A heterogeneous mixture like sand and salt can be separated by dissoving out the salt in water

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d) Components of a homogeneous mixture are visibly distinct.

FALSE

In a homogeneous mixture there is no surface of separaton or phase boundary between the components..Examples.- Solutions.

Hence the components of a homogeneous mixture are NOT visibly distinct.

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e) Heterogeneous mixtures contain more than one part, and each part has its own properties.

TRUE

A heterogeneous mixture will have more than one phase and each each phase will have its own properties.

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