1b - elements compounds and mixtures

Question 1

Explain what is meant by centrifuging

Answer 1

It is a method for separating out particles of different densities in a substance.

Question 2

What is an atom?

Answer 2

An atom is the smallest particle of a chemical element that can exist.

Question 3

What is an element?

Answer 3

An element is a substance made up of only one type of atom.

Question 4

Elements can be classified into two groups based on their properties; what are these groups?

Answer 4

Metals and non-metals

Question 5

What is a compound?

Answer 5

Two or more elements combined chemically in fixed proportions which can
be represented by formulae

Question 6

Do compounds have the same properties as their constituent elements?

Answer 6

No, they have different properties.

Question 7

What is a mixture?

Answer 7

A mixture consists of two or more elements or compounds not chemically
combined together

Question 8

What are the methods through
which mixtures can be separated
(there are five)?

Answer 8

Filtration, evaporation/crystallisation, simple distillation, fractional
distillation and chromatography

Question 9

Describe and explain simple
distillation.

Answer 9

Simple distillation is used to separate liquid from a solution – the liquid boils off and condenses in the condenser.

Question 10

Describe and explain evaporation

Answer 10

Evaporation is a technique for separation of a solid dissolved in a solvent from the solvent

Question 11

Describe and explain crystilisation

Answer 11

we remove some of the solvent by evaporation to form a saturated solution

Question 12

Describe and explain fractional distillation

Answer 12

Fractional distillation is a technique for separation of a mixture of liquids. they have to have the same bp

Question 13

Describe and explain filtration

Answer 13

Filtration is used to separate an insoluble solid suspended in a liquid. The insoluble solid gets caught in the filter paper, because the particles are too big to fit through the holes in the paper.

Question 14

Describe and explain chromatography

Answer 14

Chromatography is used to separate a mixture of substances dissolved in a solvent.

Question 15

How is Rf value calculated?

Answer 15

Distance moved by the spot / distance moved by solvent

Question 16

What is a separating funnel?

Answer 16

A separatory funnel is an apparatus for separating immiscible liquids.

Question 17

Explain the following: solute, solvent, solution, miscible, immiscible, soluble, insoluble.

Answer 17

-A solute is a substance that is dissolved in a solvent. Together they form a solution.
-Miscible refers to the substances that mix together in all
proportions, e.g. water and alcohol.
-Soluble refers to the substance that can be dissolved in a solvent, -An insoluble substance won’t dissolve in a particular solvent.

Question 18

true or false:

compounds can be separated into their elements by physical means

Answer 18

false:

compounds cannot be separated into their elements by physical means

Question 19

what is the difference between a compound and a mixture?

Answer 19

a compound consist of two or more chemically combined elements, but a mixture consists of two or more substances that aren’t chemically combined.

Question 20

what is the difference between an element and a compound?

Answer 20

an element only consists of one of itself, as for a compound consists of two or more chemically combined elements