1(b) Elements, compounds and mixtures

Question 1

1.8

Element

Answer 1

A substance made of atoms that all contain the same number of protons and cannot be split into anything simpler

Question 2

1.8

Compound

Answer 2

A substance made of two or more elements chemically bonded to each other in a fixed ratio

Question 3

1.8

Mixture

Answer 3

A combination of two or more substances (elements or compounds) that have not been chemically bonded together.

Question 4

understand that a …. substance has a fixed melting and boiling point, but that a
……. may melt or boil over a range of temperatures

Answer 4

1. Pure
2. Mixture

Question 5

1.10

Simple Distillation

Answer 5

1. Separates a liquid from a solution.
2. Heat the solution until the liquid with the lower boiling point boils. As the vapour reaches the condenser, it condenses back into a liquid and collects at the bottom of the conical flask.

Question 6

1.10

Fraction Distillation

Answer 6

1. Separate mixture of liquids with different boiling points.
2. The mixture is heated until it boils. The vapourised mixture rises through the fractional column and each liquid condenses at different heights. Each liquid goes into its own fractions based on its boiling point. Each fraction is then collected separately.

Question 7

1.10

Filtration

Answer 7

1. Separates insoluble solids from liquids and solutions.
2. Pour solution into funnel with filter paper and let it drip into a beaker. The filter paper should contain the insoluble solid once the process is finished.

Question 8

1.10

Crystallisation

Answer 8

1. The process is when a solid forms from the saturated solution as it cools.
2. Heat crysatl solution in evaporation basin. Reduce the volume by half with heating to make a saturated solution. Pour into a petri dish and wait for it to cool and crystallise.

Question 9

1.10

Paper Chromatography

Answer 9

1. Separate a mixture of soluble compounds due to their different solubilities in the solvent used.
2. Preparing a suitable solvent (mobile phase) and heating it. Lowering the paper into the solvent. The dye spreads up the paper as the paper absorbs the solvent. The paper has absorbed the solvent, and the dye has spread further up the paper. The paper used in paper chromatography is made of cellulose.
3. More solube the substance the farther it will travel up the paper.

Question 10

1.11

understand how a chromatogram provides information about the composition of a
mixture

Answer 10

By separating and identifying the components

Question 11

1.12

Rf value

Answer 11

distance spot moves/distance solvent moves

Question 12

key terms

Stationary phase

Answer 12

The chromotography paper that the mobile phase moves up

Question 13

key terms

Mobile phase

Answer 13

The solvent that moves up the chromotography paper

Question 14

key terms

Solvent

Answer 14

The liquid used to ‘run’ the chromatogram, often water used for ink and dyes

Question 15

key terms

Baseline

Answer 15

Pencil line drawn 1cm from the bottom of the paper

Question 16

1.13

practical: investigate paper chromatography using inks/food colourings