Principles Of Chemistry

Question 1

What are the three states of matter?

Answer 1

The three states of matter are solids, liquids, and gases.

Question 2

What determines the state of a substance?

Answer 2

A substance can usually exist in all three states, dependent on temperature and pressure.

Question 3

What are the state changes that occur at the melting point?

Answer 3

Melting (solid to liquid) and freezing (liquid to solid) occur at the melting point.

Question 4

What are the state changes that occur at the boiling point?

Answer 4

Boiling (liquid to gas) and condensing (gas to liquid) take place at the boiling point.

Question 5

How are the three states of matter represented in a simple model?

Answer 5

In this model, the particles are represented by small solid spheres.

Question 6

What is the arrangement of particles in a solid?

Answer 6

Regular arrangement.

Question 7

What is the movement of particles in a liquid?

Answer 7

Move around each other.

Question 8

How close are the particles in a gas?

Answer 8

Far apart.

Question 9

What affects the amount of energy needed to change states?

Answer 9

The strength of the forces between the particles.

Question 10

What happens during melting?

Answer 10

A solid changes into a liquid as heat is absorbed, transforming thermal energy into kinetic energy.

Question 11

What is the melting point?

Answer 11

Melting happens at a specific temperature known as the melting point (m.p.).

Question 12

What is the difference between boiling and evaporation?

Answer 12

In boiling, bubbles of gas form inside the liquid, while evaporation occurs only at the surface.

Question 13

What is freezing?

Answer 13

Freezing is when a liquid changes into a solid, occurring at the same temperature as melting.

Question 14

What is evaporation?

Answer 14

Evaporation occurs over a range of temperatures and can happen below the boiling point.

Question 15

What is condensation?

Answer 15

Condensation occurs when a gas changes into a liquid on cooling.

Question 16

What is sublimation?

Answer 16

When a solid changes directly into a gas.

Question 17

What is diffusion?

Answer 17

Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.

Question 18

What is a solvent?

Answer 18

The liquid in which a solute dissolves.

Question 19

What is a solute?

Answer 19

The substance which dissolves in a liquid to form a solution.

Question 20

What is a saturated solution?

Answer 20

A solution with the maximum concentration of solute dissolved in the solvent.

Question 21

What is an element?

Answer 21

A substance made of atoms that all contain the same number of protons.

Question 22

What is a compound?

Answer 22

A pure substance made up of two or more elements chemically combined.

Question 23

What is a mixture?

Answer 23

A combination of two or more substances that are not chemically combined.

Question 24

What distinguishes a pure substance from a mixture?

Answer 24

A pure substance consists of a single element or compound, while a mixture contains multiple substances.

Question 25

What is simple distillation used for?

Answer 25

To separate a liquid and soluble solid from a solution.

Question 26

What is fractional distillation used for?

Answer 26

To separate two or more liquids that are miscible with one another.

Question 27

What is filtration used for?

Answer 27

To separate an undissolved solid from a mixture of the solid and a liquid.

Question 28

What is crystallisation?

Answer 28

A method used to separate a dissolved solid from a solution.

Question 29

What is paper chromatography?

Answer 29

A technique used to separate substances that have different solubilities in a given solvent.

Question 30

What does an Rf value represent?

Answer 30

The ratio of the distance traveled by the substance to the distance traveled by the solvent front.

Question 31

What is the first step in the chromatography method?

Answer 31

Use a ruler to draw a horizontal pencil line 2 cm from the end of the chromatography paper.

Question 32

How should the coloring spots be applied?

Answer 32

Use a different capillary tube to put a tiny spot of each colouring A, B, C, and D on the line, and label each spot in pencil.

Question 33

What should be done with the unknown mixture?

Answer 33

Use the fifth tube to put a small spot of the unknown mixture U on the line.

Question 34

What is the maximum diameter for each spot?

Answer 34

Make sure each spot is no more than 2-3 mm in diameter.

Question 35

How deep should the water be in the beaker?

Answer 35

Pour water into the beaker to a depth of no more than 1 cm.

Question 36

How should the chromatography paper be positioned?

Answer 36

Clip the top of the chromatography paper to the wooden spill, ensuring the top end is furthest from the spots.

Question 37

What should the bottom edge of the paper do?

Answer 37

The bottom edge of the paper should dip into the solvent.

Question 38

How long should the solvent travel?

Answer 38

Allow the solvent to travel undisturbed at least three quarters of the way up the paper.

Question 39

What should be done after removing the paper?

Answer 39

Draw another pencil line on the dry part of the paper as close to the wet edge as possible; this is called the solvent front line.

Question 40

What is measured to determine the distance traveled?

Answer 40

Measure the distance in mm between the two pencil lines; this is the distance travelled by the water solvent.

Question 41

How should the distances for food colorings be measured?

Answer 41

For each food colour A, B, C, and D, measure the distance in mm from the start line to the middle of the spot.

Question 42

What is a practical tip for the chromatography process?

Answer 42

The pencil line must never be below the level of the solvent as the samples will be washed away.

Question 43

How should results be recorded?

Answer 43

Record your results in a suitable table with columns for food colouring, distance moved by spot (mm), distance moved by solvent (mm), and Rf value.

Question 44

What should be compared for the unknown sample?

Answer 44

The Rf values of food colours A, B, C, and D should be compared to that for the unknown sample, along with a visual comparison.

Question 45

What does it mean if substances have matching Rf values?

Answer 45

Substances with matching Rf values are the same substance and will move the same distance up the paper.