S1.1 Introduction to the particulate nature of matter

Question 1

Element

Answer 1

An element is a substance that consists of only one type of atom and cannot be broken down into simpler substances by chemical means.

Question 2

Compound

Answer 2

A compound is a pure substance composed of two or more different elements chemically combined in fixed ratios.

Question 3

How does a mixture differ from a compound?

Answer 3

Mixtures which, unlike elements and
compounds, are not classified as pure substances.

Question 4

Homogeneous

Answer 4

A type of mixture that a uniform composition and no visible phases or boundaries.

Question 5

Heterogeneous

Answer 5

A type of mixture with a non-uniform composition with visible phases or boundaries.

Question 6

What is meant by a “diatomic element” and provide three examples.

Answer 6

Diatomic elements are molecules composed of two atoms of the same element bonded together. Examples include hydrogen (H2), oxygen (O2), and nitrogen (N2).

Question 7

Describe the difference between homogeneous and heterogeneous mixtures with examples.

Answer 7

Homogeneous mixtures have a uniform composition throughout, like salt water, while heterogeneous mixtures have visibly different phases or parts, like a mixture of oil and water.

Question 8

What is filtration used for?

Answer 8

Filtration is used to separate an insoluble solid from a liquid or solution, such as separating sand from water.

Question 9

Evaporation

Answer 9

A change of state from solid to gas; also a separation technique used to separate a homogeneous mixture.

Question 10

Solvation

Answer 10

The interaction of a solvent with molecules or ions of a solute.

Question 11

Distillation

Answer 11

A separation technique used to separate a mixture of two liquids with different boiling points of volatilities.

Question 12

What principle does paper chromatography rely on for separation?

Answer 12

Paper chromatography separates solute mixtures by dissolving them in a solvent (mobile phase) and applying them to chromatography paper (stationary phase). Components move at varying rates due to solvation differences; those favoring the mobile phase travel further than those preferring the stationary phase.

Question 13

Explain recrystallization as a separation technique.

Answer 13

It is a technique to purify solids by exploiting differences in solubility at various temperatures. Initially, the impure solid is dissolved in minimal hot solvent, allowing for the removal of insoluble impurities. Upon cooling, the solubility decreases, causing the desired solid to crystallize while leaving soluble impurities in solution. The crystals are then filtered to obtain the purified product.

Question 14

What are the properties of solids

Answer 14

Solids are incompressible due to closely packed particles with minimal space between them, bound by strong forces of attraction. This results in solids having a fixed shape and volume, and they cannot flow.

Question 15

How do liquids differ from solids in terms of particle arrangement?

Answer 15

Liquids can flow and take the shape of their container due to more spaced-out particles than in solids, though they still have a fixed volume.

Question 16

Describe the properties of gases.

Answer 16

Gases do not have a fixed shape or volume, spreading out to fill the container, with particles far apart and weakly attracted to each other.

Question 17

What is sublimation in the context of states of matter?

Answer 17

Sublimation is the process where a substance changes directly from a solid to a gas without passing through the liquid state.

Question 18

What is the Kelvin scale?

Answer 18

The Kelvin scale is an absolute temperature scale where 0 K (absolute zero) represents a state where particles have zero kinetic energy.

Question 19

How is Kelvin scale related to kinetic energy?

Answer 19

Temperature in Kelvin is directly proportional to the average kinetic energy of particles.

Question 20

How to convert Celsius to Kelvin?

Answer 20

To convert Celsius to Kelvin, add 273. For example, 25 °C is equal to 298 K.

Question 21

What happens to the kinetic energy of particles as temperature increases?

Answer 21

As temperature increases, the average kinetic energy of particles also increases, leading to changes in the state of matter.

Question 22

Describe a heating curve and its significance.

Answer 22

A heating curve illustrates how the state of matter changes as heat is added, showing temperature plateaus during phase changes where heat is used to overcome intermolecular forces rather than increasing temperature.

Question 23

Which phase changes involve absorption of heat?

Answer 23

Melting, evaporation (or boiling), and sublimation are phase changes that involve the absorption of heat.