NATURE OF MATTER

Question 1

Define ELEMENTS

Answer 1

A chemical substance that cannot be broken down into a smaller substance by chemical means

Pure substance in which each atom has the same number of protons in the nucleus

Question 2

Define COMPOUNDS

Answer 2

A pure substance formed when 2 or more elements are combined chemically in a fixed ratio

Elements in a compound are chemically combined –> can only be converted into their elements again by chemical reactions

Question 3

Define MIXTURE

Answer 3

2 or more substances mixed together, not chemically bonded together

They retain their individual properties since they are not chemically bonded, and can be separated from each other by physical means

Components of a mixture can be mixed together in any proportion

Question 4

Chemical properties

Answer 4

How a substance behaves in a chemical reaction

Question 5

Physical properties

Answer 5

All other properties of a substance
eg. melting point, density, hardness, electrical conductivity

Question 6

Define HOMOGENOUS MIXTURE

Answer 6

Uniform composition throughout the mixture
Consists of only one phase
Different components can be separated by chemical means

eg. mouthwash, rainwater

Question 7

Define HETEROGENOUS MIXTURE

Answer 7

Does not have uniform composition
Consists of separate phases
Different components can be separated by chemical means

eg. oil and water

Question 8

Comparing HETEROGENOUS and HOMOGENEOUS mixtures

Answer 8

They contain 2 or more elements or compounds mixed together and can be separated by physical means

Question 9

Contrasting HETEROGENOUS and HOMOGENEOUS mixtures

Answer 9

HOMOGENOUS:
Uniform composition
Uniform properties

HETEROGENOUS:
Non-unifrom composition
Non-uniform properties

Question 10

Liquid to Gas?

Answer 10

Boiling

Question 11

Gas to Liquid?

Answer 11

Condensation
Refers to the change in physical state from gas to liquid

Question 12

Solid to Liquid?

Answer 12

Melting

Question 13

Liquid to Solid?

Answer 13

Freezing

Question 14

Gas to Solid?

Answer 14

Deposition
Refers to the change in physical state from gas to solid

Question 15

Solid to Gas?

Answer 15

Sublimation

eg. Dry ice (CO2 in solid state), Iodine,
Ammonium chloride

Question 16

Describe a solid

Answer 16

A solid’s particles are packed closely together. Due to relatively strong forces of attraction between them, particles are unable to move freely and can only vibrate about mean positions. As a result, a solid has a stable, definite shape and a definite volume. (Solids can only change shape under force, as when broken or cut.)

Question 17

Describe a liquid

Answer 17

The particles have weaker forces between them, and so are able to move around each other. As the forces between the particles are weaker than those in solids, liquids are able to flow and take the shape of the container they are in.

Question 18

Describe a gas

Answer 18

Gas is a form of matter with molecules that have weak forces of attraction between them. The particles move freely and quickly, filling the shape and volume of their container. Unlike solids and liquids, gases are easily compressed due to their weak intermolecular forces.

Question 19

Temperature definition?

Answer 19

Temperature is a measure of the average kinetic energy of the particles in a substance.
[The temperature, T, in Kelvin (K) is a measure of average kinetic energy Ek of particles]

Kelvin is the SI unit of temperature

Question 20

Temperature conversion

Answer 20

Temp (K) = Temp (C) + 273.15