1. Structures and Properties of Matter

Question 1

Chemistry

Answer 1

• the study of the structure and properties of matter, and the transformation of one form to another

Question 2

Organic chemistry

Answer 2

• the study of compounds containing carbon: proteins, carbohydrates, lipids, vitamins, DNA, RNA
• organic compounds always contain carbon and usually contain hydrogen
• organic compounds always have covalent bonds

Question 3

Inorganic chemistry

Answer 3

• the study of compounds without carbon: acids, bases, water, minerals
• inorganic compounds are usually structurally simple and may have ionic or covalent bonds

Question 4

Matter

Answer 4

• any substance that has mass + volume
• defined by physical + chemical properties
• can undergo physical + chemical change

Question 5

Properties

Answer 5

• characteristic behaviour of a substance
• enables it to be described, identified + classified

Question 6

Physical Properties

Answer 6

• characteristics of a substance that can be determined without changing the composition of the substance
• colour, shape, odour, taste, physical state, melting point, freezing point, boiling point, density, conductivity, hardness, malleability

Question 7

Chemical Properties

Answer 7

• characteristics of a substance that determine how it transforms into another substance - change in composition

Question 8

Physical change

Answer 8

• when a substance changes its appearance but not its composition
• no change in chemical properties
• usually easily reversed
• usually produced by low amounts of energy

Question 9

Chemical change

Answer 9

• a change in which one or more new substances are formed
• reactants > products
• new substances have different chemical properties to the original substance
• usually not easily reversible
• usually requires a large amount of energy
• involves the transfer of atoms and the breaking + making of chemical bonds

Question 10

Pure substance

Answer 10

• fixed composition - cannot be further purified - two types: elements + compounds

Question 11

Mixtures

Answer 11

• physical blend of two or more pure substances, each retaining its own chemical identity
• no fixed composition
• can be separated by physical means
• two types: homogeneous + heterogeneous
• example of physical separation: separating iron filings from powdered sulfur - the mixture of iron and sulfur is stirred with a magnet, which attracts the iron. Much of the iron is removed with the first stir. With continued stirring, the iron is a attracted to the magnet and completely removed

Question 12

Elements ₍₁₀₎

Answer 12

• atoms are chemically identical
• cannot be broken down into smaller substances by chemical reaction
• unique chemical symbol
• has atomic number + atomic mass
• fixed position in periodic table according to its atomic number
• either metal, non metal or metalloid
• has characteristic chemical + physical properties
• characteristic emission spectra - some exist as allotropes
• families are classified based on properties + atomic structure
• 116 known elements > 88 natural, 28 synthesised

Question 13

Allotropes

Answer 13

• the property of some elements to exist in two or more different structural forms, whereby the atoms are bonded together in a different manner
• refers only to different forms of the element in the same state
• can have different physical and chemical properties
• change between allotropic forms is triggered by the same forces that affect other structures, ie. pressure, light and temperature
• eg. the allotropes of carbon include diamond (atoms bonded in a tetrahedral lattice), graphite (atoms bonded in sheets of hexagonal lattice), graphene (single sheets of graphite), and fullerenes (atoms bonded in spherical, tubular, or ellipsoidal formations)
• non-metal allotropes: carbon, phosphorous, oxygen, sulfur, selenium
• metalloid allotropes: boron, silicon, arsenic germanium, antimony, polonium
• metal allotropes include sodium, calcium, tin, iron

Question 14

Compounds

Answer 14

• consist of two or more elements chemically bonded in fixed proportion by mass
• unique set of properties very different from component elements
• represented by a chemical formula
• classified in different ways: organic or inorganic, molecular or ionic, electrolyte or non electrolyte, crystalline or amorphous

Question 15

Homogeneous mixtures

Answer 15

• uniform composition throughout
• components are not visible

Question 16

Heterogeneous mixtures

Answer 16

• non uniform composition
• components are visible

Question 17

Solid state

Answer 17

• definite shape + volume
• particles are close together + ordered
• strong interactions between particles
• incompressible

Question 18

Liquid state

Answer 18

• definite volume but not definite shape
• particles are separated + disorganised, colliding frequently, but forming a surface
• slightly compressible

Question 19

Gas state

Answer 19

• no defined shape or volume
• expand to fill their container
• particles far apart, randomly organised, colliding occasionally
• negligible interactions between particles
• highly compressible

Question 20

Energy

Answer 20

• the capacity to do work
• two main types: kinetic & potential

Question 21

Kinetic Energy

Answer 21

• the energy of motion

Question 22

Potential Energy

Answer 22

• stored energy

Question 23

Law of Conservation of Energy

Answer 23

• energy can neither be created nor destroyed