Week 2 - Environmental Chemicals: Classes and Sources

Question 1

What is a chemical substance?

Answer 1

a form of matter having constant chemical composition and characterisitic properties

Question 2

What is matter?

Answer 2

a physical substance in general, which occupies space and possesses rest mass, especially as distinct from energy

Question 3

What is mass?

Answer 3

the quantity of matter which a body contains, as measured by its acceleration under a given force or by the force exerted on it by a gravitational field

Question 4

What is chemical composition?

Answer 4

the identities and relative numbers, of the elements that make up any particular compound

Question 5

What is an element?

Answer 5

a substance whose atoms all have the same number of protons - all of a particular element`s atoms have the same atomic number. Elements are chemically the simplest substances and hence cannot be broken down using chemical reactions.

Question 6

What is atomic number?

Answer 6

the number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table.

Question 7

What is a nucleus?

Answer 7

the centre of an atom. It is made up of nucleons called protons and neutrons and is surrounded by the electron cloud.

Question 8

What is a proton?

Answer 8

a stable subatomic particle occurring in all atomic nuclei. with a positive electric charge equal in magnitude to that of an electron.

Question 9

What is an electron?

Answer 9

a stable subatomic particle with a negative electric charge, found in all atoms and acting as the primary carrier of electricity in solids

Question 10

What is a neutron?

Answer 10

a subatomic particle of about the same mass as a proton, but without electric charge, present in all atomic nuclei except those of ordinary hydrogen

Question 11

What is the valence shell?

Answer 11

The valence shell is the outmost shell of an atom in its uncombined state, which contains the electrons most likely to account for the nature of any reaction involving the atom and of the the bonding interactions it has with other atoms

Question 12

What is an isotope?

Answer 12

variants of the same element that contains equal numbers of protons, bur different numbers of neutrons in their nuclei, and hence differ in relative atomic mass, but not i chemical properties.

Question 13

What are Pollutants?

Answer 13

Substances that are introduced to the environment and have undesired effects or adversely affect environmental resources

Question 14

What are contaminants?

Answer 14

Unwanted constituents in the environment that render air, water, soil, biota impure and in sufficient concentration are harmful

Question 15

What are poisons?

Answer 15

Substances that cause disturbance to organisms when ABSORBED at sufficient quantity

Question 16

What are toxicants?

Answer 16

poisons made or introduced to humans

Question 17

What are toxins?

Answer 17

poisons made naturally by organisms

Question 18

What are venoms?

Answer 18

Toxins injected via e.g. a bite or sting

Question 19

The three ways to classify chemicals:

Answer 19

1) By origin or use
- source, occurrence, purpose
2) By chemistry
- chemical group, base structure, physico-chemical properties, fate (bioaccumulative, persistent, long range transport)
3) By toxicology
- Toxic end-point (carcinogen, neurotoxin), mode of action

Question 20

What is a functional group?

Answer 20

a group of atoms that have predictable chemical behaviour

Question 21

What are physico-chemical properties?

Answer 21

govern the behaviour of chemicals in the environment and can be used to predict their toxicity.

Question 22

Why are partition coefficients useful?

Answer 22

can be used to predict the environmental distribution of chemicals at equilibrium and thus evaluate potential risks

Question 23

What is K_ow?

Answer 23

distribution between octanol and water
C_octanol / C_H2O
Higher value => chemical is more lipophilic
Lower value => chemical is more hydrophilic

Question 24

what is K’_H?

Answer 24

Henry’s law constant, distribution between air and water
C_air / C_H2O
High value => chemical readily volatiles from water
Low values => chemical stays in water

Question 25

What is K_oc ?

Answer 25

distribution between soil organic carbon and water
C_carbon / C_H2O

Question 26

What are point sources?

Answer 26

source of contaminants are stationary, can be pin-pointed

Question 27

What are diffuse sources?

Answer 27

Source of contaminants which are difficult to pin-pint, various origins and contain mixes of contaminants

Question 28

What are secondary sources?

Answer 28

indirect release of contaminants from other sources

Question 29

what are anthopogenic sources?

Answer 29

contaminants resulting from human activity

Question 30

What is and endocrine disruptor?

Answer 30

A substance or mixture that alters functions of the endocrine system (hormones) and can lead to adverse health effects.

Question 31

What is Xenobiotics?

Answer 31

Xenobiotics are foreign chemicals in an organism.