Chapter Two

Question 1

How do plants defend themselves

Answer 1

• Using chemical warfare

eg. black walnut trees release chemical that inhibit the growth of the other trees

   - thus other plants don't grow around the tree reducing competition for vital resources

• Or they release chemicals that limit damage from animals

Question 2

How are chemicals used by animals

Answer 2

• To mark their territory using pheromones
• To protect their territory when absent

Question 3

What does a cell consist mostly of

Answer 3

• Water and four classes of organic compounds and defensive chemicals make up relatively a small proportion of any organisms body

( Carbs; Proteins; Lipids and nucleic acids )

Question 4

What is matter

Answer 4

Any material that takes up space and has mass

Question 5

Explain matter fully

Answer 5

• Elements = fundamental types if matter
• All matter is made up of one or more elements

Question 6

What is a chemical element

Answer 6

A pure substance that cannot be broken down by chemical means into other substances

Question 7

Who invented the periodic table

Answer 7

Dmitry Mendeleyev = Russiam chemist

Question 8

Explain the periodic table fully

Answer 8

• 54 elements with its own unique atomic number and symbol
• 4 most abundant bulk elements are C;H;O;N
• Other bulk elements = P;S;Na;Mg;K;Ca

Question 9

What is an atom

Answer 9

The smallest possible piece of an element that retains the characteristics of the element

Question 10

What is meant by electrically neutral

Answer 10

Number of electrons and protons are =

Question 11

What is an ion

Answer 11

An atom / gap of atoms that has gained or lost electrons thus having a net + / - charge

Question 12

Explain isotopes fully

Answer 12

• Any of the different forms of a single element
• Radioactive isotope = an atom that emits particles or rays as it disintegrates
  • each has a characteristic half-life ( time taken for half the atoms in a sample to emit radiation or to decay to a different, more stable form )

Question 13

What is a molecule and compound

Answer 13

1. 2 chemically joined atoms eg. H2; O2; N2
2. A molecule composed of 2 or more different elements
   eg H2O; CO

Question 14

What forces hold atoms together that make up each molecules

Answer 14

• Electrons determine bonding

Question 15

Explain electronegativity

Answer 15

• The measure of the atoms ability to attract electrons on a scale of 0 to 4
• Elements with high tend to strip electrons from those with lower values
• Elements with moderate often share electrons

Question 16

Explain chemical bonds fully

Answer 16

• An attractive force that holds atoms together
• Whether electrons are shared or stolen, the transfer of them from one to another creates this bond

Question 17

Explain the 3 types of chemical bonds

Answer 17

1. Ionic =one atom transfers electrons to another
2. Covalent = electrons are shared
3. Hydrogen = made by part; charges on adjacent polar molecules

Question 18

Explain water being cohesive and adhesive

Answer 18

• Its cohesive and adhesive
• Cohesion = the tendency of water molecules to stick together
  
  • eg. filling water to the brim of a=glass but doesn’t spill over
• Water has a high surface tension because of its cohesion eg. skating across a pond without breaking surface tension
• It is Adhesive
  • The tendency to form hydrogen bonds with substances other than water

Question 19

What are the two categories that are based on a substances affinity to water

Answer 19

1. Hydrophilic = love water
2. Hydrophobic = fear water

Question 20

What are waters properties

Answer 20

• Cohesion and adhesion
• Many substances dissolve in water
• It regulates temp
• Expands when it freezes
• Participates in life’s chemical reactions
• Is cohesive and adhesive

Question 21

Explain waters expansion when freezed

Answer 21

• Hydrogen bonds in liquid water are constantly forming and breaking, and water molecules are relatively closer together
• Ice crystal = H bonds are stable and molecules are locked into a roughly hexagonal shape

Question 22

What is an acid and a base

Answer 22

Acid = chemical that adds h+ ions to a solution making the conc of H+ ions exceed the conc of the OH ions

Base = Makes conc of OH ions exceed the conc of H+ ions

If mixed together they’ll neutralise each other

Question 23

Explain the pH Scale fully

Answer 23

• Expresses acidity or alkalinity
• 7 = Neutral like pure water
• pH lower than 7 = Acidic
• pH higher than 7 = Basic / Alkaline

Question 24

Explain organic molecules in cells fully

Answer 24

• Chemical compounds that contain both hydrogen and carbon
• Plants and autotrophs produce own organic molecules compared to heterotrophs who obtain theirs from food
• Most abundant = Carbs; Lipids; Proteins and Nucleic Acids

Question 25

What do organic molecules consist of

Answer 25

- Carbon backbone - Functional Group These determine the physical; chemical and solubility properties

Question 26

What is a polymer

Answer 26

- Chains of small molecular subunits called monomers linked together - In between monomers = functional grps who participate in the reactions that creates life organisms molecules

Question 27

Explain Carbs fully

Answer 27

- Consist of C;H;O in the ratio 1:2:1 - Simplest of the 4 organic compounds - Two main groups = Simple ( fructose; glucose )| and complex carbs ( chitin; cellulose; starch ) - AKA monosaccharides and contain 5/6 carbon atoms

Question 28

What is a hydrocarbon

Answer 28

Organic molecule that consists of almost entirely Carbon and Hydrogen

Question 29

What is the molecular formula

Answer 29

- Representation of the atoms in a compound

Question 30

Explain an orbital fully

Answer 30

- Term used by chemists to describe the most likely location for an electron relative to its nucleus - No of orbitals in each shell determines the number of electrons the shell can hold

Question 31

What is a valence shell

Answer 31

An atoms outermost occupied shell