Chapter Two Flashcards
How do plants defend themselves
- 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
How are chemicals used by animals
- To mark their territory using pheromones
- To protect their territory when absent
What does a cell consist mostly of
- 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 )
What is matter
Any material that takes up space and has mass
Explain matter fully
- Elements = fundamental types if matter
- All matter is made up of one or more elements
What is a chemical element
A pure substance that cannot be broken down by chemical means into other substances
Who invented the periodic table
Dmitry Mendeleyev = Russiam chemist
Explain the periodic table fully
- 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
What is an atom
The smallest possible piece of an element that retains the characteristics of the element
What is meant by electrically neutral
Number of electrons and protons are =
What is an ion
An atom / gap of atoms that has gained or lost electrons thus having a net + / - charge
Explain isotopes fully
- 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 )
What is a molecule and compound
- 2 chemically joined atoms eg. H2; O2; N2
- A molecule composed of 2 or more different elements
eg H2O; CO
What forces hold atoms together that make up each molecules
- Electrons determine bonding
Explain electronegativity
- 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
Explain chemical bonds fully
- An attractive force that holds atoms together
- Whether electrons are shared or stolen, the transfer of them from one to another creates this bond
Explain the 3 types of chemical bonds
- Ionic =one atom transfers electrons to another
- Covalent = electrons are shared
- Hydrogen = made by part; charges on adjacent polar molecules
Explain water being cohesive and adhesive
- 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
What are the two categories that are based on a substances affinity to water
- Hydrophilic = love water
- Hydrophobic = fear water
What are waters properties
- 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
Explain waters expansion when freezed
- 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
What is an acid and a base
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
Explain the pH Scale fully
- Expresses acidity or alkalinity
- 7 = Neutral like pure water
- pH lower than 7 = Acidic
- pH higher than 7 = Basic / Alkaline
Explain organic molecules in cells fully
- 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
What do organic molecules consist of
- Carbon backbone
- Functional Group
These determine the physical; chemical and solubility properties
What is a polymer
- Chains of small molecular subunits called monomers linked together
- In between monomers = functional grps who participate in the reactions that creates life organisms molecules
Explain Carbs fully
- 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
What is a hydrocarbon
Organic molecule that consists of almost entirely Carbon and Hydrogen
What is the molecular formula
- Representation of the atoms in a compound
Explain an orbital fully
- 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
What is a valence shell
An atoms outermost occupied shell
