Chemistry 5: Chemicals Of The Natual Environment Flashcards
Dry air
Air that has all water vapour removed
Name the formula and the percentage of dry for nitrogen oxygen all gone and carbon dioxide
Nitrogen, N₂, 78%
oxygen, O₂, 21%
argon, Ar, 1%
carbon dioxide, CO₂, 0.04%
Covalent bonds
These joined together the atoms inside a molecule
How does a covalent bond form
- A covalent bond forms when atoms share a pair of electrons.
- The atoms are held together because the positively charged nuclei of both atoms attracted to the negative charge a pair of electrons
Simple molecular substances
Simple molecular substances, such as molecules in the air, have a very low melting points and boiling points
Name the melting point and boiling point of nitrogen and oxygen
Nitrogen: melting point = -210°C, boiling point = -196°C
Oxygen: melting point = -218°C, boiling point = -183°C
Why are the mounting am boiling point slow in simple molecular substances
The melting points and boiling points all day because the attractive forces between small molecules are very weak. Very little energy is needed for molecules to overcome these forces move apart
Can pure molecular substances conduct electricity?
Molecules of elements and compounds have no electrical charge, soap your molecular substances cannot conduct electricity
Describe the forces between small covalent molecules and when they melt
- For small covalent molecules, the forces between molecules are weak, but the fault is with the molecules (covalent bonds) are strong
- When a molecular substance melts, the molecules are easily separated from one another but the molecules themselves are not broken up into separate atoms
Hydrosphere
Made up of water, ice and snow on the earth surface and water vapour in the atmosphere
What is the earths hydrosphere
The earths hydrosphere is all the water and Earth, including oceans, seas, legs and rivers. The hardest bit is mostly water, with some dissolved compounds called salts
Ionic compounds
Salts made up of particles called ions which have a positive or negative electrical charge
What are salts
Salts are ionic compounds. Irons have either a positive or negative charge and I arranged in a giant 3-D pattern called a lattice
Ion
Atom (or groups of atoms) with a positive or negative charge, caused by losing all gaining electrons
Lattice
A repeating pattern and phoned by the regular 3-D arrangement of ions
Ionic bond
Chemical bond between two ions of opposite charges
What are the properties of an ionic compound
- Ionic compounds have high melting and boiling points because a large amount of energy is needed to overcome the forces between ions in the lattice
- Ionic compounds you’re not conduct electricity when solid, because The ions are not free to move.When they are melted or dissolved in water, the ion can move and they conduct electricity
Describe the formula of an ionic compound give an example
In the formula of an ionic compound, the number of positive charges just balance cancel out the negative charges, e.g. Na^+ and Cl^- make NaCl; Mg²+ and Cl make MgCl₂
Molecular ion
A charge ion composed of two or more atoms joined together by covalent bonds
Given example of a molecular ion
SO²₄^-
How do we test for ions
- Ions in a compound can be identified by their distinctive properties, for example compounds containing the copper ion are often blue
- Solutions of some ionic compounds make the precipitate of an insoluble compound when they mix. The colour of the precipitate can be used to identify the ions in the compound
- Adding an alkali, such as dilute sodium hydroxide, to different positive metal ions gives different colours of precipitate
How are negative carbonate ions identified
- Negative carbonate ions are identified by adding dilute acid and looking for fizz (effervescence)
How are negative hydroxides ions identified
Negative chloride, bromide, iodide and sulphate ions are identified by adding dilute silver nitrate or dilute barium chloride and looking for participates
Why do carbonates fizz when an acid is added?
Carbonates fizz when an acid is added because carbon dioxide gas is made in the reaction
When do participates form
Precipitates form when an insoluble solid is made in the reaction. For example, most mental hydroxides are insoluble, as is silver chloride from the reaction of silver ions and chloride ions
Give examples of ionic equations with state symbols. Positive ions reacting with hydroxide ions. Negative ions reacting with silver or barium ions.
- For positive ions reacting with hydroxide ions: Cu²^+ (aq) + 2OH^- (aq) ➡️ Cu(OH)₂ (s)
- For negative ions reacting with silver ions or barium ions: Ag^+ (aq) + Cl^- (aq) ➡️ AgCl (s)