3.1 Introduction Flashcards
What are good observations to make when describing substances in practical work?
-State
-Colour
-Crystalline or powdered? (For solids)
-Clear or cloudy? (For liquids)
What are good observations to make when describing changes during practical work?
-Fizzing?
-Has any solid appeared or disappeared?
-Has anything changed colour?
-Sounds or smells?
Physical change
-Create no new substances
-Are usually easy to reverse
-Absorb or release small amounts of energy
Chemical change
-Create new substances
-Are usually difficult to reverse
-Absorb or release large amounts of energy
What is the test for water?
-Anhydrous copper (II) sulphate
-Turns from white to blue
OR
-Melting point: 0c
-Boiling point: 100c
Define an element
An element is a substance containing only one type of atom
What are properties of metal elements?
-High MP/BP
-Electrical conductors
-Malleable
-Shiny
What are properties of non metal elements?
-Low MP/BP
-Electrical insulators
-Brittle
-Dull
Diatomic molecules
-Iodine
-Bromine
-Fluorine
-Oxygen
-Nitrogen
-Hydrogen
Define a diatomic molecule
The atoms are paired up, their chemical formula is their symbol but with a subscript “2” to show the pairings
Define a compound
A compound is a substance containing more than one type of atom, chemical bonded together
What is an example of a compound?
(This example is too dangerous substances which combine to make something edible)
Sodium + Chlorine ———> Sodium chloride
Corrosive metal + Toxic gas —-> Common salt
What are the three types of compound and what type of chemical bonding do they have?
Metals: Metallic bonding
Non-metals: Covalent bonding
Compounds of both metal and non metals: Ionic bonding
Ammonium chloride tube
-Making the compound ammonium chloride in a tube is used to illustrate diffusion of gases
-Two gases ammonia and hydrogen chloride diffuse from the ends of the sealed tube
-Where they meet, the compound forms as a white smoke
AMMONIA + HYDROGEN CHLORIDE—-> AMMONIUM CHLORIDE
-Shows that hydrogen chloride molecules must be heavier, as they diffused slower
-If you heat up the tube, the white smoke still forms faster
-because particles move faster and collide more often
-Still forms in the same place because both gases diffuse faster
Solute
The substance which is going to be dissolved
Solvent
The liquid which if going to do the dissolving
Solution
The resulting mixture of solute dissolved in solvent