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
Saturated
A solution in which no more solute can be dissolved
Suspension
A solid floating in a liquid because it cannot dissolve
Soluble
A substance which can be dissolved
Insoluble
A substance which cannot be dissolved
What is solubility measured in?
g per 100g of solvent
What does “the solubility of sodium chloride in water is 36.37g/100g” mean?
This means that up to 36.37g of sodium chloride can dissolve into 100g of water
Solubility can be scaled for different amounts of solvent: 36.37g/100g —>??
18.185g can dissolve in 50g of water (just halved)
Saturated (solubility curve)
-The line= saturated
-Shows the maximum mass of solid which can be dissolved at each temperature
Soluble (solubility curve)
-Below the line= Soluble
-Less than the maximum mass of solid, so it will all dissolve
Insoluble (Solubility curve)
-Above the line= Insoluble
-More than the maximum mass of solid, so some of it will dissolve and some won’t
-The mass that dissolves can be found by reading off the line
Define a mixture
Different substances in the same space, but not chemically combined
What is the arrangement of particles in a solid?
Regular arrangement
What is the arrangement of particles in a liquid?
Randomly arranged
What is the arrangement of particles in a gas?
Randomly arranged
What is the movement of particles in a solid?
Vibrate about a fixed position
What is the movement of particles in a liquid?
Move around each other
What is the movement of particles in a gas?
Move quickly in all directions
What is the closeness of particles in a solid?
Very close
What is the closeness of particles in a liquid?
Close
What is the closeness of particles in a gas?
Far apart
Solid to liquid
Melting
Liquid to solid
Freezing
Liquid to gas
Evaporation
Gas to liquid
Condensation
Solid to gas
Sublimation
Gas to solid
Deposition
What is the method for investigating the solubility of a solid in water at a specific temperature?
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- Prepare two beakers, one as a hot water bath and one as an ice bath
- Using a small measuring cylinder, measure out 4 cm of distilled water into a boiling tube.
- On a balance weigh out 2.6 g of ammonium chloride and add it to the boiling tube
- Place the boiling tube into the hot water bath and stir until the solid dissolves
- Transfer the boiling tube to the ice bath and allow it to cool while stirring
- Note the temperature at which crystals first appear and record it in a table of results
- Add 1 cm of distilled water then warm the solution again to dissolve the crystals
- Repeat the cooling process again noting the temperature at which crystals first appear
- Continue the steps until a total of 10 cm of water has been added
