Introduction - 3.1
No description yet. This curated deck is ready for daily study.
Card preview (21)
What are good words to use when describing substances in practical work?
• solid, liquid or gas? • coloured or colourless? • crystalline or powdered? (for solids) • clear or cloudy? (for liquids)
What are observations to make when describing changes during practical work?
• is there any fizzing • has a solid appeared or disappeared • has anything changed colour • are there any unusual sounds or smells
In general physical changes:
• create no new substances • are usually easy to reverse • absorb or release small amounts of energy
In general, chemical changes:
• create new substances • are usually difficult to reverse • absorb or release large amounts of energy
What is the chemical test for water?
anhydrous copper sulphate: turns from white to blue - this tells you water is present not how pure it is
What are the two physical tests for water?
• Melting point = 0 degrees C • Boiling point = 100 degrees C purer water matches these properties more closely
What is the definition of an element?
an element is a substance containing one type of atom
Elements: Metal vs Non-metal properties
Metal - High MP/BP - electrical conductors - malleable - shiny Non-metal - Low MP/BP - electrical insulators - brittle - dull
What is the definition of a compound?
a compound is a substance containing more than one type of atom that are chemically bonded together
How can compounds be formed?
compounds can often be formed by heating their compounds together
What are the properties of compounds?
The properties of a compound are usually totally different from the properties of the elements the compound is made from. e.g. sodium chloride
What are the types of compounds?
Metals - metallic Non-metals - covalent Both -ionic
Key practical: Ammonium Chloride Tube
Two gases, ammonia and hydrogen chloride diffuse from the ends of the sealed tube. Where they meet, the compound ammonium chloride forms as a white smoke: Ammonia + Hydrogen chloride → Ammonium chloride This shows that the hydrogen chloride molecules must be heavier, as they diffused slower.
Solute
The substance which is going to be dissolved
Solvent
The liquid which is 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 are the three key parts of a solubility curve?
• the line = saturated shows the maximum mass of solid which can be dissolved at each temperature • below = soluble less than the maximum mass of solid, so it will all dissolve • above = insoluble More than the maximum mass of solid, so some will dissolve and some won’t. The mass that dissolves can be found by reading off the line.