Chemistry 3 Flashcards
How were elements in the early periodic table arranged?
By relative atomic mass.
How did the periodic table get its name?
Similar properties appeared periodically.
What are the properties of alkali metals?
Silvery solids.
Stored in oil due to reactivity.
Low density. (First three less dense than water).
What compounds are produced when alkali metals react with non-metals?
White solids that dissolve to form colourless solutions.
How do alkali metals react with water?
Alkali metal + Water (goes to) Metal hydroxide + Hydrogen
What are the properties of halogens?
Have coloured vapours.
What are halogens called when they gain an electron?
Halide ions.
Displacement reactions with halogens.
A more reactive one will displace a less reactive one.
Properties of transition metals.
Good conductors of heat and electricity. Dense. Strong. Shiny. Form colourful compounds. Good catalysts. Can form more than one ion.
How do transition metals compare with alkali metals?
Less reactive. Denser. Stronger. Harder. Higher melting points except Mercury.
How is scum formed?
Calcium and magnesium ions in the water react with the soap to make scum.
What is scale?
It forms on the inside of pipes when temporary hard water is heated.
How do you soften temporary hard water?
1) Hydrocarbonate ions are from dissolved magnesium and calcium Hydrocarbonate.
2) When heated the Hydrocarbonate ions decompose to produce carbonate ions.
3) These combine with magnesium and calcium ions to form insoluble precipitates of magnesium and calcium carbonate.
4) These are the scale which is found in pipes.
5) As there are fewer calcium and magnesium ions in the water, it is now soft.
Why can’t you soften permanent water like temporary hard water?
Contains salts which don’t decompose and form insoluble precipitates once heated.
Softening both types of water- Adding sodium carbonate.
Added ions react with the calcium and magnesium ions to make insoluble precipitate of calcium and magnesium carbonate.
Softening both types of water- Ion exchange resins.
Columns contain many sodium ions inside of them which are trapped on insoluble resins. These ions are exchanged for magnesium or calcium ions.
Na2Resin + Ca2+ (goes to) CaResin + 2Na+
Treatment of drinking water.
1) Water goes through mesh screen to remove big things.
2) Chemicals added to make solids and microbes stick together.
3) Filtered through gravel beds.
4) Chlorine added to sterilise it. This kills microbes.
Filters.
Carbon removes chlorine taste.
Silver kills bacteria.
Advantages of adding fluorine.
Reduces tooth decay.
Advantages of adding chlorine.
Kills microbes and prevents disease.
Disadvantages of fluorine.
High doses can cause cancer.
People cannot chose if they want it.
Some areas may already have high amounts.
Disadvantages of chlorine.
Increase certain cancers.
Can react with natural substances to produce toxin by product which could cause cancer.
Pure water.
Distillation.
Boiling and condensing. Ions don’t evaporate with water so the are removed.
Expensive.
Bond making.
Exothermic.
Bond braking.
Endothermic.
Overall energy change.
Energy of bond braking - Energy of bond making.
Negative overall energy change.
Exothermic.