Chemistry Revision

8. Acids, Bases & Salts

Properties of Acids & Bases

Properties of Acids

 An acid is a compound which when dissolved in water produceshydrogen ions (H+) and are described as proton donors (H+)

 Acids turn blue litmus indicator paper (or solution) red. Have pH 1 to 6

 Acid + metal → salt + hydrogen gas

 Acid + base → salt + water

 Acid + metal carbonate → salt + carbon dioxide + water

 Strong acids completely ionize in water producing lots of H+ ions

 Weak acids partially ionize in water producing few H+ ions

Properties of Bases

 Bases are insoluble substances which neutralize acids to form asalt and water only and are proton acceptors

 Alkalis turn red litmus indicator paper (or solution) to blue.

 Have pH 8 to 14.

 Base + acid → salt + water (+ CO2 when base is a metal carbonate)

 Base + ammonium salt → salt + ammonia gas + water

 Strong alkalis completely ionize in water producing lots of OH- ions

 Weak alkalis partially ionize in water producing few OH- ions

PH Scale

Note:

 Neutral substances are pH 7.

 Acidity in soil:

o Plants grow at a pH near 7.

o If it is too acidic or alkaline they will not grow.

o Acidic soil is fixed by adding lime.

 pH is the concentration of H+ ions per dm3 of solution

Note:

 Neutral substances are pH 7.

 Acidity in soil:

o Plants grow at a pH near 7.

o If it is too acidic or alkaline they will not grow.

o Acidic soil is fixed by adding lime.

 pH is the concentration of H+ ions per dm3 of solution

An acid is a compound which when dissolved in water produces

  • hydrogen ions (H+)
  • heat and fire
  • gaseous smell aleays

Acids turn blue litmus indicator paper (or solution)

Acids turn blue litmus indicator paper (or solution) red.

Please mark the following statements correctly as true or false

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  • Acids have PH 7-14
  • Acid + metal → salt + hydrogen gas
  • Acid + base → salt + water
  • Acid + metal carbonate → salt + carbon dioxide + water
  • Strong acids completely ionize in water producing lots of H+ ions
  • Weak acids completely ionize in water producing few H+ ions

Planets of the Solar System

The Eight Planets Tour

In this video Paxi takes you on a tour of our Solar System, visiting all eight planets and other minor bodies such as asteroids, comets and the dwarf planet Pluto.

​Join Paxi on a journey through our Solar System, from the rocky inner planets close to the Sun, past the giant planets to the freezing edge, the home of comets.

 

Can you name the planets?

  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune

Find the "Gas Giants"

Order the planets according to their distance from the Sun

  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptun

Thanks and see you at the next astronomy lesson!

Your homework is to select a planet you like most, find some interesting facts about it and be ready to present these facts in class.