February 2025

Uses of sulphuric acid

By |2025-02-12T09:43:37+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

ZIMSEC O Level Combined Science Notes: Uses of sulphuric acid

  • Most of the sulphuric acid produced at Zimphos is used to
  • make fertilizers (mostly superphoshate)
  •  Some of the sulphiric acid is used to  manufacture aluminum sulphate
  • Which in turn is used as a flocculent in water purification processes
  • Bauxite from Mutare is dissolved into sulphuric acid
  • The word […]
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Experiment: Demonstrating that carbon dioxide extinguishes a burning flame

By |2025-02-12T09:10:46+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Carbon dioxide extinguishes flames Carbon dioxide extinguishes flames ZIMSEC O Level Combined Science Notes: Experiment: Demonstrating that carbon dioxide extinguishes a burning flame

Aim: to show that carbon dioxide extinguishes a flame

Materials:  3 different sized candles, vinegar, baking soda, beaker or plastic bottle, shallow dish

Method

  1. Place the 3 pieces of candle in a […]
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Experiment: Current and Voltage

By |2025-02-12T09:24:45+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

ZIMSEC O Level Combined Science Notes: Experiment: Current and Voltage 

Aim: To show how current changes with voltage and to find the resistance of a resistor

Materials: Three/Four 1.5V battery cells, ammeter, lamp,resistor, switch, leads with crocodile clips

Method

 

Current and Voltage Current and Voltage

  1. Set up the series using one cell as shown in the […]
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Lead acid accumulators

By |2025-02-12T09:40:28+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

ZIMSEC O Level Combined Science Notes:  Lead acid accumulators

  • These act as a storage cell
  • Electrical energy is passed into the cells during the charging cycle
  • It is stored in the form of chemical energy
  • \text{Chemical Energy}\xrightleftharpoons[charging]{discharging} \text{Electrical Energy}
  • Lead acid accumulators are known as secondary cells
  • Secondary cells-can be recharged once the voltage drops
  • Charging is done […]
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Electrical safety concepts

By |2025-02-12T09:06:05+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Three pin plug Three pin plug. Image credit tlc-direct.co.uk ZIMSEC O Level Combined Science Notes: Electrical safety

  • The following concepts and terms have to be understood:
  • Short circuit
  • Overloading
  • Earthing
  • Fuses
  • Three pin plug
  • Two pin plug

Short circuit

  • this is when a wire breaks and comes in contact with […]
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Timber properties and timber structures

By |2025-02-12T09:20:56+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

A wooden house. Image credit designrulz.com A wooden house. Image credit designrulz.com ZIMSEC O Level Combined Science Notes:Timber properties and timber structures

  • Wood is a popular material in the construction industry
  • Wood is light and has a high strength/mass ratio
  • Light, strong beams/trusses are a priority in the building of houses

    • […]

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Experiment: Lever position and mechanical advantage

By |2025-02-12T09:37:53+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Lever position and effort Lever position and effort ZIMSEC O Level Combined Science Notes: Experiment: Lever position and mechanical advantage

Aim: To show that mechanical advantage depends on lever position

Materials: 1m rectangular poplar wood pieces, string, measuring tape, weights, clamp

Method

  1. Cut a grooves at 20cm, 40 cm and 50 cm lengths from the right […]
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Hydraulic Jack

By |2025-02-12T09:09:30+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

ZIMSEC O Level Combined Science Notes: Hydraulic Jack

  • Has a large ram attached to the piston in a large cylinder

The diagram of the Hydraulic Jack. Image credit slideplayer.com

The diagram of the Hydraulic Jack. Image credit slideplayer.com

  • A piston in a small cylinder is worked by a handle
  • Pressure on this cylinder when […]
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Contraception: Sterilisation

By |2025-02-12T09:45:27+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Black couple. Image credit blackcouplegetaways.com Black couple. Image credit blackcouplegetaways.com ZIMSEC O Level Combined Science Notes:Contraception:Ways to prevent pregnancy

How it works

  • Can be done in both men and women
  • In men it is known as a vasectomy
    • Sperm duct is cut and tied
    • During sexual intercourse ejaculated fluid contains no sperm

    • […]

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