March 2017

Chemical building blocks of Life: Water

By |2018-03-03T10:59:46+02:00March 30th, 2017|Notes, O Level Biology Notes, Ordinary Level Notes|

Water is life

ZIMSEC O Level Biology Notes:Chemical building blocks of Life: Bio-molecules

Water

Structure of a water molecule

  • Water is essential for life.
  • Approximately 75% earth’s surface is water.
  • Life evolved in water.
  • An average adult body is 50 to 65 percent water
  • This rises to about 80% in a child
  • A water molecule is made up of 2 hydrogen atoms […]

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Biology Notes: Water and its properties: Transparency and high heat of evapouration

By |2018-03-03T12:06:15+02:00March 30th, 2017|Notes, O Level Biology Notes, Ordinary Level Notes|

ZIMSEC O Level Biology Notes: Properties and Biological significance of water

Property: High heat of vaporization

  • This is a measure of the heat energy required to vaporize a liquid to overcome the attractive forces between its molecules so that they can escape as a gas.
  • A relatively large amount of energy is needed to vaporize water.
  • This is due […]

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Biology Notes: Water and its properties: Transport medium and specific heat capacity

By |2018-03-03T10:44:39+02:00March 30th, 2017|Notes, O Level Biology Notes, Ordinary Level Notes|

ZIMSEC O Level Biology Notes:Properties and Biological significance of water

Property: Transport medium

  • Water is a neutral liquid medium because it has a pH of 7.

Biological role of this property

  • Water’s solvent properties also mean that it acts as a transport medium in the blood transporting cells, lymphatic and excretory system, the alimentary canal and in the xylem and phloem.

Property: High […]


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Biology Notes: Water and its properties: Polar solvent

By |2018-03-03T10:34:23+02:00March 30th, 2017|Notes, O Level Biology Notes, Ordinary Level Notes|

ZIMSEC O Level Biology Notes:Properties and Biological significance of water

Property: Polar solvent

  • Water is an excellent solvent for ions and polar molecules because the water molecules attract to them, collect and separate them.
  • This is what happens when a substance dissolves in water.
  • Once a chemical is in solution, it is free to move about and react with other chemicals.
  • […]


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Biology Notes: Water and its properties: Surface tension

By |2018-03-03T10:28:00+02:00March 30th, 2017|Notes, O Level Biology Notes, Ordinary Level Notes|

ZIMSEC O Level Biology Notes:Properties and Biological significance of water

Property: High surface tension and cohesion (adhesion and cohesion)

  • Cohesion is the force whereby individual molecules stick together.
  • Adhesion is the force whereby water molecules stick to other surfaces.

Biological role

  • Cohesion helps water to move as an unbroken column in the xylem tubes in plants.
  • Adhesion helps the water to stick […]

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Biology Notes: Water and its properties: Density and heat fusion

By |2018-03-03T10:22:45+02:00March 30th, 2017|Notes, O Level Biology Notes, Ordinary Level Notes|

ZIMSEC O Level Biology Notes:Properties and Biological significance of water

Property: High heat of fusion

  • This is a measure of the heat energy required to melt a solid (ice).
  • Liquid water must lose a large amount of heat energy to freeze.

Biological role

  • Contents of cells and their environment are therefore less likely to freeze.
  • This is an advantage for bodies of […]

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September 2016

Protecting Water supplies

By |2017-01-17T11:11:11+02:00September 16th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

A protected well. Image credit totallandcare.org

A protected well. Image credit totallandcare.org ZIMSEC O Level Combined Science Notes: Testing the purity of water
  • Most rural areas do not have access to running tap water
  • Their water comes from various sources including dams, wells, boreholes, springs
  • Some of these sources are produce […]

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Testing the purity of water

By |2017-01-17T11:11:12+02:00September 16th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

Milk can be used to test the purity of water. Image credit wordpress.com

Milk can be used to test the purity of water. Image credit wordpress.com ZIMSEC O Level Combined Science Notes: Testing the purity of water

Materials: 4 test tubes, sterilised fresh milk, tap water, borehole water, spring water. plugs

Method

  1. Collect water […]

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June 2015

Water in Hot Deserts

By |2017-01-17T11:21:57+02:00June 15th, 2015|Hot Deserts, Notes, O Level Geography, Ordinary Level Notes|

Flash floods in a desert. Image credit Backroadswest.com

Flash floods in a desert. Image credit Backroadswest.com ZIMSEC O Level Geography Notes: Water in Hot Deserts
  • Water action in deserts can be divided into three:
  • freak storms or rain that falls sometimes in semi-arid regions,
  • dew which plays formed as a result of temperatures […]

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