Quick Notes

Quick Notes

Science Chapter 5: Water and Solution
5.1 Physical Characteristics of Water

 

5.1  Physical Characteristics of Water

 

Physical Characteristics of Pure Water

Boiling point = \(100^\circ \text{C}\)

Freezing point = \( 0^\circ \text{C}\)

Colourless

Density = \(1\text{ g cm}^{-3}\)

Effects of absorption and release of heat on the state of water

1) Heat is absorbed

SOLID \(\begin{aligned} &\text{melting}\\ &\quad\rightarrow \end{aligned}\) LIQUID \(\begin{aligned} &\text{evaporation/boiling}\\ &\quad\rightarrow \end{aligned}\)GAS

 
SOLID \(\begin{aligned} &\text{sublimation}\\ &\quad\rightarrow \end{aligned}\) GAS
 

2) Heat is released

GAS \(\begin{aligned} &\text{condensation}\\ &\quad\rightarrow \end{aligned}\) LIQUID \(\begin{aligned} &\text{freezing}\\ &\quad\rightarrow \end{aligned}\) SOLID

 
GAS \(\begin{aligned} &\text{sublimation}\\ &\quad\rightarrow \end{aligned}\)SOLID

Composition of Water

  • Water is a compound  which is made up of 2 hydrogen atoms and 1 oxygen atom
  • Can determine the composition of elements in a water molecule through electrolysis
  • During electrolysis, oxygen gas produce at anode while hydrogen gas at cathode

Evaporation of Water

What is evaporation?
  • Evaporation of water is the process that happens at the surface of water that changes water to water vapour
 

Factors affecting the rate of evaporation

  1. Humidity
  2. Surrounding temperature
  3. Exposed surface area of water
  4. Movement of air
 

Applications of Evaporation of Water in Daily Life

  1. Clothes hung on clothes lines have large exposed surface areas. So, the clother will dry faster
  2. Sea salt is obtained from the evaporation of seawater
  3. Seafood that is dried can be kept longer as microorganisms cannot survive without water