8/2/2019 5.3 Evaporation of Water Observation)

1/22

CHAPTER 5WATER AND SOLUTION

5.3 Evaporation of water

8/2/2019 5.3 Evaporation of Water Observation)

2/22

Learning outcome:

Explain what evaporation is

Explain through examples the factorsthat affect the rate of evaporation of

water Compare and contrast evaporation

and boiling

Describe the applications of theevaporation of water in daily life

8/2/2019 5.3 Evaporation of Water Observation)

3/22

Before we go further, let watchthis video first

8/2/2019 5.3 Evaporation of Water Observation)

4/22

What you can see from the

video?

What do you understand fromthe video?

8/2/2019 5.3 Evaporation of Water Observation)

5/22

Definition

Evaporation is the process by which aliquid changes into its vapour

Example: when a plate of water is left

in the open, the water evaporates andbecomes water vapour

During this process, water molecules

receive enough energy to escape fromthe surface of water

8/2/2019 5.3 Evaporation of Water Observation)

6/22

NOW LET ANSWER MY QUESTION

8/2/2019 5.3 Evaporation of Water Observation)

7/22

A

B

8/2/2019 5.3 Evaporation of Water Observation)

8/22

Between photo A and photoB, which clothes will dry

first?

8/2/2019 5.3 Evaporation of Water Observation)

9/22

8/2/2019 5.3 Evaporation of Water Observation)

10/22

Between photo A and photo B,

which one the water inside it will

evaporate faster?

8/2/2019 5.3 Evaporation of Water Observation)

11/22

Factors that affect the rate ofevaporation of water

The temperature ofsurroundings

The surface area of water

The humidity of air

The movement of air

8/2/2019 5.3 Evaporation of Water Observation)

12/22

if the temperature of the surroundingsis higher, the surface area of water is

larger, the humidity of air is lower andthere is movement of air, so that manywater molecules on the surface will

escape to the air thus speeding upevaporation of water

8/2/2019 5.3 Evaporation of Water Observation)

13/22

Boiling and Evaporation

What the similarities of boiling and

evaporation?

What the differences between them?

ANYONE?

8/2/2019 5.3 Evaporation of Water Observation)

14/22

Similarities

Both involve the change ofstate from liquid to gas

Both process absorb heat

8/2/2019 5.3 Evaporation of Water Observation)

15/22

Differences

Evaporation Boiling

Occurs at the

liquid surface

Occurs

throughout theliquid

Occurs at all

temperaturesbelow the liquidsboiling point

Occurs at the

liquids boilingpoint

A slow process A fast process

8/2/2019 5.3 Evaporation of Water Observation)

16/22

Seebubbles?

8/2/2019 5.3 Evaporation of Water Observation)

17/22

The Application ofEvaporationDrying hair

Drying clothes

Preservation of agriculturalproducts

Processing of food

8/2/2019 5.3 Evaporation of Water Observation)

18/22

Preservation of agricultural products:

1. Agricultural products such as paddy,cocoa, black pepper and coconut are

usually dried under the sun beforebeing processed

2. These dried products can be kept

longer because microorganismscannot live without water

8/2/2019 5.3 Evaporation of Water Observation)

19/22

Processing of food:

1. Salted fish,dried prawns and saltedvegetables are dried under the sun

2. This method also used to obtain saltfrom the sea

3. Milk powder is produced by

evaporating its water content byusing special instrument at highertemperature

8/2/2019 5.3 Evaporation of Water Observation)

20/22

You can see the examples in the textbook,

page 12 and let watch this video

8/2/2019 5.3 Evaporation of Water Observation)

21/22

To test your understanding, let doexercises

from Top Gears book page 51 and 52.

We will discuss the answer together

8/2/2019 5.3 Evaporation of Water Observation)

22/22

Summary

Definition of evaporation

Factors that affect the rate ofevaporation of water

Boiling and evaporation

Application of evaporation in our dailylifes