ACID AND ALKALI YEAR 3 COMIC

8.1
ACID AND ALKALI

Learning Standard:
8.1.1 Test acidic, alkaline and neutral substances
through changes in colour of litmus paper by
carrying out investigation.
8.1.2 Make generalisation on acidic, alkaline and
neutral substances through taste and touch by
testing a few substances

YEAR 3

01 02

Introduction Acidic

Litmus paper Sour
Burning Sensation
TABLE OF
CONTENTS →

03 04

Alkaline Neutral

Bitter Tasteless, sweet, or salty
Slippery Slippery or coarse
→ ℎ

01

INTRODUCTION

Litmus paper

What is litmus paper?

Indicator that changes colour when tested.
Used to test acidic, alkaline and neutral substances.

COLOURS

Red
Blue

02

ACIDIC

Sour
Burning Sensation

→

There’s vinegar and lemon. VINEGAR
LEMON

I have vinegar and lemon.
How to test the
substances?

You can taste, touch
and test it with litmus

paper.

We can test the
properties of substances
using our senses of taste

and touch?

Yes.
However, taste and touch

are not scientific
indicators.

TASTE

LEMON

Sour

VINEGAR

Sour

TOUCH

LEMON

Burning
sensation

VINEGAR

Burning
sensation

TASTE

Most acidic substances taste sour.

TOUCH

Most acidic substances have a
burning sensation.

What is the scientific
indicator to test the

substances then?

Litmus paper.
Red and blue litmus

papers.

LITMUS PAPER

LEMON

→
→

VINEGAR

→
→

A

BLUE LITMUS PAPER

C →

Blue litmus paper changes colour to red

I

D
RED LITMUS PAPER

I →

No change in colour.

C

03

ALKALINE

Bitter
Slippery

→

What is the taste and feel
of soap and toothpaste?

SOAP

TOOTHPASTE

TASTE

TOOTHPASTE

Bitter

SOAP

Bitter

TOUCH SPLASH
SOAP
SOAP
Slippery

TOUCH TOOTH
PASTE
TOOTHPASTE
Slippery

ALKALINE SUBSTANCES

TASTE TOUCH

Most alkaline Most alkaline substances
substances taste feel slippery when
touched.
bitter.

What if we test it
using litmus
paper?

It’s a good idea since
litmus paper is a

scientific indicator.

SOAP TOOTHPASTE

→ →
→ →

A

L BLUE LITMUS PAPER
K →

No change in colour.

A

L

I RED LITMUS PAPER
N →

Red litmus paper changes colour to blue.

E

04

NEUTRAL

Tasteless, Sweet, Salty
Slippery or coarse

ℎ

It’s so hot today. I
feel so thirsty.

Why don’t we buy
some drinks from

the mart?

I would like to have MILK
some milk and mineral
MINERAL
water. WATER

Do you know what No. How can I
are the properties of know?

milk and mineral
water?

You can test it using
the senses of taste

and touch.

TASTE

MINERAL WATER

Tasteless

TASTE

MILK

Sweet

TOUCH

MINERAL WATER MILK

Soothing Soothing

Do you know that Really?
neutral substances

have different
tastes?

Yes. Let me tell you.

NEUTRAL SUBSTANCES

TASTE TOUCH

Have different tastes May feel slippery or
such as tasteless, coarse when
sweet, and salty. touched.

Now, let’s see if How?
there’s changes in
colour of litmus

paper.

You need to use both
blue and red litmus
papers.

MINERAL WATER MILK

→ →
→ →

N BLUE LITMUS PAPER
E →
U No change in colour.

T

R RED LITMUS PAPER
A →
L No change in colour.

TASTE AND
TOUCH ARE NOT

SCIENTIFIC
INDICATORS

WHY?

SUBSTANCES

What are the
properties of these

substances?

Coffee Oil

Bitter Slippery

The coffee tastes Maybe. However, you
bitter. I think it is still need to test it
using litmus paper.
alkaline.

But why?

Taste is not a scientific
indicator. Sometimes bitter

substances are acidic or
neutral.

→ See. Only blue litmus
paper changes colour

to red.

So, coffee is acidic
although it tastes

bitter.

→

The oil is slippery.
What do you think the
properties of this oil?

I think it is alkaline because
most alkaline substances
feel slippery when touched.

Let’s confirm it by
testing the oil with blue
and red litmus papers.

→

Oh, no! It’s neutral because
there’s no change in colour

for both types of litmus
paper.

→

CONCLUSION



Taste



Touch