Cambridge Lower Secondary Science Stage 7 : Student's Book>Chapter 7 - Acids and Alkalis>End of stage review>Q 2

HARD

Lower Secondary Stage 7

IMPORTANT

Earn 100

Scientists use indicators to decide whether a substance is an acid or an alkali.

A student used the following colour chart to test different liquids.

Indicator $pH 1$ $pH 4$ $pH 7$ $pH 10$ $pH 13$

Methyl orange Red Red Yellow Yellow Yellow

Phenolphthalein Colourless Colourless Colourless Pink Pink

Copy and complete the table to show the missing indicator colours.

Colour in indicator

Substance Methyl orange Phenolphthalein

Lemon juice Red Colourless

Vinegar Red

Bleach Pink

Soap solution Pink

Important Questions on Acids and Alkalis

HARD

Lower Secondary Stage 7

IMPORTANT

Cambridge Lower Secondary Science Stage 7 : Student's Book>Chapter 7 - Acids and Alkalis>End of stage review>Q 2

Scientists use indicators to decide whether a substance is an acid or an alkali.

Indicator	$pH 1$	$pH 4$	$pH 7$	$pH 10$	$pH 13$
Methyl orange	Red	Red	Yellow	Yellow	Yellow
Phenolphthalein	Colourless	Colourless	Colourless	Pink	Pink

A student used the above colour chart to test different liquids and tabulated the results as given below.

	Colour in indicator
Substance	Methyl orange	Phenolphthalein
Lemon juice	Red	Colourless
Vinegar	Red	Colourless
Bleach	Yellow	Pink
Soap solution	Yellow	Pink

Which substance in the table is the strongest acid?

HARD

Lower Secondary Stage 7

IMPORTANT

Cambridge Lower Secondary Science Stage 7 : Student's Book>Chapter 7 - Acids and Alkalis>End of stage review>Q 2

Scientists use indicators to decide whether a substance is an acid or an alkali.

Indicator	$pH 1$	$pH 4$	$pH 7$	$pH 10$	$pH 13$
Methyl orange	Red	Red	Yellow	Yellow	Yellow
Phenolphthalein	Colourless	Colourless	Colourless	Pink	Pink

A student used the above colour chart to test different liquids and tabulated the results as given below.

	Colour in indicator
Substance	Methyl orange	Phenolphthalein
Lemon juice	Red	Colourless
Vinegar	Red	Colourless
Bleach	Yellow	Pink
Soap solution	Yellow	Pink

What further test would you need to do to identify which substance is the strongest alkali?

MEDIUM

Lower Secondary Stage 7

IMPORTANT

Cambridge Lower Secondary Science Stage 7 : Student's Book>Chapter 7 - Acids and Alkalis>End of stage review>Q 3

Methane can exist in all three states of matter. Draw a diagram to show the arrangement of particles in methane when it is a gas.

MEDIUM

Lower Secondary Stage 7

IMPORTANT

Cambridge Lower Secondary Science Stage 7 : Student's Book>Chapter 7 - Acids and Alkalis>End of stage review>Q 4

Question Image

Usman buys a new saucepan. It is made of aluminium with a plastic handle.

Suggest and explain two reasons why aluminium was chosen for the pan.

MEDIUM

Lower Secondary Stage 7

IMPORTANT

Cambridge Lower Secondary Science Stage 7 : Student's Book>Chapter 7 - Acids and Alkalis>End of stage review>Q 4

Question Image

Usman buys a new saucepan. It is made of aluminium with a plastic handle.

Suggest one reason why plastic was chosen for the handle.