Bases/ Alkalis

Grade 7B
Teacher Sidra Latif

“Have you ever used soap or cleaning products at home? What do you think what makes them effective at cleaning?”
OR
I am slippery to touch, taste bitter,

and turn red litmus blue. What am I?'

BASE/ALKALIS

PROPERTIES AND USES

LEARNING OBJECTIVE:

To investigate about the bases and

explain its properties.

REAL LIFE APPLICATION:

Bases are using every day in homes,

industries and laboratories.

CROSS-CURRICULAR LINK:

Properties of bases are directly linked with the chemistry in which we deal with different substance and chemical reactions having basic properties.
Science + Sustainability + UAE Vision 2040
Sustainable practices, such as the role of base compounds in wastewater treatment, which could relate to the UAE’s efforts in water conservation and sustainability, highlighted in the UAE Vision 2040. Explore how alkalinity plays a role in cleaning and recycling water, an important process for a desert country like the UAE.

KEY CONCEPTS:

.

Alkalis

.

Hydroxide
ions

.

Neutralization
Reaction

BASES/ALKALI

Bases are those substances that have
a bitter taste, slimy and slippery feel
on fingers which turn red litmus paper
blue and which contain metal oxides
or hydroxides. If a liquid produces
more hydroxide (OH), it is a base.

The bases which are soluble in water
called Alkali.

Alkali

Formula

Sodium hydroxide

NaOH

Potassium hydroxide

KOH

Calcium hydroxide

Ca(OH)₂

Ammonium hydroxide

NH₄OH

Magnesium hydroxide

Mg(OH)2

EXAMPLES:

PROPERTIES OF BASES/ALKALI

• Aqueous solution of base has a soapy touch.

• Bases change the color of litmus from red

to blue, colorless. phenolphthalein pink,

methyl orange yellow. They turn turmeric

paper brown.

• Aqueous solution of bases are great

conductors of electricity.

• Bases react with acids to form salt and water.

(Neutralization Reaction)

Multiple Choice

Which of the following is a property of a base?

• bitter taste

• reacts with metals

• salty

• sour taste

Multiple Choice

Bases turn blue litmus paper red.

• True

• False

Multiple Choice

indicator that turns red in the presence of an acid and blue in the presence of a base

• solvent

• solute

• litmus

• temperature

Multiple Choice

An alkali is produced when

• A salt dissolves in water

• A base dissolves in water

• An acid dissolves in water

• An acid reacts with a base

​Characteristics of Bases: Taste Bitter

Example: Baking Soda, Bitter Gourd, Neem, Black Paper

Multiple Choice

Which one of the following is an example of a base?

• orange juice

• vinegar

• lemons

• dish soap

GROUP ACTIVITY ( Hand on Experiment)

(10 Minutes)

Explore the litmus paper test to identity bases.

Serial No.

Substance

Litmus paper
color

Result ( Acidic/Basic/Neutral )

1.

2.

3.

4.

5.

Individual ACTIVITY 15 minutes

Brain Booster
Identifying
base Properties

https://wordwall.net/resource/56369013/grad
e-7-acids-and-bases
OR
Identify Common Bases in Household Products: List and explain the function of common household items containing bases.

Star Scientists
Bases in
cleaning and
Industry

https://quizizz.com/join?gc=510021
OR
Investigate pH of Bases: Test and compare the pH of various bases, recording and explaining the results.

Science Explorer
Base Reactions with acids.

https://phet.colorado.edu/sims/html/acid-base-
solutions/latest/acid-base-solutions_all.html
OR
Neutralization Reaction Experiment: Observe and explain the neutralization reaction between a base and an acid.

Future Leaders
Explore industrial uses of bases.

https://quizizz.com/join?gc=826808
OR
Predict Base Strength from Chemical Formula: Analyze the chemical formula of bases to predict their strength based on hydroxide ion concentration.

​https://quizizz.com/admin/quiz/67af07ea414c6b95ce386d3f

​https://quizizz.com/admin/quiz/67af0e0da11722c152ef3ef0

NEXT LEVEL CHALLENGE:

CRITICAL THINKING

“Investigate the agricultural uses of bases, such

as lime in soil improvement. How do bases

impact soil pH, and what benefits do they

provide in terms of crop growth? Are there any

challenges or considerations associated with

using bases in agriculture?”

Wrap-Up Quiz

❑ Define base /alkalis?

❑ Give examples of base with their chemical

formulas.

❑ Briefly explain the properties of the base.

❑ What chemical processes explain the color change observed when litmus paper is dipped in a basic solution, and how does this color change reflect the properties of acids and bases in terms of pH levels and the behavior of indicators?

ASSESSMENT

Students’ Reflection form is in GCR.

https://docs.google.com/forms/d/e/1FAIpQLSdFSIiU224mMzotdqnCPy-i8ib7v9RqKDmkIvcBExBjOPSAhw/viewform?usp=header

EXTENSION/ HOMEWORK

Design an infographic or comic

strip titled 'A Day in the Life of a

Base' showing its properties and

uses.