Lesson Transcript

Class : IX

Subject : Chemistry

Unit : Nature of Materials

Topic : Capillarity

Curricular Statement

The pupils understand about the concept of capillarity through observations and

experimentations with the help of examples from daily life.

Capillarity

The upward movement of a liquid against the force of gravity inside narrow

spaces and thin tubes is called “Capillary rise”. This property of the liquid is called

Capillarity. However, liquids like Mercury which have high cohesive force shows

“Capillary fall” inside such tubes.

Activity: I

A part of cloth dipped in water slowly gets wet fully.

The teacher gives the students a piece of cloth and a bucket full of water. She

asks them to dip one end of the cloth piece into the beaker and leave the other end to

hang over the beaker. She asks them to observe what happens. The entire cloth piece

will get wet after some time. Teacher explains to the students about the action of

capillarity.

Activity: II

Capillary Action Experiment using different (narrow

and wide) straws. The students will test the

capillarity of several different straws, determinig

which kind of straw has the strongest capillary

action.

The teacher gives the students three different straws (narrow, wide and

wider) and a glass filled with coloured water. She asks them to dip one end of the

straws into the beaker but don’t let them touch the bottom of the glass. Count for

thirty. She asks them to observe what happens. How the capillarity differs in different

sized straws. Teacher explains to the students about the action of capillarity depends

on the capillary tube.

Activity: III

Experiment to show how plants use capillary action to grow on soil by using a

translucent plant.

Mashithandu or Vettapocha is the household name of the plant Peperomia reflexa. The

teacher familiarizes this plant with the students and dips the stem of the plant to some

coloured water. Teacher tells the student to observe the capillary action through the

translucent body of the plant. Teacher explains how the plants use capillary action to

grow on soil.

The Teacher ends the class with review questions

1) What is Capillarity?

2) Differentiate between Capillary Rise and Capillary Fall?

Class : IX

Subject : Chemistry

Unit : Nature of Materials

Topic : Surface Tension

Curricular Statement

The pupils understand about the concepts of surface tension through

observations and experimentations with the help of examples from daily life.

Surface Tension

Surface tension is the elastic tendency of liquids which makes them

acquire the least surface area possible. This property can be understood at the

particulate level in terms of the strengths of the attractive forces among the

particles that make up the liquid. Strong attractive forces lead to high surface

tension.

Activity: I

Video to show how the liquid drops attain the smallest surface area when it is broken

into small pieces. Students will watch the video and discuss about it.

The teacher shows a video of falling of a small liquid drop. By naked eye, one cannot

identify the shape of the liquid drop but this slow motion video (2500 frame per

second) clearly shows the shape of the liquid drop which is spherical in shape. The

teacher explains the students about the properties of surface tension.

Activity: II

Experiment to show how two liquids separate each other when the liquids have

different surface tensions.

The teacher mix oil with water in a closed container and

shake it well such that the two liquids form a mixture.

Teacher tells the student to observe the container. After

some time the two liquids will separate each other. The

teacher discusses about the surface tension of different

liquids.

Activity: III

Video showing how different insects can walk on the surface of water. Discuss the

properties of surface tension with the students.

Teacher introduce the students to the The common basilisk (Basiliscus basiliscus) is a

lizard found in Central and South American rainforests near rivers and streams which

is commonly known as the jesus christ lizard. Teacher shows the students the video

that how the lizards run through the surface of water and discusses about the

properties of surface tension.

The Teacher ends the class with review questions

1) What is Surface Tension?

2) How liquid drops attain spherical shape?

Class : IX

Subject : Chemistry

Unit : Nature of Materials

Topic : Cohesion and Adhesion

Curricular Statement

The pupils understand about the concepts of adhesion and cohesion through

observations and experimentations with the help of examples from daily life.

Adhesion and Cohesion

Cohesion: Water is attracted to water. Adhesion: Water is attracted to other

substances. Adhesion and cohesion are water properties that affect every water

molecule on earth and also the interaction of water molecules with molecules of other

substances.

Activity: I

Demonstration to show how soap can eliminate water's cohesive property

The teacher takes two containers, one container with strong

soap (dish wash) solution and in the other container with normal water. The teacher

sprinkle small amount of pepper powder to the normal water so that it is evenly

coated. The teacher dunk her finger into the soap solution and take some of the

solution with her. She gently touches the pepper coated water with her finger. The

teacher tells the students to observe the effect of soap water on the pepper coated

normal water. The Teacher explains the students about cohesive properties of water

and how soap breaks the cohesion between molecules.

Activity: II

Demonstration of cohesive forces in water and how these forces can be disrupted.

The teacher takes a shallow container with water. She cuts

out a boat from an index card as shown in the figure. The teacher places the boat onto

the water so that it is floating in the middle of the tray. She drops a liquid soap in the

center of the “V” shape at the rear of the boat. The teacher tells the students to observe

and record what happens to the boat. The Teacher explains the students about

cohesive properties of water and how soap breaks the cohesion between molecules.

Activity: III

Video showing 36 Drops of Water on a coin.

The teacher shows a video which clearly depicts the adhesive

and cohesive properties of water. In this video, it shows 36 drops of water adhere on a

coin. The Teacher discuss to students about the cohesive and adhesive properties of

water.

The Teacher ends the class with review questions

1) What is Adhesion?

2) What is Cohesion?

Class : IX

Subject : Chemistry

Unit : Acids and Bases

Topic : Acid Base Indicators

Curricular Statement

The pupils understand about acid base indicators through

observations and experimentations with the help of examples from daily life.

Acid - Base indicators

Acid - Base indicators (also known as pH indicators) are substances which

change colour with pH. They are usually weak acids or bases, which when

dissolved in water dissociate slightly and form ions.

Activity: I

Finding the solution whether it is acid or base using china rose stained paper.

The teacher takes china roses with her and she stains it on

drawing sheet. She uses the given solution (Vinegar) and makes a spot on the stained

paper. She tells the students to observe the colour change and report. Then the teacher

uses another solution (washing soda) and makes a spot on the paper. Again the

students observe the colour change and report. The teacher discuss with students about

acids and bases and how china rose acted as an indicator.

Activity: II

Shows the video how beetroot acts as Ph indicator

The teacher shows how beetroot acts as Ph indicator when it

is used with different liquids such as vinegar, milk, baking soda and bleach. The

students will observe the colour change with each liquids and report. The teacher

discuss with the students about pH value of different liquids.

Activity: III

Makes a greeting Card using turmeric and soap solution

The teacher applies turmeric paste on a sheet of plane white paper and dries it. The

teacher draws a beautiful flower with soap solution with the help of a cotton bud. The

students observe and get a beautiful greeting card.

The Teacher ends the class with review questions

1) What is an acid-base indicator?

2) Discuss about pH scale?

Class : IX

Subject : Chemistry

Unit : Acids and Bases

Topic : Neutralization

Curricular Statement

The pupils understand about Neutralization reaction through

observations and experimentations with the help of examples from daily life.

Neutralization

When solution of acid is mixed with the solution of base,

both of them neutralize each other and a third substance; called salt; is formed. Such

phenomenon is called neutralization or neutralization reaction.

Activity: I

Demonstration of neutralisation reaction using turmeric, lemon and soap water

The teacher takes three glass bowls, one with turmeric

solution, other with soap solution and another with lemon juice. She drops two drops

of turmeric solution into the soap water and the soap water changes the color to dark

red. She tells the students to observe the color change. Again the teacher drops lime

juice drop by drop to the above solution till the color disappears to yellow. The

students observe the reactions. The teacher discusses about the neutralization reaction.

Activity: II

Tells about the neutralization reaction in everyday life- How ant sting is neutralized

using moist baking soda.

The teacher tells the students about ant bites. She describes

how ant bites can be healed using neutralization reaction. When an ant bites, it injects

the acidic liquid into the skin. The effect of the sting can be neutralised by rubbing

moist baking soda (sodium hydrogen carbonate) or calamine solution, which contains

zinc carbonate. The teacher explains the importance of neutralization reaction in

everyday life.

Activity: III

Animation on Neutralization reactions

The teacher shows an animation in which the neutralization reaction is shown in

details even to the molecular level.

The Teacher ends the class with review questions

1) What is Neutralization?

2) What is the end product formed after every neutralization reaction?