Disappearing Ink

Imagine getting a secret note which only you can read. I would love that. As I was researching about this, I read that spies used lemon juice, milk, vinegar, onion juice or even urine as an invisible ink during the 1st World War. Low tech intelligence, I guess.

Try this fun experiment with your child with all the ingredients from your kitchen pantry.

Ingredients:

Any one of these or all:

  • lemon juice
  • vinegar
  • milk
  • 1 tbsp Baking soda mixed with 2 tbsp  water

cotton swab/ Q tips

white paper

heat source – lamp, iron box,  or a flame (Use with caution)

Directions:

Step 1: Dip the cotton swab in any of ingredients (lemon juice, vinegar, milk or baking soda solution)

Write with it on the piece of paper. Let it dry. I left it to dry and went back to it in an hour.

Step 2: Under parental guidance only

If using the light bulb, turn it on and let it heat up. I found using the iron box was easier.

light bulb: Hold it over the lightbulb for a few minutes and watch your secret message appear. Be careful not to burn the paper.

iron: Place paper between two pieces of cloth and iron.

open flame: Hold over an open flame and watch the message appear.

 

The science behind the experiment:

Most of the ingredients given are acidic except for baking soda. With baking soda, you can paint the paper over with grape juice. The color of the writing changes. This is because the acid (grape juice) reacts with the baking soda (a base) to discolor the paper.

Lemon juice, milk, and vinegar are acidic. The acid weakens the fibers of the paper. When heated, some of the chemical bonds break down and carbon is released. When carbon comes in contact with air (oxygen), the carbon in the paper oxidizes and turns brown. (A cut piece of apple also oxidizes (turns brown) but without heating)

 

Salad Dressings and Density of Fluids

A salad dressing always heightens the taste of a salad. The simplest salad dressing is oil, vinegar, salt, and pepper. You could add honey to sweeten it or some dijon mustard. Have you noticed that when you pour oil and vinegar, they do not mix? Have you ever wondered why?

Salad dressing reciipes1 (1)

Salad dressing reciipes1 (2)

I had written about density in my previous blog – Float or Sink, but here is a recap. Density is how much ‘stuff’ is packed in a certain volume. The density of a liquid is the mass per unit volume (1kg/m3). For all practical purposes, if you take 1 liter of liquid and measure the mass (weight on earth), the density of that liquid (for example) 1.2 Kgs, then the density of that liquid is 1.2/1 =1.2.

Here is an easy and fun experiment to do with kids about the density of liquids. If you color the liquids, it would be a fun addition to their room.

Use the same volume of liquids. I used 1/4 cup each.

The liquids I used were honey, vegetable oil, water, dish soap, and milk. I had to use a baster and add milk gently which I did not and it did not work, so I redid the experiment without milk. You can also add vinegar.

Ingredients:

  • 1/4 cup honey
  • 1/4 cup vegetable oil (you could mix an oil based food coloring)
  • 1/4 cup water mixed with some water-based food colour
  • 1/4 cup dish soap
  • a tall glass
  • cherry and other small objects

 

Directions:

Pour equal volume of the different liquids in cups and place them in order of liquids being added. (honey, dish soap, water, and vegetable oil.  I also labeled the cups.

Pour the honey carefully into the cup without touching the sides of the cup. Carefully add dish soap. If you have a baster, use that.

Then add water and then vegetable oil. It is ok if it mixes a little.

Leave it for an hour to settle, you will see the different layers.

Why does this happen? Liquids have different densities. The heavier liquids like honey have a higher density and therefore will sink below the lighter liquids.

Screenshot 2018-10-21 at 8.58.47 PM

The same rule for float or sink works here too. Denser solids will sink and solids that are less dense like a walnut will float. A cherry is denser than water and oil so it settles on top of the honey. Try different objects, how about a ping pong ball. Experiment with different liquids like vinegar, baby oil, lamp oil, corn syrup or maple syrup. Ask your child to hypothesize and then document the results.

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Adding solids to the liquids

 

 

 

 

 

 

Kitchen Science – Sink or Float – Bobbing for Apples (and other vegetables and fruits)

It is almost Halloween and this game is often played by children. So the question is do all apples float? That led to more questions – what about pumpkins, lime, banana, pomegranates or coconuts? Why do they float or sink? Inspired by the thought, I decided to check it out on my own. I started with an apple, pomegranate, and coconut. I then started taking vegetables out of my fridge and started playing with what I have. There were some surprises.

So here are my results:

Fruits and vegetables that float: apple, banana,  tomato, madras cucumber (squash family), coconut, eggplant, capsicum and believe it or not, watermelon.

Fruits and vegetables that sink: pomegranate, lime (surprises), potato

Why do coconuts and watermelons float? Think about it!

Why do some sink and some float?

This is because of the density of the fruits/ vegetables (in this case).

Density is defined as mass per unit volume or the measure of how heavy a substance is for its bulk or volume. But what does density have to do with floating or sinking? We all have heard about Archimedes, the guy who ran out of his bathtub into the street, butt naked, shouting  “Eureka”. But do we know why he shouted Eureka? Well, he discovered the principle, ‘The Archimedes Principle’ that governs whether an object floats or sinks in a fluid. He is also credited for calculating the value of pi.

Explanation of Archimedes Principle: Archimedes Principle states that when an object is immersed in a fluid, the buoyant force is equal to the weight of the fluid displaced by the object. This is what we learned in school. But what does it mean?

Let us go back to our bobbing of apples. If our bowl is filled completely with water and then an apple is added to it, some water spills out (just like the water that spilled out of the bathtub when Archimedes got into the tub). If you weight the water that spills out, it would equal the upward force (buoyant force) on the object. From that buoyant force, the density of the apple can be determined. or we can also say that the apple is kept afloat (buoyed up) by a force equal to the weight of the water it displaces.

So, if the object’s (vegetables and fruits in this case) density is less than that of water, it will float and if its density is greater than that of water, it will sink.

Let us look at examples in the kitchen while cooking.

  1. When ravioli, and gnocchi are cooked, they first sink when you put them in the boiling water. This is because they are more dense than water. But as their starch granules expand in the hot water, their density decreases. When their density becomes less than the density of water, they float and we know that they are cooked.
  2. When we fry vadas (Indian savory fried snack) or doughnut holes in hot oil, they are less dense than oil and floats. But as the bottom surface cooks, it loses water and becomes more dense. The bottom is now more dense than the top and it turns and cooks on the other side.

Sources:

Wolke, R. L. (2005). What Einstein Told His Cook 2. New York: W.W. Norton and Company.

https://www.livescience.com/58839-archimedes-principle.html

 

Kitchen Science – We are all Chemists! Yeast Talk

I wonder if I can add chemist to my profile which includes baker, cook, teacher. While writing the blog post on pizza, the teacher in me started wondering about the science behind making pizza. This morning I made appam and stew and seeing the small holes in the appam, I was explaining why it had those holes.

In every south Indian house, for generations, (before dosa and idli batters came in bags in the cold section of a supermarket), cooks ground the batter and left it overnight for it to ferment. Every Indian household made yogurt using a starter, heating the milk to the right temperature, adding the starter, keeping it in a draught-free warm place for it to set. That is chemistry.

Most kids think of chemistry as blowing up stuff; hardly thinking that cooking and baking involves chemistry. Yes, we bakers and home cooks do not wear lab coats and look cool in safety glasses, but we do make chemical reactions happen and know how and why some things work. One of the books, I love and learn from is the book by Robert Wolke, professor of Chemistry and author of the book, What Einstein Told His Cook. He explains the chemistry and the concepts behind cooking in the kitchen. He encourages asking ‘Why’ something happens. Encourage your child/student to ask questions – the scientific process starts with a question!

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Since I was baking pizza and making appam today, I decided to look more closely at yeast.

What is yeast?

As I taught my 5th graders, yeast is unicellular fungus (microbe). It is a living organism.

What is the Scientific Name of Baker’s Yeast?

Saccharomyces cerevisiae. It means ‘sugar-eating fungus’

Where are they used?

They are used to make bread and beer amongst other things. They are also used to mold cheese and make antibiotics. Yeast is studied extensively in biology as an ideal experimental organism.

What do they feed on?

The yeast is dormant till it comes in contact with a liquid. Yeast loves sugar in various forms (sucrose, fructose, glucose, maltose). That is why when yeast is used, a teaspoon of sugar is added to the yeast along with lukewarm water. The yeast, however, continues to eat the sugar in the dough.  Fermentation is the process of breaking down of the starch into sugars for their energy.

Why are they used in baking and other cooking?

The by-product is carbon dioxide (CO2) and ethyl alcohol or lactic acid which it gives out and is very useful for bread. When the carbon dioxide cannot escape from the dough because it is elastic and stretchable. This makes the dough rise and cause air bubbles in the dough. The ethyl alcohol produced during this process has a particular aroma and taste which we can taste in the bread.

Perfect Temperature

The optimum temperature for yeast to grow is 27º – 32º

This is what my pizza dough looked like from proofing of the yeast and the rising of the dough:

 

Fun Fact:

It takes 20,000,000,000 (twenty billion) yeast cells to weigh one gram.

Yeast Experiment

Note to parents and teachers: Before you explain to your child/student what yeast is and what it does. let them conduct the experiment. This is a simple experiment which can be done in groups. Let the child hypothesize what could happen. Different groups could change the amount of yeast or sugar or amount or temperature of water and hypothesize what could happen. Let them feel the wonder and awe while watching the balloon inflate. Then this leads to inquiry and learning.

A fun experiment to do with the kids to show the process. This is a slow process which takes around 20 – 30 minutes. So you start it and watch it every 5 minutes. (I did this experiment one evening at home – the balloon was inflating even after I threw it in the dustbin).

In a bottle, add 1 tbsp yeast (active dry yeast), 1 tbsp sugar, ½ cup lukewarm water and place a balloon over the bottle. Observe what happens.

Children can change the amount of yeast, sugar, and temperature of water and hypothesize what may happen. (changing one condition at a time)

Why does the balloon inflate?

The yeast feeds on the sugar and produces carbon dioxide. As there is no place to go, the gas fills the balloon and the balloon inflates. The very same process that happens in bread when the dough rises. The carbon dioxide fills a lot of balloon-like bubbles in the dough which gives the bread an airy texture.

Sources:

https://www.stufftoblowyourmind.com/blogs/yeast-bread.htm

https://redstaryeast.com/science-yeast/what-is-yeast/

https://www.exploratorium.edu/cooking/bread/activity-yeast.html

 

The Tenth Rasa – An Anthology of Indian Nonsense

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Many many years ago, as part of a language class, we introduced gibberish and nonsense to shatter inhibitions in learning a new language. We used the navarasas (the nine emotions – laughter, compassion, anger, courage, surprise, love etc) and a line of gibberish to act out and play different ‘nonsense’ games. Students loved it and as we used different second languages they became more comfortable with the language.

Eight years later, I picked up ‘The Tenth Rasa – An anthology of Indian Nonsense”, edited by Michael Heyman. Since it was a selection of stories and poems, I first started reading poems which caught my attention and then read the rest. The tenth rasa (coined by Sukumar Ray) is whimsy.

So, what is ‘Nonsense’? According to the Merriam Webster dictionary, it is ‘words or language having no meaning or conveying no intelligible ideas’. Heyman, however, writes that nonsense usually emerges from an excess of sense, not lack of it. We have all read ‘The Mad Tea Party’ in Alice in Wonderland and the ‘Jabberwocky’ from the Looking Glass and Dr. Suess who uses ‘nonsensical’ words. One of the most famous is Edward Lear’s, ‘Owl and the Pussy Cat’ which we have read as kids is an example of literary nonsense.

In the book, there is a chapter, Nonsense in Hindi Films. One of it was the famous scene in Namak Halaal where Amitabh Bachan and his ‘I can talk English, I can walk English, I can laugh English….’ Another interesting poem isUncle Tetra Hedran in a Pyramid, Egypt playing with the idea of a tetrahedron being a triangular pyramid.

The book has a section called Folk nonsense which includes nursery rhymes and children’s games. An interesting Tamil poem is Mister Rat (translated by V Geetha)

Mister Rat, Mister Rat

Where are you going?

I’m going off to London

To see Elizabeth Queen

You will get hungry on the way

Pray, what will you eat?

I’ll buy bajjis and vadas, hot

and give myself a treat.

Thought the poem seems similar to ‘Pussy Cat, Pussy Cat, Where have you been?’ In the Tamil poem, the poet is making fun of the Indian expats, eating their bajjis and vadas even in London, holding on to their roots from across the ocean. Some poems are anti-colonial and some ridiculing the caste system. A lot of nonsense poems play with words which make them interesting.

When we were kids we played a lot of games. Avallaki pavalkki kanchina mina mina dam dum das bus qui qotar was one of them. The hide and seek song we played as kids was kanna muche kade goode, udinna moote…

Another one was

Achachu Belagachu

Alli Nodu (look there)

Illi Nodu (look here)

Sampangimaradalli gumpu nodu (see the group in the margosa tree)

yaava gumpu (which group)

kaage gumpu (a group of crows)

Yaava kaage (what crow)

Kappu kaage (black crow)

Yaava kappu (What black)

and it goes on..

The book has examples of many chain verses and game rhymes from many Indian languages. I enjoyed reading the book but it would have been nice if the original text in the given language was also there. I would have loved to read the Tamil, Kannada and Malayalam texts.

Sources

https://www.carleton.edu/departments/ENGL/Alice/CritNonsense.html

http://departingthetext.blogspot.com/2012/03/inspiration-of-jabberwocky-dr-seuss.html

https://en.wikipedia.org/wiki/Nonsense_verse

http://www.thehindu.com/todays-paper/tp-features/tp-metroplus/making-sense-of-nonsense/article2238819.ece

Read!

20180602_082109I don’t remember much of what my teachers told me in school. But I remember my library teacher telling us read – It does not matter what you read, just read! I remember the love of reading started in school. My mother would take me to the British library to borrow books and I remember the aisles of bookshelves of all types; borrowing them and reading them. I remember acting like I was studying with a novel hidden between my textbooks; I wished they would make textbooks more interesting.

I always had a love for cooking. I could not afford to buy many cookbooks when I was a kid nor were there much choice. I would meticulously copy recipes from books, magazines, and newspapers – days before the internet. I found one recipe book which I may have started in high school and continued much later. I wish I had written dates.

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Don’t miss the price on the book

Even today, I love reading cookbooks. Cookbooks are like reading an atlas, a memoir, a travel book and a food chronicle all rolled in. The recipe is important, but the story of the writer that goes with it, the style, the anecdotes, their notes all make it an enjoyable read. The recipes do not have to be made, just getting lost in the book is enough. Read!

I plan to read and write about books – cookbooks, children’s books and others – this year. Here are some images of my recipe book from yonder years.