Thread by @IdolScribblings

#ScienceLessonAtHome of the Day - Indicators and Invisible Inks

You will need:

✅Some strongly coloured fruit and veg. You can try carrots, beetroot, blackcurrant, red onion, onion, red cabbage, grapes or red apple peel.

(Continued 🧵)

https://twitter.com/IdolScribblings/status/1241986107346223105

✅Lemon juice (an acid)
✅Bicarbonate of Soda dissolved in a little water (alkali)
✅A pestle and mortar or a blender
✅A funnel and a large glass
✅A coffee filter paper or piece of strong kitchen paper towel
✅Two paintbrushes, one fine, one large
✅Two sheets of paper

1. Using the two sheets of paper & the fine paintbrush, write two secret messages. Use the lemon juice to write one, & the Bicarbonate solution to write the other. Be careful to wash the brush really well in between. Leave them somewhere cool to dry. Do not expose them to heat.

2. Take your fruit or vegetable of choice and mush it up well using either the pestle and mortar or a blender. For non-juicy fruit and veg you will need to add a little water.

3. Now place the coffee filter paper in your funnel and stand it in the large glass. Use this to filter the juice from your pulped plant material.

4. Use the resulting juice and the large paintbrush to paint an even wash over both of the secret messages you painted earlier. Your messages will be revealed!

5. You can repeat steps 1-4 with different plant materials. This chart shows what colours can be achieved with different plants.

Safety: Be careful to only use known edible plants. Be mindful allergies.
Some juices sting if they get in the eye, so waering a pair of goggles is a good idea for less coordinated children. If any of these chemicals do get in the eye, rinse with plenty of clean fresh water.

Some of these juices will stain clothes etc. So wear something old and maybe an apron.

Science Principles Shown:

Acids and Alkalis -

Acids and Alkalis are all around us. Citrus fruits and other sour tasting foods (like lemon juice) are weak acids.

We can test whether something is an acid or alkali using an INDICATOR. Indicators react with acids and alkalis and change colour. Your plant extract juice is acting as an indicator.

Filtration -

An important method of separation used in chemistry. Used to separate insoluble solids from liquids. There are tiny holes in the filter paper. The liquid is allowed through, the solid matter is not and is collected in the filter paper.

Secondary Pupils:

Older kids will still enjoy this one. They should extend the activity by finding out about the different indicators used in chemistry. What are they made from? What colour are they at different pHs? (They could draw a really pretty chart).

Try Phenolphthalein, Methyl Orange, Methyl Red, Litmus and Thymol Blue to get started.

Universal Indicator is a mixture of indicators. Find out which ones.

Interesting Person:

Mary Herbert (nee Sidney) is a rare example of a female experimental chemist from Tudor times.

She invented some invisible inks amongst other things. Read more about her rather interesting life here en.m.wikipedia.org/wiki/Mary_Sidn…

Have colourful fun! I would love to see pictures of your secret messages!

@Cockleonius @AntRDean tagging you so you don't miss this thread!