7 useful for household chemistry reactions

Many chem­i­cal re­ac­tions take place around us. Chem­istry is present ev­ery time that we cook, breathe or chew. Com­plex chem­i­cal and bio­chem­i­cal pro­cess­es take place in fry­ing pans and saucepans.

1. An anal­y­sis of sub­stances us­ing an in­di­ca­tor liq­uid

Ma­te­ri­als and tools:

• red cab­bage;

• lemon;

• kitchen salt;

• wa­ter;

• a knife;

• a saucepan;

• a stove;

• a sieve;

• a glass jar;

• a tea­spoon;

• three cups.

Ex­per­i­ment pro­ce­dure

1. Cut the red cab­bage into thin strips and cov­er with boil­ing wa­ter.
2. When the wa­ter turns pur­ple, pour it through the sieve into the jar
3. In one cup, add wa­ter and the juice of one lemon, in a sec­ond cup add wa­ter with kitchen soda, while the third cup should con­tain wa­ter by it­self.
4. Add a spoon­ful of in­di­ca­tor liq­uid to each cup

Ex­per­i­ment re­sult

The wa­ter with the lemon turns pink, the wa­ter with soda turns a col­or be­tween blue and green, and the pure wa­ter turns the col­or of the in­di­ca­tor liq­uid.

Sci­en­tif­ic ex­pla­na­tion

The red cab­bage broth is an in­di­ca­tor – a sub­stance which can change col­or de­pend­ing on whether it re­acts with acid (turns pink) or with a base (turns blue or green). In the ex­per­i­ment, the in­di­ca­tor liq­uid made it clear that there was an acidic sub­stance in the first glass, that soda is a base, and that wa­ter is a neu­tral sub­stance

2. How do we re­move a de­posit in a ket­tle?

Ma­te­ri­als and tools:

• ket­tle;

• cit­ric acid;

• wa­ter.

Ex­per­i­ment pro­ce­dure

1. Add 1-2 tea­spoons of acid to 1 liter of wa­ter.
2. Pour the so­lu­tion into the ket­tle and boil.
3. Wash the ket­tle and boil wa­ter in it again, and tip the wa­ter out.

Ex­per­i­ment re­sult

The de­posit dis­ap­pears with­out trace, af­ter eas­i­ly peel­ing off from the ef­fects of the acid

Sci­en­tif­ic ex­pla­na­tion

The de­posit main­ly con­sists of cal­ci­um car­bon­ate, which forms in the break­down of cal­ci­um bi­car­bon­ate, which is con­tained in nat­u­ral wa­ter. In the re­ac­tion, the cit­ric acid caus­es wa­ter sol­u­ble cal­ci­um cit­rate, car­bon diox­ide and wa­ter to form.

2C₆H₈O₇ + 3Ca­CO₃ = Ca₃(C₆H₅O₇)2 + 3CO₂ + 3H₂O

3. Is this fish fresh?

Ma­te­ri­als and tools:

• fish;

• in­di­ca­tor liq­uid (see 1);

• tea­spoon.

Ex­per­i­ment pro­ce­dure:

1. Make a deep cut in the fish
2. Add a spoon­ful of in­di­ca­tor liq­uid to the cut

Ex­per­i­ment re­sult

If the cut turns pink or lilac, then we con­clude that the fish is fresh. A blue or green col­or shows that the fish is not fresh.

Sci­en­tif­ic ex­pla­na­tion

The broth of red cab­bage is an in­di­ca­tor – a sub­stance that can change col­or de­pend­ing on whether it is re­act­ing with an acid (turns pink) or a base (turns blue or green), or a neu­tral medi­um. A pale lilac or pink col­or shows a neu­tral or low acidic re­ac­tion – the fish is of good qual­i­ty. A blue or green col­or shows an al­ka­line medi­um, which means the fish has spoiled.

By the way, there are oth­er nat­u­ral pH-in­di­ca­tors you can use at home. Click here to find out more.

4. Is there starch in milk?

The best way of de­ter­min­ing whether there is starch in milk is to add a drop of io­dine. In the man­u­fac­ture of milk, starch is of­ten added to skim milk to make it thick­er.

Ma­te­ri­als and tools:

• milk;

• io­dine so­lu­tion;

• cup;

• pipette.

Ex­per­i­ment pro­ce­dure

1. Pour a lit­tle milk into a cup.
2. Add a drop of io­dine.
3. Watch the re­ac­tion.

Ex­per­i­ment re­sult

If the liq­uid turns blue, then there is starch in the milk. If yel­low cir­cles form, then you’re lucky – there are no ad­di­tives in this milk.

Sci­en­tif­ic ex­pla­na­tion

The io­dine so­lu­tion worked as an in­di­ca­tor, and changed col­or on touch­ing the starch, show­ing its pres­ence.

5. Is this milk fresh?

Ma­te­ri­als and tools:

• milk;

• kitchen soda;

• glass.

Ex­per­i­ment pro­ce­dure

1. Fill a glass half fill with milk.
2. Add half a tea­spoon of salt.
3. Watch the re­ac­tion.

Ex­per­i­ment re­sult

If foam ap­pears, the milk is not fresh.

Sci­en­tif­ic ex­pla­na­tion When sodi­um bi­car­bon­ate (soda) is added to an acidic medi­um, a neu­tral­iza­tion re­ac­tion takes place. The acid in­ter­acts with the al­ka­li (soda), and they neu­tral­ize each oth­er, re­leas­ing car­bon diox­ide which caus­es the mix­ture to foam.

6. Mak­ing lemon­ade

Ma­te­ri­als and tools:

• cit­ric acid;

• kitchen soda;

• sug­ar;

• cup;

• spoon.

Ex­per­i­ment pro­ce­dure

1. Pour cit­ric acid pow­der and soda into a test tube (1 tea­spoon each) and sug­ar pow­der (2 tea­spoons).
2. Pour this mix­ture into a dry, clean cup, and mix thor­ough­ly. 3.. Sep­a­rate the mix­ture into sev­er­al equal parts. Each part can be put in a pack­et.
3. Pour one of these pow­ders into a cup and add wa­ter to it.

Ex­per­i­ment re­sult

A fizzy and foamy drink forms, which is re­fresh­ing like lemon­ade.

Sci­en­tif­ic ex­pla­na­tion

In the in­ter­ac­tion be­tween cit­ric acid and sodi­um bi­car­bon­ate, a neu­tral­iza­tion re­ac­tion takes place. We get sodi­um cit­rate, car­bon diox­ide and wa­ter.

Н₃С₆Н₅О₇ + 3NaH­CO₃ –> Na₃C₆H₅O₇ + 3CO₂ + 3H₂O

7. How can we boil a cracked egg?

Ma­te­ri­als and tools:

• egg;

• salt;

• wa­ter.

Ex­per­i­ment pro­ce­dure

In boil­ing salty wa­ter, place the egg and boil for 5 min­utes.

Ex­per­i­ment re­sult

The egg boils and does not leak.

Sci­en­tif­ic ex­pla­na­tion

The salt acts on the pro­tein as a co­ag­u­lant on the col­loidal so­lu­tion. The pro­tein co­ag­u­lates in the eggshell crack.