Baking Soda vs Baking Powder: Control the Gas

Put a spoon of baking soda in a glass of cold water and almost nothing happens. Put the same spoon in vinegar and it erupts. Put baking powder in cold water and it fizzes gently all by itself, then fizzes again when you heat it. Those four glasses are the whole baking soda vs baking powder experiment, and they take four minutes. What they reveal is that baking powder is not simply baking soda with filler. It is a timed-release device, engineered so that some of the gas arrives in the bowl and the rest arrives in the oven.

Key Takeaways

• Four glasses, four minutes: soda in water, soda in vinegar, powder in cold water, powder heated. Then three pancakes to see it in food.
• The concept is controlled gas production: sodium bicarbonate needs an acid, and baking powder brings its own acids, one fast and one slow.
• Good for ages 8 to 14. No heat beyond warming a small pan.
• The thing that surprises everyone: adding more baking soda does not give more rise. With no acid left to react with, it just tastes soapy.
• The pancakes are food. The glasses are not for drinking, and nobody should eat spoonfuls of baking soda.

What You’ll Need

Item	How much	Where to get it	If you don’t have it
Baking soda (sodium bicarbonate)	20 g total	Supermarket, pharmacy	No substitute; baking powder is not the same thing
Baking powder	20 g total	Baking aisle	Check the label for “double acting”; single-acting powder changes the result
White vinegar, 5%	120 mL	Supermarket	Lemon juice works and is slightly weaker
Water	240 mL	Tap	Cold, so the slow acid stays asleep
Four identical narrow glasses	4	Kitchen	Narrow matters: foam height is your measurement
Ruler	1	Pencil case	Tape it to the outside of a glass, or mark levels with a marker
Small pan	1	Kitchen	For the heated trial
Flour, milk, egg, oil (contains wheat, milk, egg)	for 3 small batches of pancake batter	Kitchen	Any plain pancake recipe, divided into three
Frying pan and timer	1 each	Kitchen	Same pan, same heat, same minutes per pancake

Time: glasses 15 min, pancakes 25 min, eating 5 min Cost: everything is probably in your kitchen Mess level: medium. The vinegar glass overflows if you use a short one.

Do the Experiment

Step 1 — Line up four identical glasses and mark them

Tape a ruler to one or mark 1 cm intervals on all four with a marker. Put 5 g of baking soda in glasses one and two, and 5 g of baking powder in glasses three and four. Narrow glasses give taller foam and a clearer reading.

Step 2 — Predict before adding any liquid

Ask your kid to rank the four from least to most fizz. Almost everyone puts soda-in-water above powder-in-water, because soda sounds stronger. Write the prediction down, because this one is usually wrong.

Step 3 — Add 60 mL of liquid to each and time it

Water into glass one, vinegar into glass two, water into glass three, water into glass four. Record the foam height at 10, 30 and 60 seconds for each. One person pours, one person watches the clock, one person writes.

Step 4 — Heat glass four’s mixture

Tip the contents of glass four into the small pan and warm it gently on the stove, watching closely. Something should happen that did not happen in the cold glass. This is the step that demonstrates the second acid.

Step 5 — Make three pancakes

Divide a plain pancake batter into three. Add 1 tsp of baking soda to the first, 1 tsp of baking powder to the second, and 1 tsp of baking soda plus 1 tbsp of vinegar to the third. Cook each in the same pan for the same time. Measure the thickness with a ruler, look at the colour, then taste them.

What you should see: Glass one, soda in plain water, does almost nothing: a few bubbles of dissolved air and then stillness. Glass two erupts within two seconds and is finished in under thirty, often overflowing. Glass three fizzes steadily for about a minute and builds a foam two to four centimetres tall. Glass four behaves like glass three, and then produces a second noticeable burst of bubbles when the pan reaches 50 to 60 °C. The pancakes are the payoff: the baking powder one rises evenly and tastes normal; the soda-plus-vinegar one rises most and fastest; the soda-only one is flatter, noticeably more brown, and tastes soapy and faintly metallic.

What’s Actually Going On in the Baking Soda vs Baking Powder Experiment

Baking soda is a single chemical, sodium bicarbonate, listed as GRAS under 21 CFR 184.1736 and catalogued in PubChem as CID 516892. Add any acid and it gives up its carbon dioxide immediately: bicarbonate plus a hydrogen ion makes water, a sodium ion and CO2 gas. The quantities are worth doing. Sodium bicarbonate has a molar mass of 84 grams per mole, so one gram is about 11.9 millimoles, and one mole of gas occupies roughly 22.4 litres at zero degrees and one atmosphere. That works out to about 265 millilitres of carbon dioxide per gram, closer to 290 at room temperature. A single teaspoon, around 4.6 grams, can produce well over a litre of gas.

So why does glass one, soda in plain water, do nothing? Because water is not an acid. Without a proton donor, bicarbonate simply dissolves and sits there. It will decompose on its own, but only with heat, above roughly 50 °C and properly above 80, and that reaction is different: two bicarbonate units give one carbonate, one water and one CO2. Note the stoichiometry. Thermal decomposition releases only half as much gas per unit of bicarbonate, and it leaves sodium carbonate behind.

Sodium carbonate is why the soda-only pancake tastes wrong. It is strongly alkaline, it tastes soapy and metallic, and there is no way to hide it. That also explains the colour: an alkaline batter accelerates Maillard browning, for the same reason the baking soda slice goes darkest in the toast browning experiment. More brown and worse tasting, from the same cause.

Baking powder solves the problem by packaging the acid. Brodie and Godber’s account of chemical leavening agents in the Kirk-Othmer Encyclopedia of Chemical Technology describes the design: sodium bicarbonate, one or more dry acid salts, and a starch filler that keeps them apart and soaks up atmospheric moisture so they do not react in the tin. Add water and the acid dissolves, meets the bicarbonate and the reaction starts.

The clever part is the word “double acting”. Such powders contain two acids with different triggers. A fast acid, typically monocalcium phosphate, reacts as soon as it is wet. A slow acid, such as sodium acid pyrophosphate or sodium aluminium sulfate, is much less soluble or needs heat to get going. That is exactly what glasses three and four showed you: an immediate fizz, and then a second release when heated. The engineering goal is not maximum gas. It is gas arriving at the right moment, some to create bubble nuclei while mixing and the rest to expand them once the batter is in the oven and starting to set.

Two practical consequences follow. First, the substitution ratio. One teaspoon of baking powder is roughly equivalent to a quarter teaspoon of baking soda plus half a teaspoon of cream of tartar, because baking powder is only about a quarter to a third bicarbonate by mass. Second, and more useful, more is not better. Soda beyond what the recipe’s acid can neutralise cannot make gas. It just stays as carbonate and ruins the flavour, which is why doubling the raising agent makes a cake taste of soap rather than rise twice as high.

How to Explain It to Your Kid

Ages 5-8: One needs a partner, the other brings one

Tell them baking soda is like someone who can only dance with a partner, and the partner has to be something sour. Water is not sour, so nothing happens. Vinegar is very sour, so it goes wild. Baking powder already has a partner packed in the tin with it, which is why it works in plain water. Let them pour the vinegar glass, which is the fun one.

Ages 9-12: Count the gas

Do the arithmetic with them. One gram of baking soda makes around 265 millilitres of carbon dioxide, so a teaspoon makes over a litre. Then ask the obvious question: where does a litre of gas go in a pancake? The answer, that it is trapped as thousands of tiny bubbles and the batter sets around them, is the whole point of baking.

Ages 13+: Stoichiometry and timed release

This is a good place to meet a limiting reagent. Have them work out how much vinegar is needed to fully react 5 grams of baking soda, using the mole ratio and the 5% acetic acid concentration, then test it by adding exactly that much and seeing whether any solid remains. Then discuss timed release as a design problem: why would an engineer deliberately split the gas production into two stages?

The question to ask: “If I put baking soda in a cake with no acid in it at all, and the cake still rose a little in the oven, where did that gas come from and what got left behind?”

Why Teaching This Early Pays Off

This is one of the few places where a child can see that an everyday product is a designed system rather than just a substance. Baking powder has three components doing three different jobs, two of them on different timescales, and all of it is on the label if you read it. That shift, from seeing a product as a thing to seeing it as a set of deliberate choices, is the beginning of engineering literacy.

The chemistry transfers too. Acid-base reactions, gas production, stoichiometry and limiting reagents are all on the secondary syllabus, and the pancake makes the limiting reagent idea concrete: once the acid runs out, extra soda is dead weight. That is a hard idea in a textbook and an obvious one in a frying pan.

The honest framing: this is a guided demonstration, not an open investigation, and that is deliberate. Kirschner, Sweller and Clark argued in 2006 that minimal-guidance discovery tends to fail because learners cannot tell which features matter. Here the feature that matters is whether an acid is present, and telling a child that in one sentence before they pour means the four glasses actually teach something. Then let them design the stoichiometry test themselves, which is where real discovery belongs.

Before You Start: What Parents Should Know

Best age	8 to 14. Below 8, the four glasses are still fun but the explanation will not stick.
Supervision	Light for the glasses, close for the pan and the pancakes.
Real hazards	None beyond normal kitchen care. Baking soda powder irritates eyes, so no blowing it at each other. Pancake batter contains wheat, milk and egg. The warm pan and the frying pan are the only hot items.
Don’t	Never cap or seal a bottle during the soda and vinegar reaction. A sealed container pressurises quickly and can burst. Also, do not let a child eat spoonfuls of baking soda: large doses of sodium bicarbonate cause real clinical problems, and it tastes terrible anyway.

On eating it: the pancakes are food, all three, and tasting them side by side is the most instructive part. The soda-only one is unpleasant rather than unsafe, and that unpleasantness is the lesson. The four glasses are not drinks. Soda and vinegar produces sodium acetate and water, which is harmless but tastes awful, and the baking powder glasses contain phosphate and possibly aluminium salts at concentrations that have no business being drunk. Tip them down the sink.

When It Doesn’t Work

• Glass one fizzed quite a lot. Your water is slightly acidic, or there was vinegar residue in the glass. Rinse all four glasses with plain water and dry them first. Some mineral waters are carbonated, which also does it.
• Glasses three and four behaved identically with no second burst. Your baking powder is single-acting, containing only a fast acid. Check the label. Single-acting powders are common in some countries and the experiment still works, you just have one fewer result.
• Nothing happened in the powder glasses at all. The powder is old. Baking powder absorbs atmospheric moisture through the tin and slowly self-reacts. Test it before you start: a teaspoon in hot water should fizz vigorously.
• All three pancakes looked the same. Your batter was too thick to show differences, or you overmixed and knocked the bubbles out. Use a thinner batter and fold just until combined.
• The vinegar glass overflowed everywhere. Expected with a short glass. Use the tallest narrow glass you have, stand it on a tray, and keep the ruler on the outside.

Take It Further

Measure the gas properly with a balloon. Put 5 g of baking soda in a small bottle, stretch a balloon over the neck, and add 60 mL of vinegar through a funnel quickly before fitting the balloon. Measure the balloon’s circumference at full inflation and calculate the volume. Compare it to the 265 mL per gram you predicted. Getting within 30% at home is a good result, and the gap is worth discussing.

Find the limiting reagent. Fix the baking soda at 5 g and vary the vinegar: 15, 30, 60 and 120 mL. Measure the balloon volume each time. Gas output rises with vinegar and then stops rising, because the soda has run out. Plot it, and you have found a reaction’s stoichiometric point by experiment, which is the same thing the vinegar and baking soda volcano does without ever telling you.

What to Watch For Over the Next 3 Months

• Week 4: They check whether a recipe contains an acid when it calls for baking soda, usually buttermilk, yoghurt, cocoa or lemon.
• Month 2: The phrase “it needs an acid” appears unprompted, or they correct someone who swaps the two in a recipe.
• Month 3: They read a product label looking for how it works rather than just what is in it. That habit generalises far beyond baking.

Frequently Asked Questions

Can I substitute baking powder for baking soda?

Not one for one. Baking powder is only about a quarter to a third bicarbonate by mass, so you would need roughly three times as much, and you would also be adding acid the recipe did not ask for. Going the other way, one teaspoon of powder is about a quarter teaspoon of soda plus half a teaspoon of cream of tartar.

Why does too much baking soda taste soapy?

Because any soda with no acid to react with stays behind, and on heating it becomes sodium carbonate, which is strongly alkaline and tastes soapy and metallic. Extra soda cannot make extra gas once the acid is used up.

What does “double acting” mean?

The powder contains two acids. One reacts as soon as the mixture is wet, creating bubbles during mixing, and the other needs heat, releasing more gas once the batter is in the oven. That timing is the whole design.

How do I test whether my baking powder is still good?

Drop a teaspoon into a small glass of hot water. Fresh powder fizzes vigorously within a couple of seconds. If it only bubbles weakly, it has absorbed moisture in the tin and partly reacted already, and your cakes will be dense.

Is it safe for kids to handle baking soda?

Yes, with normal care. It is a food ingredient and a common antacid. Keep the powder out of eyes, do not let anyone eat spoonfuls of it, and never seal a container during the vinegar reaction.

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About the author

Ricky Flores is the founder of HiWave Makers and an electrical engineer with 15+ years of experience building consumer technology at Apple, Samsung, and Texas Instruments. He writes about how kids learn to build, think, and create in a tech-saturated world. Read more at hiwavemakers.com.

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Sources

1. Brodie, J., & Godber, J. (2007). “Bakery processes, chemical leavening agents.” In Kirk-Othmer Encyclopedia of Chemical Technology. Wiley. https://doi.org/10.1002/0471238961.0308051303082114.a01.pub2
2. U.S. Food and Drug Administration. 21 CFR 184.1736, “Sodium bicarbonate.” Code of Federal Regulations. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-184/subpart-B/section-184.1736
3. National Center for Biotechnology Information. “Sodium bicarbonate, CID 516892.” PubChem Compound Summary. https://pubchem.ncbi.nlm.nih.gov/compound/516892
4. National Center for Biotechnology Information. “Acetic acid, CID 176.” PubChem Compound Summary. https://pubchem.ncbi.nlm.nih.gov/compound/176
5. McGee, H. (2004). On Food and Cooking: The Science and Lore of the Kitchen, 2nd edition. Scribner.
6. Kirschner, P. A., Sweller, J., & Clark, R. E. (2006). “Why minimal guidance during instruction does not work.” Educational Psychologist, 41(2), 75-86. https://doi.org/10.1207/s15326985ep4102_1
7. National Research Council. (2012). A Framework for K-12 Science Education. National Academies Press. https://doi.org/10.17226/13165