Witness a fizzy, frothy baking soda reaction while making yummy biscuits for afternoon tea. Fun, edible, food science project for kids.
We’ve made Anzac biscuits at our place dozens of times. They are always a winner! And the baking soda reaction is impressive every single time. This particular recipe is a simplified version, which makes it easy enough for even very young kids to help make.
Suitable for
I’ve done this activity with toddlers, preschoolers, and kindergarteners. Bumble was 2 years, 10 months old in these photos.
What are Anzac Biscuits
ANZAC stands for Australian New Zealand Army Corps and is a term used to commemorate Australian and New Zealand fallen soldiers, in the first world war, and in all wars. Anzac Day (25th April) is a national day of remembrance, commemorating all Australians and New Zealanders “who served”.
No one is 100% sure however, how ‘Anzac biscuits’ themselves got their name. Some say that, because these biscuits travel well and don’t go stale, they were made by Australian women who sent them to their men fighting the war, and that they were originally called “Soldier’s Biscuits”. Others say that they were not named until after the war, when they were made and sold as fund-raisers for returned soldiers.
Either way, Anzac Biscuits are as yummy as they are iconically Australian, and are fun to make at home, for Anzac Day, or at any time of year!
To make Anzac Biscuits, you need:
- 1 cup traditional (old fashioned) rolled oats
- 1 cup plain (all purpose) flour
- 1 cup caster (fine white baking) sugar
- 3/4 cup desiccated (finely shredded) coconut
- 125g butter
- 2 tbsp golden syrup
- 1 tsp baking soda (sodium bicarbonate)
- 2 tbsp hot water
Our supplies are all Australian brands, purchased from local grocery stores. I’ve added a few (affiliate*) links above to similar products where appropriate to help clarify.
You’ll also need some common kitchen supplies: measuring cup and spoons, kitchen scales, spoons for stirring, mixing bowl, small bowl, large saucepan, cookie trays and baking paper (or reusable silicon baking mats).
We often make this recipe with wholemeal (whole wheat) flour. I like to think this makes slightly healthier biscuits, and they taste just as good.
Golden syrup is an common pantry ingredient in Australian households, but it may be harder to find in some parts of the world. It’s made from sugar cane, so it’s not the same as corn syrup or maple syrup. You might find it with the pancake ingredients or in the baking ingredients aisle. Otherwise, check your speciality stores, and if all else fails, then it’s worth buying some online.
You can find sodium bicarbonate in the baking section of your grocery store. Depending on where you live, it may also be called baking soda, bicarbonate of soda, bicarb, bread soda or cooking soda. Note: it is not the same thing as baking powder. (Baking powder is not the same. It’s a mixture of both baking soda and cream of tartar, just FYI.)
What to do
1. Preheat the oven to a slow 150oC (or 300oF).
2. Combine oats, flour, coconut and sugar in a large bowl.
My kids love to help measure, pour and stir. Five year old Jewel can do this part all by herself. Two and a half year old Bumble doesn’t quite have the fine motor skills to measure accurately yet, but she’s happy if I hand her the pre-measured out ingredients, as long as she can pour them in and stir.
3. In a small bowl, combine 2 tablespoons of hot water and 1 teaspoon of baking soda to make a slurry.
If Bumble is helping stir, then I tend to use hot water from the tap, rather than from the kettle. I also supervise closely, as a highly concentrated alkaline slurry would be dangerous for young kids to drink.
4. Adults required for this step. Melt the butter and golden syrup in a large saucepan over low heat.
5. Call the kids over to watch. Pour in the baking soda slurry. Be amazed as the mixture fizzes, and bubbles and grows!
If the bubbles start to slow down, give it a tiny stir, and it should start foaming again. Be careful that it doesn’t overflow! (Now you know why I specified a ‘large’ saucepan.)
In about a minute the mixture should have doubled (or tripled) in size.
6. Stir the butter mixture into the dry ingredients while still frothy and warm.
The heat will dissipate quickly as you mix. When it is no longer too hot to touch, I let the kids take over stirring. (But don’t be surprised if they sneak in a taste or two – the uncooked biscuit dough is alarmingly delicious at this point.)
7. Place heaped teaspoons of the biscuit mixture about 4cm apart on cookie trays pre-lined with baking paper (or reusable silicon baking mats).
Bumble loves to help spoon out small piles, and I subtly rearrange them so they are equally sized and spaced on the trays.
8. Bake, uncovered, for about 20 minutes until dark golden brown (or 18 minutes if you prefer soft, chewy biscuits).
Cool on wire racks (or transfer to the cool stove top, like I do). Be sure to separate any biscuits that are touching while they are still warm.
And enjoy!
Fun Science Fact
Baking soda, or sodium bicarbonate (NAHCO3) reacts with acids. Citrus juice, buttermilk, molasses, honey, vinegar and chocolate are all acidic. So is the golden syrup that we use in our recipe. When baking soda mixes with the melted butter / golden syrup mixture, a chemical reaction occurs forming an unstable carbonic acid, which breaks down into carbon dioxide (CO2). Carbon dioxide is a gas – the same gas that makes fizzy drinks all fizzy – and this is what causes our mixture to froth up and appear to grow in size. Heat speeds up the reaction.
Please note…
Mixing together pantry ingredients is a safe and fun way to explore chemical reactions with kids. The ingredients used here are all generally taste-safe, except for the sodium bicarbonate in it’s concentrated form. (It’s OK once it’s mixed with the other ingredients).
This recipe contains gluten and dairy which are common allergens.
As always, be very careful with kids around hot stove tops, gas flames, when handling boiling hot ingredients and using the oven.
All kids’ activities on this blog require attentive adult supervision. Parents and carers will need to judge whether a particular activity is appropriate their child’s age and skill level. Click here for more information.
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