Science Buddies: "Ask an Expert"

Hello,

My daughter and I have a procedural question regarding this experiment: https://www.sciencebuddies.org/science- ... n-a-recipe. In the Variations section of the procedure it states, "All of the combinations above had a ratio of two parts cream of tartar to one part baking soda." However, in step 5a of the procedure it calls for 0 teaspoons cream of tartar, 3/4 teaspoons baking soda. Obviously, this is not a 2-1 ratio of cream of tarter to baking soda. Is this a typo or is there a reason for this? All of the other measurements in step 5 are 2-1 ratios.

Thanks so much for your assistance!

That's a good question - and it's great that you and your student are carefully reading through the procedure and variations.

For the three combinations shown that include cream of tartar, the ratio of cream of tartar to baking soda is 2:1. The first of the four batches doesn't include cream of tartar at all (and also uses less baking soda than the standard recipe). This might help to demonstrate the role of the baking soda overall.

The one that uses 0 cream of tartar wouldn't really be a combination, but I agree the phrasing in the variation could be improved. I've flagged this for our team to update.

If your student decides to do a variation looking at different ratios, you might compare different ratios to the standard recipe that uses only baking soda.

Amy
Science Buddies

Thanks for the clarification! I appreciate it!