When the hydrogen ions come into contact with the pH indicator, the solution changes color.įill a clear container with vinegar to a 3-cm depth. What do you notice?Īs an acid, vinegar has a large number of hydrogen ions. Using a dropper, add a few drops of vinegar.

Place a few millileters of the pH indicator into a small container ( either bromothymol blue or phenolphthalein). The sets need to match in order to compare the color change later on in the Snack. If you're using phenolphthalein, you should have two sets of pink cubes. If you're using bromothymol blue, you should have two sets of blue cubes. Remove the agar blocks from the molds or cut in the pan with a sharp knife to obtain two sets of cubes of three sizes: 1 x 1 x 1 cm, 2 x 2 x 2 cm, and 3 x 3 x 3 cm.

Let the agar cool until it solidifies (an hour is usually sufficient).

If you don’t have enough solution, make more using the ratio of 0.8 g agar-agar powder to 100 ml water. Make sure the agar block(s) will be at least 3 cm deep when they solidify.

Carefully pour the agar solution into silicone ice-cube molds or a small glass baking pan.

Add ammonia drop by drop until the mixture turns (and remains) a bright pink color (see photo below). If you're using phenolphthalein, add enough indicator so that the mixture turns pale pink.

If it has a greenish hue, add ammonia a drop at a time until it is blue (see photo below). If you’re using bromothymol blue, add enough indicator so that the mixture turns blue. Choose ONE pH indictor to work with ( either bromothymol blue or phenolphthalein) and add a few drops of it to the agar solution.(Keep your eye on it as it can boil over very easily!) When done, remove the container, and set it on a trivet or other heat-safe surface. Repeat this process until the mixture boils. Remove to a heat-safe surface using a hot pad or oven mitts, stir, and return to the microwave for 30 seconds. Heat the solution in the microwave on high for 30 seconds.Mix them together with a whisk or fork in a large microwave-safe bowl. Measure out 1.6 g of agar-agar and 200 ml water.

Name each of these bacteria shapes