1. A chemistry class is experimenting with iodine to see which common white powder items will react and make the iodine change color. Which item listed will have a chemical reaction with iodine?(1 point)
A. salt
B. cornstarch***
C. baking soda
D. powdered sugar
2. When performing a scientific investigation on an unknown substance, how can an indicator help you determine if the substance is a starch?
A.The indicator will change the smell of the substance
B.The indicator will change the color of the substance.***
C.The indicator will change the color of the substance.
D.The indicator will change the state of the substance.
3. A student has an unknown powder and wants to determine what it is. Based on appearance, the student believes it is baking soda. When performing the vinegar test, what can the student expect to happen if it is baking soda?
A. it will turn a blue black color
B.it will turn into a solid glass like substance
C.it will crystalise into a sugar like substance
D. it will bubble and foam***
4.A student is performing a Benedict’s test on an unknown substance. The student adds the reagent (the chemical required to make a color change), and nothing happens. Which conclusion can the student make?
A. The substance is not glucosed based
B. The test was inconclusive because the student needed to also test with iodine or vinegar.
C.The test was inconclusive because the student forgot to add heat.***
D.The substance is glucose based.
1. Cornstarch
Correct!
Reason: Starch is a common white powder that will have a color change when reacting with iodine molecules, often used in lads to detect starch, or starchy substances.
2. The indicator will change the color of the substance.
Correct!
Reason: Just as the reason above, the color helps out a lot! They use iodine to see if the color will change.
3. it will bubble and foam
Correct!
Reason: When Vinegar and baking soda reacted to each other they become foamy and are used a lot for the volcano experiment.
4. The test was inconclusive because the student forgot to add heat.
Correct!
Reason: Look up this, it will tell you everything about the test.
Summer Research Program for Science Teachers
Barbara Lillien
Identifying Food Nutrients
These should be correct / 100% !
1. Well, it seems like the iodine has some beef with B. cornstarch. It's going to react and change color! Who knew iodine could be so picky?
2. B. The indicator is like a chameleon and changes the color of the substance if it's a starch. It's like a little fashion show for chemicals!
3. D. If it's baking soda, get ready for a foamy party! It'll bubble and foam like a caffeinated soda on a hot summer day.
4. C. Uh-oh, it seems like the student forgot to turn up the heat! Without it, the test is like a bland dish with no spices. Inconclusive, my friend.
1. In order to determine which common white powder items will have a chemical reaction with iodine, the chemistry class can perform a simple experiment. They can take small samples of each item (salt, cornstarch, baking soda, powdered sugar) and place them separately on a clean surface. Then, they can add a few drops of iodine onto each sample and observe any color changes that occur. If the iodine reacts with any of the samples and changes color, that would indicate a chemical reaction. Based on the options given, the correct answer is B. cornstarch because it will have a chemical reaction with iodine and change color.
2. When trying to determine if an unknown substance is a starch, an indicator can be used to help with identification. An indicator is a substance that changes color in the presence of specific chemicals or conditions. In this case, a starch indicator such as iodine solution can be used. To perform the test, the student can place a small amount of the unknown substance on a clean surface or in a test tube. Then, they can add a few drops of iodine solution onto the substance. If the substance is a starch, it will undergo a color change, typically turning blue or dark purple. Therefore, the correct answer is B. The indicator will change the color of the substance.
3. If the student believes the unknown powder is baking soda and wants to confirm it through the vinegar test, they can follow a simple procedure. The student can take a small amount of the powder and place it in a container or on a surface. Then, they can add a few drops of vinegar onto the powder. If the powder is indeed baking soda, it will start to bubble and foam, indicating a chemical reaction between the baking soda and the vinegar. Thus, the correct answer is D. It will bubble and foam.
4. In the given scenario, the student is performing a Benedict's test on an unknown substance, but no color change occurs after adding the reagent. The Benedict's test is used to detect the presence of reducing sugars, such as glucose. From the options provided, the correct answer is C. The test was inconclusive because the student forgot to add heat. In the Benedict's test, heat is required to initiate the reaction and produce a color change. Without heat, the test might not be able to accurately determine if the substance is glucose-based or not.
I actually have the key and all of these are wrong
thx and mine were
B
D
B
D
Kit and others should be smarter than posting junk like this!
Potential users of these answers need to hope that the same questions are always used -- and in the same order. In these days of online testing, questions and answer choices can easily be changed from test to test -- and often are to thwart cheaters!