Archive for February, 2010
Question: science question about gravity and weight?
so my teacher demonstrated an experiment for us. She held a ball, the same size of a basketball, with a mass of 40 oz, and a regular basketball in each hand. Then she touched both to the ceiling tiles, and dropped them. Both balls hit the ground at the same time. Then she demonstrated by releasing three coffee filters from the ceiling and one coffee filter at the same time. The one coffee filter flipped around and was kind of slow, and the three coffee filters fell in a more straight path, although I do believe both hit the ground at the same time (I’m not sure though, because I couldn’t see). So my question is, why would the heavier objects not fall faster? Does gravity have the same downward push on every object no matter what mass, weight, or size it has? Why did the balls hit the ground at the same time? thank you so very much!!
Answer: Air resistance counters the travel of the bodies falling.
The balls, if they are the same size, have the same air resistance yet the heavier one will actually fall faster because gravity pulls it more strongly to counter that air resistance. The difference was not noticeable but it was there. To really illustrate this, you could use a basketball and a balloon inflated to the same size and shape as the basketball. Gravity pulls less on the balloon than the ball, so the ball falls faster.
Another illustration is two people with parachutes falling. One opens his chute, the other does not. The guy with the open chute has much more air resistance so he falls slower even though the force of gravity pulls equally on them.
The coffee filters illustrated this more clearly. The three combined and the one alone are the same shape and have the same air resistance. Yet, the heavier ones fell faster because gravity pulled them more strongly.
In a VACUUM, we would see different results.
Science / Physics Experiment: Watch to believe!!!! Water level rising against gravity.
Question: Science experiment – glucose, amylase – help?
We carried out an experiment to see the effects of amylase on starch solution.
But I am confused with the method and results/analysis.
This is the method:
Visking tube – 3 parts amylase to 1 part starch
Put in a beaker of water for 15 minutes
After 15 minutes added a small amout to spotting tile with drop of iodine.
Next, took a test tube and added Benedict’s solution to a mixture of amylase and starch solution.
Placed in water bath for 15 minutes.
Is this correct? I am confused on what the analysis/results are.
Help is much appreciated.
Am I right in thinking that there was no starch present in the beaker of water as when tested with iodine – it turned blue/black = no starch present. The molecules were too big?
Answer: Basically – the amylase hydrolyses (breaks down) the starch down into mono- and disaccherides.
You test with iodine to demonstrate the presence or absence of starch. If it turns blue/ black, there IS starch present. As the starch is is broken down, you will not get the colour change.
Benedicts solution is used to test for the presence of reducing sugars, including all monosaccharides and the disaccharides mannose, lactose and maltose. In other words you are using it to test for the PRODUCT of the hydrolysis of starch by amylase.
I suspect the beakers of water may have been to do with maintaining particular temperatures to allow the amylase and Benedicts reagent to work properly.
If I follow your description you should have got:
Start – starch turns blue/black with iodine
Mixed with amylase and incubated for 15 mins
Test with iodine again. You should have got less or no reaction with the iodine as the starch would have been hydrolysed to sugars.
You then test with Benedicts solution. If you got a red, green or yellow precipitate, it indicates the presence of reducing sugars showing that the starch has been hydrolysed to sugars (ideally in a perfect world you’d have testing your starting starch solution with Benedicts to show that you didn’t have sugars in there to start off with).
CNN Finally Reports on Dispersant Corexit ‘science experiment’
Question: Chemistry Gas experiment?
I dont know the name to this experiment, so I couldnt find any help online. Basically we used two glass beakers, one big and one small. We filled the big one up with a little bit of water, then flipped the small beaker upside down and put it inside the bigger beaker. We put color dye into the water and heated it on a hot plate. It started bubbling and releasing water vapor. After it boiled, we took it off the hot plate and onto the table. All the water outside the smaller beaker got sucked in, and all the water filled up in the small beaker and the outside bigger one was empty. What happened?? I dont understand it.
Answer: I have never seen this experiment, but from your observations I would say that as you heated the large beaker of water, the air in the small inverted beaker escaped in part, leaving a partial vacuum. When the beakers were removed from the heat, they obviously cooled, and the volume of the remaining air in the small inverted beaker got smaller, and the air that had escaped was replaced by water from the large beaker. Nature hates vacuums, and will fill them with any type of matter, in this case water.
Free 9th Grade Science and Chemistry Experiments Online Vid