Science Experiments

The concentrations of the components of a mixture may vary. However, a pure substance has a definite composition that does not vary.

You place the salt / sand mixture in warm water. The salt will dissolve in the water and you than then four the salt solution off the sand, leaning just sand. Then boil the salt solution untill all the water evaporates, leaving the salt.

one limitation is a very small data set (it's hard to tell if the result is going to be different next time). Which brings up the subject of variability - are the initial conditions always the same (will my beaker be a little dirty or contaminated next time, will my lab partner click the stopwatch at exactly the same time, will I be distracted at the end of the experiment and miss an important detail...).

A good experiment is repeatable, a bad one gets different results each time.

Double blind experiments, in the context of medicine, are those in which neither the participants nor the experimenter is aware of who is receiving a treatment and who is receiving a placebo. This removes bias from both the participant and the experimenter.

For instance, it has been shown that a participant who believes they are receiving the real treatment will experience a measurable or perceived change, usually an improvement. This effect occurs even if the participant is actually receiving the placebo and is thus known as the placebo effect.

Basically the participant believes they have improved and this can sometimes be reflected in an actual change in whatever is being tested for experimentally, e.g. improved health in a drug trial. The other aspect is that if the participant knows they are on the placebo, they will not experience the placebo effect and, for instance in the case of drug trials, may become worse due to a psychological effect, i.e. depression over not receiving a real drug.

So, if the participant knows what they are taking, the results for whatever is being experimentally tested for would be distorted, e.g. an over- or underestimation of a drug's potential. As such, participants are not told whether they are receiving the placebo or the treatment. In this way, the placebo effect is either removed, reduced or equivalent across all participants.

The second part is that the experimenter also does not know what is being given to a participant. Generally, participants are randomly assigned by computer to either the real drug or the placebo and the experimenter is not allowed to know what the participant is taking until the experiment is over and all measurements have been completed. This avoids the experimenter bias as if they know what a participant is taking, they may be tempted to over- or underestimate the effect.

For instance, in a drug trial, an experimenter may see more of an improvement in a treated participant than a placebo participant. This may be an unconscious or conscious action, however, either way it will distort the result. Additionally, an experimenter may accidentally or unconsciously reveal to a participant whether they are on the placebo or drug, which will in turn cause the placebo effect as described earlier. As such, if the experimenter does not know what the participant is taking, they should not suffer from bias nor reveal to the participant.

However, this system is not perfect as an experimenter will generally know enough about experiment to be able to work out which participant is taking what, i.e. a drug may exhibit a particular smell or colour or other identifiable characteristic or change in participant. In these cases, the experiment may be handed over to other people to perform, e.g. nurses or doctors, to avoid any chance of bias.

The disadvantage to double blind experiments is that they are more costly and difficult to set up, as they will usually require a greater number of people, more rigorous controls. Additionally, the entire experiment must be completed before any conclusions can be made. It may also be impossible to perform some experiments double blind. There may also be other safety, legal and moral constraints as well. For instance, is it morally right to purposely not treat the placebo group of participants who may be seriously or terminally ill?

Overall, the double blind experiment is still the "gold standard" in experiments, as it theoretically removes all bias, treats all participants the same whether they are receiving placebo or drug and comes with a negative control.

it is difficult to control all variables except the one being tested

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"Forget The Stain, Remember The Detergent"

The Experiment was created on 2002-05-01.

The control remains the same in an experiment so that you have something to compare the outcome to.

The decolorizing agent in the acid fast stain is acid alcohol. The decolorizing agent in the gram stain is ethanol.

In an experiment, a mean needs to be determined if the experiment is quantifiable. The mean usually indicates the variation in the results.

I Have this same question and i dont know what to put any help ?

Proteins

to help researchers conclude that results are related to the new drug and not to the orange juice <APEX> ^_^

Rust occurs when a metal oxidizes. The ingredients needed to make a metal rust is oxygen and breaking compounds such as the citric acid in orange juice or salty water in oceans.

Evidence is data from an experiment which is used to verify or reject the original hypothesis in the conclusion. Evidence is gathered through the scientific method.

Copy, clone, duplicate, facsimile, counterfeit, twin, etc etc

Does makeup make a person more attractive?

The IKI Is small so the pores of in the bag allow it to go throuch but the starch is to big. So based on the size of the molecules, the glucose and IKI would move out of the bag, the water in, and the starch left in the beaker.

it is the test where a sample is treated like the other experimental groups. IV isn't applied in this.

In an aromatic sulfonation reaction, a sulfonyl group (-SO3H) replaces a hydrogen on an aromatic ring (such as benzene). This is done by refluxing (heating to boiling with a reflux condenser) the aromatic with fuming sulfuric acid (concentrated sulfuric acid with gaseous SO3 present).

This reaction is reversible, so mixing the aryl sulfonic acid with a dilute acid will reform the sulfuric acid and remove the sulfonyl group from the arene.

1) at the top of the swing, the swinging object has all potential energy and no kinetic energy (no speed at that moment)

while at the bottom there is no potential energy but a maximum in kinetic energy, so that the swinging object is fastest at the bottom.

Polyurethane isn't epoxy, but they're both resins. They're also both reaction copolymers--you get either one through a chemical reaction between two components.

The difference is, epoxy contains epoxide and polyamine; polyurethane contains a complex alcohol (either a "diol" or a "polyol") plus an isocyanate.