​That's a great question!  A hypothesis is an educated guess about what you think will happen in an experiment.  

For example: Let's say you are performing an experiment on pea plants, and you have some plants that will get fertilizer and others that will not get any fertilizer, and you want to see which plants will grow taller.  You believe that the plants that get fertilizer will grow taller than the ones that get no fertilizer, so your hypothesis is:  Pea plants which get fertilizer will grow taller than pea plants that get no fertilizer.  

It's OK if your hypothesis is wrong, too.  You are just guessing about what you think will happen.  

Great question, Lyana!  There are several different ways you can produce heat:

1.       You can focus the sun’s rays using a magnifying glass, but watch where you point the focused beam of light because it can set things on fire!

2.       You can use friction—by rubbing two objects together, the friction between them creates heat.  You can prove this to yourself just by rubbing your hands together; as you rub them together they will begin to feel warm.

3.       You can use chemicals to create heat.  As some chemicals dissolve in water, they give off heat.  This is called an exothermic reaction.  One such chemical is magnesium sulfate (MgSO4), which you can purchase inexpensively on the internet (http://www.ebay.com/itm/like/280605941369?lpid=82)

I would suggest you use the chemical approach, and ask your parents to help you purchase some MgSO4, and dissolve about ½ cup of it in 1-2 cups of water in a plastic bottle.  Shake the bottle well to dissolve the MgSO4.  Have your teacher and classmates touch the bottle, and feel how warm it gets (be careful—it could get very warm!).


For more information about exothermic chemical reactions, please visit http://en.wikipedia.org/wiki/Exothermic_reaction

Great question!  There are a lot of really good chemical reactions that a 9-10 year old could demonstrate to a class safely.  The question is which one is likely to be new to the crowd.  For your daughter I'd recommend the "Invisible Ink" reaction:

http://discoveryexpress.weebly.com/homeblog/invisible-ink-how-acid-and-heat-can-reveal-messages

You will use lemon juice (acid) and a clothes iron set at its highest setting (heat) to demonstrate how the acid in the lemon juice breaks down the cellulose in the paper to more combustible compounds.  She could even go on to use other compounds, as suggested in the exercise.

A few others you could try:

http://discoveryexpress.weebly.com/homeblog/what-is-solubility

http://discoveryexpress.weebly.com/homeblog/use-vinegar-and-baking-soda-to-blow-up-a-balloon

Thanks for your question, Robin!

            When you look in a mirror, you see a reflection of yourself.  Naturally, you expect that image of yourself to appear as it would to anyone standing in front of you looking at you.  But that’s not exactly what happens!  If you stand in front of a mirror wearing a shirt with letters on it, those letters will appear reversed in the mirror. 

The reason this happens is because the mirror does not simply present an image of you, it presents a reflection of you.   That is, when you stand in front of the mirror light is traveling away from you in a straight line, hitting the mirror, and bouncing back to you.  The light bouncing back creates the image you actually see in the mirror.

            Think of it like this: imagine you are bouncing a ball off the mirror.  If you throw the ball straight at the mirror with your right hand, it will bounce back to your right hand.  If the ball bounces off your head toward the mirror, it will bounce back at your head!  This is exactly what the light is doing; traveling away from you, and bouncing off the mirror.  This bouncing light is what you see in the mirror—your reflection. 

            The way this bounced light presents an image of you is a bit like the way a piece of paper presents an image of a rubber stamp.  Take a look at the bottom of a rubber stamp: if there are words on it, they appear reversed.  When you dip the stamp in ink, and press it on paper, the words appear as they should.  It’s the same if the stamp is a picture—the picture on the stamp itself is reversed compared to the image on the paper.  The paper is like the mirror, and the ink is like the light bouncing off the mirror—it is creating an image of you that is the reverse of what you actually look like. 

That's a great question, Vansh.  First we have to discuss how water is purified.  There are several different ways to purify water--that is, to take any salts, solids, microorganisms, or anything else you would not want to drink out of the water.  One way is to filter it, or to pass it through a physical barrier which allows the water through, but holds most of the bad things back.  Depending on the filter, some things in the water may be small enough to pass through, like salts or viruses.

Another way is to add chemicals, like chlorine or ozone, to the water, or bombard the water with ultraviolet radiation.  These methods will kill microorganisms that could make you sick.  This will make most water safe to drink, but will not remove large solids like dirt.

Another way to clean up water for drinking is to distill it, or to cause it to vaporize away from the other things contaminating it.  In this process you heat up the water, causing it to form steam.  The steam rises away from the other things in the water like salts or microorganisms (which do not vaporize).  When the steam lands on something cold it will condense to form water again, but this water does not carry the same solids as the water before.  If you can collect this water in a container like a bowl or bottle, it should be much cleaner than the original water, and hopefully safe to drink! 

NOTE:  If you try this with water from your kitchen sink, the filtered or distilled water will very likely be good to drink.  However, if you try this with murky lake or pond water, I don't recommend drinking it after only one filtration or distillation!!  Sometimes water can hold dangerous viruses that a filter will not remove, and some of the dirty water could splash during distillation, putting some microorganisms in your clean water. 


We found a great website that shows how to make a filter that uses cotton, gravel and sand, and an empty plastic water bottle.  Please visit Instructables.com to see how they made their simple water filter.  This one would be very good for a school project!

We also tried making a water distillation system ourselves using a pot of boiling water on a stove, a large pot lid, a bowl, and a bag of ice.  You assemble the system as in the figure below:

Put the pot on the stove to boil the water, place the lid on the top at an angle, so the lid slopes downward to the bowl.  Put the bag of ice on top of the lid, and watch as clean water drips into the bowl! 

We tried this, and it worked well!  Please watch our YouTube video and see!

Great question!  All clouds are made of very small droplets of condensed water vapor.  They form when water from the Earth’s surface evaporates and travels up into the atmosphere.  As this water vapor (water in the gas form) rises further and further, the air begins to get colder.  Eventually the air gets cold enough that the water vapor condenses back into liquid water, or even ice.  (Condensation is just what happens when water vapor becomes cool enough to turn back into liquid water.  You've probably seen this in your bathroom after a shower--the bathroom mirror is all foggy!  This is because the mirror is cool, and when the water vapor from the hot shower touches the mirror, it turns back into water!) This condensation of water vapor in the air forms a cloud!  The diagram below shows the steps that make a cloud:

1)      The sun heats up the earth.

2)      This heat causes the water on the Earth’s surface to turn to water vapor, and begin to evaporate.

3)      The water vapor moves higher and higher into the atmosphere.

4)      When the air is cold enough, the water vapor turns to liquid water or ice, forming the cloud.

According to animalplanet.com when cats are relaxed and happy, the muscles of the cat's larynx (also called the voice box) act as a valve for the air they breathe, causing them to vibrate as they breathe in and out.  That's what makes the purring sound.  It's a bit like the muscle reactions we have when we are happy:  when a human is happy, we smile or laugh.  Cat's don't have the same control of their face muscles as we do, but they have control of their voice box that we do not.  Other creatures purr, too, such as bears, racoons, and badgers (for more animals that purr, see this article at Wikipedia)! 

For many years it was thought that lactic acid that builds up in your muscles as you exercise was what caused them to be sore 24 to 48 hours after a workout.  However, scientists have found that this is not the case at all!  Actually, your muscles use lactic acid for fuel during your workout, and so the buildup of lactic acid only lasts a few hours, so naturally this cannot be the reason why your muscles hurt 24 hours later.  

The real reason you are sore is that as you exercised, you actually made very small tears in your muscles. 
(Don't worry, these tears are extremely small, and are not dangerous.  They are just part of how your muscles get stronger!)  As your muscles are healing these tears, they swell up and experience inflammation, which is where the pain comes from.  If you do this kind of activity often, your muscles will adapt to the effort, and the tears will not occur, so you won’t feel sore.  

On a final note, the pain from tiny muscle tears that mean you are getting stronger should always occur 24 hours or so after you exersise.  If you find this pain occuring during your exersise, you should talk to your
doctor. 

First off, molarity is just a way of expressing the concentration of a solution.  The molarity is the number of moles per liter of solution.  A mole is defined as 6.022 x 1023 (also called Avogadro’s constant) molecules—that’s basically a six with 23 numbers behind it!    

Secondly, every element or molecule has a molecular weight, or a mass per molecule of that compound. 
For example, sodium chloride—NaCl—has a molecular weight of 58.443 grams per mole.  This is, conveniently, also the number of grams per mole of this compound. Therefore, one mole of sodium chloride will weigh 58.443 grams.  

Finally, if you know how much of your sodium chloride is in the solution, and you know how much liquid it is dissolved in, you can find the molar concentration.  
 
Here’s an example:  
 
You have 26 grams of NaCl dissolved in 0.6 liters of water.  What is the molarity?


We know that NaCl is 58.443 grams per mole, and that we have 0.6 liters of water.  We need to find
how many moles of NaCl there are per liter of water to get the molarity.  Here is how we set the problem
up:

So the final answer is 0.742 molar (M) NaCl.

A: Hi Kelly.  That's a great question!  When I need answers to health and body related questions, one place I like to look is Discovery Health's website (health.discovery.com).  Honestly, I think they do such a good job of answering your question, I'll suggest you visit their by clicking here. 

Thanks for asking, and keep those questions comming!!