# Hot Education Posts

### How To: Determine the empirical and molecular formulas for a compound in chemistry

In this free video science lesson from Internet pedagogical superstar Salman Khan, you'll learn how to determine the empircal and molecular formulas of a substance given percent composition. Whether you need help studying for that next big test or could just use a hand finishing your homework, you're sure to be well served by this video lesson. For more information, including detailed, step-by-step instructions, take a look.

### How To: Find eigenvectors and eigenspaces of a 2x2 matrix

Need help figuring out how to find eigenvectors and spaces for 2x2 matrices in linear algebra? From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll see...

### How To: Find surface area and volume of a sphere

In this how to video, you will learn how to find the volume of a sphere and surface area. Let's say you need to find the volume of a sphere with a surface area of 200 cm cubed. You will need to know the formulas for surface area and volume of a sphere. The formula for surface area is 4 pi r squared. The formula for volume is 4/3 pi r cubed. Plug in the surface area of 200 cm cubed and plug it into the formula. You should get an answer of about 3.99 cm. Now you just have to solve for the radiu...

### How To: Find least common multiple in rational expressions

This series walks you through the steps of finding the least common multiple in rational expressions. This excellent video shows you a clean board, with the instructors voice showing exactly what to do. Don't fret, any question you may have, will be answered. Watching this video will make you feel like your back in the classroom but rather comfortably from your home.

### How To: Find the Percent Given Two Numbers

Whether you're shopping for deals, need help with a little math, or any number of other occasions, it's a valuable skill to know how to quickly figure out a percentage given two numbers.

### How To: Make a never ending foam snake

In this video the author shows how to make a never ending foam snake. He starts by speaking about how hydrogen peroxide can be fun. He starts with the requirements first which are a dish soap, a bottle of hydrogen peroxide, some dry yeast, and a red fruit color. Now he fills up a cup with hydrogen peroxide, adds the color and two table spoons of dish soap. Now he shows how to use yeast which is used to remove the oxygen from the hydrogen peroxide. And finally he demonstrates the never ending ...

### How To: Divide small numbers by big numbers

This is a mathematical educational video on how to divide a small number by a larger number. You are aware that it is easy to divide a larger number by a small number. For example, if you want to divide 379 by 9 it is easy to do so. But if you have to divide 9 by 379 it is a bit difficult. You have to add a zero and see if you can divide. You need to add one more zero so that you can divide 900 by 379. But you should know that the answer would start like this 0.0 as we have added 2 zeros alre...

### How To: Find the volume of a regular pyramid

In this video, you will learn how to find the volume of a regular pyramid. Finding this volume is one of the basic steps in high school geometry. This tutorial will show you all of the steps and equations you need to solve this problem and soon you will be heading straight to the top of the class!

### How To: Find a missing angle outside of a triangle

For people who are having problems with certain parts of geometry, this video will offer you advice on how to find a missing angle on the outside of a triangle when you are provided with the measurements of the other two angles in the triangle. Since the sum of the angles in a triangle is always 180 degrees, you should first take the sum of the other two angles and then subtract this from 180 in order to find the measurement of the missing angle in the triangle. Next, since there are also 180...

### How To: Find the surface area of a cylinder easily

In this video tutorial the author shows how to find the surface area of a cylinder. He shows a four step approach to solve this problem. First he gives us a formula to find the surface area of a cylinder, where Surface area A = 2 * Pi * R * R + 2 * Pi * R * H, where R is the radius of the base of the cylinder and H is the height of the cylinder. Now he identifies those values and substitutes them in the formula giving the surface area of the cylinder. This video shows how to compute the surfa...

### How To: Calculate percentage

Not sure exactly how to calculate a twenty percent tip for your waitress? Or how about how to figure out how much less your cost will be with that thirty percent off tag? Use these steps to calculate percentage, without a calculator.

### How To: Use matrices, Gaussian elimination, and determinants

A close look at using matrices, Gaussian elimination, and determinants. This video is good for beginners who have never used a matrix before.

### How To: Instantly freeze soda experiment

The trick in this how-to video works with any carbonated beverage (never use beer). Take your beverage and cool it down to a temperature around 20F or -7C. Either the freezer or outside if it is cold enough. When opened it will freeze instantly.

### How To: Operate electrogravitics lifter & fight gravity

This video is showing lifter technology in action. Providing basic information on how to construct, power and operate a Lifter, along with a brief explanation of electrogravitic theory, as suggested by T. Townsend Brown.

### How To: Make Soap Out of Guava Leaf Extract for a Science Investigatory Project

Unless you're a high-schooler building a nuclear fusion reactor, the hardest part of a science investigatory project often is coming up with a good idea. You want it to be cool yet feasible, novel but still useful.

### How To: Find the perimeter & area of a complex figure

In this video tutorial the author shows how to find the perimeter and area of a complex figure. He shows that a complex figure can be subdivided into standard geometric figures. In the current example he divides the complex figure into a rectangle and a triangle. Now he computes the perimeter by adding the three sides of the rectangle and the two sides of the triangle. Similarly he computes the individual areas of the rectangle and the triangle and finally adds then up to find the area of the...

### How To: Make boric acid from borax

This is a video tutorial in the Education category where you are going to learn how to make boric acid from borax. For this experiment you will need borax (disodium tetra borate) and conc. hydrochloric acid. Take 25 ml of hydrochloric acid and dilute it with 75 ml of water. Next take 6 - 7 gms of borax and dissolve it in boiling water. Now add equal amount of hydrochloric acid. Crystals of boric acid will start forming. They are completely insoluble in cold water. After about half an hour, fi...

### How To: Find a number given Its percent

This how-to video is about how to find a number when its percent is given. This video is really helpful and effective in finding the number when the percent is given, the following steps are explained in the video to find the number when its percent is given:

### How To: There's Metal Hiding in Your Pepto-Bismol and Here's How You Extract It

Got an upset stomach or a little heartburn? America's favorite pink pill will cure it right up. But did you know that there's actually metal hiding in those chewable Pepto-Bismol tablets? Yes, metal. Technically, it's a poor metal, but metal's metal, right? Well, we do tend to eat a lot of iron in our diets, because it carries oxygen throughout our bodies, so consuming metallic minerals isn't anything abnormal. But you'd never think that Pepto-Bismol is actually made up of metal.

### How To: Make iodine from hydrochloric acid and H2O2

Watch this science video tutorial from Nurd Rage on how to make iodine from an alkali metal iodide, hydrochloric acid (HCI), and hydroxide peroxide (H2O2).

### How To: Make Water Freeze into Ice Instantaneously

Have you ever seen water freeze instantly? This "Quick Clip" shows some of my personal experiences with making instant ice using a bottle of water supercooled in a freezer.

### Classic Chemistry: Colorize Colorless Liquids with "Black" Magic, AKA the Iodine Clock Reaction

Want to make boring old colorless water brighten up on command? Well, you can control the color of water with this little magic trick. Actually, it's not really magic, but a classic science experiment known commonly as the iodine clock reaction, which uses the reactions between water and chemicals to instantly colorize water, seemingly by command. You can use different colorless chemicals to produce different colors, and you can even make the color vanish to make the water clear again.

### How To: Make chlorine gas with pool chlorine and hydrochloric acid

Chlorine gas is a very useful oxidant, which was first introduced as a toxic weapon by the German Army. Even today, it's still used as a weapon, most recently in the Iraq War by insurgents. But chlorine gas has more useful (and less lethal) applications, and if you want to learn how to make some at home, NurdRage has the answers.

### How To: Test paint for the presence toxic lead

In this tutorial, we learn how to test paint for the presence toxic lead. You will first need to make up two solutions. One will need sodium sulfide and water mixed together in a small container. Then, add acidic acid and water into another container. Drop small amounts of the mixtures into containers, then add in the paint to the containers. Watch and see how the reaction of the paint is with the mixture. If you start to see a black reaction occur in the container, you will know that your pa...

### How To: "Back out the tax" from a receipt

In this video, we learn how to back out the tax from a receipt. If you have a receipt where you see how much you paid and know the tax rate, except you want to figure out the cost of the item before the tax. First, take the cost of the item including tax and what the tax rate is. To figure out the original price, let x equal the cost of the item. Add the tax to the cost of the item which will equal the cost you paid. Perform the equation 1x+(tax rate)= (total price). After you figure this equ...

### How To: Find a slope of a straight line with: Ax + By + C = 0

In this video the instructor shows how to find the slope of an equation which is in the form Ax + By + C = 0. He says that the formula to find the slope of a line in the above form is slope m = -A/B, where A and B are the numeric constants of the variables x and y in the given equation. He goes on and further shows how to do this with a couple of examples. He shows how to reduce any equation into the general form and how to apply the slope formula then. This video shows how to find the slope ...

### How To: Make fireballs you can hold in your hand

This flame you CAN hold, without burning your skin off. Learn to make fireballs you can hold in your hand. This amazing video tutorial shows you how to do it. All you'll need for this little science experiment or fiery weapon is 100% cotton cloth, scissors, lighter fuel, cotton string, and a needle. Be careful to follow the directions in this how-to video carefully otherwise you'll really be playing with fire.

### How To: Make fire 4 ways without matches by using chemistry

Watch this science video tutorial from Nurd Rage on how to make fire 4 ways without matches by using chemistry, without matches or lighters.

### How To: Make a chemiluminescent reaction with home chemicals

Watch this science video tutorial from Nurd Rage on how to make a chemiluminescent reaction with home chemicals. Make a chemiluminescent singlet oxygen red light pulse from two simple chemicals almost anyone can buy: pool chlorine and hydrogen peroxide.

### How To: Make Your Own Homemade Glow Sticks

Glow sticks, a popular favor at parties and outdoor events, and a must-have on Halloween, can be traced back to the United States Navy in the mid-1960s. The military desired improved visibility during night operations, and glow sticks, with their small-size portability and lack of batteries, were a perfect tactical solution.

### How To: Make a Soda Can Stirling Engine

Ever wonder how to make an engine out of soda cans? Not even sure if it's possible? These videos will show you how to build a working Stirling engine out of cans and other general materials. Here it is in action:

### How To: Calculate sums in standard form

When a number is expressed in the form of x multiplied by 10^y such that, x < 10 and y is an integer, the number is said to be in standard form. Standard form of expressing numbers finds its use in scientific and statistical fields. This video demostrates how to express, as well as perform basic mathematical operations namely, addition/subtraction, multiplication and division of numbers in the standard form using four examples/mathematical problems. The first two examples demostrate multiplic...

### HowTo: DIY Glow Sticks

WonderHowTo favorite (and pal) NurdRage brings us another great science tutorial. Making glow sticks at home is not necessarily cheaper, but it's a great science project. Check out the video below to learn not only how to make the glow sticks, but also all about fluorescent dyes (and why Mountain Dew will not do the same thing). Previously, NurdRage Shatters Mysteriously Procured Human Heart.

### How To: Dissolve ruthenium metal with household bleach

You've manage to get your hands on some ruthenium, and now you want to destroy the hard silvery-white metal of the transition series. Well, you're going to try all kinds of ways to dissolve this odd metal, but the only successful way to dissolve ruthenium is with a common household cleaner… bleach.

### How To: Do a sodium and water experiment

In this video tutorial, viewers learn how to do a sodium and water experiment. Sodium is a silver metal that is very reactive. When exposed oxygen in the air, an outer coding of sodium oxide will form. Simply drop a piece of sodium into a cup of water. When dropped in water, sodium reacts to form sodium hydroxide and hydrogen gas. The sodium will constant move around in the water. Sometimes the heated reaction will cause the nitrogen gas to ignite. Under the right condition, it may even cause...

### How To: Turn water into ice without a freezer

Here's a fun experiment you can do that will demonstrate the effects that pressure has on the freezing point of a liquid. You will amaze your friends as you do what seems to be impossible, turning water into ice without sticking it in the freezer.

### How To: Solve for the missing ratios or proportions

In this video the tutor shows how to solve the missing ratios or proportions. He explains it with an example, where a number in one of the ratios is missing and he intends to find this value. He shows the example of cross multiplication, where you multiply the values on the either side of the equation diagonally and finally solves the equation which results in the value of the unknown value. This is an introductory video explaining how to use rations and proportions to find missing values.

### How To: Remember "greater than" & "less than" symbols

This video shows you how to easily remember "greater than" and "less than" math symbols. The first thing you have to remember is that "less than" symbol looks like the letter L ("less than" symbol is "<"). When you see this sign, remember that < looks like L and means "less than". The other symbol, "greater than" does not look like the letter L, therefore it cannot be "less than" and it's easier to remember. The "greater than" symbol is ">". That's it! Good Luck!

### How To: Make instant flying condoms

Learn how to make a self inflating, flying condom! We should you how to make an instant flying condom using a few household items. Fantastic and fun science experiment! You will need one condom, one bag of hydrogen peroxide and dishwasher limescale remover.

### How To: Use a Volumetric Flask in the Chemistry Lab

Find out how everything in a chemistry lab works, from pipettes to burners to recrystallization to storage. You'll get precise instructions on how to work and perform certain scientific duties in the chem lab, whether it's chemical or just ordinary high school science.