How to Mix Acid and Water Safely

How to Mix Acid and Water Safely When you mix acid  with water, its extremely important to add the acid to the water rather than the other way around. This is  because acid and water react in a vigorous exothermic reaction, releasing heat, sometimes boiling the liquid. If you add acid to water, the water is unlikely to splash up, however, even if it did, its less likely to cause injuries than if you make the mistake of adding water to acid. When you add water to acid, the water boils and  the acid may splatter and splash! Extra Caution With Strong Acids This rule is particularly important if you are working with strong acids that react completely with water. Mixing sulfuric acid and water is particularly risky because any splashed acid is corrosive enough to immediately burn skin and clothing. When mixing sulfuric acid or another strong acid, start with a volume of water large enough to absorb the heat of the reaction. Add the acid in small amounts of volume and stir thoroughly prior to adding more. Just Remember: Add the Acid An easy way to remember the rule  is Add the Acid. Protective Gear and a Fume Hood Because of the risk of splashes and the release of dangerous fumes, acids and water should be mixed inside a fume hood. Protective goggles, gloves, and a lab coat should be worn. If Acid Splashes In most cases, an acid splash should be treated by immediately rinsing the affected area with running water. Acid splashes on a lab bench or other surfaces may be neutralized by adding a weak base solution (e.g., baking soda in water). Although a strong base will neutralize an acid more quickly than a weak base, a strong base should never be used because the reaction between a strong base and acid releases a great deal of heat.

Chemistry Experiments With Pennies

Chemistry Experiments With Pennies Use pennies, nails, and a few simple household ingredients to explore some of the properties of metals: Materials Needed 20-30 dull pennies1/4 cup white vinegar (dilute acetic acid)1 teaspoon salt (NaCl)1 shallow, clear glass or plastic bowl (not metal)1-2 clean steel screws or nailswatermeasuring spoonspaper towels Shiny Clean Pennies Pour the salt and vinegar into the bowl.Stir until the salt dissolves.Dip a penny halfway into the liquid and hold it there for 10-20 seconds. Remove the penny from the liquid. What do you see?Dump the rest of the pennies into the liquid. The cleaning action will be visible for several seconds. Leave the pennies in the liquid for 5 minutes.Proceed to Instant Verdigris! Pennies get dull over time because the copper in the pennies slowly reacts with air to form copper oxide. Pure copper metal is bright and shiny, but the oxide is dull and greenish. When you place the pennies in the salt and vinegar solution, the acetic acid from the vinegar dissolves the copper oxide, leaving behind shiny clean pennies. The copper from the copper oxide stays in the liquid. You could use other acids instead of vinegar, like lemon juice. Instant Verdigris! Note: You want to keep the liquid you used to clean the pennies, so dont dump it down the drain!After the 5 minutes required for Shiny Clean Pennies, take half of the pennies out of the liquid and place them on a paper towel to dry.Remove the rest of the pennies and rinse them well under running water. Place these pennies on a second paper towel to dry.Allow about an hour to pass and take a look at the pennies you have placed on the paper towels. Write labels on your paper towels so you will know which towel has the rinsed pennies.While you are waiting for the pennies to do their thing on the paper towels, use the salt and vinegar solution to make Copper Plated Nails. Rinsing the pennies with water stops the reaction between the salt/vinegar and the pennies. They will slowly turn dull again over time, but not quickly enough for you to watch! On the other hand, the salt/vinegar residue on the unrinsed pennies promotes a reaction between the copper and the oxygen in the air. The resulting blue-green copper oxide is commonly called verdigris. It is a type of patina found on a metal, similar to tarnish on silver. The oxide forms in nature as well, producing minerals such as malachite and azurite. Copper Plated Nails Place a nail or screw so that it is half in and half out of the solution you used to clean the pennies. If you have a second nail/screw, you can let it sit completely immersed in the solution.Do you see bubbles rising from the nail or the threads of the screw?Allow 10 minutes to pass and then take a look at the nail/screw. Is it two different colors? If not, return the nail to its position and check it again after an hour. The copper that coats the nail/screw comes from the pennies. However, it exists in the salt/vinegar solution as positively charged copper ions as opposed to neutral copper metal. Nails and screws are made of steel, an alloy primarily composed of iron. The salt/vinegar solution dissolves some of the iron and its oxides on the surface of the nail, leaving a negative charge on the surface of the nail. Opposite charges attract, but the copper ions are more strongly attracted to the nail than the iron ions, so a copper coating forms on the nail. At the same time, the reactions involving the hydrogen ions from the acid and the metal/oxides produce some hydrogen gas, which bubbles up from the site of the reaction - the surface of the nail or screw. Design Your Own Experiments with Pennies Explore chemistry using pennies and ingredients from your kitchen. Household chemicals that can clean or discolor your pennies include baking soda, vinegar, ketchup, salsa, pickle juice, detergent, soap, fruit juice... the possibilities are limited only by your imagination. Make a prediction about what you think will happen and then see if your hypothesis is supported.