Science Notes Posts

Lemon juice has a low pH, mainly due to the high concentration of citric acid. — Acids in Lemon Juice Lemon Juice and Your Body References Penniston, K.L.; Nakada, S.Y.; Holmes, R.P.; Assimos, D.G. (2008). “Quantitative Assessment of Citric Acid in Lemon Juice, Lime Juice, and Commercially-Available Fruit Juice Products.” Journal of Endourology. 22 (3): 567–570. doi:10.1089/end.2007.0304 Rauf, A.; Uddin, G.; Ali, J. (2014). “Phytochemical analysis […]
What Is the pH of Lemon Juice?

Calculators often indicate scientific notation with capital letter E or EE. — Scientific notation is a method of writing very large or very small numbers in decimal form. The method is used by scientists, engineers, and mathematicians. Scientific notation is also called standard form, standard index form, or scientific form. Examples of large numbers written in scientific notation include Avogadro’s number (6.022 […]

Scientific Notation – Working With Exponents Recently updated !

This entry was posted on April 2, 2020 by Anne Helmenstine (updated on April 2, 2020)

You can substitute baking powder for baking soda, but not the other way around. — Baking can be more of a challenge if you discover all your baking soda got used up for chemical volcanoes! Baking powder and baking soda are both leavening agents that make baked good rise. Baking soda combines with water and an acidic ingredient to produce carbon dioxide bubbles, while baking […]

How to Substitute Baking Powder and Baking Soda Recently updated !

This entry was posted on April 1, 2020 by Anne Helmenstine (updated on April 1, 2020)

The shelf life of chlorine bleach is about 3 months. — Did you know chlorine bleach has a shelf life? Whether the container has been opened or not, bleach loses its activity over time. Using bleach past its shelf life results in reduced bleaching and disinfecting capacity. How Long Is Bleach Good? How long bleach lasts depends mainly on temperature. So, […]

Chlorine Bleach Shelf Life Recently updated !

This entry was posted on March 31, 2020 by Anne Helmenstine (updated on March 31, 2020)

Distilled water is free of minerals. — Distilled water is water purified by condensing water vapor into liquid water. Usually, the distillation process involves boiling impure water and collected the condensed vapor in a fresh container. However, you can obtain distilled water from damp soil, plants, snow, and rain, too. You can distill water to make drinking […]

How to Make Distilled Water – 5 Easy Methods Recently updated !

This entry was posted on March 30, 2020 by Anne Helmenstine (updated on March 30, 2020)

Hot ice is another name for sodium acetate. — Hot ice is another name for sodium acetate (CH3COONa or NaOAc). It is the sodium salt of acetic acid, which is the key component of vinegar. Hot ice gets its name from the way it solidifies. A solution of sodium acetate supercooled below its melting point suddenly crystallizes. Heat is […]

Make Hot Ice From Baking Soda and Vinegar Recently updated !

This entry was posted on March 29, 2020 by Anne Helmenstine (updated on March 29, 2020)

Quartz crystals commonly occur in nature. — A crystal is a form of matter in which the atoms, molecules, or ions are arranged in a highly ordered three-dimensional lattice. Crystals are also called crystalline solids because most crystals are solid. However, liquid crystals also exist. The word “crystal” comes from the Greek word krustallos, which means both […]

What Is a Crystal? Definition and Examples Recently updated !

This entry was posted on March 28, 2020 by Anne Helmenstine (updated on March 28, 2020)

Metallic microlattice is so light that a dandelion head can support it without being crushed. — Can you name the lightest metal? Most metals are heavy or dense, yet some metals can float on water while others are nearly as light as air. Learn about the lightest elemental metal and the lightest alloy. Lightest Metal That Is an Element When we talk about a material being […]

What Is the Lightest Metal? Recently updated !

This entry was posted on March 26, 2020 by Anne Helmenstine (updated on March 26, 2020)

A seed crystal is a small crystal used to promote growth of a larger one. — A seed crystal is a small crystal that is used as a base to grow a large single crystal. Without a seed, crystals form slowly from random intermolecular interactions. When the seed is placed in a saturated or supersaturated solution it acts as a nucleation site. This decreases the time […]

How to Grow a Seed Crystal Recently updated !

This entry was posted on March 25, 2020 by Anne Helmenstine (updated on March 28, 2020)

Fire writing with invisible ink — Fire writing is a fun science project. You write a message using invisible ink, let it dry, and then reveal the secret by touching a flame to the edge of the text. The message burns away, leaving the paper untouched except for the fire writing. Fire Writing Materials You only […]

Fire Writing With Invisible Ink

This entry was posted on March 24, 2020 by Anne Helmenstine (updated on March 24, 2020)

Sulfuric acid is an example of a diprotic acid. — A diprotic acid is an acid that can donate two hydrogen ions (H+) or protons per molecule in an aqueous solution. Another name for a diprotic acid is a dibasic acid. A diprotic acid is a type of polyprotic acid, which is an acid able to donate more than one […]

Diprotic Acid Definition and Examples

This entry was posted on March 23, 2020 by Anne Helmenstine (updated on March 23, 2020)

Brainstorm to get elementary school science project ideas. — Elementary school science projects are fun and educational, but coming up with a great idea can be challenging. If the project is for a science fair, there’s competition to win. But, the focus of the project should be on engaging a child in science and raising interest in how the […]

Elementary School Science Project Ideas

This entry was posted on March 22, 2020 by Anne Helmenstine (updated on March 22, 2020)

Green Crystal Needles — Grow a quick cup of crystal needles in your refrigerator. The whole project takes between 15 minutes and 2 hours, from start to finish. All you need is Epsom salt, water, and a little food dye if you want a pop of color. Materials Epsom salt (magnesium sulfate) Water (hot […]

How to Grow a Cup of Quick Crystal Needles Recently updated !

This entry was posted on March 20, 2020 by Anne Helmenstine (updated on March 28, 2020)

Hand washing removes bacteria and viruses while hand sanitizer kills them. — Washing hands and using hand sanitizer are two important steps to take to avoid getting sick or spreading germs to other people. However, there is confusion about how they work and why washing hands is better than using hand sanitizer. Here’s what you need to know. Hand Washing vs Hand […]

Hand Washing vs Hand Sanitizer – Why Washing Your Hands ...

This entry was posted on March 19, 2020 by Anne Helmenstine (updated on March 19, 2020)

Intensive and extensive properties of matter are distinguished by whether the amount of matter changes the property. — Intensive and extensive properties are the two classes of physical properties of matter. A physical property, in turn, is one which can be observed and measured without changing the chemical composition of the sample. Physical chemist and physicist Richard C. Tolman coined the terms “intensive” and “extensive” in 1917. Here […]

Difference Between Intensive and Extensive Properties of Matter

This entry was posted on March 18, 2020 by Anne Helmenstine (updated on March 18, 2020)

Mixing disinfectants is dangerous! Bleach and alcohol combine to produce chloroform. — Disinfectants are important for preventing the spread of diseases like coronavirus, but don’t mix them! Mixing bleach and alcohol forms chloroform, a sedative powerful enough to make you pass out or potentially die. Actually, you should avoid mixing bleach with any disinfectant or cleaner to avoid producing toxic fumes. Bleach […]

Bleach and Alcohol Make Chloroform – Why You Shouldn’t Mix ...

This entry was posted on March 17, 2020 by Anne Helmenstine (updated on March 17, 2020)

You can't use pH paper to measure negative pH. — Have you ever wondered whether a negative pH value is possible in chemistry? The answer is yes! The pH scale usually runs from 0 to 14, but if the molarity of hydrogen ions in a strong acid is greater than one you’ll calculate a negative pH value. For example, the […]

Is Negative pH Possible? How It Works and Where to ...

This entry was posted on March 16, 2020 by Anne Helmenstine (updated on March 16, 2020)

Ethanol is one type of alcohol. — The words ethanol and alcohol are not interchangeable. Put simply, ethanol is the only type of alcohol safe to drink. Ethanol is also called ethyl alcohol or grain alcohol. It is one member of a larger class of molecules called alcohols. All ethanol is alcohol; not all alcohol is ethanol. […]

Know the Difference Between Ethanol and Alcohol

This entry was posted on March 15, 2020 by Anne Helmenstine (updated on March 15, 2020)

There are many molecules and atoms in a drop of water. — Have you ever wondered how many molecules or atoms are in a drop of water? This is a common chemistry problem students solve because it deals with several important concepts, including chemical formulas, unit conversions, volume, mass, density, using the periodic table, the mole, and Avogadro’s number. Here is a […]

How Many Molecules and Atoms in a Drop of Water?

This entry was posted on March 12, 2020 by Anne Helmenstine (updated on March 12, 2020)

Drinking hand sanitizer gel is dangerous. — Some people drink hand sanitizer to get a buzz or get drunk. Kids have been known to lick hand sanitizer off their hands, resulting in a panicked call to Poison Control. How dangerous is it to drink hand sanitizer? What are the risks? What do you do if a child […]

Can You Drink Hand Sanitizer?

This entry was posted on March 11, 2020 by Anne Helmenstine (updated on March 11, 2020)

Thundersnow — Thundersnow is a snowstorm with lightning and thunder. It’s also called a thunder snowstorm. Thundersnow is rare, even where snow is common. It only occurs during serious snowstorms and blizzards. Examples of storms that produced thundersnow include the Blizzard of 1978, the 2018 bomb cyclone that hit the eastern United […]

What Is Thundersnow? How It Works and Where to Find ...

This entry was posted on March 10, 2020 by Anne Helmenstine (updated on March 10, 2020)

The white smoke demonstration is a simple, visually appealing chemistry project. Pour a clear liquid into a seemingly empty and watch clouds of white vapor appear. It makes a nice science magic trick and is a great introduction to a discussion of acid-base and synthesis reactions. Materials This is a […]

White Smoke Demonstration (Ammonium Chloride Synthesis)

This entry was posted on March 8, 2020 by Anne Helmenstine (updated on March 8, 2020)

Bath bombs dissolve in an endothermic reaction — An endothermic reaction is a chemical reaction that absorbs heat from its environment. Like any chemical reaction, an endothermic reaction requires activation energy to proceed. Then, it continues to absorb energy. Such reactions feel cold. In contrast, exothermic reactions release more heat than they absorb and feel hot. Not all […]

Easy Endothermic Reaction Demonstration

This entry was posted on March 7, 2020 by Anne Helmenstine (updated on March 7, 2020)

Adding Positive Negative Numbers — Positive and negative numbers are two broad classes of numbers that are used in math and also everyday transactions, like managing money or measuring weight. A positive number has a value greater than zero. Its sign is positive, but it is usually written without a plus sign in front of […]

Rules for Positive and Negative Numbers

This entry was posted on March 5, 2020 by Anne Helmenstine (updated on March 5, 2020)

Coronavirus (COVID-19) — The coronavirus responsible for the disease COVID-19 has spread from China to 75 countries worldwide. Harvard epidemiologist Marc Lipsitch estimates between 40% and 70% of the world population will be infected with coronavirus sometime this year. So, chances are good you or someone you know will catch coronavirus. How will […]

How to Know If You’re Infected With Coronavirus: Coronavirus Symptoms

This entry was posted on March 4, 2020 by Anne Helmenstine (updated on March 4, 2020)

It’s easy to make a simple, effective homemade hand sanitizer. Why would you want to bother? Sometimes it’s hard to find hand sanitizer in a store, it might contain ingredients you don’t want, and it’s cheaper to make it yourself. Here is a basic homemade hand sanitizer recipe that you […]

Easy and Effective Homemade Hand Sanitizer Recipe

This entry was posted on March 2, 2020 by Anne Helmenstine (updated on March 19, 2020)

Hydrofluoric Acid (HF) Molecule — Hydrofluoric acid or HF is an extremely powerful, corrosive acid. However, it’s classified as a weak acid rather than a strong acid. This makes HF the only hydrohalic acid that isn’t classified as a strong acid (e.g., HCl, HBr, HI). Why Hydrofluoric Acid Is a Weak Acid The simple reason […]

Is Hydrofluoric Acid a Strong or Weak Acid?

This entry was posted on March 1, 2020 by Anne Helmenstine (updated on March 1, 2020)

Strong and Weak Acids — Strong and weak acids are key concepts in chemistry. Strong acids completely dissociate into their ions in water, while weak acids incompletely dissociate. There are only a few strong acids, but many weak acids. Strong Acids Strong acids completely dissociate in water into their ions and produce one of more […]

List of Common Strong and Weak Acids

This entry was posted on February 28, 2020 by Anne Helmenstine (updated on February 28, 2020)

Here are the names, element symbols, and atomic numbers of the first 20 elements of the periodic table. — It’s handy to know the first 20 elements of the periodic table. Around 99% of the mass of the human body is made of six of these elements. The first 20 elements are also a good overview of the different element groups. The elements are listed in order of increasing […]

First 20 Elements of the Periodic Table

This entry was posted on February 26, 2020 by Anne Helmenstine (updated on February 26, 2020)

Gatorade and drain cleaner color change — The Gatorade and drain cleaner color change chemistry demonstration is a variant of the classic blue bottle demo. You can customize the demo to get a range of colors. The best part is you don’t need access to a chemistry lab for the materials, so this is a great project […]

Gatorade and Drain Cleaner Color Change Chem Demo

This entry was posted on February 25, 2020 by Anne Helmenstine (updated on February 28, 2020)

Hot and Cold Volcanoes — Learn about endothermic and exothermic reactions by making cold and hot chemical volcanoes. This project is more entertaining than mixing chemicals in beakers and measuring their temperatures. The volcanoes use common, safe household ingredients. Endothermic and Exothermic Reactions An endothermic chemical reaction absorbs energy from its environment, so the reaction […]

Hot and Cold Volcano: Easy Endothermic and Exothermic Reactions

This entry was posted on February 23, 2020 by Anne Helmenstine (updated on March 7, 2020)

Magicians and chemistry teachers know how to turn water into wine or blood. Of course, this is simply a chemical reaction that causes a clear liquid to turn pink or red. If the conditions are right, the color shifts back and forth. The water into wine demonstration is the easiest […]

Water Into Wine or Blood Chem Demo

This entry was posted on February 20, 2020 by Anne Helmenstine (updated on February 21, 2020)

Protons and neutrons aren’t electrically attracted to each other, so have you ever wondered why they stick together in the atomic nucleus? The strong interaction produces the strong nuclear force, which holds matter together when the particles are close enough. The Strong Force The strong force is one of the […]

Why Protons Stick to Neutrons in the Atomic Nucleus

This entry was posted on February 19, 2020 by Anne Helmenstine (updated on March 24, 2020)

Atoms are often considered to be the building blocks of matter because they are the smallest units of chemical elements. These 10 atom facts cover basic information about atoms and some fun facts as well. The word atom comes from the Greek word atomos, which means “undivided” or “uncut.” The […]

10 Interesting Atom Facts

This entry was posted on February 19, 2020 by Anne Helmenstine (updated on February 19, 2020)

The elephant toothpaste chemistry demonstration produces a steaming tube of foam that erupts like an elephant squeezing a giant tube of toothpaste. The classic demo isn’t appropriate for kids because it uses 30% hydrogen peroxide, but there is a safe, easy version, too. The kid-friendly elephant toothpaste demo uses ordinary […]

Kid-Friendly Elephant Toothpaste Demo

This entry was posted on February 17, 2020 by Anne Helmenstine (updated on February 17, 2020)

Lightning Strike — The phrase “lightning never strikes the same place twice” means when something really bad (or really good) happens, it won’t happen again. Of course, that isn’t always true. It’s also a myth that lightning never strikes the same place twice. In the short term, lightning is more likely to follow […]

Can Lightning Strike the Same Place Twice? Recently updated !

This entry was posted on February 16, 2020 by Anne Helmenstine (updated on March 28, 2020)

Cute tiles in love — Chemistry pick up lines can be cute, corny, cheesy, or funny. They might even work! To increase the odds of chemical attraction, try delivering one of these lines while wearing a lab coat or safety glasses. Or, offer your intended a cocktail that changes colors. Most of these pick up […]

Cute Chemistry Pick Up Lines Recently updated !

This entry was posted on February 15, 2020 by Anne Helmenstine (updated on March 28, 2020)

How many zeros in...? — Have ever wondered how many zeros are in a million, billion, or trillion? Do you know how many zeros are in a vigintillion or a googol? Knowing how to write ordinary large numbers is useful for science or math class (or your bank account, if you are rich). Use your knowledge […]

How Many Zeros in a Million, Billion, and Trillion?

This entry was posted on February 15, 2020 by Anne Helmenstine (updated on February 15, 2020)

Cube with dimensions shown — Surface area formulas and volume formulas appear time and again in calculations and homework problems. Pressure is a force per area and density is mass per volume. These are just two simple types of calculations that involve these formulas. This is a short list of common geometric shapes and their […]

Surface Area Formulas and Volume Formulas of 3D Shapes

This entry was posted on June 25, 2017 by Todd Helmenstine (updated on February 15, 2020)

March 14 is traditionally Pi Day since 3-14 are the first three digits of pi. The year 2015 added little more significance because the next two digits are 15. The year 2016 worked too, since you could round pi to 3.1416. Anyway, the digits of pi are important. That hasn’t stopped […]

Pi Day and the Indiana Pi Bill

This entry was posted on March 12, 2015 by Todd Helmenstine (updated on March 9, 2020)

Diatomic Elements — A diatomic element is a molecule of an element consisting of two atoms. It is a form of homonuclear diatomic molecule. There are only 7 diatomic elements in total and only 5 diatomic elements at standard temperature and pressure (STP). The diatomic elements are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, […]

What Are Diatomic Elements? Definition and List Recently updated !

This entry was posted on September 28, 2014 by Anne Helmenstine (updated on March 30, 2020)

Periodic Table Metals - 2017 — Most elements can be considered metals. They are grouped together in the middle to the left-hand side of the periodic table. The metals consist of the alkali metals, alkaline earths, transition metals, lanthanides, and actinides. Properties of Metals The metals share several common properties, including: solid at room temperature (with […]

List of Metals

This entry was posted on September 3, 2014 by Todd Helmenstine (updated on August 4, 2019)