Temperature

 Temperature 

What is temperature? 

Temperature can be a difficult property to define. In our everyday lives we use the word temperature to describe the hotness or coldness of an object. In physics, the temperature is the average kinetic energy of the moving particles in a substance. 

How is temperature measured? 

Temperature is measured using a thermometer. There are different scales and standards for measuring temperature including Celsius, Fahrenheit, and Kelvin. These are discussed in more detail below.

 How does a thermometer work? 

Thermometers take advantage of a scientific property called thermal expansion. Most substances will expand and take up more volume as they get hotter. Liquid thermometers have some sort of substance (this used to be mercury, but today is generally alcohol) that is enclosed in a small glass tube. As the temperature rises, the liquid expands and fills up more of the tube. When the temperature drops, the liquid contracts and takes up less of the tube. The temperature can then be read by the lines calibrated on the side of the tube. 

Temperature Scales

 There are three main temperature scales that are used today: Celsius, Fahrenheit, and Kelvin. Celsius - The most common temperature scale in the world is Celsius. Celsius uses the unit "degrees" and is abbreviated as °C. The scale sets the freezing point of water at 0 °C and the boiling point of water at 100 °C. Fahrenheit - The temperature scale most common in the United States is the Fahrenheit scale. Fahrenheit sets the freezing point of water at 32 °F and the boiling point at 212 °F. Kelvin - The standard unit of temperature that is most used by scientists is Kelvin. Kelvin doesn't use the ° symbol like the other two scales. When writing a temperature in Kelvin you just use the letter K. Kelvin uses absolute zero as the 0 point of its scale. It has the same increments as Celsius in that there are 100 increments between the freezing and boiling points of water.

 Converting Between Scales 

Celsius and Fahrenheit 

°C = (°F - 32)/1.8 

°F = 1.8 * °C + 32° 

Celsius and Kelvin

 K = °C + 273.15

 °C = K - 273.15° 

Absolute Zero 

Absolute zero is the coldest possible temperature that any substance can reach. It is equal to 0 Kelvin or -273.15 °C (-459.67°F). 

Temperature and the State of Matter 

Temperature has an effect on the state of matter. Each substance of matter will go through different phases as the temperature increases including solid, liquid, and gas. One example of this is water which changes from ice (solid) to water (liquid) to vapor (gas) as the temperature increases. You can learn more about this subject at our phases of matter page. 

Interesting Facts about Temperature 

Temperature is independent of the size or quantity of an object. 

This is called an intensive property. 

The Fahrenheit scale is named after Dutch physicist Daniel Fahrenheit. 

Temperature is a different quantity from the total amount of thermal energy in a substance, which is dependent on the size of the object. 

Celsius was named after the Swedish astronomer Anders Celsius. 

Celsius was originally known as "centigrade." 

As substances approach absolute zero they can achieve some interesting properties such as superfluidity and superconductivity.

Science of Heat

 Science of Heat

Heat is the transfer of energy from a one object to another due to a difference in temperature. Heat can be measured in joules, BTUs (British thermal unit), or calories. Heat and temperature are closely related, but they are not the same thing. The temperature of an object is determined by how fast its molecules are moving. The faster the molecules are moving the higher the temperature. We say objects that have a high temperature are hot and objects with a low temperature are cold.

 Transferring of Heat 

When two items are combined or touching each other, their molecules will transfer energy called heat. They will try to come to a point where they both have the same temperature. This is called equilibrium. Heat will flow from the hotter object to the colder. The molecules in the hotter object will slow down and the molecules in the colder object will speed up. Eventually they will get to the point where they have the same temperature. This happens all the time around you. For example, when you take an ice cube and put it into a warm soda. The ice cube will become warmer and melt, while the soda will cool down. 

Hot Objects Expand

 When something gets hotter it will expand, or get bigger. At the same time, when something gets colder it will shrink. This property is used to make mercury thermometers. The line in the thermometer is actually liquid mercury. As the liquid gets hotter, it will expand and rise in the thermometer to show a higher temperature. It's the expansion and contraction due to temperature that allows the thermometer to work.

 Heat Conduction 

When heat transfers from one object to another, this is called conduction. Some materials conduct heat better than others. Metal, for example, is a good conductor of heat. We use metal in pots and pans to cook because it will move the heat from the flame to our food quickly. Cloth, like a blanket, isn't a good conductor of heat. Because it's not a good conductor, a blanket works well to keep us warm at night as it won't conduct the heat from our bodies out to the cold air. 

Matter Changing State 

Heat has an impact on the state of matter. Matter can change state based on heat or temperature. There are three states that matter can take depending on its temperature: solid, liquid, and gas. For example, if water is cold and its molecules are moving very slow, it will be a solid (ice). If it warms up some, the ice will melt and water becomes a liquid. If you add a lot of heat to water, the molecules will move very fast and it will become a gas (steam).

 

Copper ‘foam’ could be used as filters for COVID-19 masks

The lightweight new material is washable and recyclable

Face masks have become a vital tool in slowing the spread of the virus that causes COVID-19. They help filter or block spit or mucus droplets that carry infectious particles. Even homemade fabric masks can do a good job. But many are not very durable. Now, researchers have come up with a new sort of filter for use in masks. Made of copper, it’s sturdy and lightweight. The sponge-like material also is easy to clean and can be recycled. In tests, it performed as well in filtering as a standard N95 mask. It might even trap and kill bacteria, its developers say.

Masks to guard against viruses can be made of many different materials. Some fabric ones even use extra layers — often cotton, silk or some synthetic — to boost their filtering prowess. Others use paper similar to coffee filters. With so many people now being asked to wear masks during the pandemic, researchers began scrambling to identify new and better filters. Kai Liu was among them.

This materials scientist thought his team at Georgetown University in Washington, D.C., had a head start. They already had been testing materials to filter small particles out of polluted air.

Recalls Liu, “We saw that small droplets carrying viruses were the same size as some atmospheric pollutants.” Right away, he says, “we thought we should check our materials to see if they might make good filters for face masks.”

Liu’s team soon began cranking out new batches of a material they call copper foam.

They started with templates to make copper nanowires. The diameter of each wire was typically about 200 nanometers, says Liu — or less than one ten-millionth of an inch. After dumping those wires into ultrapure water, they flash-froze the mix in liquid nitrogen. Afterward, they put the copper-filled ice in a vacuum chamber. It drove off the ice to freeze dry the now loosely packed mass of tiny copper wires. Finally, they heated the mass of wires to 300° Celsius (572° Fahrenheit). This fostered chemical reactions that helped bind them into a mesh.

Unfortunately, that mesh was super flimsy, says Liu. Tests showed it would collapse if someone breathed on it. Obviously, that would not work well in masks. So, the researchers kept tweaking the process.

They bathed the weak mesh in a liquid that included copper ions. Then they sent an electric current through this chemical bath. That deposited more copper onto the nanowires, thickening them. Liu says it also helped weld the wires at points where they touched. In tests, some samples of this material could now support about 10,000 times their own weight without collapsing. That was true even when the material was 85 percent air.

More importantly, this 85-percent-air foam filtered out tiny particles. A sample 2.5 millimeters (0.1 inch) thick captured 97 percent of particles between 0.1 to 0.4 micrometers in diameter. Such super-small particles not only are the hardest to trap but also the size of the smallest aerosol droplets that can carry virus particles. These particles don’t just get trapped by the material’s tiny pores, Liu explains. The particles are particularly attracted to the enormous surface area that the nanowires provide. They get stuck there on it as they try to move through the wire maze between the outer and inner edges of the filter. Liu and his colleagues described their innovative new foam April 14 in Nano Letters.

 

Chemists win Nobel Prize for faster, cleaner way of making molecules

Making molecules is hard work. Atoms must be bonded together in specific arrangements through a series of chemical reactions. Those reactions often are slow and far from straightforward. They also can waste resources. The 2021 Nobel Prize in chemistry goes to two scientists who developed a tool some 20 years ago that revolutionized how chemists create new molecules. Their process is not only faster but also friendlier to the environment.

“This is a fitting recognition of very important work,” says H.N. Cheng. He’s president of the American Chemical Society, based in Washington, D.C. “We can think of chemists as magicians having magic wands in the lab,” Cheng says. “We wave the wand and a reaction goes on.” These Nobel laureates gave chemists “a new wand,” that’s drastically more efficient and less wasteful, he says.

That wand is a new way to speed the reactions that build specific molecules. It’s a process known as asymmetric organocatalysis (AY-sih-MEH-trik Or-gan-oh-kah-TAL-ih-sis). This year’s winners came up with the idea for it independently. One of the chemists, Benjamin List, works at the Max Planck Institute for Coal Research. It’s in Mülheim an der Ruhr, Germany. The other is David MacMillan. He works at Princeton University in New Jersey.

List’s and MacMillan’s work prompted others to seek out more organic catalysts and to study how they might be used. These catalysts tend to be small carbon-and-hydrogen molecules which might also include oxygen, nitrogen, sulfur and/or phosphorus.

Catalysis is a big deal. Roughly one-third of the world’s collective income depends on it, notes Peter Somfai. He’s a chemist at Lund University in Sweden and another member of the Nobel Committee for Chemistry. At an October 6 news conference announcing the new winners, he noted “We now have a new powerful tool available for making organic molecules.” He said it’s one that can be drastically more efficient and “greener” than previous methods.

And because this process eliminates use of toxic chemicals, it’s also a far more environmentally friendly process.

If building new molecules is like playing chess, asymmetric organocatalysis has “completely changed the game,” Somfai said. “It’s like adding a new chess piece that can move in different ways.”

For their achievements, List and MacMillan will each get a medal and share 10 million Swedish kroner (more than $1.1 million).

Molecule

 

Molecule (noun, “MOLL-eh-kewl”)

A molecule is usually two or more atoms held together with chemical bonds.

Molecules can be homonuclear. That means they contain atoms of only one element. The oxygen we breathe, for example, is a molecule of two oxygen atoms — O2. Other molecules are heteronuclear — made of more than one element. A molecule of water — H2O — is made of two hydrogen atoms bonded to one oxygen atom.

Molecules make up your own body, the air we breathe, everything living around us. A molecule is the smallest particle of a substance that still has all the chemical properties of that substance. For example, a single molecule of water — H2O — has all the properties of water. But split it apart into its atoms, and it will not be water anymore.

Smaller molecules can join together to make up large ones. A single strand of DNA, for instance, is one large molecule. That one molecule of DNA is made from many smaller molecules, including sugars and phosphates. Take apart a DNA molecule and it will not be able to do what DNA does — provide the instructions cells need to survive.

Put together, the atoms in most molecules have a neutral electrical charge — neither positive nor negative. But some atoms — such as helium — don’t have any electrical charge, even by themselves. Some people count these single atoms as molecules too. And some molecules do have an electrical charge. These charged molecules are called ions.

What If The EARTH Stopped Spinning?

Physics Quiz

 Physics Quiz

Test how much you know about physics by trying our fun physics quiz. There’s a range of questions about topics such as energy, motion, friction, magnets, force, gravity and light.

Take the challenge and pick up some interesting physics facts and trivia along the way. Once you’ve finished with the questions, scroll down the page and check your answers to see what you got right.