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Feedback Comments on Matter

by Ron Kurtus

A total of 252 comments and questions have been sent in. They are listed according to date.

List of most recent 10 letters




Atoms Is an atom electrically neutral? Nigeria
Density Finding the density of an object Tanzania
Kinetic Theory of Matter What is a solid, liquid and gas? India
Atom as Solar System Why isn't the solar system a giant atom? USA
Density Factors How physical conditions affect density USA
Evaporation How are water molecules able to escape gravity? USA
Changing States of Matter What if matter did not change its state? Pakistan
Pressure and States of Matter Permission to use images USA
Dry Ice Using CO2 for supercritical extraction USA
Dry Ice Info on dry ice USA

Next 10


Is an atom electrically neutral?

Topic: Atoms


April 26, 2018

An atom is said to be electrically neutral?

melody - Nigeria



It is true that an atom is electrically neutral, because it has the same number of positive (+) and negative (-) particles.

See Structure of the Atom for more information.

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Finding the density of an object

Topic: Density


April 15, 2018

1. An object with the volume of 150 cubic centimetre has a percentage of volume submerged of 60% when immerse into water. What is the density of the object?

can I get books of supplement material which have enough questions on densities, relative densities etc

Denis - Tanzania



If 60% is submerged in the water, that means that the volume of water displaced is 150 * 0.6 = 90 cc. Since the density of water is 1, the mass of 90 cc of water is 90 g.

Thus, the mass of the object is the mass of the displace water 90 g divided by 0.6 equals 150 g.

The density of the object is its mass divided by its volume or 150/90 = 1.67.

That seems to be a round-about way, but I hope it explains the subject.
Also refer to: Density of Matter and Factors Affecting Density of Matter.

Best wishes for success in your studies.

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What is a solid, liquid and gas?

Topic: Kinetic Theory of Matter


November 7, 2017

Q1. What is solid, liquids, gas

MD - India



See States of Matter for an explanation.

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Why isn't the solar system a giant atom?

Topic: Atom as Solar System


October 5, 2017

I had a question about the article you wrote regarding Bohr's Model of an atom. Why do you disagree with the fact that our solar system can't be just one "giant" atom. I was hoping to get in touch with you to discuss this?

Tristan - USA



Although our solar system looks like it could be a giant atom, there are a number of problems in the analogy. One it that electrons in an atom have an electrical charge, while there is nothing similar in the solar system. Also, the nucleus of an atom is made up of protons and neutrons, while the Sun is a mass of hot gases.

On the quantum scale, atomic particles are not tiny spheres but are wave packets.

Still, the similarity between the solar systems and atoms is intriguing.

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How physical conditions affect density

Topic: Density Factors


September 30, 2017

Describe how physical conditions affect density

kiprotich - USA



Density is mass divided by volume. Compressing an object decreases its volume and thus increases its density.

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How are water molecules able to escape gravity?

Topic: Evaporation


September 22, 2017

How are water molecules able to escape gravity? In other words, gravity withholds H2O from leaving the surface of the earth, but that same body of water evaporates and those molecules are unaffected by gravity.

Travis - USA



With water, the velocity of the molecules is not great enough to overcome their molecular attraction, and thus the material is a liquid that is kept toward the surface of the Earth. However, when H20 becomes a gas, the velocities of the molecules is much greater, such that they move about freely.

Most of those molecules velocities that are low enough to be constrained to the Earth's atmosphere. But some of the molecules of the gas or steam become accelerated due to radiation from the Sn, such that they have enough kinetic energy or velocity to escape the Earth's gravity.

Fortunately, the loss of water vapor molecules into space it very small.

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What if matter did not change its state?

Topic: Changing States of Matter


August 25, 2017

Explain that what happened if there would be no change in states of matter?


Aamish - Pakistan



If all matter stayed in its existing state or phase, ice would not melt to become water, and water could not boil into steam. Also, there would be no evaporation of water. Just these factors alone would affect living beings in a short time.

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Permission to use images

Topic: Pressure and States of Matter


August 14, 2017

I would like to use the phase diagram figures that you have on this page:

in an article that I am writing for the Health Physics Society. I understand that I need permission to use the figures. Is that possible that I could have permission to use your figures?

Thanks so much,

Linda - USA



Yes, you have permission to use the diagrams provided you cite the source.

Best wished for success in your article. Let me know when it is published.

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Using CO2 for supercritical extraction

Topic: Dry Ice


January 29, 2017

I would like to discuss some commercial uses for Dry Ice and it's conversion to Co2 for supercritical extraction.
Please let me know if you are available to discuss.

Thank you in advance,

Gary - USA



Dry ice is a convenient source of CO2. Allowing the gas from the dry ice to heat to about 31 degree C should help in the supercritical extraction process.

I hope that helps. Unfortunately, I am not an expert in this field.

Best wishes for success in your work.

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Info on dry ice

Topic: Dry Ice


March 11, 2016

To whom this may concern,

I am a sixth grader at Kennedy Middle School. Our school is participating in something called Genius Hour which allows us to research a topic that interests us. We are required to interview a professional who is knowledgeable about our topic. My topic is dry ice.
If you could please answer the questions below as soon as you get the chance, it would be greatly appreciated. Thank you for taking time out of your day to respond to this email.

Thank you for your time,

Gianna G.

My questions are:

Where was dry ice first found?

How long does dry ice last in water?

What gas is given off of dry ice?

How is dry ice created?

What is inside dry ice?

How long can you touch dry ice with bare hands?

Can you make dry ice?

Gianna - USA



Dry ice was first observed in 1835 in France. It is frozen carbon dioxide (CO2). When it melts, it turns to CO2 gas. You should only hold dry ice a fraction of a second. Special equipment is used to make dry ice.

See our lesson on Dry Ice is the Solid State of Carbon Dioxide for more information. Also see Dry Ice Wiki for detailed info.

Best wishes for success in your report.

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