What is the difference between cathode rays and beta rays?

cathode 'rays' were observed in electrical experiments because of their fluorescent effect near a negatively charged plate (called the cathode) in a vacuum. They were only later found to be negatively charged electrons emitted from negatively charged plates and accelerating toward positively charged ones. (Like charges repel, unlike charges attract.)

Beta 'rays' were first observed being emitted from certain unstable (radioactive) isotopes, and behaved unlike the alpha and gamma radiation also found in radioactivity. It wasn't until later that both alpha and beta 'radiation' were discovered to actually be particles; only gamma rays consist of true electromagnetic radiation. Beta 'rays' are actually electrons ejected from decaying neutrons, and are now more often referred to as Beta emission or Beta particles. 

So electrons can be described differently, not based on WHAT they are but HOW they are created or observed.

How fast do electrons travel when moving as an electrical current through copper wire?

The actual velocity of electrons through a conductor is measured as an average speed called drift velocity. This is because individual electrons do not traverse straight line paths in conductors, instead they move in a random zig-zag motion, changing directions as they collide with atoms in the conductor. Thus, the actual speed of the electrons through the conductor is very small in the direction of current.

For example, the drift speed through a copper wire of cross-sectional area 3.00 x 10^-6 m², with a current of 10 A will be approximately 2.5 x 10^-4 m/s or about a quarter of a milimeter per second.

What is Plasma?

A plasma (or, more properly, an electromagnetic plasma) is a phase of matter that has enough energy for the electrons to separated from the nucleus. It consists of independently moving electrons and nuclei, and thus has some rather interesting properties, such as very good magnetic shielding. It can be found in places such as the center of the sun, and also, in small quantities, surrounding a lightening bolt. 

Many people consider solid, liquid, gas and plasma to be the only four phases of matter. This is not true, as there exist many others, but they are generally more exotic with names like hadron gas or Bose-Einstein Condensate.

How did atom obtain its name?

The word is derived from the Greek word "atomos", meaning indivisible. The concept of the atom originated round 440 BC. In Greek, the prefix "a" means "not" and the word "tomos" means cut. Word "atom" therefore comes from "atomos", a Greek word meaning uncuttable. 

In 1803, John Dalton formulated the "atomic theory" of matter based on experiments that quantified the weights of elements formed when compounds were broken down. Based on experimental evidence, Dalton proposed that atoms really do exist as fundamental units of all elements. 

Twentieth century physics was able to probe atoms and prove that they are not, in fact, indivisible. But the name stuck, and still has meaning in that atoms are the smallest, indivisible part of any element. If you do divide them into smaller pieces of protons, neutrons and electrons, you no longer have the original element.

What is Dry Ice?

Dry ice is nothing but solidified Carbon Dioxide (CO₂). When Carbondioxide is cooled to a very low temperature it transforms into solid. The  temperature is about -78 deg centigrade. 

Carbon Dioxide is an interesting material because, at normal atmospheric pressures, it has no liquid state. It can only obtain a liquid state under very high pressure in a containment vessel.

So, when you have a frozen chunk of carbon dioxide out in the open where you can see it, it will transform directly from its solid state to a gas state with no intermediate liquid state. This process is known as 'sublimation'.

Dry ice freeze water vapor in the air near it producing visible vapor all by itself, however adding water will also add substantial heat which will cause the solid CO₂ to sublimate at a greatly accelerated rate thus producing much more visible vapor.

What is Heavy water?

Normal water is made of two Hydrogen atoms and one Oxygen atom. Hydrogen atom and Oxygen atoms are covalently bonded together. Normal water is designated by H₂O.

Heavy water also has same molecular structure but Hydrogen atoms are replaced by isotopes of Hydrogen called 'Deuterium'. Standard hydrogen has one Proton in its nucleus (Relative Molecular Mass = 1), Deuterium has one Proton and  one Neutron in it nucleus, (Relative Molecular Mass = 2). Hence it is 'heavier' than normal hydrogen. This leads to the water being heavier.