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Chemical reactions happen when _____. a.atoms attract or repel one another b.heat is created by friction c. two or more substanc

melomori [17]

Answer:

A

Explanation:

5 0

2 years ago

What element is this? How do you know?

postnew [5]

Atom is the most basic unit of matter. They are the general term used to describe pieces of matter. But a different kind of atom makes up an element. A combination of atom of different elements creates a molecule. For example, you have water; it has a chemical formula of H2O. If you separate H from O, you have two atoms. Two atoms for hydrogen and one atom for oxygen. However, they are of different elements. And when you combine them to form H2O, you create a molecule.

4 0

2 years ago

A thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper; the aluminum and the copper are in

Illusion [34]

Answer:

Copper is the object that experiences the greater temperature change.

Explanation:

Thermally isolated system means that the system does not exchange thermal energy with the surroundings.

Hence, any thermal exchange, in virtue of the temperature difference of the aluminum and copper pieces, is between them.

In consequence, the law of conservation of energy states that the heat lost by the hot substance will be gained by the cold matter.

In equations, that is:

Heat lost by aluminum = heat gained by copper.

Now, the gain or loss or heat of a substance, Q, is related with the mass (m), the specific heat (Cs), and the cahnge of temperature (ΔT), per the equation:

Q = m × Cs × ΔT

∴ Q lost by aluminum = Q gained copper ⇒

[m × Cs × ΔT ] aluminum = [m × Cs × ΔT ] copper.

Under the reasoning assumption that the masses of aluminum and copper are equal, the equations is simplified to:

[Cs × ΔT ] aluminum = [Cs × ΔT ] copper.

Cs aluminum / Cs copper = ΔT copper / ΔT aluminum

Cs aluminum > 2 × Cs copper ⇒ Cs

Cs aluminum / Cs copper > 2 ΔT copper / ΔT aluminum

ΔT copper / ΔT aluminum > 2

ΔT copper > 2 × ΔT aluminum

In words, since it is stated that the specific heat of aluminum is more than double that of copper, in order to keep the equality, ΔT of copper shall be more than double ΔT of aluminum.

Hence, the conclusion is that the object that experiences the greater temperature change is copper (the one with the lower specific heat), under the assumption that both objects have the same amount of matter (mass).

6 0

2 years ago

What does moderate mean in chemistry?

Eduardwww [97]

Answer:

Moderate reaction means those reactions which proceed with a measurable rates at the normal room temperature.

7 0

2 years ago

How to find how many electrons are in an element

Murljashka [212]

Explanation:

1) Locate the atomic number in the upper left corner of the square. The atomic number will tell you the number of protons

2) In a neutral state, the element will contain the same number of protons as it will electrons.

--> Boron (B) has an atomic number of 5, so it has 5 protons.

--> Having 5 protons (+1 charge each) means to be balanced, it must have 5 electrons (-1 charge each)

However, what if it's not in a neutral state?

If it's not in a neutral state, it will look something like this:

Ca ^ 2+

Btw, the "^" means that it will be written like it's an exponent. That confuses people sometimes.

Anyways, the "2+" means it's an ion with a positive charge of 2. For us to have a positive charge, it means it's lost two electrons (cause electrons are negative, so taking them away means we are left with a more positive charge).

To get the number of remaining electrons, subtract the 2 from the atomic mass. In this case, that would be 20.

20 - 2 = 18 electrons

Another example:

N ^3-

Atomic Number: 7

7 + 3 = 10 electrons.

Why did I add here instead of subtracting? It's cause the 3- means we have added electrons, resulting in the ion having a negative charge. It's got more electrons than usual.

Hopefully this helps a bit.

5 0

2 years ago