Answer:
- <em><u>A physical change has occurred, with no energy change.</u></em>
Explanation:
When a pencil lead is broken there is not change of any chemical properties, therefore it is not a chemical change, but just a physical change. In this case the change is just the number of pieces and dimensions.
Chemical changes always involve the formation of new different substances; the bonds between the atoms of the starting substances (reactants) breake and new bonds are formed leading to new substances (products) with different chemical composition (arrange of atoms). Chemical changes occur through chemical reactions.
Hence, if there is not change on the chemical composition, you think on physical changes. Physical changes include change in shape, size, state of matter (e.g. solid, liquid, gas). In the case of a pencil lead breaking, it is a change in shape and size.
Also, since energy has not been absorbed or released during the change, the energy of the pencil lead before having been broken is equal to the sum of the energies of the pieces of pencil lead obtained. So, this is a physical change with no energy changes.
Some examples of physical changes that include change in energy are the change of state (e.g. solid to liquid or liquid to gas) and the dissolution of a compound.
Answer:
1) 94.0° C, 2) 34.7°C
Explanation:
1)
Q=mcΔt° =mc(t2 - t1)
2350 J = 85.0 g* 0.385 J/(g*°C) *(t2 - 22.2°C)
t2 - 22.2°C = 71.81°C
t2 = 94.0° C
2)
Q=mcΔt° =mc(t2 - t1)
- 2070 J = 75.0 g * 0.903 J/(g*°C) *(t2 -65.3°C)
t2 - 65.3°C = - 30.56°C
t2 = 34.7°C
Answer:
(I). The most likely to lose electron is Rubidium
(II). The most likely to lose electron is Bromine
Explanation:
Given that,
Radium, Indium, Phosphorus, Tellurium, Bromine and Rubidium
We know that,
Metal :
They atom which to lose electron these is called metal.
When the atom loses the electron then the positive charge come on the atom.
The most likely to lose electron is Rubidium
Non metal :
They atome which is gains electron. It is called non metal.
So, we can say that, the non metal gains electron.
When the atom gains the electron then the negative charge come on the atom.
The most likely to gain electron is Bromine
Hence, This is required answer.
Answer: Option (b) is the correct answer.
Explanation:
A statement which states a scientifically acceptable general principle that is experimentally tested or verified is defined as a theory.
A theory is the sum of a number of observations which are tested in order to get the true result so that a statement can be framed.
Thus, we can conclude that out of the given options, a theory is a well-tested explanation for a broad set of observations.
