That friend is not correct. Physical change is characterized by a change in appearance without any change in composition. So, if the appearance did not change in the situation, then there is no change in the system. This type of change affects the form of a substance but not the composition or the structure of the molecules. Examples of this type of change are ice melting, cutting a paper into half, clay is molded to a new shape, butter melting, water evaporating. The change that involves a change in chemical composition is classified a chemical change. In this type of change, chemical reactions would take place.
Answer:
A small mass of positive charge was discovered in the center of the atom.
Explanation:
Atoms is the combination of protons, neutrons, as well as electrons particles. The particles that are in the centre of atom is Protons and neutrons, which made up the nucleus, this nucleus is surrounded by electron.
The discovery that directly caused scientists to revise this model of the atom is that A small mass of positive charge known as proton, and a positive charge particle was discovered by Ernest Rutherford, in the center of the atom in the year 1900. Ernest Rutherford through his research resulted to splitting of the atom during nuclear reaction and proton was discovered.
Answer:
The percentage composition of the compound is 81.72% of C and 18.28% of H.
Explanation: Percentage composition is the percentage by mass of each element in a compound. It is the ratio of an amount of each element to the total amount of individual elements in a compound, which is then multiplied with 100.
Since the compound above contains only carbon and hydrogen, we will have to find the sum of their masses.
Given 36.03g of Carbon and 8.06g of hydrogen,
36.03g + 8.06g = 44.09g of the compound
%composition= gram of element/gram of compound × 100
%C = 36.03/44.09 × 100
%C= 0.8172 × 100
℅C= 81.72%
Likewise for H
%H= 8.06/44.09 × 100
%H= 0.1828 × 100
%H= 18.28%
Therefore, the compound can be said to contain 81.72% of C and 18.28% of H
Answer : The limiting reactant is, carbon (C)
Explanation : Given,
Moles of 
= 2 moles
Moles of C = 5 moles
Now we have to calculate the limiting and excess reagent.
The given balanced chemical reaction is:
From the balanced reaction we conclude that
As, 3 mole of 
react with 1 mole of
So, 5 moles of react with 
moles of
From this we conclude that, is an excess reagent because the given moles are greater than the required moles and is a limiting reagent and it limits the formation of product.
Thus, the limiting reactant is, carbon (C)
<em>Advantages</em>
Chemistry helps you to understand the world around you.
Basic knowledge of chemistry helps you to read and understand product labels.
Chemistry can help you make informed decisions.
Chemistry is at the heart of cooking.
A command of chemistry can help keep you safe!
<em>Disadvantages</em><em> </em>
It isn't a sustainable form of energy.
It can be expensive.
Some forms of chemical energy are quite rare.
It can produce harmful waste.
It can be used to create devastating weapons.
It offers short-term benefits for long-term consequences.
