Dimitri Mendeleev was inspired primarily by the work of Antoine Lavoisier and his work on writing the first extensive list of known elements. Lavoisier also collaborated in the construction of the metric system and worked to develop a better nomenclature for chemical compounds which parts are still used today.
The sand to pass through, but not the gravel. Hope this helps!
Answer: The reaction is exothermic reaction as the energy of products is less than the energy of reactants.
Explanation: Exothermic reactions are defined as the reactions in which energy of the product is less than the energy of the reactants. The total energy is released in the form of heat and 
for the reaction comes out to be negative.
Labeling of the parts in the diagram:
A represents the activation energy which is the energy required by reactants to cross the energy barrier to get converted to products.
E represents the potential energy of the reactants.
B represents the activated complex.
D represents the potential energy of the products.
C represents the total enthalpy change of the reaction, which comes out to be negative for exothermic reactions.
Answer:
b) sharpening a pencil
Explanation:
If you melt lead, boil water, or dissolve sugar in water, you can return all of them back to their original state. If you sharpen a pencil, you can't reattach the shavings as they were originally.
The three sub-atomic particles that made up an atom are electron, proton and neutron. The proton and neutron are present in the nucleus of an atom whereas electrons revolve around the nucleus in the orbits. The atoms are electrically neutral that is they have no charge due to the presence of equal number of protons (which is positively charged) and electrons (which is negatively charged).
All the atoms have negatively charged electrons which are counter balanced by the presence of equal number of protons in the nucleus of an atom and thus, the element is neutral in nature and possess no charge.
