Bond angle of a molecule is related to the electronegativity of the central atom. The more electronegative the central atom is, the greater the bond angle.
As electronegativity of the central atom increases, the magnitude of bond pair- bond pair repulsion increases leading to increase in bond angle.
Hence, oxygen, being more electronegative than sulphur asserts a greater bond pair- bond pair repulsion leading to a greater bond angle in water.
A chemical change is a change in the chemical makeup of a substance and results in a new substance. Ice and water both have the same chemical makeup - ice is just a different state and has the same atoms but in an expanded form.
The function of a lysosome is to rid of any unwanted waste. Acid hydrolase aids in that process. Therefore, the acid would make the most sense to be found in lysosomes.
