The answer is (2) Copper. Because copper is consist of atom. If it is decomposed, the atom will be changed. While chemical change is just the break down and form of chemical bonds between atoms.
For the first one it’s 69 just count the little lines from the side.
Answer:
The final balanced equation is :

Explanation:

Balancing in acidic medium:
First we will determine the oxidation and reduction reaction from the givne reaction :
Oxidation:

Balance the charge by adding 2 electrons on product side:
....[1]
Reduction :

Balance O by adding water on required side:

Now, balance H by adding
on the required side:

At last balance the charge by adding electrons on the side where positive charge is more:
..[2]
Adding [1] and [2]:

The final balanced equation is :

Answer:
the answer is b
Explanation:
convection is caused by density differences whereby warm air with less density rise above a heater and sink near a cold wind.
The chemical formula for the compound strontium sulphide would be SrS.