Aplant uses carbon dioxide and water to form food and oxygen. why is this a chemical change? the mass of the plant increases greatly. the properties of water and food are same. the plant increases in height as food is produced. the properties of carbon dioxide and oxygen are different.

A chemical change is defined as something that changes the substance of something (such as the creation of water from hydrogen and water), and can be figured out if chemical or physical based on different changes and properties. Your answer will be D because these are two different elements (compounds in case of CO2) that combine to form a different substance, thus changing the identity of the substance. 

29.1-12=17.1the answer is this one

Electrical charges of ionic bonds