Answer:
One way you can know that something is a chemical change is when it is accompanied by a change in physical or chemical properties. For example, when sodium (Na) reacts with chlorine (Cl), it forms table salt (NaCl), which has different physical and chemical properties from its starting materials. Another example is the combustion of methane, in which carbon and hydrogen atoms react with oxygen to form carbon dioxide and water. This is a chemical reaction because it causes a change in physical and chemical properties.
One way you can know that something isn't a chemical change is when it is accompanied by no obvious changes in physical or chemical properties. For example, melting ice does not involve a chemical change, but rather a change in physical state. Similarly, dissolving sugar in water is not a chemical reaction, but rather a physical change. Similarly, mixing two solutions with identical properties, such as two water solutions with the same concentration of the same salt, does not result in a chemical reaction.
Step-by-step explanation: