Investigations were carried out in a science lab to explore the topic of chemical and physical changes. investigation a step 1. add 5 tsp. salt to 100 ml warm water. and stir until most or all of the salt is no longer visible. step 2. heat the salt solution on a burner until only a white solid remains. investigation b step 1. mix 10 tsp. white sugar into 100 ml water and stir until most or all of the sugar is no longer visible. step 2. heat the sugar solution on a burner until the solution thickens and turns brown. in which step(s) did a chemical change most likely occur?

Investigation B, Step 2

Explanation:

The colour change is a good indication of a chemical change. The sugar molecules were most likely changing into something else.

Investigation A, Step 1. Wrong. The dissolving of salt is a physical process.

Investigation A, Step 2. Wrong. You simply boiled off the water (a physical process) and recovered the salt.

Investigation B, Step 1. Wrong. The dissolving of sugar is a physical process.

explanation:

the largest database of organic compounds lists about 10 million substances, which include compounds originating from living organisms and those synthesized by chemists. the number of potential organic compounds has been estimated at 1060—an astronomically high number. the existence of so many organic molecules is a consequence of the ability of carbon atoms to form up to four strong bonds to other carbon atoms, resulting in chains and rings of many different sizes, shapes, and complexities. the simplest organic compounds contain only the elements carbon and hydrogen, and are called hydrocarbons. even though they are composed of only two types of atoms, there is a wide variety of hydrocarbons because they may consist of varying lengths of chains, branched chains, and rings of carbon atoms, or combinations of these structures. in addition, hydrocarbons may differ in the types of carbon-carbon bonds present in their molecules. many hydrocarbons are found in plants, animals, and their fossils; other hydrocarbons have been prepared in the laboratory. we use hydrocarbons every day, mainly as fuels, such as natural gas, acetylene, propane, butane, and the principal components of gasoline, diesel fuel, and heating oil. the familiar plastics polyethylene, polypropylene, and polystyrene are also hydrocarbons. we can distinguish several types of hydrocarbons by differences in the bonding between carbon atoms. this leads to differences in geometries and in the hybridization of the carbon orbitals.