Why is the law of conservation of mass true? a. all atoms at the start of a chemical reaction are present at the end of the reaction

b. All the molecules in a substance remain intact during a chemical reaction

c. The substances at the start of a chemical reaction gather more atoms to make up for those lost in the reaction

d. all molecules at the start of a chemical reaction are present at the end of the reaction

Janel’s class studied properties of matter and how matter can change. janel decided she would do an experiment mixing baking soda and vinegar. question: describe the properties of baking soda and vinegar, and explain the changes that janel should see when she mixes the two types of matter. •first, identify the physical state of matter of baking soda. describe another property of baking soda. •next, identify the physical state of matter of vinegar. describe another property of vinegar. •then, explain what janel should see when she mixes the baking soda and vinegar. •describe the states of matter of the new materials that are formed. •explain how janel can be certain a change has occurred. me

An electron moved from shell n = 2 to shell n = 1. what most likely happened during the transition? a fraction of a photon was added. a photon of energy was absorbed. a fraction of a photon was removed. a photon of energy was released.

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.