1. which of these is an indication that a chemical reaction has occurred? a. formation of a precipitate b. melting of a substance c. boiling of a substance d. freezing of a substance 2. if decreases in temperature accompanies a reaction, what occurred? a. energy was destroyed b. energy was created c. energy was absorbed d. energy was released 3. which of these accurately describes the products of a reaction? a. new substances that are present at the end of a reaction b. substances that were not used up in a reaction c. substances that are used in a reaction d. substances that do not participate in a reaction 4. which of these describes an exothermic reaction? a. energy is released by the reaction b. energy is created in the reaction c. energy is absorbed by the reaction d. no energy is transferred by the reaction 5. what occurs in a chemical reaction a. reactants are formed without chemical bonds being broken b. reactants are formed from products by the breaking and forming of bonds c. products are formed without chemical bonds being broken d. products are formed reactants by the breaking and forming of new bonds.

Quickly! brainliest if two people answer! 1. the blood has red blood cells, white blood cells and platelets. red blood cells carry oxygen to other cells in the body. cells need oxygen to live. white blood cells destroy certain germs. they protect our bodies from disease. which question is answered in this paragraph? (a) what is the role of blood vessels? (b) what type of cells are attached to bones? (c) what type of blood cell to clot your blood? (d) what are the different types of blood cells? 2. which sentence from the section "stem cells" best explains the role of stem cells? (a) when one kind of cell stops working, stem cells can . (b) they can turn into that cell and take its place. (c) scientists are studying new ways to use stem cells. (d) these cells can people heal faster. 3. read the selection from the section "nerve cells." nerve cells send messages to the rest of our bodies. these messages move between the brain, spinal cord and various organs. nerve cells are also called neurons. fill in the blank. a "neuron" is a (a) cell that moves information from the brain to other parts of the body (b) stem cell that has both an axon and a dendrite (c) cell that controls the fingers of a body (d) cell that makes up the spinal cord 4. some muscles in our body move without us telling them to. these are called involuntary muscles. some examples are the cardiac muscle cells inside the heart. these cells the heart relax and fill with blood. what is the best definition of "involuntary" based on the context clues? (a) something that happens on its own (b) trying hard to do something (c) something moving back and forth (d) easily moved

Melting and boiling are endothermic processes. this means that these processes absorb energy from their surroundings in order to occur. use this information and the data you collected in the phase change gizmo to describe what happens to the temperature of water when you boil it, then explain why this result occurs.

Which diagram shows the correct way to represent an ionic compound of magnesium oxide?