The wax seems to disappear as a candle burns. How can the law of conservation of mass apply to this reaction?

Explain why the production of a gas does not always mean that a chemical reaction has occurred.

Describe clues you might observe during the following events that could support the conclusion that a chemical change is occurring. a. An antacid tablet is dropped into water. b. A ring of scum forms around abathtub. c. Iron rusts. d. Afirecracker explodes. e. Bubbles form when hydrogen peroxide is poured onto an open wound f. A hamburger cooks.

Each day you encounter some chemical changes that are helpful and some that are harmful to humans or the environment. Cite three examples of each type. For each example, list the clues that identified the change as a chemical change.

Five elements make up $97.9 \%$ of the mass of the human body. These elements are oxygen (64.8%), carbon (18.1%), hydrogen (10.0%), nitrogen (3.1%), and calcium (1.9%). Compare these data with those in the pie graph below, which shows the five most abundant elements by mass in Earth's crust, oceans, and atmosphere.

a. Which elements are abundant in both Earth's surface and the human body? b. Which elements are abundant in Earth's surface but not in the human body? c. Would you expect the compounds making up the human body to be the same as or different from those found in rocks, water, and air? Explain your answer based on the evidence in the pie graph and the data above.

The mass of the elements iron and oxygen were measured in four samples of a rust-colored substance believed to be a compound. The amount of iron and oxygen found in each sample is shown on the graph. a. Do you think each sample is of the same compound? Explain. b. Another sample of similar material was found to contain $9.9 \mathrm{~g}$ of iron and $3.4 \mathrm{~g}$ of oxygen. Is this the same substance as the other four? Explain.

A change in odor can also be a clue that a chemical change has occurred Describe at least one situation in which you might be likely to detect such a change in odour in a kitchen.

When powdered iron is left exposed to the air, it rusts. Explain why the mass of the rust is greater than the mass of the powdered iron.

Sara has just taken a job as the middle school assistant principal for an area school district. Prior to this, she was a teacher. She has received the following performance measurements for her first administrative job. Her first order of business is to determine if these performance measurements are short-term goals or long-term goals based on her individual situation. She has completed her administrative degree but has not yet worked as an administrator. Identify each of the following goals as short term or long term. H. Assist the building principal in all job duties and responsibilities.

Is the freezing of mercury a reversible or irreversible physical change? Explain your answer.

In what ways did Shays' Rebellion reveal the weaknesses of the Articles of Confederation?

The lettered choices below refer to this Question. A lettered choice may be used once, more than once, or not at all. A) compound B) heterogeneous mixture C) element D) homogeneous mixture Which description correctly identifies each of the following materials? carbon monoxide

Use Table to answer this question. a. Which substances in the table are in the liquid state at 125$\degree$C? b. Use the physical properties of one of these substances to explain how you figured out the answer to previous question. c. The substances in the table are listed in order of increasing melting point. Propose another way that these data could be arranged.

Is malleability an extensive property or an intensive property? Explain.