Chemistry Unit Test 1 Regrade

Question #9: The reactants of a chemical reaction have_____.

 Correct Answer: chemical properties different from the products

 I understand that this is the correct answer because, in a chemical reaction, the reactants and the products are not exactly the same. For example, When two hydrogen atoms and one oxygen atom have a chemical reaction, they form water. The properties are different because hydrogen and oxygen are gases and water is a liquid. Many of the properties are different.
Question #11: Copper (Cu) reacts with oxygen (O) to form copper oxide (CuO). The properties of CuO are most likely_____.

 Correct Answer: Different from copper or oxygen

 I know this is the correct answer because, in a chemical reaction, the reactants and products do not have the same properties. Copper is soft and malleable, and oxygen is a gas. When they have a chemical reaction, they form copper oxide, which is a black solid. The properties are once again different.

Question #12: Which of the following forms of energy is released or absorbed in most chemical reactions?

 Correct Answer: Heat Energy

 I know this is the correct answer because for example when cooking or baking, you can see the steam coming from the reaction, meaning it is heat. Another example is when you are straightening your hair. You can see the heat, or steam coming from the reaction



Question #14: Which of the following is the best evidence for a chemical reaction?

 Correct Answer: formation of a new substance

 I know this is the right answer because, in a chemical reaction, two substances or atoms form together to create a new substance. For example, hydrogen and oxygen have a chemical reaction to create a new substance, water. Since this is what happens in a chemical reaction, this is the best evidence a chemical reaction has occurred.

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