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Science - Ch. 13, Sec. 1 - Questions
Terms in this set (17)
The change of color in the fall is a result of _________________ in the leaves.
Describe how a leaf changes from green to orange and yellow colors in the fall.
Leaves contain a lot of chlorophyll during the spring and summer. But when temperatures drop and there's less sunlight, the chlorophyll breaks down to form new substances that have no color. Since the chlorophyll is no longer present to mask the other colors, the colors show in the leaves.
A ___________________ is a process in which one or more substances change to make one or more new/different substances.
A __________ is a solid substance that is formed in a solution.
What are some signs of a chemical reaction?
energy change (given off and/or taken in)
True/False. The more signs you see, the more likely a chemical reaction is taking place.
What is a common chemical reaction that is seen during laundry?
When chlorine bleach is spilled on jeans, the bleach reacts with the blue dye on the fabric and causes the material to change color.
When you mix water with baking powder, substances in the baking powder react to form bubbles of ________________. These bubbles give the muffin its ___________-like texture.
carbon dioxide gas
Does the presence of these signs guarantee that a chemical reaction is happening? Why or why not?
No. Sometimes these signs can also be produced during a physical (not a chemical) change.
What is the most important sign that a chemical reaction, rather than a physical change, has occurred?
New substances are formed and the properties of the new substance are very different from the properties of the original substances.
Most chemical reactions
a. result in substances that have different properties.
b. do not break bonds.
c. do not rearrange atoms.
d. have no effects that can be seen.
If the chemical properties of a substance have not changed, has a chemical reaction occurred? Why or why not?
No, because the chemical and physical properties of the new substance must be different from the old substances.
A _________________ is a force that holds two atoms together in a molecule. For a chemical reaction to take place, the original bonds must ___________ and ________ bonds must form.
What happens to the bonds of substances during a chemical reaction?
First the chemical bonds in the original substances must break. Then the atoms rearrange and form new bonds to make new substances.
___________ molecules are two atoms that are bonded together.
How are the properties of salt different from the properties of sodium and chlorine?
Table salt has very different properties than the substances that make it up. Sodium reacts violently in water and chlorine is a poisonous gas. But when sodium and chlorine come together, they form table salt which is a new substance that it harmless.
Steam is escaping from a teapot. Is this a chemical or physical change? Explain.
Steam is a physical change, not a chemical change. Even though the physical properties of the water have changed, the chemical properties have not changed. It is still water, just in a different physical state.
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