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Apologia Chem M 6
Apologia Chemistry M6: Changes in Matter and Chemical reactions
Question | Answer |
---|---|
chemical change | a change that affects the TYPE of molecules or atoms in a substance |
physical change | a change in which the atoms or molecules in a substance stay the SAME |
element | when ATOMS of the same type are collected |
compounds | when MOLECULES of the same type are collected |
example of a chemical change | burning a piece of paper |
example of a physical change | ripping a sheet of paper in half |
sugar dissolved in water | a physical change (can be separated out later) |
Dissolving an element or compound is an example of a physical change because | it does not affect the TYPE of atoms or molecules. |
can "easily" be reversed | a physical change |
cannot "easily" be reversed | a chemical change |
3 states of matter | ALSO called phases of matter |
A phase change is | when a substance CHANGES from one STATE to another; all that is required is energy. |
The kinetic theory of matter states that | atoms or molecules that make up a substance are in constant motion; the higher their temperature, the greater their speed. |
solid molecules (or atoms) | vibrate a few billion times per second |
liquid molecules (or atoms) | move around, not just vibrate |
gas molecules (or atoms) | travel faster & have fewer collisions because they are farther apart from one another |
The main difference between phases of matter is | the volume they occupy. |
Most substances take up the least amount of volume in their | solid phase. |
Most substances take up the largest amount of volume in their | gas phase. |
Motion requires | work. |
Work requires | energy. |
The HIGHER the temperature of the surroundings, | the FASTER the molecules move around. |
melting point | temperature at which a substance changes from solid to liquid |
boiling point | temperature at which a substance changes from liquid phase to gas phase |
condensing | phase change from gas to liquid, requires that energy be removed |
freezing | phase change from liquid to solid, requires that energy be removed |
Molecules and atoms are in | constant motion. |
density | an object's mass divided by the volume that the object occupies |
Density is a very important quantity in chemistry because it | gives an idea of how tightly packed matter is in an object. |
To QUALITATIVELY determine something is | to OBSERVE it. |
To QUANTITATIVELY determine something is | to MEASURE it. |
Water is an exception to the phase change rule because | solid water occupies MORE volume than liquid water & it STAYS a liquid at room temperature. |
All substances that are chemically similar to water | are GASES at room temperature. |
Chemical equations form | the basis for most of the work done in chemistry. |
reactants | substances on the left side of a chemical equation; they REACT together |
products | atoms/molecules on the right side of a chemical equation; the substances PRODUCED by the reaction |
An unbalanced chemical equation | will result in NOT all products being made or in LEFTOVER atoms (or both). |
The COEFFICIENTS in a chemical equation tell us | how many of each molecule we are dealing with. |
The SUBSCRIPTS in a chemical equation are | a part of the molecule's chemical formula. |
An equation is balanced if the # of each type of atom on the reactants side of the equation | equals the # of that type of atom on the products side of the equation. |
You alter the number of molecules involved in an equation by | changing the COEFFICIENTS that appear to the left of each molecule. |
When balancing equations, you CANNOT change | the numbers that appear in the SUBSCRIPTS. |
When balancing equations, START with atoms that | appear in only 1 molecule on each side of the equation. |
You absolutely must be able to | balance chemical equations before you can continue to Module 7! |