8th Study Guide Chemical Reactions

Question Answer
A chemical change is different than a physical change because in a chemical change _______. A new substance is formed and in a physical change no new substance is formed .
In a chemical reaction______ The atoms of the reactants unbond, rearrange, and then rebond to form the products
In the chemical reaction CH4+202 –> CO2 + 2H20, there are reactants on the left of the equation and products on the right. I you count the atoms in the reactants, there are how many of each? 1 Carbon atom, 4 Hydrogen atoms and 4 Oxygen atoms.
In a chemical reaction, mass is conserved. This means that_____. the type and number of atoms in the reactants equals the type and number of atoms in the products.
If the reactants on the left side of a chemical equation are C3H8 + 5O2, the products in a balanced equation could be________ 3CO2 +4H2O
If more reactants are used in a chemical reaction, more products will be produced. This is because _______. more reactants have more atoms to react to form more products.
One clue of a chemical change is the formation of a precipitate. A precipitate is formed when _____. two liquids react and a solid is formed
In a chemical reaction, if the reactants are heated, the reaction usually happens______. Faster
Some chemical reactions require a substance called a catalyst. The main purpose of a catalyst is _______. to speed up the reaction
One characteristic property of a substance is the way it reacts chemically with another substance Another way of saying this is that substances react chemically in characteristic ways, this means______. A substance will always react the same way when tested with the same chemical
If two substances react and the temperature of the mixture increases, the reaction is ? Exothermic
If two substances react and the temperature of the mixture decreases, the reaction is ? Endothermic
Is dissolving a chemical reaction? No
Are products in a chemical reaction are usually formed more quickly at higher temperatures? Yes
Because substances react chemically in characteristic ways, can you use the way they react to identify an unknown? Yes
In a chemical reaction, no new atoms are created, and no atoms are _______. destroyed
In a chemical reaction, only the atoms present in the ______ can end up in the products. reactants
What is the term for a solid that is formed by mixing together new solutions? Precipitate
Can atoms that are not in the reactants end end up n the products of a chemical reaction? Why or Why not? Atoms that are not in the reactants side can not end up in the products side because the products are made up from the atoms on the reactants side.
When you combine vinegar and baking soda , a gas is produced. Why is the as considered evidence that a chemical reaction occurs? Because a gas was produced where there hadn't been one before, it would be considered a new substance . That would mean that a chemical change took place.
A glow stick works when two chemicals in the glow stick mix and have a chemical reaction that produces certain products and light. How does the warm glow stick glow brighter than a cold glow stick. If the glow stick is warm the molecules of the reactants move faster. If they are moving faster molecules are bouncing off of each other causing more reaction. The cooler the reactants the slower the reaction.
When you combine calcium chloride solution with baking soda solution, a precipitate is formed. Why is the precipitate considered evidence that a chemical reaction occurred? Two liquids were combined and a solid precipitate is produced, this is a solid and a clue that a chemical reaction took place.
Explain Exothermic Reaction? The arrows will show that there is more energy released when the bonds in the products are formed, than there is used to break bonds of the reactants
Explain Endothermic Reaction. The arrows will show that it takes more energy to break the bonds of the reactants than the bonds on the products side .
In an Exothermic reaction, where will the large arrows be and will it be showing toward or outward? It will take more energy to break the bonds in the products side so the larger arrows will be showing outward from the products side.
In an Endothermic reaction, where will the large arrows be and will it be showing toward or outward It will take more energy to break the bonds of the reactants so the larger arrows will be pointing toward the reactants side.

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