Show:
Observing Chemical and Physical Change
Describing Chemical Reactions
Controlling Chemical Reactions
Fire and Fire Safety
Vocabulary
100
Matter can be be described in terms of two kinds of properties, what are they? Also, changes in matter can be described in terms of what?
Matter can be be described in terms of two kinds of properties, physical and chemical properties. Changes in matter can be described in terms of physical changes and chemical changes.
100
What is the difference between a coefficient and a subscript?
A coefficient is the number before the formula of a molecule that shows how many molecules there are. A subscript is the small number after a single atom that shows how many of that atom there are in total. Whereas a coefficient shows the amount of molecules, a subscript shows the amount of one kind of atom in it.
100
What is activation energy and why is it necessary in all chemical reactions? Give an example.
Activation is the least amount of energy it takes to begin a chemical reaction. It is necessary because without energy, chemical reactions won't start. An example is a spark.
100
What are the three things needed to make fire and keep it going?
Three things needed to start and maintain a fire are fuel, oxygen, and heat. If you take one of these elements away, the fire diminishes.
100
Define chemical and physical property.
Chemical property - a characteristic of a substance that describes its ability to change into other substances [during a chemical reaction] Physical property - A characteristic of a substance that can be observed without changing the chemical composition of the substance.
200
True or false: physical change affects the chemical composition of a substance.
False
200
What is the law of conservation of mass?
It is a law that states that during a chemical reaction, matter is not created or destroyed. All the atoms present at the start of a reaction are also present at the end.
200
What is the difference between exothermic and endothermic reactions? Give an example of each.
Exothermic reactions involve giving off energy as heat. Endothermic reactions involve absorbing energy as heat to occur. Some endothermic reactions require constant heat while others need very little. An exothermic reaction would be the burning of fuel and an endothermic reaction would be the baking of bread.
200
What are the three most common sources of home fires?
Some common sources are small heaters, cooking, and faulty or open electric wires.
200
Define precipitate.
Precipitate - A solid that forms from solution during a chemical reaction.
300
Some evidence of a chemical reaction might be...
A change in color, temperature, or a release of gas might signify a chemical reaction.
300
How is an open system different than a closed system? Give an example of each.
An open system allows matter to enter or escape the surrounding area whereas closed systems keep all the matter confined to a certain area. An example of an open system could be a burning match. An example of a closed system is a pear decaying under glass or a chemical reaction occurring in a closed beaker.
300
What are five things that can control the rate of a reaction?
Increasing surface area is one because it takes less time to dissolve something small than something big. Temperature increase makes particles move faster, causing them to bump into each other more and have more energy. Decreasing temperature slows down particles and decreases energy, making it take longer for particles to combine. Increase of concentration of the reactants speeds things up because there is more of a chance that the reactants will collide. Catalysts and inhibitors also speed up and slow down reactions.
300
Name two parts of the fire triangle that water takes away and how.
Water removes heat and fuel. Water covers the fuel, which keeps it from contacting oxygen. The amount of heat it takes for water to evaporate is large, so when it evaporates, it cools down the fuel and removes the energy in the form of heat.
300
What is the difference between a product and a reaction?
A reactant is a substance that takes part in a chemical reaction. A product is the result of a chemical reaction.
400
Explain the difference between an endothermic reaction and as exothermic reaction.
An endothermic reaction involves absorbing energy while exothermic reactions involves releasing energy
400
H2+ O2 -> H2O. Is this a balanced equation? Why or why not? How do you balance it?
This is not a balanced equation because the ratio of hydrogen to oxygen is 1:1, but it needs to be 2:1. This is because to combine equally, two hydrogen molecules are needed for every one oxygen molecule. You can fix this by adding a coefficient of 2 in front of the reactant hydrogen. To balance the other side, add another coefficient of 2 before the entire water molecule. This makes two oxygen and four hydrogen on each side.
400
What is the difference between a catalyst and an inhibitor?
Catalysts lower the amount of activation energy needed to have a reaction by bringing the elements closer together so they do not have to exert as much energy to get closer. Inhibitors attach to elements to prevent them from reacting with other elements. Some inhibitors include preservatives.
400
Is fire in a fireplace with a chimney endothermic or exothermic? Is it an open or closed system?
Fire in a fireplace is endothermic because it needs heat to keep going. It is an open system because any gas created by combustion can leave the system through the chimney.
400
Define combustion.
Combustion is a rapid reaction between oxygen and a substance called a fuel.
500
Is evaporation a physical or chemical change? Why?
Evaporation is a physical change because it does not effect the chemical composition of water. It changes the state of matter, but not the atoms in it or how it is formed.
500
What is the difference between decomposition, synthesis and replacement? How are they similar?
Synthesis is when two or more compounds or elements combine to form a more complex substance. Decomposition is when compounds are broken down into simpler compounds or elements. Replacement is when one element takes the place of another in a compound. These are all similar because they involve the rearranging of elements and compounds.
500
Why does your body need a certain kind of catalyst? What is it called?
Your body needs a certain kind of catalyst because your body can't stand the amount of heat and energy necessary to make the compounds you need to live. This type of catalyst is called an enzyme. They are located in your cells and help your body safely make compounds that you need to survive.
500
Why does baking soda stop a fire?
When baking soda is burned, it gives off carbon dioxide gas which can smother a fire by preventing contact between the fuel and the oxygen.
500
Define Fire Triangle.
The fire triangle is a system of three things necessary for fire - fuel, oxygen and heat.