Question | Answer |
Physical Property | - A characteristic of a substance that can be observed without the substance changing into another substance.
- Ex. Color, hardness, Texture, shine, and flexibility. Ice cube melting to water. |
Chemical Property | - A characteristic that shows how substances change into different substances.
- Chemical properties can be used to classify substances.
- Ex. Rusting, Tarnishing |
Endothermic reaction | - This is when energy is absorbed in a chemical reaction. |
Exothermic reaction | - This is when energy is released in a chemical reaction. |
Reactant | - The substances that you begin with in a reaction |
Product | - the substances you get from the reaction |
Conservation of Mass | - In a chemical reaction, the total mass of the reactants must equal the total mass of the products. |
Coefficient | - A coefficient is a number placed in front of a chemical formula that tells you how many atoms or molecules of a reactant or product take place in the equation. (1 is implied) |
Synthesis | - to synthesize means to put together
- In chemistry, when two or more substance are put together to make a more complex substance, its called synthesis. |
Decomposition | - Decomposition breaks down compounds to simpler compounds |
Replacement | - when one element replaces another in a compound
- or when two elements trade places |
Activaiton energy | - the minimum amount of energy needed to start a chemical reaction. |
Changes in properties | - Ways to detect chemical reactions.
- Changes in properties emerge when new substances form.
- Ex. Color changes, precipitates form (solids that form from solutions during a chemical reaction), gas bubbles or temperature change. |
Surface Area | - The part of a substance that comes in contact with the other reactant.
- more surface area = faster reaction. |
Temperature | - Higher temperature = faster reaction
- particles move faster, creating more energy to get to activation point.
- particles bump into each other more increasing chances of a reaction. |
Concentration | - If you increase the concentration of the reactants, there are more particles to
react-> greater chance of reaction
- ex. Teaspoon of sugar in lemonade vs. tablespoon of sugar in lemonade |
Catalysts | - A catalyst is a material that lowers the activation energy, therefore increasing the speed of the reaction.
- Catalysts are not reactants because they are not permanently changed by chemical reactions.
- Enzymes are catalysts. |
Inhibotors | - inhibitors are used to slow down a chemical reaction. Most prevent reactants from coming together, or combine with a reactant permanently or temporarily.
- (makes activation energy higher) |
Increase reaction speed | - To make a chemical reactions faster, you get more reactant particles together more often with more energy.
- Chemists control rates of reactions with surface area, temperature, and concentration by using catalysts and inhibitors. |
Decerase reaction speed | - To make a chemical reaction slower, you get less reactant particles together less often with less energy.
- You can also raise the activation energy |
Combustion | - COmbustion is the reaction of oxygen and a fuel |
Fuel | - A fuel is a material that releases anergy when it burns. |
Fire triangle | - Fuel, Oxygen and heat are the 3 things neede to start and maintain a fire |
Controlling Fire | - A sauce pan, baking soda, or water can put out a fire.
- Ex. First water covers the fuel which keeps it from coming into contact with oxygen. Second, evaporation of the water uses a large amount of heat, causing the fire to cool. |
3 most common sources of home fires | - faulty electrical wiring, small heaters, and cooking. |
Open system | - A chemical reaction that allows for molecules to escape into their surroundings, and allows other molecules to come into the reaction. It is also a system that can not contain all the atoms.
- Ex. A burning match |
Closed system | - A chemical reaction that contains all the atoms and molecules. Molecules can not escape or come in.
- Ex. A pear decaying in a plastic bag. |