8.5E Chemical Reactions
Physical change
A change that does not yield a new substance. The substance does NOT have new properties and no atomic bonds were broken or made.
Chemical change
A change that produces a new substance. The new substance has new properties and is bonded differently to atoms. Atomic bonds were broken or made.
Evidence of chemical change
1. Gas formation. 2. Precipitate formation, 3. Temperature change, 4. Color change, and 5. Release of energy through light or sound
Endothermic
A reaction that gets cold because heat energy is absorbed from the surrounding area. (Absorbs heat)
Exothermic
A reaction that gets hot as heat energy is released to the surrounding area. (Releases heat)
Experimental control
A scientific experiment in which experimental conditions are kept the same as the variable but the treatment is not applied, it does not change, and is used as a reference point or baseline to compare the experimental variable to.
Experimental variable
A scientific experiment in which the treatment is applied in order to observe a change. The changes are carefully observed and compared to the control experiment.
Products
A substance produced during a chemical reaction. (What you get after a chemical reaction)
Reactants
A substance that takes part in and undergoes change during a reaction. (What you will combine in a chemical reaction)
Chemical Equation
Chemical formulas and symbols written to represent a reaction.
Substance
Elements or compounds that can only be separated or combined to make substances with new properties by means of a chemical reaction.
Evidence
Something Noticeable: the five signs of a chemical reaction are: production of a (1) gas formation, (2) formation of a precipitate, (3) temperature change (4) color change, and (5) light or sound.
Temperature change
The observation of a reaction solution either heating up or cooling down as it reacts.
Precipitate formation
The observation of a solid forming at the bottom of a test tube when two liquid substances are mixed
Color change
The observation of a solution changing from one color to another in a chemical reaction
Release of energy through light or sound
The observation of big flashes of light or loud booms in a chemical reaction
Gas formation
The observation of bubbles in a chemical reaction
Chemical Reaction
The process by which one or more substances change to produce one or more different substances.
Precipitate
The solid substance that forms at the bottom of a test tube from the chemical reaction of two liquids