Evidence of a Chemical Reaction
What is one sign that a chemical reaction has occurred?
Color change, temperature change, gas formation, or precipitate forms
What is an atom?
The smallest unit of an element
What type of reaction absorbs energy?
Endothermic
What are the 3 conditions that can cause a chemical reaction?
heating, cooling, mixing
What is a molecule?
Two or more atoms bonded together
What type of reaction releases energy?
Exothermic
If a solid forms after mixing two liquids, what does that show?
A precipitate is formed (new substance), therefore a chemical reaction occurred.
During a chemical reaction, what happens to the atoms?
They rearrange to form new substances
What happens to temperature in an endothermic reaction?
Temperature decreases as energy is absorbed
What’s the difference between a physical change and a chemical change?
A chemical change forms new substances; physical change doesn’t
What law states that matter cannot be created nor destroyed?
Law of Conservation of Matter
What happens to temperature in an exothermic reaction?
Temperature increases as energy is released
Give two pieces of evidence that baking soda and vinegar react chemically.
Bubbles (gas) and temperature drop or color change
How many atoms of each element are in the products/reactants in the following chemical equation:
2 H2 + O2 → 2 H2O
4 H
2 O
Give one real-world example of each type of reaction.
Endothermic: ice melting or photosynthesis, baking soda/vinegar, cooking food
Exothermic: combustion or freezing water, fireworks