Observing Chemical Change
What is matter?
Matter is anything that has mass and takes up space.
What is the purpose of a chemical equation?
A chemical equation uses symbols to represent a chemical reaction and shows the reactants and products.
Name one of the three types of chemical reactions.
Synthesis, decomposition, or replacement.
What is activation energy?
The minimum amount of energy needed to start a chemical reaction.
What does it mean for an equation to be balanced?
The number of atoms of each element is the same on both sides of the equation.
Name one example of a physical property.
Temperature, color, density, texture, or conductivity.
What is the law of conservation of mass?
Matter is not created or destroyed during a chemical reaction; the atoms at the start are present at the end.
What happens during a synthesis reaction?
Two or more substances combine to make a more complex substance.
How does temperature affect the rate of a chemical reaction?
Higher temperature increases particle movement, causing more collisions and faster reactions.
Why must equations obey the law of conservation of mass?
Because matter cannot be created or destroyed in a chemical reaction.
How can you tell if a chemical reaction has occurred?
By observing changes in properties such as color change, gas production, or the formation of a precipitate
What does the arrow ("→") in a chemical equation mean?
The arrow means "yields" or "produces."
What is the main characteristic of a decomposition reaction?
A compound breaks down into simpler substances.
What is a catalyst, and how does it work?
A catalyst speeds up a chemical reaction by lowering the activation energy.
What is a coefficient in a chemical equation?
A number placed in front of a chemical formula to balance the equation.
What is a precipitate, and how is it formed?
A precipitate is a solid that forms from liquids during a chemical reaction.
Explain the difference between an open and closed system in chemical reactions.
In an open system, matter can enter or escape to the surroundings (e.g., a fishbowl). In a closed system, matter does not enter or leave.
Describe how a replacement reaction works.
One element replaces another in a compound, or two elements in different compounds trade places.
Why does breaking a solid into smaller pieces speed up a reaction?
It increases surface area, exposing more particles to react.
Balance this equation: CH₄ + O₂ → CO₂ + H₂O.
CH₄ + 2O₂ → CO₂ + 2H₂O.
Give an example of how energy changes in a chemical reaction (exothermic or endothermic).
In an exothermic reaction, heat or light is released (e.g., burning wood). In an endothermic reaction, energy is absorbed (e.g., mixing baking soda and vinegar).
What numbers are needed to balance the equation: H₂ + O₂ → H₂O.
2H₂ + O₂ → 2H₂O.
Give a real-life example of each type of chemical reaction.
How does concentration affect the rate of a chemical reaction? Give an example.
Higher concentration means more particles are available to collide, speeding up the reaction. Example: Higher concentration of hydrogen peroxide in the "Elephant Toothpaste" experiment produces more bubbles quickly.
Describe the four steps to balance a chemical equation.