Chemical Reactions and Energy Changes Quiz Lesson 1

A process where atoms rearrange to form new substances with different properties.

A visual change in the appearance of a substance during a chemical reaction.

The release of gas during a chemical reaction.

The formation of a solid substance out of a solution during a chemical reaction.

A change in the smell of a substance during a chemical reaction.

A unique abbreviation representing an element, like 'H' for hydrogen and 'O' for oxygen.

Uses chemical symbols and numbers to represent a substance. The numbers, written as subscripts, show how many atoms of each element are present in a molecule.

Starting substances in a chemical reaction, found on the left side of a chemical equation.

Substances formed during a chemical reaction, found on the right side of a chemical equation.

The arrow in a chemical equation, indicating the transformation of reactants into products.

A chemical reaction that absorbs energy from the surroundings. These reactions often feel cold because they take in heat energy.

A chemical reaction that releases energy to the surroundings. These reactions often feel warm because they release heat energy.

An example of an endothermic process where plants use sunlight to convert carbon dioxide and water into oxygen and glucose. The process absorbs more energy than it releases.

An example of an exothermic reaction where energy is released as heat and light.

Chemical reactions involve changes in energy. They can either release energy (exothermic) or absorb energy (endothermic).

The principle that energy cannot be created or destroyed, only transformed from one form to another. The total amount of energy in a closed system remains constant.

The energy stored in the chemical bonds of the reactants is converted into heat and light, which are released into the surroundings. The products have less stored energy than the reactants.

The total amount of energy remains constant, even though it changes forms. The energy stored in the bonds of the reactants equals the energy released plus the energy stored in the bonds of the products.

States that matter cannot be created or destroyed in ordinary chemical and physical changes. This means the same types and number of atoms must be present on both sides of a chemical equation.

Ensuring that the same number of atoms of each element are present on both sides of a chemical equation.

Numbers placed in front of a chemical formula in an equation. They determine the number of molecules or atoms needed to balance the equation.

Numbers written below and to the right of an element symbol in a chemical formula. They indicate the number of atoms of that element in a molecule.

Coefficients multiply the entire number of atoms in a molecule while subscripts indicate the number of atoms of a particular element within a molecule.

Changing subscripts changes the chemical composition of the substance, creating a different compound. We can't make water into hydrogen peroxide just by changing a subscript!

The balanced equation is: 2C + O₂ -> 2CO

1. Identify the elements and their number of atoms on both sides. 2. Use coefficients in front of formulas to adjust the number of atoms. 3. Make sure the number of each element is the same on both sides.

How fast a chemical reaction happens.

Conditions that influence how quickly a reaction proceeds.

Higher reactant concentration means more collisions, leading to a faster reaction.

More exposed surface area of reactants promotes more collisions, speeding up the reaction.

Higher temperature means particles move faster, leading to more frequent and energetic collisions, thus a faster reaction.

Substances that speed up reactions without being consumed in the process.

Biological catalysts found in living organisms, accelerating specific reactions.

Catalysts increase the rate of a reaction by lowering the activation energy needed for the reaction to start.