Chapter 4 Test Flashcards
How is matter described
by its characteristics/properties and how it changes (physical and chemical changes)
What is a physical change
any change that alters the form or appearance of a substance without changing it to another substance
What is a chemical change
Any change in matter that produces one or more new substances
What happens when something undergoes a chemical change
it gains new properties and changes in energy
What is a reactant
Substances that undergo the chemical changes
What are products
The substances that form from reactants in a chemical change
When do atoms form bonds
when they share or transfer electrons
What is a precipitate
a solid that forms from liquids during a chemical reaction
What 3 ways can you observe a chemical change
precipitate, gas production, and color change
What does forming bonds release
energy
What is an exothermic reaction
a reaction where the energy released as the products form is greater than the energy required to break the bonds for the reactants
What is an endothermic reaction
a reaction where more energy is required to break the bonds of the reactants than is released by the formation of the products
What is a chemical equation
a way to show a chemical reaction using symbols instead of words, tells you reactants and products
What is a chemical formula
a combination of symbols that represents the elements in a compound (an equation uses several chem formulas)
What does the arrow mean in a chem. equation
“yields”
What does the plus mean in a chem. equation
“combines(/combined) with”
Which French scientist first demonstrated the law of conservation of mass
Antoine Lavoisier
What is the law of conservation of mass
during a chemical equation matter is not created or destroyed only rearranged
What makes an equation balanced
when the same amout of atoms are present on both sides of an equation
When was Antoine Lavoisier killed
The French Revolution
What was Antoine Lavoisier other than a scientist
a lawyer and tax collector
What happens in an open system
matter can enter from or escape to the surroundings
What happens in a closed system
matter doesn’t enter or leave
What is used to balance equations
coefficients
What is a coefficient
a number placed in front of a chemical formula in an equation that tells you the amount of a reactant or product that takes part in a reaction
What are the 3 types of Chemical Reactions
synthesis, decomposition, and (double/single) replacement
What is synthesis
when 2 or more elements/compounds combine to make a more complex substance
What is decomposition
when compounds break down into simpler products
What is replacement
when one element replaces another element in a compound or if 2 elements in a compound trade places
When fuel burns to produce CO2 what type of chemical reaction is occuring
a exothermic synthesis chemical reaction
What is activation energy
the amount of energy needed to break the chemical bonds of the reactants and then form the new bonds (the minimum amount of energy needed to start a chemical reaction)
What do endothermic reactions need that exothermic reactions don’t
energy to continue the reaction
What do the product in endothermic reactions have
more energy than the reactants
What needs to happen for a chemical reaction to happen faster
the particles of the reactants need to collide either quicker or with more energy (they also happen quicker if there is more particles)
What factors can affect the rates of reactions
surface area, temperature, concentration, and the presence of catalysts or inhibitors
Why does temperature affect the speed of a reaction
because the particles move quicker from thermal energy
Why does concentration affect the speed of a reaction
because there are more particles to react
What do catalysts do
they lower the amount of activation energy needed for a reaction to start
What are enzymes
biological catalysts that help reactions occur at body temperature
How do enzymes work
they bring reactant molecules close together
What is an inhibitor (aka preservative)
a material used to decrease the rate of a chemical reaction
