Acids, Bases and Thermochemistry Flashcards
memorise (13 cards)
Define acid and base
Acid: An acid is a substance that tastes sour and it releases hydrogen ions (H⁺) when dissolved in water.
ex, lemon juice and vinegar.
Base: A base is a substance that tastes bitter and it releases hydroxide ions (OH⁻) when dissolved in water.
ex, soap and baking soda.
What makes an acid more acidic
An acid becomes more acidic depending on the concentration of hydrogen ions (H⁺) it releases when dissolved in water.
The more hydrogen ions present, the stronger the acid, and the lower its pH value.
state the general formula for a neutralisation reaction
Acid + Base → Salt + Water
state the general formula for an acid + metal reaction
Acid + Metal → Salt + Hydrogen gas
Define exothermic reaction
An exothermic reaction is a chemical reaction that gives off heat. This means the reaction releases energy, making the surroundings warmer. For example, when you burn wood, the heat you feel is from an exothermic reaction.
Define endothermic reaction
An endothermic reaction is a chemical reaction that takes in heat from its surroundings. This means the reaction absorbs energy, making the surroundings cooler. An example is when ice melts; it absorbs heat, causing the area around it to cool down.
Identify the signs of an exothermic reaction
Temperature increases
Total energy decreases
Identify the signs of an endothermic reaction
Temperature decreases
Total energy increases
Define rate of reaction
Rate of reaction is the speed at which reactants are converted into products in a chemical reaction.
Explain how a chemical reaction happens using the collision theory
It can only happen with enough activation energy and the atoms in the reactants collide with each other in a specific orientation.
Describe the factors that increase the rate of reaction.
Increase temperature
hotter temperatures increase the amount of kinetic energy the atoms have, causing them to collide more frequently.
Increase concentration of reactants
increasing concentration of reactants increases the number of atoms available for collision to make a reaction happen
Increase pressure of reactants Increase
increasing the pressure of reactants decreases the amount of space the atoms have to collide with each other
surface area
increase the surface area of solid reactants means there is more exposed space that atoms can collide with to make a reaction happen
Use a catalyst
a catalyst is a substance that is added to a chemical reaction to increase the rate of reaction without being chemically charged or used up
Define enzyme
Enzymes are naturally occurring inside the body of an organism. Same as catalyst where they are not chemically charged or used up.
Define activation energy
Activation energy is the minimum energy required to start a chemical reaction.
