Introduction to Chemical Reactions Flashcards
What is a chemical reaction?
the process by which a chemical change happens.
What are all chemical reactions accompanied by?
changes in energy
Define Endothermic Reactions.
reactions that absorb heat
What is the formula for an endothermic reaction?
Reactants + Heat →products
What is an exothermic reaction?
a chemical reaction that releases energy.
What is an example of a fast chemical reaction?
when rocket fuel burns
What is an example of a slow chemical reaction?
the formation of rust on a bicycle
The chemical reactions in your own body, which are keeping you alive, are among the fastest chemical reactions known.
Why are scientists constantly working to find new kinds of chemical reactions?
To produce new substances with useful properties.
What are reactants?
the starting material
What are the products?
the new substances or results
The products have different properties than the reactants.
What is a physical property?
a description of a substance that does not involve forming a new substance.
What are examples of physical properties?
- colour
- texture
- state
- density
- solubility
- melting point
What is a chemical property?
A description of what a substance does as it changes into one or more new substances.
What are examples of chemical properties?
- combustibility
- corrosion
- reaction with acid
- bleaching abilit
What is a property?
it describes what a substance is like- similar to an adjective.
What is a change?
if describes what the substance is doing - descriptions like a verb
What is a physical change?
the change in the state or form of a substance that does not change the original substance - can result in new physical properties but not new chemical properties.
What are the two types of physical change? - with examples
change in state -> dissolving, evaporation
change in form -> cutting paper in half
What is a chemical change?
the transformation of one or more substances into new substances with new properties.
What are the visual clues to a chemical change?
- the presence of a new colour
- the formation of a precipitate
- release or absorption of heat
- release of light
- production of gas or bubbles
What is a chemical equation?
a chemical equation uses either words or symbols and formulas to describe the changes that occur during a chemical reaction.
What must every chemical reaction have?
- one or more reactants
- one or more products
- an arrow between the reactants and products
- and plus sign for multiple reactants or products.
Remember diatomic molecules
What is a catalyst?
a substance that makes a reaction happen faster without itself being consumed in the reaction
What is a coefficient?
a whole number that is placed in front of the symbol of an element to show the ratios of the different substances that are present in the chemical reaction
What is a chemical equation that does not have coefficients called?
and unbalanced or skeleton equation.
What is the law of conservation of mass?
in a chemical reaction, the mass of the products always equals the mass of the reactants. - the mass is conserved
Describe the conservation of mass in a chemical reaction.
- no atoms are destroyed and no new atoms are produced
- instead, the atoms in the reactants are simply rearranged to form the products
chemical bonds between atoms are broken with new ones being formed
When is an equation said to be balanced?
when the number of each kind of atom is the same in the reactants and products
Never change a subscript in a formula to help make atoms balance
