Chapter 12-Physical and chemical change Flashcards
Define the term catalyst.
A substance which speeds up the rate of a chemical reaction without its chemical composition being changed by the reaction.
Define the term synthesis reaction.
A chemical reaction where the product that is formed is more complex than each of the reactants.
Define the term decomposition reaction.
A chemical reaction where the product breaks down to form simpler substances.
Define the term exothermic reaction.
Reactions which transform chemical potential energy into thermal energy.(release heat and thus increase the temperature of the reaction mixture)
Define the term endothermic reaction.
Reactions which transform thermal energy into chemical potential energy.(absorb heat and thus decrease the temperature of the reaction mixture)
Define the law of conservation of energy
In an isolated system energy cannot be created nor destroyed, it can only be transferred from one place to another.
define the law of constant proportions
Some elements in a chemical compound that bond in a fixed ratio with one another.
Describe physical change.
Only the physical properties of a substance change.
The colour, the size, shape, mass, density, phase of the substance- are all physical properties- can change.
What happens to metals when heated or cooled down?
Most metals expand when they are heated and contracts when they are cooled down.
Describe chemical change.
New substance is formed during a chemical reaction. Which lead to the rearrangement of atoms to form new products so the new product may physically look different to the original substance.
