Chemistry Revision Flashcards
(23 cards)
What is a physical change?
A change in physical properties like position, shape, size, state of matter.
What is a chemical change?
A change in matter forming one or more new substances.
Physical vs Chemical changes
A physical change alters a substance’s form without changing its composition while a chemical change creates new substances with different properties. Physical changes are often reversible; chemical changes are not.
Signs of a chemical change
Release of light/sound, formation of gas/precipitate, change in colour/temperature
Law of conservation of mass
The mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction, this is because atoms cannot be created nor destroyed.
How are atoms re-arranged in a chemical reaction?
Bonds in reactants break, and new bonds form to create products. The same atoms remain, just rearranged
What is the Haber process?
A method to produce ammonia from nitrogen and hydrogen.
What is a reactant in chemistry?
A substance that takes undergoes change during a reaction.
What does understanding chemical reactions help us do?
Predict changes and create useful synthetic materials.
What is a single displacement reaction?
A reaction where one element replaces another in a compound.
What is a double displacement reaction?
A reaction where two compounds exchange elements to form two new compounds.
Single vs Double Displacement
In a single displacement reaction one element is replaced, compared to a double displacement reaction where elements in two compounds are exchanged.
What is a composition reaction?
A reaction where two or more reactants combine to form a single product.
What is a decomposition reaction?
A reaction where a single reactant breaks down into two or more products.
Composition vs Decomposition Reaction
A composition reaction combines two or more reactants to form a single product, whereas a decomposition reaction breaks down a single reactant into two or more products
What is another name for a composition reaction?
Combination or synthesis reaction.
What triggers decomposition reactions?
An input of energy, is needed to break the bonds in the reactant.
What is an exothermic reaction?
A chemical reaction that needs energy to break bonds and releases energy into its surroundings when forming new ones.
Lighting a match, combustion releases light + heat.
What is an endothermic reaction?
An endothermic reaction is a reaction that absorbs heat. Melting ice. Heat is absorbed to change ice into water.
Endothermic vs Exothermic Reaction
Endothermic reaction absorbs heat, whereas an exothermic reaction releases heat.
Reactants vs Products
Reactants - substances present at the start of a chemical reaction.
Products: Substances formed as a result of the reaction.
What is the activation energy of a reaction?
Minimum energy needed to break bonds so a chemical reaction can occur.
Describe an endothermic reaction in terms of the energy of its reactants and products.
Products have more energy than reactants because the reaction absorbs energy from the surroundings.
