pt2

• chemical reactions can be exothermic (release energy) or endothermic (absorb energy)
• a chemical reaction is when two or more substances react to form one or more new substances with different properties.
• the three states of matter are solid, liquid, gas
• the reactants are the substances that take part in a reaction
• examples of chemical reactions include burning, rusting, digestion
• the products are the substances formed by a reaction
• gases have neither fixed shape nor volume
• in an exothermic reaction, heat is released into its surroundings as it occurs
• liquid has fixed volume but not shape
• solids have fixed shape and volume
• reactants are the starting materials that undergo change during a chemical reaction
• the products are what is left over when all the reactants have been used up
• the products are the new substances formed by the reaction
• in an endothermic reaction, heat is absorbed from its surroundings
• in an exothermic reaction, heat is released into its surroundings
• an example of an exothermic reaction is combustion
• liquids have fixed volume but not shape
• solids have both fixed shape and volume
• chemical changes can be reversed if conditions change (eg heating water turns it back into steam)
• a catalyst speeds up a reaction without being used up or changed itself
• an endothermic reaction absorbs energy from its surroundings as it occurs
• a soluble substance dissolves to form a solution when mixed with water
• a solvent dissolves another substance (called solute) to form a solution
• a solvent dissolves another substance to form a solution
• energy transfer can be by conduction (heat), convection or radiation
• exothermic reactions release energy to their surroundings
• an endothermic reaction absorbs energy from its surroundings to occur
• a reversible reaction can go either way depending on conditions
• a catalyst speeds up a reaction without being changed itself