What must happen before a chemical reaction can begin? the activation energy must be exceeded. the activation energy must be reached. the concentrations of products and reactants must be equal. the concentration of reactant molecules must be reduced.

Elements and compounds are pure substances that cannot be broken down physically into a simpler substance. a physical change doesn’t break the bonds between atoms of a substance or form new ones. compounds can be broken down by a chemical change. a chemical change breaks chemical bonds and/or forms new ones between atoms of a substance. what simple substance would a compound break into? the basic elements that make it up! for example, if you passed a very strong electric current through water you’d break the chemical bonds in water and be left with oxygen and hydrogen. which of the following is an example of a chemical change? a separating water into different glasses b breaking frozen ice cubes with a hammer c running an electric current through water d boiling water to evaporate it on a stove

German cockroaches, bulging eyes, bu, are recessive to normal eyes, bu , and curved wings, cv, are recessive to straight wings, cv . both traits are encoded by autosomal genes that are linked. a cockroach has genotype bu bu cv cv, and the genes are in repulsion. which set of genes will be found in the most common gametes produced by this cockroach?

How many cells are our body made of ? ♡