Which of the following is NOT evidence that a chemical reaction has occurred?    Group of answer choicescolor change when chemicals are contacted with each othersolid formation when chemicals are contacted with each othergas formation when chemicals are contacted with each otheremission of light when chemicals are contact with each otherAll of the above are evidence of a chemical reaction.

Which of the following statement is true?Water changing to ice is an example of chemical change.You always need a catalyst to execute a chemical reaction.Burning of candle is an example of chemical change only.Burning of magnesium in air is an example of combination reaction.

During a chemical reaction new substances are formed from old ones. Which of the following is NOT ALWAYS true?     [1]ANew substances can be changed back to the original onesBThere is often a colour changeCThere is often a temperature change

Describe four signs that a chemical reaction has taken place, and give an example of each sign.

A chemical reaction occurs. Which statement is true of the reactants and the products in the reaction? A. The atoms in the products were regrouped into different molecules to form the reactants. B. The atoms in the reactants were regrouped into different molecules to form the products. C. The atoms in the products were destroyed and new molecules appeared to form the reactants. D. The atoms in the reactants were destroyed and new molecules appeared to form the products.

Which of the following describes a chemical reaction?A.Atoms in substances react with each other.B.Molecules mix without interacting.C.Molecules interact without bonds breaking.D.Substances change shape but not properties.