react together in a chemical reaction? a) Products b) Compounds (c) Reactants d) Elements 6. What happens to paper when it burns? a) It changes into water b) It changes into ash .carbon dioxide, and water vapour c) It remains the same d) It melts 7. What is a sign that a chemical reaction has occurred? a) No change at all (b)Bubbles, change in colour,or change in temperature c)Only physical changes d) Just a change in shape 8. What happens when vinegar reacts with an eggshell? a) It changes to stone (b)It forms bubbles of carbon dioxide gas c) It becomes stronger d) It turns to rus

6. **What happens to paper when it burns?****(b) It changes into ash, carbon dioxide, and water vapor.**Burning paper is a chemical reaction. The cellulose in the paper reacts with oxygen in the air, producing ash (which contains various inorganic compounds), carbon dioxide, and water vapor.7. **What is a sign that a chemical reaction has occurred?****(b) Bubbles, change in color, or change in temperature.**These are all common indicators of a chemical reaction. Bubbles suggest the formation of a gas. A color change indicates a change in the chemical composition of the substances involved. A change in temperature (either increase or decrease) shows that energy is being released or absorbed during the reaction.8. **What happens when vinegar reacts with an eggshell?****(b) It forms bubbles of carbon dioxide gas.**Vinegar is a dilute solution of acetic acid. Eggshells are primarily composed of calcium carbonate. The acetic acid in vinegar reacts with the calcium carbonate in the eggshell, producing carbon dioxide gas (the bubbles), water, and calcium acetate. This is a classic example of an acid-base reaction.