Chemical Processes and Equations Review

Which of these describes a physical change?

• Wood logs are burned in a fire.

• Coconut oil begins to crystallize (turn into a solid) after being placed in a freezer.

• Milk left out of the refrigerator for a week starts to smell different.

• Sodium hydroxide and hydrochloric acid are mixed in water to form a salt.

Which process is an example of a chemical change?

• cooking a steak

• chopping a tree

• heating a cup of tea

• drying clothes in the dryer

Which statement indicates that a chemical reaction has taken place?

• A loud noise is produced by crushing a can.

• A puddle is produced by melting an ice cube.

• A new odor is produced by burning a sugar cube.

• A shard of glass is produced by breaking a bottle.

A chemical reaction occurs. Which statement is true of the reactants and the products in the reaction?

• The atoms in the products were regrouped into different molecules to form the reactants.

• The atoms in the reactants were regrouped into different molecules to form the products.

• The atoms in the products were destroyed and new molecules appeared to form the reactants.

• The atoms in the reactants were destroyed and new molecules appeared to form the products.

Which process is an example of a chemical change?

• Salt mixes with water and dissolves.

• An aspirin tablet is crushed into a fine powder.

• Water droplets form on the outside of a cold drink glass.

• An antacid tablet is added to water and bubbles are produced

In the chemical equation how many atoms of carbon are represented? C (subscript 2) H (with subscript 4)

• 4 atoms

• 2 atoms

• 5 atoms

• 1 atom

Which types of changes observe the law of conservation of mass?

• only changes of state

• only physical changes

• only chemical changes

• physical changes and chemical changes

Morgan adds 10 g of baking soda to 100 g of vinegar in a beaker. The mixture begins to bubble. When the bubbling stops, Morgan finds the mass of the resulting mixture. She determines its mass is 105 g. Why is the mass after the reaction less than before?

• A gas has formed and left the mixture because it was not done in a closed container.

• Chemical reactions always result in a change in mass.

• Mixtures always are less massive than their parts.

• Mass was destroyed when the vinegar reacted with the baking soda.

Ethane is one of many compounds that burns in oxygen, to form carbon dioxide and water. What is true of the chemical equation shown? C (subscript 2) H (subscript 6) + O (subscript 2) ------> CO (suscript 2) + H (subscript 2) O

• The positions of the reactants and the products are reversed.

• The formulas of the reactants and the products are not correct.

• The equation is not balanced, so it does not show conservation of mass.

• The types of atoms present on the reactant side are not the same as those on the product side

Does lowering the temperature speed up or slow down a chemical reaction?

• Speed up

• Slow down