Two clear liquids are mixed. The cup turns cloudy, and a white solid settles at the bottom. What conclusion is best supported?

Baking soda is added to vinegar. Bubbles appear and a balloon over the bottle inflates. What evidence best shows a chemical reaction happened?

Damp steel wool is left in air for several days. It changes from gray metal to reddish-brown rust. What does this observation show?

When lemon juice is stirred into milk, white clumps form and do not disappear after stirring. What evidence supports a reaction?

Sugar is stirred into water. The liquid stays clear, no gas or solid forms, and the temperature stays 22°C. What conclusion fits the evidence?

An antacid tablet is dropped into water. Many bubbles rise from the tablet as it breaks apart. What is the strongest evidence for a reaction?

Two colorless solutions are mixed. Within seconds the liquid turns yellow, with no heating or added dye. What evidence supports a chemical change?

Two droppers add clear solutions A and B to one beaker. A student wants to show that any solid that forms comes from A and B reacting together. What else should she test?

Solution A and solution B are each 22°C before mixing. After mixing, the beaker rises to 38°C without heating. What does the temperature change support?

Two room-temperature solutions at 21°C are mixed. The cup drops to 5°C even though it stays on the table. What claim is best supported?

A glow stick is bent so two liquids mix. It gives off light without a battery or flame. What does this observation support?

A metal ribbon is placed in acid. The liquid quickly warms and bubbles rise from the metal. Which energy evidence supports a reaction?

Two dry chemicals are mixed in a dish. A bright flash occurs, and a white solid remains. What conclusion is best supported?

Equal amounts of water at 60°C and 20°C are mixed, and the mixture reaches 40°C. Is this temperature change evidence of a chemical reaction?

A shiny brown copper wire is heated in air. Afterward, it has a dull black coating that flakes off. What before-and-after evidence points to a product?

Vinegar is a clear acidic liquid, and an antacid tablet is a chalky solid. After mixing, the tablet breaks apart, gas escapes, the liquid stays clear, and it is less acidic. Which changes show new substances formed?

Liquid A is blue, and liquid B is clear. After mixing, there is more total liquid, the liquid is green, and gas bubbles off. What before-and-after evidence is strongest?

Before mixing with water, two powders are dry and white. After mixing, a hard insoluble solid forms. What does the property change show?

Iron and sulfur powders can be partly separated with a magnet before heating. After heating, the black solid is not separated the same way. What is supported?

A gray iron nail sits in blue copper sulfate solution. Later, reddish metal coats the nail and the blue color fades. What evidence supports a reaction?