A student predicts that water is denser than iron and cork. To test the prediction, the student pours 200 mL of water in a beaker and places a cork and an iron nail in the beaker. The image shows the student’s observations.

Is the student’s prediction correct, and why?

• No. The iron nail sinks in water, indicating that iron is denser than water.

• No. The cork floats on water, indicating that cork is denser than water.

• Yes. The cork floats on water, indicating that water is denser than cork.

• Yes. The iron nail sinks in water, indicating that water is denser than iron.

A teacher prepares to dissolve 50 g of a solute. How does the surface area of the solute affect the rate at which the solute dissolves?

• The larger the total surface area of the solute, the faster the solute dissolves.

• The rougher the surface area of the solute, the faster the solute dissolves.

• The smaller the total surface area of the solute, the faster the solute dissolves.

• The smoother the surface area of the solute, the faster the solute dissolves.

A student places a 200 g chocolate bar in a pan, heats the pan, and observes that the bar melts. The student removes the pan from the heat and leaves the chocolate undisturbed to cool. After an hour, the student observes that the chocolate has become a hard solid with a mass of 200 g.

How can the student classify this change?

• It is a reversible change because the mass of the chocolate is the same after cooling.

• It is an irreversible change because the shape of the chocolate changes.

• It is a reversible change because the chocolate returns to its solid state after cooling.

• It is an irreversible change because the solid chocolate changes into a liquid.

A student uses the setup shown to perform an experiment

The student observes that as marble chips are dissolved in the acid, bubbles start to form. The student also notices that the flask is warm to touch.

What evidence identifies the type of change taking place in the experiment?

• The rise in temperature indicates a chemical change.

• The dissolving marble chips indicate a physical change.

• The rise in temperature indicates a physical change.

• The change of phase of the marble chips indicates a chemical change.

A student places four same-sized blocks (P, Q, R, and S) made of different materials in a beaker with water. The student observes what happens to each block and makes a list of conclusions.

What conclusions are correct?

• 1 and 3

• 2 and 3

• 1 and 2

• 2 and 4

The table shows the physical properties of two materials (X and Y).

Which statement is correct?

• Both Materials X and Y are liquids.

• Material X is a solid, and Material Y is a gas.

• Material X is a liquid, and Material Y is a gas.

• Both Materials X and Y are solids.

A student makes two solutions (A and B). Solution A contains 200 mL of water and 20 g of sugar. Solution B contains 100 mL of water and 20 g of sugar.

Which solution is more concentrated, and why?

• Solution A; the amount of solvent is greater in solution A than in solution B.

• Solution A; the amount of solute is greater in solution A than in solution B.

• Solution B; the amount of solvent is less in solution B than in solution A.

• Solution B; the amount of solute is less in solution B than in solution A.

Which activity will result in a new substance when completed?

• softening butter

• chopping wood

• breaking a pencil in half

• roasting a marshmallow

Potassium nitrate is a salt that dissolves in water. A teacher fills three beakers with 100 mL of water at different temperatures (20°C, 40°C, and 60°C) and adds salt to each beaker in small amounts until no more salt can be dissolved. The graph shows the amount of salt dissolved in each beaker.

What can be concluded from the graph?

• The solubility of the salt increases with temperature.

• Water dissolves salts only at high temperatures.

• The salt needs large amounts of water to be dissolved.

• More salt dissolves in water at lower temperatures.

Examine substances X and Y, each placed in identical containers.

Which table correctly classifies each substance?

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