In an acid base reaction, an acid reacts with a base to produce water and a salt. The pH scale can be used to describe the acidity of a liquid. Look at the diagram below. Which two liquids could undergo an acid base reaction?

Correct Answer: D 🗳️
It is the only pair of liquids listed in which one is acidic (vinegarpH 3) and the other basic (bleachpH 9).

According to Newtons laws of motion, an object set in motion remains in motion unless a force acts on it. If you suspend an object from a string and make it swing, the object will swing for a while, then slow down and stop. Why does the suspended object stop swinging?

Correct Answer: E 🗳️
The object set in motion slows down and stops swinging because the force of friction acts on it. The kinetic energy of the object is converted to heat energy through friction with air. Statements a, c, and d are true but are not the reason why the object stops swinging. An object having any mass can maintain motion, so the statement in choice b is wrong.

In an exothermic process, heat is released by the process to the surroundings. An example of an exothermic process is burning wood. An endothermic process requires the input of heat from the surroundings. An example of an endothermic process is boiling water. Which of the following is an endothermic process?

Correct Answer: B 🗳️
An endothermic process requires the input of heat energy. The only one that requires input of energy (heat) is melting ice (ice melts when heated). The rest of the processes listed give off heat, so they are exothermic.

Ice floats on water because -

Correct Answer: A 🗳️
Things that float are less dense than the substance in which they float.