Water acts as an acid (donates H+) when it reacts with a stronger base, say sodium hydroxide. Water acts as a base (accepts H+) when it reacts with a stronger acid, say hydrochloric acid. If the medium is water, water, having a pH of 7, is considered neutral.
6. A 7. B 8. D 9. C 10. A 11. B.
Answer: A. Metalloids exhibit properties of both metals and nonmetals
Explanation: Metalloids are elements that has a metallic appearance such as shiny, dull amd ductile but they possess the properties of nonmetals in which they are intermediately poor conductors of heat and electricity in which they are good semiconductors.
Answer: C, an apple staying at rest on the ground.
Explanation: When one or more unbalanced forces are acting on an object, it causes change (eg. the apple falling on the ground would be a result of gravity being stronger than the kinetic energy that the tree is putting on the apple). Even in D, the apple is not moving, but the tree branch is still exerting force to keep the apple hanging there.
PS: I studied net forces last year. Hope this helps!