18. a) The materials that are in contact. The two materials and the nature of their surfaces. ...
b) The force pushing the two surfaces together. Pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other.
19. the quantity of motion of a moving body, measured as a product of its mass and velocity.
20. According to Newton's third law of motion, action force is equal to reaction but acts on two different bodies and in opposite directions. When a horse pushes the ground, the ground reacts and exerts a force on the horse in the forward direction. This force is able to overcome friction force of the cart and it moves.
21. The mass of an object is a measure of the object's inertial property, or the amount of matter it contains. The weight of an object is a measure of the force exerted on the object by gravity, or the force needed to support it. The pull of gravity on the earth gives an object a downward acceleration of about 9.8 m/s2.
22. R12. Mass is more fundamental because it is an intrinsic property of an object. Weight varies with location depending upon the acceleration due to gravity eg. for a mass m = 10kg on Earth it`s weight is W = mg = 10 x 10 = 100N.
Answer:
Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen: 2 H2O → 2 H2 + O. Efficient and economical photochemical water splitting would be a technological breakthrough that could underpin a hydrogen economy.
Explanation: 2 H2O → 2 H2 + O.
Answer: emission spectrum
Explanation:
The correct answer is:
C. valence.
Explanation:
The valence or valency of an element is a stratagem of its connecting power with other atoms when it makes chemical compounds or molecules.
A valence electron is an outer shell electron that is connected with an atom, and that can compete in the formation of a chemical bond if the outer shell is not closed; in a single covalent bond, both atoms in the bond provide one valence electron in order to form a shared pair
