I think your in the wrong section kid. This should be in Earth and Space Science.
Answer:
a balance and a beaker of water
Explanation:
The mass can easily be measured with balance. If you drop the key in a beaker of water, the water inside the beaker will increase and this increases the volume of water that will be equal to volume of key.
Answer:
Amplitude
Explanation:
Amplitude is the vertical distance between the baseline to the crest or the horizontal diatance between crest and trough of a wave. Trough is the lowest point of the wave hence called the baseline while crest is the highest point of a wave. The horizontal distance between two successive waves is however called the wavelength and the product of wavelength and frequency gives the velocity of the waves. Note that amplitude has no effect on the velocity of the waves.
An atom is the building block of all matter. Electrons, protons and neutrons make up the atom. protons and neutrons make up the nucleus of the atom, and the electrons are on the electron shell.