Question

1. the amount of mass per unit volume refers to the
2. state he si unit for each:

a) energy
b) mass
c) volume
d) length

1. this law states that in a chemical change, matter is neither created nor destroyed, but only changed from one form to another.
2. state the property is used to separate substance using the following methods:

a) filtration
b) distillation
c) chromatography

1. state the change of state occurs for each:

melting
freezing
vaporization
condensation
sublimation
deposition

1. classify the following as homogeneous or heterogeneous: a) tap water

b) distilled water
c) ) a mixture of salt and water
e) a mixture of oil and water
f) a pizza
g) steel
h) iron

1. tap water is classified as but distilled water is
2. define atom -
3. state the name of the scientist that:

a) discovered the electron
b) discovered the proton
c) discovered the neutron
d) did the gold foil experiment

1. who discovered radioactivity? (3 scientists)
2. what are the 3 subatomic particles? give the charge for each. which is the smallest?
3. the number of protons in the nucleus of an atom is called its
4. how many protons, neutrons and electrons are there in each

a)
b)
c)

Explanation:

These questions are related to basic concepts in Chemistry, such as definitions of terms (density, atom), SI units, chemical laws (conservation of matter), separation techniques, states of matter, mixture classification, atomic structure, and scientists' contributions. Chemistry is a subfield of Natural Science that deals with matter, its properties, and changes.

Answer:

Question 12:

The amount of mass per unit volume refers to the density.

Question 13:

a) energy: $\boldsymbol{\text{Joule (J)}}$
b) mass: $\boldsymbol{\text{Kilogram (kg)}}$
c) volume: $\boldsymbol{\text{Cubic meter (m}^3\text{)}}$ (or liter, L, for common use)
d) length: $\boldsymbol{\text{Meter (m)}}$

Question 14:

This law is the Law of Conservation of Mass (or Law of Conservation of Matter).

Question 15:

a) filtration: $\boldsymbol{\text{Particle size (solid - liquid separation, based on solubility/particle size)}}$
b) distillation: $\boldsymbol{\text{Boiling point (volatility of liquids)}}$
c) chromatography: $\boldsymbol{\text{Solubility/Adsorption (affinity for stationary/mobile phase)}}$

Question 16:

• melting: $\boldsymbol{\text{Solid} \to \text{Liquid}}$
• freezing: $\boldsymbol{\text{Liquid} \to \text{Solid}}$
• vaporization: $\boldsymbol{\text{Liquid} \to \text{Gas}}$
• condensation: $\boldsymbol{\text{Gas} \to \text{Liquid}}$
• sublimation: $\boldsymbol{\text{Solid} \to \text{Gas}}$
• deposition: $\boldsymbol{\text{Gas} \to \text{Solid}}$

Question 17:

a) tap water: $\boldsymbol{\text{Heterogeneous}}$ (may contain dissolved solids, small particles)
b) distilled water: $\boldsymbol{\text{Homogeneous}}$ (pure, uniform composition)
c) mixture of salt and water: $\boldsymbol{\text{Homogeneous}}$ (solution, uniform)
e) mixture of oil and water: $\boldsymbol{\text{Heterogeneous}}$ (immiscible, forms layers)
f) a pizza: $\boldsymbol{\text{Heterogeneous}}$ (distinct components: dough, cheese, toppings)
g) steel: $\boldsymbol{\text{Homogeneous}}$ (alloy, uniform at macroscopic level)
h) iron: $\boldsymbol{\text{Homogeneous}}$ (pure element, uniform)

Question 18:

Tap water is classified as a $\boldsymbol{\text{mixture}}$ (contains dissolved minerals, impurities), but distilled water is a $\boldsymbol{\text{pure substance}}$ (or compound, $\ce{H2O}$).

Question 19:

An atom is the smallest unit of an element that retains the chemical properties of that element. It consists of a nucleus (protons + neutrons) and electrons orbiting the nucleus.

Question 20:

a) discovered the electron: $\boldsymbol{\text{J.J. Thomson}}$
b) discovered the proton: $\boldsymbol{\text{Eugen Goldstein}}$ (or Ernest Rutherford, for experimental confirmation of protons in the nucleus)
c) discovered the neutron: $\boldsymbol{\text{James Chadwick}}$
d) did the gold foil experiment: $\boldsymbol{\text{Ernest Rutherford}}$ (led to the nuclear model of the atom)

Question 21:

Radioactivity was discovered by $\boldsymbol{\text{Henri Becquerel}}$, with further contributions from $\boldsymbol{\text{Marie Curie}}$ and $\boldsymbol{\text{Pierre Curie}}$.

Question 22:

The 3 subatomic particles are:

• Proton: Charge = $\boldsymbol{+1}$ (positive), located in the nucleus.
• Neutron: Charge = $\boldsymbol{0}$ (neutral), located in the nucleus.
• Electron: Charge = $\boldsymbol{-1}$ (negative), orbits the nucleus.

The electron is the smallest (mass ≈ $9.11 \times 10^{-31}\ \text{kg}$, much smaller than proton/neutron).

Question 23 (partial, assuming typo: "The number of protons..."):

The number of protons in the nucleus of an atom is called its atomic number ($Z$).

Question 24 (protons, neutrons, electrons):

For a nuclide $\ce{^A_Z X^{n+}}$:

• Protons ($p^+$) = $Z$
• Electrons ($e^-$) = $Z - n$ (for cations, $n+$ charge means lost $n$ electrons)
• Neutrons ($n^0$) = $A - Z$

a) $\ce{^{35}_{17}Cl}$:

• Protons: $17$
• Electrons: $17$ (neutral atom)
• Neutrons: $35 - 17 = 18$

b) $\ce{^{127}_{53}I^-}$:

• Protons: $53$
• Electrons: $53 + 1 = 54$ (anion, $1-$ charge means gained 1 electron)
• Neutrons: $127 - 53 = 74$

c) $\ce{^{59}_{28}Ni^{3+}}$:

• Protons: $28$
• Electrons: $28 - 3 = 25$ (cation, $3+$ charge means lost 3 electrons)
• Neutrons: $59 - 28 = 31$