The use of more advanced tools made of stone, wood, and bone, such as the ones illustrated below, was typical of which period of human history?a. Paleolithic era
b. Neolithic era
c. Bronze Age
d. Iron Age

Answers

Answer 1

Answer: Paleolithic Era
During the Paleolithic Era, early humans used mostly stone tools but at times also used wood or bone tools.

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a cylinder of oxygen gas is cooled from 300K to 150K by what factor does the average kinetic energy of the oxygen molecules in the cylinder decrease

Answers

Answer:

The factor by which the average kinetic energy of the oxygen molecules in the cylinder decreases is '0.5'.

Explanation:

Average kinetic energy is defined as the average of the kinetic energies of all the particles present in a system. It is determined by the equation:

$K=(3RT)/(2N_A)$

where,

K = Average kinetic energy

R = Gas constant

T = Temperature of the system

$N_A$ = Avogadro's number

Average kinetic energy of oxygen gas molecule at 300 K.

$K.E=(3R* 300 K)/(2N_A)$ ..[1]

Average kinetic energy of oxygen gas molecule at 150 K.

$K.E'=(3R* 150 K)/(2N_A)$ ..[2]

[1] ÷ [2]

$(K.E)/(K.E')=((3R* 300 K)/(2N_A))/((3R* 150 K)/(2N_A))=(300)/(150)=2$

$K.E'=0.5* K.E$

The factor by which the average kinetic energy of the oxygen molecules in the cylinder decreases is '0.5'.

Temperature is a measure of average kinetic energy thus absolute temperature is proportional to average kinetic energy. It should be half: same factor as the temperature.

In the late 1800s, the British scientist J. J. Thomson discovered that atoms were composed of positively-charged and negatively-charged particles. He proposed that these two types of particles were evenly mixed throughout the structure of the atom. How does this atomic model differ from current atomic models?A. Current atomic models show that atoms do not have positively-charged particles.

B. Current atomic models show an atom's positively-charged particles concentrated in the center of the atom.

C. Current atomic models show that atoms do not have negatively-charged particles.

Answers

Option B.

Current atomic models show the positive charged particles (protons) concentrated in the center (nucleus) of the atom, along with the neutrons, and the negative charged particles (electrons) distributed around (far from) the nucleus.

The closeness of a measurement to the actual value of what is being measured

Answers

Hey!

This is known accuracy. Think of accuracy as like shooting at the bulls eye on a target.

However think of precision like if all your darts fell on the lower left side of the target. Precision is just how close together the measurements are with each other.

How is geometrical symmetry related to the polarity of a molecule?

Answers

A symmetric shape means the bonds' polarities are exactly equal then it means the polarities cancel each other, resulting to a nonpolar molecule. This is because there will be no available polarity for other substance to attach.

Explanation :

As we know that the geometrical symmetry of the molecule and the polarity of the bonds both are equally important for determining the polarity of the molecule.

The molecule that has zero dipole moment that means it is a geometrical symmetric molecule and the molecule that has some dipole moment that means it is a geometrical asymmetric molecule.

As the molecule is symmetric, the dipole moment will be zero and the molecule will be non-polar.

As the molecule is asymmetric, the dipole moment will not be zero and the molecule will be polar.

Thus, we can say that the a symmetry molecule is non-polar in nature and an asymmetry molecule is a polar molecule.

The leading cause for dementia is Alzheimer's disease.
True
False

Answers

True.

Dementia's main cause is Alzheimer's disease (50%-70% of cases). You can find it in the DSM-5 as Major Neurocognitive Disorder due to Alzheimer's Disease.

Two pieces of silk have an electric charge after being rubbed on a piece of amber. What will happen when the two silk pieces are brought close together?A.They will repel one another.
B. They will attract one another.
C. They will transfer their electrons from one to the other.
D. They will not affect one another.