A student measures the mass of an 8 cm^3 block of brown sugar to be 12.9 g. What is the density of

Your feet get hot walking across a beach. which type of heat transfer is occurring from the sand to your feet?

Andrews [41]

The heat transfer just occurred is mainly conduction.

Conduction happens when two objects are in contact with each other. In the hotter object, the molecules and/or free electrons have a higher kinetic energy, thus they'll travel and collide into other molecules, resulting in spreading the energy to the other object.

The heat transfer happens until thermal equilibrium, where both objects have the same temperature and their molecules have the same kinetic energy rate.

In addition, radiation is also happening since everything that has a higher temperature than the environment is a net emitter. They release electromagnetic waves that turn out to be radiation. These occur even without the presence of air.

5 0

3 years ago

Ions are formed when atoms a) gain or lose protonsb) gain or lose electronsc) gain or lose neutrons d) each of these results in

lesya692 [45]

Answer:

b) Gain or lose electrons

Explanation:

An ion is an electrically charged particle. For an atom to be charged, it must have gained or lost electron in the process and therefore, it becomes an ion.

The loss or gain of electrons is what makes an atom charged and eventually becomes an ion.

A positively charged ion is one that has lost an electron and it is called a cation. In such an ion, the number of electrons are lesser than those of protons. This is why they are cations

A negatively charged ion is one that has gained electrons. They are called anions. In such an ion, the number of electrons are greater than that of protons.

5 0

3 years ago

When two liquids are combined and form a solid (but didn't freeze) the solid that was formed is called

ludmilkaskok [199]

The answer is nucleation because can turn liquids into solids.

4 0

3 years ago

Which of these would be a good topic for a descriptive investigation? A. how the Moon's appearance changes B. what kind of dog f

katen-ka-za [31]

A. how the Moon's appearance changes

Explanation:

Descriptive investigation use very careful observations and measurements to develop findings.

Most geologists, meteorologists and astronomers use descriptive investigation to develop their findings.

Since most of their subject matter is inaccessible.
Descriptive investigation is used for indirectly making inquiries
It involves the development of an inquiry without formulating any hypothesis.

learn more:

Experiments brainly.com/question/1621519

#learnwithBrainly

6 0

3 years ago

Read 2 more answers

Given a sample of poly[ethylene-stat-(vinyl acetate)] A.Calculate the mean repeat unit molar mass for a sample of poly[ethylene-

AlladinOne [14]

Answer:

a) The mean repeat unit molar mass for PEVA is 30.72 g/mol

b) degree of polymerization of the copolymer is 1300

Explanation:

Given that;

the wt% of copolymer consist of 12.9 wt% of vinyl acetate and 87.1 wt% Ethylene.

Basis: 100 g of PEVA consist of 12.9 of vinyl acetate and 87.1g of Ethylene.

now we calculate the mole fraction of vinyl acetate Ethylene in the copolymer;

the molecular weights of vinyl acetate and ethylene are 86.09 g/mol and 28.05 g/mol respectively

so

moles of vinyl acetate = wt. of vinyl acetate / molecular weights of vinyl acetate

moles of vinyl acetate = 12.9 g / 86.09 g/mol

moles of vinyl acetate = 0.1498 mol

moles of Ethylene = wt. of Ethylene / molecular weights of Ethylene

moles of Ethylene = 87.1 g / 28.05 d/mol

moles of Ethylene = 3.1052 mol

Total moles = 0.1498 mol + 3.1052 mol = 3.255 mol

Next we calculate the mole percent;

mole percent of vinyl acetate $X_{V}$ = moles of vinyl acetate / total moles

$X_{V}$ = (0.1498 mol / 3.255 mol) × 100

$X_{V}$ = 4.6%

mole percent of Ethylene $X_{E}$ = moles of Ethylene / total moles

$X_{E}$ = (3.1052 mol / 3.255 mol) × 100

$X_{E}$ = 95.397% ≈ 95.4%

we know that, mean repeat unit molar mass for a sample = ∑ $X_{i}$ $M_{i}$

where $X_{i}$ is the fraction ratio and $M_{i}$ is the molecular weight

so or the PEVA

mean repeat unit molar mass M = ( $X_{V}$ $M_{V}$ ) + ( $X_{E}$ $M_{E}$ )

so we substitute

M = ( 4.6% × 86.09) + ( 95.4% × 28.05 )

M = 3.96014 + 26.7597

M = 30.72 g/mol

Therefore, The mean repeat unit molar mass for PEVA is 30.72 g/mol

b)

Degree of polymerization

$DP_{n}$ = $\frac{M_{n} }{M}$

where $M_{n}$ is the number average molecular weight ( 39,870 g/mol )

so we substitute

$DP_{n}$ = 39,870 g/mol / 30.72 g/mol

$DP_{n}$ = 1297.85 ≈ 1300 { 3 significance figure }

Therefore, degree of polymerization of the copolymer is 1300

5 0

2 years ago