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elena55 [62]
3 years ago
10

Chemists and physicists often have to manipulate and control a variable that they want to study. Scientists who need to control

a variable must perform which type of scientific investigation?
A. experimental
C. comparative
B. free exploration
D. observational
Chemistry
2 answers:
artcher [175]3 years ago
7 0
Answer is d observational
Inessa05 [86]3 years ago
4 0
The answer is D I took the test
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Why is nucleus of an atom charged is negatively charged?
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Answer:

Charge is caused by a flow of electrons, since electrons are around the nucleus they can be lost or gained by atoms. When an atom gets charged, it gains a charge, that is, it gains an electron. Since electrons are negatively charged, when an atom gains one, it also becomes negatively charged.

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3 years ago
How many molecules are in 42.3g sample of water
Helga [31]

Answer:

The number of molecules is 1.4140*10^24 molecules

Explanation:

To know the number of molecules, we need to determine how many moles of water we have, water has molar mass of 18.015g/mol

This means that one mole of water molecules has a mass of 18.015g.

42.3g * 1 mole H2O/18.015g

= 2.3480 moles H2O

We are using avogadros number to find the number of molecules of water

2.3480 H2O * 6.022*10^ 23moles/ 1mole of H2O

That's 2.3480 multiplied by 6.022*10^23 divided by 1 mole of H2O

Number of molecules = 1.4140 *10^24 molecules

5 0
3 years ago
For an experiment, you place 15 g of ice with a temperature of -10 C into a cup and label
melamori03 [73]
The correct answer is c. Temperature is the average kinetic energy of a sample so if two samples have the same temperature they will also have the same average kinetic energy. I hope this helps. Let me know if anything is unclear.
6 0
3 years ago
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The radius of a uranium atom is 149 pm. How many uranium atoms would have to be laid side by side to span a distance of 4.96 mm?
nikitadnepr [17]

Answer:

4960000000 pm

Explanation:

4.96*1000000000= 4960000000

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3 years ago
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What accommodations have been designed to protect astronauts from micrometeoroids hitting their spacesuits?
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Answer:

They are multilayered

Spacesuits provide protection from radiation and offer normal air pressure inside

Explanation:

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