Multiple Choice
1. Which of the following is a chemical change? (1 point)
boiling of water
melting a cube of ice
dissolving 10 grams of salt in water
splitting water into hydrogen and oxygen *
2. What is the mass of water that results from combining 2.0 g of hydrogen with 16.0 g of oxygen? (1 point)
14.0 g *
16.0 g
18.0 g
20.0 g
3. Why are plastic building blocks good for modeling molecules? (1 point)
They come in thousands of shapes and sizes.
They can be combined in many* different ways.
They are rigid and do not easily separate.
There are as many different colors as there are atoms.
4. What did Antoine Lavoisier’s experiments demonstrate? (1 point)
Atoms always split into pairs during a chemical change.
Mass is neither lost nor gained during a chemical change.
Matter can be created during a * chemical change.
Energy is neither lost nor gained during a chemical change.
D
C
B
B
junior thx i got a 100 TRUST JUNIOR IF U ARE IN CONNEXUS ACADEMY😃😃👌
Plz can someone check this?
I agree with 1 and 3 but not 2 and 4.
The answer to number 2 was the third and the answer to number 4 was the 2nd
i didnt rly trust em but hes right 100%
To determine the correct answers to the multiple-choice questions provided:
1. Which of the following is a chemical change?
- In order to answer this question correctly, we need to identify the characteristic of a chemical change. A chemical change involves the formation of new substances with different properties from the original substances.
- The options are:
- Boiling of water: This is a physical change as it involves a change in state from liquid to gas while maintaining the composition of water.
- Melting a cube of ice: This is also a physical change as it involves a change in state from solid to liquid while still being water.
- Dissolving 10 grams of salt in water: This is a physical change as it involves the separation of sodium and chloride ions, but the composition of the salt remains the same.
- Splitting water into hydrogen and oxygen: This is a chemical change since water (H2O) is being broken down into hydrogen (H2) and oxygen (O2), resulting in new substances.
- Therefore, the correct answer is "splitting water into hydrogen and oxygen."
2. What is the mass of water that results from combining 2.0 g of hydrogen with 16.0 g of oxygen?
- To determine the mass of water formed, we need to consider the balanced chemical equation for the formation of water: 2H2 + O2 → 2H2O. According to the equation, 2 moles of hydrogen combine with 1 mole of oxygen to form 2 moles of water.
- To find the mass, we need to convert the given masses of hydrogen and oxygen to moles. The molar mass of hydrogen (H2) is 2.0 g/mol, and the molar mass of oxygen (O2) is 32.0 g/mol.
- Therefore, the number of moles of hydrogen is 2.0 g / 2.0 g/mol = 1 mol, and the number of moles of oxygen is 16.0 g / 32.0 g/mol = 0.5 mol.
- According to the balanced equation, 2 moles of water are formed for every 2 moles of hydrogen. Therefore, if 1 mole of hydrogen is used, 1 mole of water is formed.
- The molar mass of water (H2O) is 18.0 g/mol.
- Therefore, the mass of water formed is 1 mol * 18.0 g/mol = 18.0 g.
- Therefore, the correct answer is "18.0 g."
3. Why are plastic building blocks good for modeling molecules?
- To determine the correct answer, we need to consider the properties of plastic building blocks and how they relate to modeling molecules.
- The options are:
- They come in thousands of shapes and sizes: Although this may be true, it does not directly relate to why plastic building blocks are good for modeling molecules.
- They can be combined in many different ways: This is the correct answer, as plastic building blocks can be connected in various arrangements to represent different molecular structures.
- They are rigid and do not easily separate: While this may be a useful property, it does not directly relate to modeling molecules.
- There are as many different colors as there are atoms: This is unrelated to the modeling of molecules.
- Therefore, the correct answer is "They can be combined in many different ways."
4. What did Antoine Lavoisier’s experiments demonstrate?
- To determine the correct answer, we need to consider Antoine Lavoisier's contributions to the understanding of chemical changes.
- The options are:
- Atoms always split into pairs during a chemical change: This is not correct, as Lavoisier's experiments did not demonstrate this concept.
- Mass is neither lost nor gained during a chemical change: This is the correct answer, as Lavoisier's experiments showed that the total mass before and after a chemical change remains constant.
- Matter can be created during a chemical change: This is not correct, as Lavoisier's experiments disproved the theory of matter being created or destroyed during a chemical change.
- Energy is neither lost nor gained during a chemical change: This is not correct, as Lavoisier's experiments did not specifically address the conservation of energy.
- Therefore, the correct answer is "Mass is neither lost nor gained during a chemical change."