Answer: Option (d) is the correct answer.
Explanation:
In solids, molecules are held together by strong intermolecular forces of attraction. As a result, they are unable to move from their initial position and can only vibrate at their mean position.
Hence, a solid has definite shape and volume. Solids cannot be compressed.
Whereas in plasma, molecules are hot ionized which include positively charged ions and negatively charged electrons. They collide much more rapidly with each other and are widely spreaded out.
Therefore, they occupy the volume of container in which they are placed. Plasma can be compressed.
Thus, we can conclude that substance X is a solid and substance Y is a plasma.
Explanation:
Steps followed to practice laboratory safety during the experiment are as follows.
- Used tongs or a test tube holder to hold materials over the Bunsen burner flame.
- Wore gloves and goggles.
- Made careful observations of the products and reactants.
- Did not smell the gases produced.
When we heat a test tube over bunsen flame then the tube gets hot and when we hold it with bare hands then out hands will burn. Therefore, it is advised to hold test tube with the help of tongs or a holder so that our hands did not burn.
We should also wear gloves and goggles so that any acid would not spill directly on our hands, skin and eyes as it can affect or damage the skin severely.
Careful observations were made so that correct calculations about the experiment can be carried out.
It is also advised that we should not smell the gases produced but gases move freely from one place to another in a laboratory or any where else.
So, we can try to avoid it by covering our mouth with a cloth but we cannot stop it. If we keep on inhaling the gases produced in a laboratory then it can also lead to severe disease or defect in the human body.
Answer:
c. Mercury is used in barometers because it has a high density
Explanation:
Chemical change -
It refers to any change in a chemical process , where there is formation of any new substance , is referred to as a chemical change .
The indication of any chemical change is the formation of some new substance.
Hence, from the question,
The process which does not involve chemical change is -
The use of mercury in barometer , to measure pressure , in this process no new substance is formed i.e. , now change in mercury.
Answer: during a chemical reaction, matter cannot be created or destroyed
Explanation:
