False solutions are natural gas, nuclear power and industrial biomass incineration.
sugar in water is an example of true solution.
Answer:
- <em><u>A physical change has occurred, with no energy change.</u></em>
Explanation:
When a pencil lead is broken there is not change of any chemical properties, therefore it is not a chemical change, but just a physical change. In this case the change is just the number of pieces and dimensions.
Chemical changes always involve the formation of new different substances; the bonds between the atoms of the starting substances (reactants) breake and new bonds are formed leading to new substances (products) with different chemical composition (arrange of atoms). Chemical changes occur through chemical reactions.
Hence, if there is not change on the chemical composition, you think on physical changes. Physical changes include change in shape, size, state of matter (e.g. solid, liquid, gas). In the case of a pencil lead breaking, it is a change in shape and size.
Also, since energy has not been absorbed or released during the change, the energy of the pencil lead before having been broken is equal to the sum of the energies of the pieces of pencil lead obtained. So, this is a physical change with no energy changes.
Some examples of physical changes that include change in energy are the change of state (e.g. solid to liquid or liquid to gas) and the dissolution of a compound.
Answer:
Yes, it is correct.
Explanation:
400 cm = 4 m
40 m = 40 m
0.4 km = 400m
Therefore, 400 cm < 40 m < 0.4 km
The atomic number is the number of protons meaning that there are 14 protons in an atom of silicon. The mass number is the sum of the protons and neutrons. 28 - 14 = 14. There are 14 protons and 14 neutrons in silicon.
Explanation:
As a number of glassware are used in lab experiments so it is necessary that they should be cleaned properly after and before the experiment.
This can be done as follows.
1). At first acetone is used to rinse the glassware. If water soluble contents present in the glassware then use deionized water after rinsing it with acetone and if ethanol soluble components are present there then rinse with ethanol followed by rinses with deionized water.
2). When glassware are dirty in such a manner that they cannot be washed immediately then soak them in water for a certain period of time. This can help in removing the dirt or chemicals easily from the glassware.
3). The laboratory glassware can be easily washed with detergents or products like lab wash, alconox etc. Once these glassware are thoroughly cleaned then rinse them 3 times with deionized water.