Viruses inject dna or rna into the nucleus of a cell to reproduce
Answer:
Because they don't have fertilizer.
Explanation:
Well, if this was a long time ago, then farmers did not have fertilizer. So, there are bacteria on the roots of plants that convert nitrogen into a usable form. It's very important for growing, and when farmers harvest the crop, not much of the nitrogen is returned to the land, so it is not as fertile. Fertilizer is largely consisted of nitrogen, so that is why farmers use fertilizers today. But "a long time ago," farmers did not have fertilizer.
Answer:
Physical Change:
- Boiling water
- Breaking a pencil
- Water evaporating
- Denting a car door in an accident
- Tearing paper
- Ice melting
- dissolving
Chemical Change:
- Something rusting
- photosynthesis
- metabolism/digestion
- Nuclear power [atoms are arranged differently]
- Smashing paper with two metal balls, burns paper
- Electricity in water, breaks H2O into H2 and O2
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physical change is when there is only physical change occurring--and it can typically be undone easily,
whereas chemical change is when there is chemical change--which changes the chemical properties of something, which cannot be undone simply.
hope this helps!!