Page 120 - ICSE Chemistry 8

Review Your Learning

A. Answer in one word/a few words.
1. The simplest form of a pure substance which is made up of only one kind of atom _____________
2. A pure substance which is formed when two or more elements chemically
combine in a defi nite propor on by mass _____________
3. The electrons present in the outermost shell of an atom _____________
4. An ion formed when an atom or a group of atoms accepts electron(s) by
developing a nega ve charge _____________
5. A group of diff erent atoms present as a single unit having a posi ve or nega ve
charge on it _____________

B. State whether the given statements are true (T) or false (F).
1. Carbon dioxide is represented using the formula CO .
2
2. The elements exhibi ng valency 4 are called pentavalent elements.
3. A ca on is formed when an atom or a group of atoms loses electron(s) by developing a posi ve
charge.
4. A word equa on represents the chemical reac on wri en using only the names of the reactants
involved and the products formed.
5. Same catalyst can be used to alter the rate of diff erent reac ons.

C. Defi ne the following terms.
1. Element 2. Compound 3. Valency 4. Ca on
5. Radical 6. Balanced equa on 7. Posi ve catalyst 8. Exothermic reac on
D. Balance the following chemical equa ons.
1. CO + H O  H CO 2. Fe + HCl  FeCl + H 2 3. N + H  NH 3
2
3
2
2
2
2
2
4. H + O  H O 5. Na O + H O  NaOH 6. Zn + HCl  ZnCl + H
2 2 2 2 2 2 2
E. Write the balanced chemical equa ons for the following word equa ons.
1. Calcium oxide + Water  Calcium hydroxide
2. Calcium carbonate  Calcium oxide + Carbon dioxide
3. Methane + Oxygen  Carbon dioxide + Water
4. Hydrogen + Chlorine Hydrogen chloride
5. Iron + Oxygen Iron oxide
F. Answer the following ques ons.
1. What is an ion? Diff eren ate between a ca on and an anion.
2. How is a chemical formula derived? Derive the chemical formula of calcium hydroxide and sodium
carbonate.
3. What does the atomic theory state? How is it diff erent from the law of conserva on of mass?
4. What all informa on do you get from a chemical equa on?
5. What are the limita ons of a chemical reac on?

PROJECT
Create a PowerPoint presenta on on the topic ‘Forma on of Compounds’. Find the related informa on and
images using the Internet. Add audio and visual eff ects to your presenta on. Format it as per your choice.

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