Academic Year 2016- 2017
First Term
Science Revision sheets (Answer key)
Name: ________________________
Grade: 7
(A)
Date: _______________
Section: _____________
Science Practice :
Q1: Choose the letter of the choice that best answer the questions:
1.
Which of the following is an example of an exothermic chemical reaction?
A. photosynthesis
B.
burning wood
C. melting ice cubes
D.
boiling water
2. Which formula represents a carbohydrate ?
A. Butane (C4H10)
B. Octane ( C8H18)
C. Ethanol ( C2H6O)
D. Isobutance (C4H10)
3. What does an alpha particle consist of?
A. two protons and two neutrons
B. two electrons
C.two neutrons and two electrons
D. one positron
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4. Saltwater is an example of a solution. Compared to the salt, which term best
describes the water in the solution?
A.
solute
B.
solvent
C.
mixture
D.
suspension
5. The chemical formula of acetate is shown below.
How many atoms of carbon are in one molecule of acetate?
A. 1
C. 3
B. 2
D. 7
C2H3O2
6. Which of the following will slow the rate at which sugar dissolves in water?
A.
cooling the water
B.
crushing the sugar
C.
increasing the amount of sugar
D.
stirring the sugar into the water
7. Which of the following is an example of an exothermic chemical reaction?
A.
photosynthesis
B.
burning wood
C.
melting ice cubes
D.
boiling water
8. How is a salt formed during a neutralization reaction?
A. A hydrogen ion reacts with a hydroxide ion.
B. An acid changes to a different state of matter.
C.
A metal ion takes the place of the hydrogen of an acid.
D. The water molecule breaks into hydroxide and hydrogen ions
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9.
Which property of acids and bases do most acid-base indicators use?
A. Acids and bases can react together to form salts.
B. Acids and bases give off specific tastes that are easy to recognize.
C. Acids and bases can react with certain objects to wear them away.
D. Acids and bases react with certain compounds to cause a change in color .
10. A chemist is working with a liquid substance that tastes bitter, feels
slippery, and conducts an electric current. Which of the following is the
chemist most likely working with?
A.
a salt
B.
a base
C.
an acid
D.
distilled water
11. Fluorine has 7 valence electrons. How many more electrons does it need to
achieve a full outermost energy level?
A.
1
B.
7
C.
3
D.
10
12. What happens to an acid when it dissolves in water?
A. It increases the number of hydroxide ions in water.
B. It increases the number of hydrogen ions in water.
C.
It produces a salt that collects at the bottom of the container.
D. It breaks water into individual atoms of hydrogen and oxygen
13. Glucose (C6H12O6) is a kind of sugar molecule. How many atoms are in a
molecule of glucose?
A.
6
B.
12
C.
18
D.
24
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14. The equation below describes a neutralization reaction.
Which substance is missing from the product side of the equation?
A.
water
B.
oxygen
C.
hydrogen ion
D.
hydroxide ion
15. Vinegar is a solution of acetic acid in water. Which term best describes
water in this solution?
A. solute
B.
solvent
C.
D.
concentration
solubility
16. A man ate a tablet to neutralize too much acid in his stomach. What can
you conclude about the tablet?
A. It must have been a salt.
B.
It must have been sugar.
C. It must have been a base.
D.
It must have been an acid.
17. Which of the following is an example of a salt commonly used by people?
A. chalk
B.
bleach
C. ammonia
D.
milk of magnesia
18. Which product is formed when acids react with most metals?
A. water
B.
oxygen gas
C. hydrogen gas
D.
hydroxide ions
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19. What happens to a base when it dissolves in water?
A. It increases the number of hydroxide ions in the water.
B. It increases the number of hydrogen ions in the water.
C. It produces a salt that sinks to the bottom of the water.
D. It breaks the water into individual atoms of hydrogen and oxygen
20. A chemical reaction is shown below.
What are the products in the equation?
A.
Fe3O4 only
B.
Fe only
C.
Fe and H2O
D.
Fe3O4 and H2
Fe + H2O  Fe3O4 + H2
II. Fill in the blanks :
1.
The _______________
is the substance in the solution that does the
Solvent
dissolving .
Acid
2. An _________________
increases the number of positively charged
H3O+ions when it dissolves in water
Strength
3. The ____________________
of an acid or base depend on the
percentage of its particles that break apart to form ions in a solution.
Double
4. A _______________
bond is made up of two pairs of electrons.
Solution
5. A _________________
is a mixture in which two or more substance are
completely blended and evenly distributed and cannot identify the
different parts.
Structural Formula
6. A ________________________
shows that how atoms are connected.
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Law of conservation of mass
7. The ________________________________________
states that
matter is neither created nor destroyed in ordinary physical and chemical
changes .
8. The four electrons in the outer level form bond with other atoms are
Valance electrons
called _________________________
9.
Nitrogen
_____________________
is found in nucleic acid that make up DNA.
10. A chemical reaction in which energy is released to the surroundings is
Exothermic
called ______________________________
reaction.
III. State whether each statement is ‘ True ’ or ’ False ’ :
True
1. Plants absorbs energy when they carry out photosynthesis .___________
2. Product are the substances formed in a reaction . _______________
True
3. In a nuclear reaction, atoms are rearranged and bond can be broken or
False
formed . ___________________
4. The amount of solute needed to make a saturated solution depends on the
True
solubility of a solute in a particular solvent. __________________
False
5. Heating a mixture can help a solid dissolve very slowly in a liquid ._______
6. A Salt is a covalent compound that forms when a metal atom replace the
False
hydrogen of an acid . _____________
7. Solubility is the ability of one substance to dissolve in another at a given
True
temperature of an acid . ______________
8. Acid turns blue litmus paper red . ______________
True
True
9. Bases form hydroxide ions in water. _____________
False
10. Two product of neutralization reactions are water and acid . __________
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IV. Match the following :
A
Ans
1. Acid
e
B
a. ability of a substance to dissolve in
another at given temperature and pressure.
2. Nuclear fission
c
b. water and salt
3. Salt
g
c. large nucleus split into two nuclei
4. Solubility
a
d. indicator
5. Chemical reaction
f
e. H3O+
6. Neutralization reaction
b
f. rearrangements of atoms
7. Litmus paper
d.
g. ionic compound
V. Unscramble the letters below and make a meaningful word :
1. ASLT
:
____________________ ( SALT )
2. OUTSEL
:
______________________ ( SOLUTE )
3. TOPISOES : ______________________ ( ISOTOPES )
4. OUNDSO
: ______________________ ( SOUND)
VI. Answer the following :
1. What are the evidence that a chemical reaction has taken place ?
1. Color change
3. Change on odor
2. . Precipitate formation
4. Appearance of gas bubbles
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2. What type of indicators can you use to determine the presence of an acid
or base in a solution?
Ans : Acid – base indicator such as red and blue litmus paper are useful
to determine the presence of an acid base solution.
3. Describe the difference between a strong acid and a weak acid ?
Ans : A strong acid breaks apart in water . A weak acid remains mostly
intact
4. Salad dressing and apple juice are both examples of mixtures .
(a)
Which one is a solution ?
Ans : Apple juice
5. Give an example of an acid and explain how it is used in everyday life ?
Ans : sulfuric , nitric hydrochloric hydrofluoric acid
Uses : industrial processes , cleaning , breaking down food
6 What ions form when HCl dissolves in water ?
Ans : Hydronium ions ( H3O+) and chloride ions ( Cl )
7. How does a strong base behave differently from a weak base ?
Ans : A strong base breaks apart into ions .A weak base remains mostly
unchanged .
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8. What is an organic acid?
Ans : An organic compound that has acid properties .
9. Use this chemical structure to answer the following questions :
(a)What type of bonds are present in this molecule ?
Ans : Single
(b) What elements are present in this molecule ?
Ans : carbon , hydrogen
(c)What is the chemical formula of this organic compound ?
Ans : C6H14
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