10) Why is it important to keep control variables the same?
To ensure a fair test
To increase the temperature
To make the experiment more fun
To change the results
The flare includes .........................., which makes a red flame.
strontium nitrate
1) Which statement best describes an exothermic reaction?
A reaction that absorbs heat from its surroundings
A reaction that releases heat to its surroundings
A reaction that does not involve energy
A reaction that only happens in cold conditions
4) After reacting hydrochloric acid with sodium hydroxide, the temperature has increased from 21˚C to 52˚C. This reaction is
Endothermic
Exothermic
isothermic
Athermic
6) Which is the best scientific question for investigating fuels?
Why are fuels important?
Which fuel is the best?
Which fuel releases the most heat energy when burned?
Which fuel looks nicer?
sodium peroxide symbol
Na2O2
9) Which of the following should be kept as a control variable?
Volume of water in the container
Type of fuel
Temperature change
Amount of heat released
2) Which of the following is an example of an endothermic reaction?
Burning wood
Ice melting into water
Explosion of fireworks
A candle flame giving off heat
True& false Magnesium is more reactive than Sodium
False
5) Which process releases heat energy to the surroundings?
Melting wax
Cooking an egg
Boiling water
Freezing water
Word chemical equation Magnesium reacts with oxygen
magnesium + oxygen-> magnesium oxide
7) In an investigation comparing fuels, what is the independent variable?
The type of fuel used
The size of the container
The temperature change of water
The amount of heat released
3) A grade 7 student wants to know if the reaction of hydrochloric acid and sodium hydroxide solution is exothermic or endothermic. He did an experiment for this reaction. Give the name of this reaction:
Dissolving
Neutralization
Burning
Combustion
True& false Some metals react with oxygen to make oxides.
True
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