Which is NOT an indicator of a chemical reaction?
Formation of a precipitate
Change in volume
Emission of odor
Change in texture
Which of the following is a physical change?
Burning of bread
Melting of wax
Rusting of iron
Turning milk into yogurt
What is a physical change?
A change in chemical composition
A change in color only
Formation of new substances
A change in state or shape without altering composition
Why are houses in hot areas painted white?
To conduct heat
To reflect heat
To absorb heat
To store heat
Which type of clothing is preferred in summer?
Black and heavy
Dark and tight
Shiny and thick
Light and loose
How is heat transferred through ironing clothes?
By convection
By evaporation
By radiation
By conduction
Why is adding food coloring to water not a chemical reaction?
Because no new substance is formed
Because it is irreversible
Because it changes color
Because it forms a new substance
The browning of an apple after cutting is considered:
A physical change
A chemical reaction
Melting
A change of state
What indicates a chemical reaction between baking soda and vinegar?
Temperature decrease
Color change
Gas bubbles
What is thermography used for?
Measuring volume
Detecting sound
Measuring mass
Detecting heat radiation
What happens in a chemical reaction at the molecular level?
Atoms are rearranged
Atoms are created
Atoms remain unchanged
Atoms are destroyed
How is heat transferred in fluids?
By insulation
What happens when two systems at different temperatures come into contact?
Heat flows from the hotter system to the colder system
Heat flows from the colder system to the hotter system
Both systems become colder
No heat flows between them
What is the scientific term for a change that produces new substances?
Temporary change
Reversible change
Physical change
Chemical change
What is thermal conductivity?
The ability to absorb heat
The ability to transfer heat through a material
The ability to reflect heat
The ability to store heat
What do all hot objects emit?
Infrared radiation
Light only
Ultraviolet rays
Sound waves
What is thermal equilibrium?
When two systems have the same mass and same temperature
When two systems have the same volume
When two systems have the same density
When two systems have the same temperature
Why is the heating coil placed at the bottom of an electric kettle?
To heat water by conduction
To reduce electricity use
To heat water by convection
To heat water by radiation
What is a chemical reaction?
A change in shape
A process where new substances are formed
A change in state
A change in temperature
What indicates a chemical reaction when sugar is burned?
It melts
It changes color and emits smoke
It becomes harder
It dissolves
What indicates a chemical reaction when oil reacts with caustic soda?
Gas evolution
Formation of a solid
Emission of light
In which case is heat transferred only by radiation?
Rubbing hands together
Heating air in the room with a radiator
Heating water on a stove
Heating a rock by the Sun
What causes sea breeze during the day?
The sea and land heat equally
The sea heats faster than the land
The land heats faster than the sea
The land cools faster than the sea
What safety precaution is needed when burning magnesium?
Use a plastic container
Use water to cool it
Use a protective mask
Use bare hands
How is heat transferred from a heater to a thermometer?
Conduction only
Convection only
Radiation only
All three methods
What happens when an ice cube is placed in boiling water?
Heat flows from water to ice
Heat flows from ice to water
Ice gains energy from surroundings
No heat flows
When iron is exposed to moist air, it undergoes:
Rusting
Dissolving
Evaporation
Why does ice melt faster on some materials?
Due to thickness
Due to shape
Due to color
Due to higher thermal conductivity
Why are cooking pot handles made of plastic or wood?
They are cheap
They are good conductors
They are good insulators
They are strong
When sugar is heated, it turns brown due to:
Condensation
What is the scientific term for energy transferred due to temperature difference?
Heat
Light
Power
Work
Which of the following is a chemical change?
Breaking glass
Melting ice
Burning wood
Dissolving sugar
What is the definition of heat?
The mass of an object
Energy transferred due to a temperature difference
A form of matter
A type of radiation
Why are cooling systems used in electronic devices?
To increase weight
To remove excess heat
To reduce noise
To increase performance
How is heat transferred from the Sun to the Earth?
By reflection
Which of the following is a good thermal conductor?
Wood
Plastic
Copper
Cardboard
What is the state when two systems reach the same temperature?
Thermal conduction
Thermal radiation
Thermal expansion
Thermal equilibrium
How is heat transferred in a vacuum?
Not transferred
A physical change is characterized by:
The composition of the matter changes
The composition of the matter does not change
Accompanied by light emission
Produces new substances
Which material is a poor conductor of heat?
Aluminum
Silver
How is heat transferred along a metal rod?
Which is a good heat insulator?
Iron
When hydrochloric acid is added to magnesium, it produces:
Carbon dioxide
Hydrogen
Oxygen
Nitrogen
Is the expansion of water in a sealed bottle in a freezer a chemical reaction?
Yes, because it changes state
No, because it is reversible
Yes, because it changes volume
No, because no new substance is formed
When 30°C metal balls are mixed with 20°C water, why is the final temperature not 25°C?
Because the mixture has the same specific heat
Because the mixture has the same mass
Because the mixture is made of substances with different masses and specific heats
Because the mixture is not stirred