chemical reactions
what is a chemical reaction?
A process where substances (reactants) transform into new substances (products) with different properties.
How are elements arranged in the periodic table?
By increasing atomic number and grouped by similar properties.
What type of wave is sound?
A longitudinal wave that travels through vibrations in a medium.
What type of wave is light?
A transverse electromagnetic wave.
Define adaptation.
A trait that helps an organism survive in its environment
What are the signs that a chemical reaction has occurred?
Color change, gas production, temperature change, or formation of a precipitate.
What do elements in the same group share?
he same number of electrons and similar chemical properties.
How does pitch relate to frequency?
Higher frequency = higher pitch; lower frequency = lower pitch.
What is the speed of light in a vacuum?
3×108 m/s
What is natural selection?
Organisms with advantageous traits survive and reproduce, passing on those traits.
Balance this equation: H2+O2→H2O
2H2+O2→2H2O
Name the three subatomic particles and their charges.
Proton (+1), neutron (0), electron (-1).
Why can’t sound travel in a vacuum?
It needs a medium (solid, liquid, gas) to vibrate.
Describe refraction with an example.
Light bends when passing through different mediums (e.g., a straw appearing bent in water).
How are dominant and recessive traits different?
Dominant traits overshadow recessive ones in most scenarios.
What is the difference between exothermic and endothermic reactions?
Exothermic releases heat (e.g., combustion), while endothermic absorbs heat (e.g., photosynthesis).
Why are noble gases unreactive?
They have a full outer electron shell, making them stable.
What is the range of human hearing in hertz{Hz}?
20 Hz to 20,000 Hz.
How does a convex lens affect light?
it converges light rays to a focal point, magnifying images.
Give an example of an inherited and environmental variation.
Inherited = eye color; environmental = scars or language spoken.
Explain the role of a catalyst in a reaction.
A catalyst speeds up the reaction without being consumed (e.g., enzymes in digestion).
Compare metals and non-metals in terms of conductivity and reactivity.
Metals conduct heat/electricity and lose electrons; non-metals are insulators and gain electrons.
Explain how echoes are formed.
Sound waves reflect off hard surfaces, returning to the listener after a delay.
What is the difference between reflection and refraction?
Reflection is bouncing off a surface,refraction is the fact or phenomenon of light, radio waves, etc. being deflected in passing obliquely
Explain Darwin’s theory of evolution.
Species change over time via natural selection, leading to biodiversity.