chemical reaction
What is a chemical reaction?
A chemical reaction is a process where substances (reactants) change to form new substances (products).
What is sound?
Sound is a type of energy made by vibrations that travel through a medium (like air, water, or solids) to reach our ears.
What is the main source of light for Earth?
The sun .
What nutrient do we need for energy?
Carbohydrates.
What is the chemical symbol for oxygen?
O
What is the difference between a physical change and a chemical change?
A physical change doesn't create a new substance (e.g., melting ice), while a chemical change forms a new substance (e.g., burning wood).
What part of the ear helps you hear sound vibrations?
The eardrum (and inner ear parts like the cochlea help too).
Does light travel faster than sound?
YES.
Name one health risk of eating too much sugar.
Tooth decay or obesity.
Which metal is the lightest and is found at the top of Group 1?
Lithium
What are the signs that a chemical reaction has taken place?
Signs include: color change, temperature change, gas being produced (bubbles), light being given off, or a solid (precipitate) forming.
Through which medium does sound travel fastest — air, water, or solid?
Solid, because particles are packed closer together.
What do we call materials that let light pass through completely?
Transparent materials.
Why is protein important for the body?
It helps build and repair body tissues.
What do elements in the same group of the periodic table have in common?
They have similar chemical properties and the same number of outer electrons.
Why does increasing the temperature speed up a chemical reaction?
Higher temperatures give particles more energy, making them move faster and collide more often and with more energy — this increases the reaction rate.
What is the difference between pitch and volume in sound?
Pitch is how high or low a sound is; volume is how loud or quiet it is.
What happens when light passes from air into water?
It bends or refracts.
What can happen if someone doesn’t get enough vitamins or minerals?
They can develop a deficiency disease (e.g., scurvy from lack of vitamin C).
Why are Group 0 elements (noble gases) unreactive?
Because they have a full outer shell of electrons.
What does the Law of Conservation of Mass mean in a chemical reaction?
It means that the total mass of the reactants is the same as the total mass of the products. No atoms are lost or made — they are just rearranged.
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Why can’t sound travel through space?
Because space is a vacuum with no particles for the sound waves to vibrate through.
Why does a red apple appear red under white light?
It reflects red light and absorbs all other colours.
How does regular exercise help your cardiovascular system?
It strengthens the heart, improves circulation, and lowers the risk of heart disease.
What happens to the reactivity of Group 1 metals as you go down the group, and why?
Reactivity increases because the outer electron is further from the nucleus and easier to lose.