Chemical reaction
What is a chemical reaction?
A process where one or more substances change into new substances.
What do we call the back-and-forth movement that creates sound?
Vibration
What do we call objects that emit their own light?
Luminous objects (e.g., the Sun, fire, a candle flame)
Why is it important to wash your hands before eating?
to remove germs and help prevent illness.
What is the periodic table?
A chart that organizes all the known elements.
What are two signs that a chemical reaction is happening?
Signs include bubbles (gas), color change, smell, or temperature change.
Through which states of matter can sound travel?
Sound can travel through solids, liquids, and gases.
What is the law of reflection?
The angle of incidence is always equal to the angle of reflection
How many portions of fruit and vegetables should you try to eat every day?
at least 5 portions (a mix of fruit and vegetables)
What are the small boxes on the periodic table called?
Elements
Name one everyday example of a chemical reaction
Cooking food, burning wood, or rusting metal.
Why can you hear better when you put your ear on a table and someone taps the other end, compared to just listening through the air?
Sound travels faster and more efficiently through solids than through air, so the vibrations reach your ear more clearly.
Why can’t we see objects in a completely dark room, but we can see objects outside through a window?
In a dark room, there is no light to reflect from objects into our eyes, so we cannot see them. Objects outside are visible because light reflects from them into our eyes
What are two benefits of regular exercise?
Stronger bones and muscles, better mood, helps prevent illness, improves sleep, etc.
What is the chemical symbol for oxygen?
O.
What is the main difference between a chemical change and a physical change?
In a chemical change, new substances are formed. In a physical change, the substance stays the same, just its form changes (like melting ice).
If a sound wave has a frequency of 500 Hz and a wavelength of 0.68 meters, what is the speed of sound in that medium?
Speed = frequency × wavelength = 500 Hz × 0.68 m = 340 m/s.
What happens to a ray of light when it passes from air into water, and why?
The ray of light bends towards the normal because water is denser than air. This bending is called refraction
Why is sleep important for your health?
Sleep helps your body and brain recover, improves memory, and keeps you alert and healthy
Where are the metals mostly found on the periodic table?
On the left and in the middle.
What is produced when a metal carbonate reacts with an acid?
A salt, water, and carbon dioxide gas
Why can't astronauts hear each other if they are floating in space without radios, even if they are very close together?
Because space is a vacuum and has no air (or any other medium), sound waves cannot travel, so astronauts cannot hear each other without radios.
Two plane mirrors are placed parallel and facing each other. How many times can a ray of light be reflected between them?
An infinite number of times, because the light keeps bouncing back and forth between the mirrors
What is one way to help avoid getting sick from germs?
Wash your hands regularly, avoid touching your face, and keep surfaces clean
What do elements in the same group have in common?
They have similar properties.